Becoming Vegan: Comprehensive Edition

In 1900, in many urban centers in the northeastern United States, 80 percent of children had rickets; in Java during the late nineteenth century, a three-month prison sentence could lead to death from lack of thiamine. Throughout history, mankind has known that certain foods, or time spent outdoors in sunny areas, had mysterious properties that could prevent or cure illness, and that a lack thereof could threaten a person’s well-being. Yet, the recognition of the existence of specific vitamins is just a century old; vitamin A was first identified in 1913.

Essential to life, vitamins can’t be synthesized by the body in adequate amounts; outside sources must be obtained. Although also found in food and equally essential for health, minerals are simply single elements. Vitamins are more-complex molecules that combine carbon with other elements, such as hydrogen, oxygen, and sometimes nitrogen. The total amount of vitamins the body needs is tiny—only 0.5 gram per day—but the functions they perform are vital. Some vitamins act like hormones, with far-reaching effects in the body; vitamin A governs certain aspects of growth and vitamin D regulates mineral metabolism. Many vitamins are coenzymes that assist enzymes in vital metabolic functions. Vitamins work as teams, to protect the body from free radical damage (vitamins A, C, and E) or convert carbohydrate, fat, and protein into a form of energy the body can use (the B vitamins).

Dodging Deficiencies

VITAMIN B₁₂ *

Vitamin B₁₂ in Perspective

Vitamin B₁₂ has the largest molecular structure of any vitamin, with the mineral cobalt at its center. Lack of vitamin B₁₂ is responsible for the lion’s share of bad press that vegan diets receive. Yet a shortfall is easily averted by B₁₂ supplements and/or fortified foods. Sadly, from time to time, two scenarios appear in medical literature or newspaper headlines. One features adults who don’t properly supplement with B₁₂; the other documents developmental problems in infants whose mothers consumed insufficient B₁₂ during pregnancy and whose intake was inadequate after birth.

Function

B₁₂ is part of the vitamin team that converts carbohydrate, fat, and protein into useable energy. It’s required for DNA synthesis and thus is crucial for cells that reproduce rapidly (for instance, during periods of growth) and for the red blood cells produced in bone marrow. It also maintains the protective myelin sheaths that surround nerve fibers.

As one aspect of its interaction with amino acids, vitamin B₁₂ helps to rid the body of homocysteine, a potentially harmful breakdown product of protein and specifically of the amino acid methionine. Homocysteine can injure the delicate inner lining of artery walls and can trigger heart disease. Over time, such damage can occur in those who appear healthy in other respects.^2–5

Vitamin B₁₂ is produced by bacteria present in the gastrointestinal tract (for example, in the mouth and lower bowel), yet this internal production can’t be relied upon to prevent deficiency. The amount made in the mouth is insufficient, and anything created in the lower bowel is too low in the digestive tract to be absorbed, so the vitamin is passed in the feces.^2,4,5

Deficiency Symptoms

In cases of vitamin B₁₂ deficiency (either from insufficient intake or from inadequate absorption of this vitamin), some combination of the following symptoms or conditions can appear:^2,5,6

These problems are easily avoided by ensuring a reliable source of this essential nutrient. Deficiency symptoms in adults typically can be reversed when the situation is caught and attended to early enough.^2–5,8–10

Deficiencies early in pregnancy may be linked to neural tube defects. Breast-fed infants whose mothers consume insufficient dietary B₁₂ and other infants whose diets are low in B₁₂ can develop serious and permanent damage to the nervous system. According to Dr. James Mills, a senior investigator with the US National Institute of Child Health and Human Development, any woman of childbearing age should be particularly careful to maintain adequate B₁₂ levels.^11,12

Infants typically show a more rapid onset of symptoms than adults. A B₁₂ deficiency may lead to loss of energy and appetite and failure to thrive, but there’s no entirely consistent pattern of symptoms. Infants are more vulnerable to permanent damage than adults; if not promptly corrected, deficiency can progress to coma or death. Some infants make a full recovery with proper treatment, but others show delayed development.^4,9,13,14

Laboratory Tests for Vitamin B₁₂

Several lab tests are used to detect vitamin B₁₂ status; the first two listed below are particularly reliable and sensitive. However, physicians and lab technicians may be unfamiliar with some of these tests. (For links to more information on such lab tests, see Resources on page 449.)^2,4,15–18

• Methylmalonic acid (MMA). The best marker of B₁₂ status when stores are depleted and deficiency has been reached is a compound called MMA. In cases of B₁₂ deficiency, MMA accumulates and can be measured in blood or (taken more easily) in urine.^15,18,23

• Homocysteine. Another compound that can build up in blood when B₁₂ is in short supply is homocysteine. Though testing for homocysteine levels is more commonly used to check for increased risk of heart disease, high blood homocysteine levels can indicate vitamin B₁₂ deficiency. The test lacks specificity, because high homocysteine levels can also signal a lack of folate, although most vegans get plenty of folate. (For more information on homocysteine, see page 216.)^15,23

• Serum or plasma vitamin B₁₂. A measure often used to assess B₁₂ status is serum or plasma B₁₂. In the past, biological assays couldn’t distinguish between the true vitamin and substances in the blood known as inactive B₁₂ analogs. As a result, cases of B₁₂ deficiency were missed.

Inactive analogs are molecules that resemble B₁₂ in physical structure; however, they’re not identical and can’t perform the vitamin’s roles in the body. For example, when people who were short of vitamin B₁₂ and who also consumed sources of inactive analogs (such as spirulina or seaweeds) were tested, their serum or plasma B₁₂ results indicated normal B₁₂ levels despite deficiency.^15,18,24 Modern radioisotope and immunoassay methods can more accurately measure the active form of B₁₂.

The lower end of the reference range for serum B₁₂ may have been set too low. The lower end point used by many laboratories for serum B₁₂ has been 200 pg/ml (150 pmol/L); however, many experts recommend this minimum be doubled to 405 pg/ml (300 pmol/L) or more. In Japan, the low end of the serum B₁₂ range considered acceptable has been as high as 550 pg/ml (400 pmol/L) for many years.^22,25,26 People whose lab test results are toward the lower end of the reference range yet within the range of some laboratories may still experience or develop some symptoms of vitamin B₁₂ deficiency.

• Mean corpuscular volume (MCV). A test that can indicate possible vitamin B₁₂ deficiency is MCV, an indicator of macrocytic anemia (meaning red blood cells that are larger than normal) that points to possible vitamin B₁₂ deficiency. Testing MCV doesn’t work for detecting B₁₂ deficiency in people with high intakes of folate (from green vegetables, oranges, legumes, and other folate-rich foods), because folate helps to prevent macrocytic anemia even when a vitamin B₁₂ deficiency exists. As a result, a B₁₂ deficiency can remain undetected by an MCV test, while the underlying damage to nerves proceeds and homocysteine levels rise.^2,4,17

For a person experiencing or wondering about symptoms of B₁₂ deficiency, it can be of value to arrange to have two of the tests listed, such as serum B₁₂ (a measure of the vitamin) plus MMA (a metabolic indicator). To avoid a potential deficiency, it makes even more sense to ensure that intake is adequate.^15,17,26,27

Follow one or a combination of these approaches:

1. Every day, take a B₁₂ (cyanocobalamin) supplement. Choose one that includes at least 25 micrograms (mcg) of B₁₂; most multivitamin supplements provide 25 mcg and often much more. Some experts recommend as much as 250 mcg daily for adults up to age 65, and 500 or 1,000 mcg for seniors (excess is excreted).32–34,37

2. Twice a week, take 2,000 to 2,500 mcg of vitamin B₁₂ in supplement form, either sublingually or swallowed. Some experts note that, taken twice a week, 1,000 mcg vitamin B₁₂ supplements will suffice, with just over 1 percent absorbed. Search online for inexpensive sources.

3. Every day, consume three servings of B₁₂ fortified foods, with each serving providing at least 2 mcg of vitamin B₁₂ (33 percent of the Daily Value, or DV). Typical examples are fortified nondairy milks, vegan meat substitutes, breakfast cereals, and bars (page 221). Another choice is 2 teaspoons (10 ml or 5 g) of Red Star Vegetarian Support Formula nutritional yeast, which is fortified with vitamin B₁₂.^2,4,16,17,38

Recommended Intake

The body requires vitamin B₁₂ in miniscule amounts; the official Recommended Dietary Allowance (RDA) for adults is 2.4 mcg per day, the amount needed to prevent macrocytic anemia. However, recent research suggests an intake of 4 to 7 mcg per day is necessary to prevent buildup of homocysteine and MMA.^16,28 The RDA assumes that the total intake of B₁₂ comes from two or three sources (such as fortified foods) that are eaten at different times of the day (the body’s B₁₂ receptors may become saturated with amounts as small as 1 to 1.5 mcg, though this varies with dose). Because the amount of vitamin B₁₂ in fortified foods (page 221) can differ from one batch to another, it’s wise to combine fortified foods with occasional supplement use because supplements are more tightly standardized.^29,30

If the whole amount of vitamin B₁₂ is consumed at once (as with a supplement), the body absorbs only a fraction of the total. For example, with a 250 mcg dose, the body’s B₁₂ receptors only take in about 1.5 mcg and can’t absorb more for four to six hours. Beyond the absorption at the B₁₂ receptor sites, an entirely different mechanism—passive diffusion—allows for the uptake of about 1 percent of the B₁₂ ingested.^{16,26,31–34} As a result, the less frequently vitamin B₁₂ is ingested, the higher the dose needed (see “How to Obtain Adequate Vitamin B₁₂”).

Based on a lack of reports of vitamin B₁₂ toxicity in the general population or during pregnancy, the Institute of Medicine (IOM) concluded there’s no basis to establish a UL. Exceeding recommended intakes is considered to be safe; the excess is simply excreted in the urine.^23,28,35 Cobalamin itself appears to be nontoxic; at the same time, daily intake of 1,000 mcg of cyanocobalamin doses is a growing phenomenon whose long-term effects are unknown.¹⁹⁴

These recommendations also are suitable during pregnancy or lactation; for other ages, see page 446. For updates about vitamin B₁₂ and the lively field of research surrounding it, see Resources on page 449.

B₁₂ Recycling and Avoiding Deficiency

As noted earlier, the effects of a vitamin B₁₂ deficiency can be devastating. Fortunately, the body can be adept at recovering and reusing vitamin B₁₂. Some people are better recyclers than others; in fact, a few avoid deficiency symptoms for many years despite having no reported dietary source. However, recycling shouldn’t be relied upon to maintain adequate B₁₂ levels. Adult stores may last for a year or more, although deficiency symptoms can be experienced within several months.

Vegans who don’t include a reliable source of vitamin B₁₂ will eventually become deficient. For some, this will happen in a matter of months; for others, it could take years. The consequences of this deficiency depend on how soon the deficiency is recognized and remedied. The damage can be dramatic and—in a few unfortunate cases of long-term deficiency—irreversible.

Early symptoms, such as weakness, fatigue, and mood changes, are nonspecific and easily mistaken for stress or aging, but the longer it takes to recognize the source of the problem, the greater the risk of permanent damage. People older than 50 (on any diet) should be alert regarding signs of B₁₂ deficiency, because malabsorption problems may occur with age. If a B₁₂ deficiency is suspected, lab tests can be arranged by a physician (see page 215). If the tests are carried out and B₁₂ deficiency is diagnosed, supplementation can begin immediately and further health consequences can be averted. However, if B₁₂ isn’t added to the diet at this stage, nervous-system damage will accelerate, and symptoms become more severe. A person with a B₁₂ deficiency runs the risk of heart disease; in pregnant women, a deficiency could be disastrous for the infant.

Makes 1½ cups (375 ml)

The name “Liquid Gold” denotes nutritional wealth that goes far beyond color; this creamy dressing is packed with riboflavin and other B vitamins. Three tablespoons (45 ml) can provide half the day’s B₁₂ requirement when prepared with fortified Red Star Vegetarian Support Formula nutritional yeast. (It also provides a day’s supply of omega-3 fatty acids.) Use this tasty dressing on salads, rice, baked potatoes, steamed broccoli, and other vegetables. (Add 1 teaspoon turmeric for more golden color plus protective circumin, and increase its absorption with a little black pepper.)

½ cup (125 ml) flaxseed oil

½ cup (125 ml) water

⅓ cup (85 ml) lemon juice

1 tablespoon (15 ml) cider vinegar, balsamic vinegar, or raspberry vinegar

2 tablespoons (30 ml) tamari or Bragg Liquid Aminos

½ cup (125 ml) nutritional yeast

1 tablespoon (15 ml) ground flaxseeds

2 teaspoons (10 ml) Dijon mustard

1 teaspoon (5 ml) ground cumin

Put all the ingredients in a blender and process until smooth. Stored in a covered jar in the refrigerator, the dressing will keep for 2 weeks.

Vegan Intakes from Food and Supplements

Studies show average vegan intakes of vitamin B₁₂ to be far below the RDA, with many participants having levels 25 percent or less than these recommended adult intakes.^17,40,41 Those who met the RDA typically included B₁₂ supplements. Two of three studies assessing intakes of vegan children and teens indicated insufficient vitamin B₁₂.¹⁷ Since these studies were conducted, responsible vegetarian societies (including raw foods groups) have recognized the need for vegans to ensure a reliable source of this essential nutrient; data from future studies should reflect improved vitamin B₁₂ intakes.

Vitamin B₁₂ Status of Vegans

A North American study reported results from 49 adults who had followed a vegan or near-vegan diet for two to four years without vitamin B₁₂ supplementation; three-quarters of the participants had insufficient serum B₁₂ or high MMA levels. Deficiencies were in the early stages, and participants didn’t report having symptoms. Some participants believed they had received adequate intakes of vitamin B₁₂ from raw fruits and vegetables, probiotics, fermented foods, dried greens, dulse, nori, blue-green algae, or spirulina, or from intestinal production; however, this proved not to be the case. In a follow-up study, 25 of those with vitamin B₁₂ deficiency continued their diet for three weeks, but with an important adjustment. They were divided into three groups:

• The second group consumed Red Star Vegetarian Support Formula nutritional yeast on a regular basis.

The vitamin B₁₂ supplements proved to be powerfully effective in quickly reversing deficiency. The nutritional yeast had some impact but was found to be less reliable than supplements; one person’s deficiency was not completely remedied within the three-week time period. Probiotics were ineffective at reversing vitamin B₁₂ deficiency.^29,44

Unreliable B₁₂ Sources

None of the following can be relied upon as sources of vitamin B₁₂: fermented foods, sprouts, mushrooms, seaweeds, spirulina, sprouts, or raw plant foods. Little or no true vitamin B₁₂ is available from these foods, and some may instead provide analog forms that are worse than useless because they fail to meet human requirements and can interfere with the action of true B₁₂. Though sea vegetables can be of value for some nutrients, they shouldn’t be relied upon as B₁₂ sources, because deficiency symptoms or lab results have been shown to worsen when vegans try to use nori, dulse, and spirulina as sources of this essential nutrient.^{16,17,24,38,44}

Reliable B₁₂ Sources

The proven vegan B₁₂ sources are supplements—an excellent choice—and foods fortified with B₁₂.^44–46 B₁₂ is the one vitamin that humans can’t get from a varied diet of whole plant foods plus some sun exposure. B₁₂ doesn’t originate from animal products either; whether it exists in fortified foods, supplements, or meat, it all comes from microorganisms.

Vitamin B₁₂ at the Beginning of Life

A reliable source of vitamin B₁₂ is especially important for mother and child during pregnancy and lactation. When a lactating woman consumes vitamin B₁₂ supplements and fortified foods, the vitamin is readily transferred to her infant via her milk. The RDA for a lactating woman is 2.8 mcg per day; amounts consumed should be greater. (See “How to Obtain Adequate Vitamin B₁₂” on page 217 for options based on several servings of fortified foods through the day, daily supplements, or biweekly supplements.)

In medical literature, the most prominent and sometimes tragic cases of B₁₂ deficiency involve infants. Without vitamin B₁₂, an infant can develop irreversible brain damage in a few months. Infants who haven’t built up their reserves of this nutrient must have adequate supplies. (Vitamin B₁₂ drops are one option to guarantee adequate intake).^4,11–14,16

Vitamin B₁₂ for Older Adults

The absorption of vitamin B₁₂ is a highly complex process that depends on the normal functioning of the gastrointestinal tract. However, about 2 to 3 percent of seniors (regardless of diet) fail to produce enough of a B₁₂ carrier (intrinsic factor, or IF) that’s essential for B₁₂ absorption. IF comes from parietal cells in the stomach lining, though this production typically diminishes with age. Normally, the vitamin B₁₂ from supplements and fortified foods first attaches to carriers present in saliva (called R-factors) that conduct B₁₂ to the upper part of the small intestine. There, pancreatic secretions partially degrade R-factors and IF takes over, transporting the cobalamin-IF complex to the B₁₂ absorption sites in the terminal ileum. For individuals whose absorption is impaired by lack of IF, monthly injections of vitamin B₁₂ have been a common remedy. As it turns out, oral doses (2,000 mcg per day) are proving an easier, effective, and less invasive solution. To diagnose a lack of IF and resultant low B₁₂, people over 50 are well-advised to have their B₁₂ status tested every five years.2,6,15,17,26,39,53–55

For a separate reason, the body’s ability to extract and absorb the form of vitamin B₁₂ present in animal products diminishes with age. In animal products, B₁₂ is tightly bound to protein, and the body must use hydrochloric acid and proteases to cleave B₁₂ from the protein. As bodies age, and gastritis or gastric atrophy occur, production of the gastric acid and of the enzymes lessens. (The use of protein pump inhibitors also reduces acid production.) As a result, one in three individuals age 50 or older may lose the capacity to absorb B₁₂ from animal products and must rely on the B₁₂ sources used by vegans, which are not protein-bound in this way. Thus, the IOM recommends that those over the age of 50 (regardless of dietary pattern) rely either on supplements or vitamin B₁₂-fortified foods to meet B₁₂ needs.^2,56 Some experts suggest that adults older than 65 increase their daily intake to 500 or 1,000 mcg of B₁₂.¹⁶ Older vegans have an advantage if they’ve already developed the habit of consuming B₁₂ in supplements and fortified foods. (See “How to Obtain Adequate Vitamin B₁₂” on page 217.)

Vitamin B₁₂ can be effective in treating cognitive impairment and dementia in the small proportion of cases where vitamin B₁₂ deficiency exists.^57,58 Deficiency also may be related to depression in later life.⁵⁹

VITAMIN D

Vitamin D in Perspective

From Roman times and in early China, bone deformities in children were observed and noted. The first detailed medical descriptions of rickets appeared in England around 1650, as the industrial revolution arose and families began to move from farms to smoky, smoggy cities. Many urban children worked long hours indoors, and when they got a chance to play, their play areas weren’t sunlit pastures but narrow, dark alleys. It’s estimated that by 1900, 80 percent of the children in Boston, New York, and other industrialized cities of the northeastern United States and northern Europe had this devastating skeletal disease.^4,62–68

In 1822, an observant Polish physician noted that the bowed legs and deformed skeletons of rickets were almost unheard of in rural areas, where children enjoyed plenty of exposure to sunlight for most of the year. Also, a nineteenth-century French physician noticed that a remedy used along coastal areas of northern Europe—oil from the liver of codfish—could prevent or treat this condition. As it turned out, eating fish liver directly was also protective. In Vienna, shortly after World War I, Dr. Harriette Chick and her coworkers were able to confirm two effective ways to prevent rickets in infants: ultraviolet radiation from the sun or a lamp, and a fat-soluble substance, which became known as vitamin D. In succeeding decades, researchers in the United States, England, and Germany showed that forms of vitamin D could be produced both by sun exposure on the skin and by irradiation (exposure to light) of plant sterols.^4,62–68

In 1971, vitamin D was reclassified as a “vitamin D hormone,” meaning that it can act both as a vitamin and as a hormone. In people who live near the equator and who are consistently exposed to sunlight throughout the year, “vitamin D” is a hormone that their bodies can build in sufficient amounts; for them, a dietary or supplementary source isn’t necessary. So technically, the substance known as vitamin D doesn’t qualify as a “vitamin” when sufficient sunlight is available. Yet for people who live far from the equator, where sunlight is limited during winter months, an alternate source becomes necessary. This is also true for people in any part of the world (regardless of location or climate) who remain indoors or completely cover their bodies with clothing. In these circumstances, foods naturally rich in vitamin D (such as liver or certain mushrooms that have been exposed to light), vitamin D–fortified foods, or supplements are essential.^4,62–68

The deep pigmentation of the skin of people indigenous to tropical areas absorbs shortwave ultraviolet light and acts as a natural sunscreen. As people with dark skins migrate farther from the equator, this protective melanin pigment can become a disadvantage because it also diminishes the production of vitamin D when skin is exposed to sunlight. Where sunlight is limited, paler skin can be an advantage, allowing more vitamin D production.^4,62–68

Function

Vitamin D enables the body to increase calcium absorption when needed, maintain critical blood levels of calcium, and limit urinary losses of this mineral. It also supports phosphorus absorption. Vitamin D’s role in maintaining healthy bones has been known for decades, and the research is now flowing in on its additional functions. The body can absorb a fraction of its daily calcium requirement by passive diffusion. However, the body’s calcium transport mechanism is required to meet the needs for this mineral, and that depends on vitamin D. Thus a partnership of adequate vitamin D and sufficient calcium is necessary.⁶⁹ For example, the optimal effect in reducing the risk of fractures and bone loss in people age 50 and older was seen with a combination of at least 20 mcg (800 IU) of vitamin D plus 1,200 mg of calcium supplementation daily.⁷⁰

Many vitamin D experts suggest that significantly higher intakes of vitamin D are advantageous for overall health.^65,69,71,115 Vitamin D functions throughout the body (including in the heart, brain, pancreas, thyroid, and muscles), enabling body systems to respond to everyday stresses and repairing assaults to those body systems. Vitamin D controls the growth and maturation of cells, such as those in bones and the immune system. Through its impact on the immune system, it helps to fight infectious diseases and reduce the risk of Crohn’s disease, multiple sclerosis, and rheumatoid arthritis. It regulates insulin production in the pancreas and can protect against type 1 and type 2 diabetes. Due to its active role in the muscles of blood vessels, it helps to regulate blood pressure and prevent cardiovascular disease and stroke. Vitamin D is important for reproductive success and to help preserve cognitive function during aging. Evidence of its benefits continues to accumulate.65,69,72,73,78,79,115,159

Low vitamin D intakes and low serum vitamin D levels are associated with increased risk of colon cancer and other cancers; adequate vitamin D seems to protect against breast cancer recurrence. A distinguished researcher—Edward Giovanucci of the Department of Medicine, Harvard School of Public Health—said, “I would challenge anyone to find an area or nutrient or factor that has such consistent anticancer benefits as vitamin D.” He added that vitamin D may prevent thirty deaths for every death caused by skin cancer.^{4,64,69,74–77}

The Body’s Production of Vitamin D

Either exposure to the sun on a regular basis or consumption of supplements and fortified foods—or a combination of all three—is effective in raising vitamin D levels. When skin is exposed to sunlight, ultraviolet rays stimulate the cholesterol compound called 7-dehydrocholesterol to become vitamin D₃ (cholecalciferol). Vitamin D₃ then enters the bloodstream and is carried to the liver, where it’s converted to vitamin D (25-hydroxyvitamin D), the main form circulating in the blood. The latter form is inactive and is measured in lab tests. This is transported to the kidneys, where it’s converted to the active form of vitamin D (1, 25 dihydroxyvitamin D). From there, vitamin D moves to the small intestine (where it stimulates calcium absorption) and to cells throughout the body.⁷³

The body needs ultraviolet B (UVB), 290 to 315 nanometers in wavelength, to make vitamin D from the 7-dehydrocholesterol in skin. These light rays are plentiful all year in equatorial regions between 30 degrees north and south latitude. Yet large populations spend daytime hours indoors or reside in less-sunny locations and must resort to other options for vitamin D production. Skin production depends on geographic latitude, time of year, time of day, cloud cover, skin color, age, and body weight, as well as use of sunscreen, how much skin is exposed, and the length of exposure to UVB light.^{17,62,66,75,80}

• Latitude and time of year. The strength of UVB radiation doesn’t vary exactly with latitude; however, people who live farther from the equator than the 30th parallel generally can’t get adequate vitamin D production from the sun’s rays during “vitamin D winter.” Serum vitamin D levels, an indicator of vitamin D status, drop significantly during vitamin D winter. As distances from the equator increase, so does the length of this winter. For example, Boston (latitude 42 degrees N) doesn’t receive enough UVB light for adequate vitamin D production from November through February. In Edmonton, Alberta, (latitude 52 degrees N), the vitamin D winter extends from October through March even if skies are clear. As many as 97 percent of Canadians (on any diet) who live north of the 49th parallel show inadequate vitamin D levels at some time during the winter or spring.^81–85

• Time of day. The UVB rays that stimulate vitamin D production are maximal between 10 a.m. and 3 p.m. The optimal time of day occurs when the person’s shadow is shorter than the person is tall.

• Materials that block UVB rays. UVB rays don’t penetrate glass (windows), plastic, sunscreen, or clothing. People who are seldom outdoors or whose skin is covered with sunscreen will have little or no vitamin D production. Women who cover most of their bodies with clothing for cultural or religious reasons will not make sufficient vitamin D, no matter what their latitude, and can develop the adult form of rickets known as osteomalacia.

• UVB sun lamp. For some people, using a tanning bed with an ultraviolet vitamin D lamp once or twice a week is a suitable solution, especially in winter. The use of tanning beds is controversial; certainly, care must be taken to avoid overexposure, and many experts advise that supplements are a safer option.⁶⁵

• Skin color. The minimal amount of sunlight needed is affected by skin color. As skin tone deepens, two to six times as much sun exposure is required, in terms of either length of time or area of skin exposed, with very dark skin needing two to six times as much exposure as pale skin for the same amount of vitamin D production. The skin self-regulates so the body doesn’t overproduce vitamin D.⁶²

• Area of skin exposure. The amount of skin exposed is a factor. A twenty-minute walk at lunch, with face and forearms exposed, can be equivalent to five minutes in a bikini at poolside in terms of vitamin D production.

• Age. Vitamin D production becomes less efficient with age. Light-skinned elderly people may need at least thirty minutes of sun exposure. However, a combination of dietary or supplement intake plus sunlight is likely to be most effective.

• Body weight. Being overweight or obese increases the likelihood of having a vitamin D deficiency.^86–88

Vitamin D from Sun Exposure

Even in sunny climates, sunlight’s effects can be hard to predict, with considerable variability from one individual to another. Recent studies in Hawaii, Arizona, Australia, and other sunny regions have shown inadequate vitamin D production among some residents, including a number who were regularly outdoors and without sunscreen.^86,89–93 In a study of 93 adults (average age 24) with medium- to light-colored skin, during winter months in Honolulu (latitude 21 degrees N), 51 percent had low vitamin D status, as shown by serum vitamin D of less than 30 ng/ml, despite twenty-eighty hours of exposure per week without sunscreen. In fact, 10 percent had serum vitamin D of less than 20 ng/ml.

The risks and benefits of sun exposure are a hot topic for debate. While overexposure to the sun may increase the risk of skin cancer, inadequate vitamin D levels increase the risk of cancers of the breast, ovary, prostate, and colon. Due to the many variables, guidelines for sun exposure tend to be somewhat vague or open to interpretation. Some experts advise getting sun exposure on the face, arms, legs, or back (without sunscreen) for five to thirty minutes between 10 a.m. and 2 or 3 p.m., three times a week. Others suggest daily exposure of the face and forearms for ten to thirty minutes. (After thirty minutes, sunscreen can be applied.)^{2,17,74,75,80,89,94,95} A realistic approach is to spend a moderate amount of time outdoors in the sun when possible—taking care to avoid overexposure—and combine this, when needed, with a vitamin D supplement or fortified food.^{2,17,75,80,95}

*Forms of vitamin B₁₂ include cyanocobalamin, methylcobalamin, and adenosylcobalamin.

From Sunlight

Depending on location, on clear days in seasons with warm sunshine, a person with light skin may make sufficient vitamin D with sun exposure on the face and lower arms (without sunscreen) between 10 a.m. and 3 p.m. for an average of fifteen minutes daily. Someone with dark skin may require thirty minutes. More time or skin exposure may be needed for the elderly or the overweight. To determine effectiveness, arrange to have serum vitamin D tested. Supplementary vitamin D may be needed.

From Foods or Supplements

During “vitamin D winter” or if serum vitamin D levels are low, supplements and/or fortified foods should be relied upon. Recommended intakes of vitamin D are expressed in micrograms (mcg) of vitamin D₃. The RDA for vitamin D from foods, fortified foods, or supplements for those from 1 to 70 years old is 15 mcg (600 IU) per day, and 20 mcg (800 IU) for those over 70. For optimal health, many experts suggest 25 to 50 mcg (1,000 to 2,000 IU) or more of vitamin D₂ or D₃ per day; the Tolerable Upper Intake Level (UL) is 100 mcg (4,000 IU) without medical supervision. Recommended intakes for vitamin D are a subject of lively debate.2,33,63–65,82,95,96,101,102

Testing

To check whether intake and/or the pattern of sun exposure is effective in meeting an individual’s vitamin D requirements, serum levels of vitamin D can be checked by a physician or use of a self-testing kit.^85,103 Currently, standards for healthy serum levels vary greatly; one expert says the serum levels of vitamin D should be at least 40 ng/ml (nanograms per milliliter in conventional units), or 100 nmol/L (nanomoles per liter in the International System of Units); however, most labs consider lower amounts “normal,” and the serum range used for that classification varies.

Vitamin D Supplements

Vitamin D is commonly taken alone as a tablet, an oral spray, in a multivitamin-mineral supplement, or in a supplement that contains vitamin D plus calcium (and perhaps magnesium).⁹⁵ Vitamin D₂ (ergocalciferol) is vegan and not of animal origin. Vitamin D₃ (cholecalciferol) has traditionally come from animal sources, such as fish, animal hides, or wool; however, vegan vitamin D₃ (from lichen) is now available. Search online for “vegan vitamin D”; specify a preference for D₂ or D₃.

Vegan Food Sources of Vitamin D

Few foods, plant or animal, contain vitamin D. The vegan members of this select group are mushrooms exposed to UVB rays, because mushrooms contain a compound that can be converted to vitamin D₂.⁹⁸ Convincing evidence was provided by a study in which 700 mcg (28,000 IU) of vitamin D was given to two groups of people deficient in vitamin D. One group received the vitamin D in the form of irradiated button mushrooms prepared as mushroom soup (100 g of mushrooms contained 491 mcg of vitamin D.) The other group was given a supplement with the same amount of vitamin D. Both treatments were effective in raising study participants’ serum vitamin D.⁹⁹

A growing number of vitamin D–fortified vegan foods are available, including nondairy milks, juices, and breakfast cereals. The availability of fortified foods varies from one country to another, depending on legislation, advances in science, and pressures from the food industry and the public.^17,45,92,95 Typical amounts of vitamin D in various fortified foods are shown in table 7.1; also check labels.⁹⁶ (Unfortified nondairy milks, margarine, and cereals provide no vitamin D). In margarines that contain vitamin D₃, the origin is typically from animals; contact the manufacturer for more specific information. Because the DV used on food labels is 10 mcg or 400 IU, a serving that provides 50 percent of the DV yields 5 mcg (200 IU) of vitamin D.

Vegan Intakes from Food and Supplements

Vegan dietary intakes of vitamin D have been far below recommended levels. Vegan intakes of vitamin D are lower than those of lactovegetarians and of nonvegetarians, unless vegans regularly use supplements or fortified foods. This situation of widespread deficiency isn’t limited to vegans; North American, European, and Australian surveys showed half, three-quarters, or even more of adults in the general population to have low intakes and low serum levels of vitamin D, depending on the optimal ranges chosen. Most intakes ranged from 2 to 10 percent of the RDA of 15 mcg (600 IU) for adults under 70; even the highest intakes were typically a little more than half this recommended level.^17,104–108 Food fortification policies are changing, which may help the situation.

Laboratory Tests for Vitamin D

Debate exists concerning what constitutes optimal levels of 25-hydroxyvitamin D in the body, and the IOM has recognized the need for further research. Currently, the IOM considers serum levels of 50 nmol/L or 20 ng/ml to be adequate. Many experts and laboratories suggest that for optimal health, blood levels of vitamin D should be higher, at about 75 to 100 nmol/L (30 to 40 ng/ml).

Tests reflect vitamin D provided by diet, supplements, and the body’s own synthesis.^{66,77,85,86,104,110} Tests can be arranged through a physician, or the Vitamin D Council provides a self-test kit (see Resources on page 449). Such tests can be repeated after three months to determine the effectiveness of a chosen plan in reaching desired blood levels of vitamin D.^77,103

Vitamin D Status of Vegans

When vegans consider vitamin D, a number of questions arise. Which standard of sufficiency for serum vitamin D should be used, that of the IOM or higher levels? Are vitamin D–fortified foods available and used? Are supplements used? What are an individual’s latitude, skin color, and extent of sun exposure? Studies show that some vegans appear to be doing well when it comes to vitamin D, and some are not.

In the United Kingdom (latitude 50 to 55 degrees N), a study that included 89 light-skinned Caucasians who had followed a vegan diet for about ten years showed their average plasma vitamin D to be 55.8 nmol/L (above the IOM recommendation but below the higher optimal levels of 75 or 100 nmol/L). The study’s 1,598 nonvegetarians also were somewhat low in vitamin D, though the vegan levels were lower still. The vitamin D levels of study participants dropped considerably in the winter and were insufficient. In the winter and spring, just 20 percent of the vegans had plasma vitamin D levels above 75 nmol/L. In summer and autumn, levels had risen; 45 percent of the vegans had plasma vitamin D levels above 75 nmol/L. Dietary sources available to British vegans at the time of the study included cereals, nondairy beverages, and margarines fortified with vitamin D. The vegans were slimmer (average BMI 22.3; see page 363) than the nonvegetarians (average BMI 25), and 51 percent used vitamin D supplements; those who used supplements had significantly higher plasma levels of vitamin D.104

A 2009 study of Seventh-day Adventist vegans and lactovegetarians living at latitudes between 30 and 50 degrees N across North America (roughly between the latitudes of New Orleans and Winnipeg) showed differences in serum vitamin D that varied with skin color. Half of the non-Hispanic whites but only one-quarter of the blacks had serum vitamin D levels in the optimal range (above 75 nmol/L or 30 ng/ml). In addition to average reported daily intakes from food and supplements of 8.8 mcg (350 IU) for those with light skin color and 9.4 mcg (375 IU) for those with dark skin color, study participants spent an average of about ninety minutes daily in the sun, with 9 percent of their skin exposed.⁸⁶ A more recent study of 100 American vegans showed none of those surveyed met recommended intakes of vitamin D through supplements.¹¹¹

A study based in St. Louis, Mo. (latitude 38 degrees N), showed 11 men and 7 women (with an average age of 54) who had been on raw vegan diets for an average of 3.6 years to have serum vitamin D levels of 42 ng/ml despite negligible intakes of vitamin D–fortified foods or supplements. In fact, the serum vitamin D levels of these vegans were more than double those of a control group of nonvegetarians of similar age and gender. These raw foods enthusiasts made an effort to spend time in the sun on a regular basis.¹⁰⁵

A study in the Netherlands (latitude between 51 and 54 degrees N) of infants in families on macrobiotic diets showed that half the infants had some signs of rickets when there was no use of vitamin D supplements or fortified foods. These babies also had low plasma levels of vitamin D, which dropped even lower in winter. Infants who regularly received a supplement and vitamin D-fortified beverages showed no signs of rickets.^17,112

A study in Ho Chi Minh City, Vietnam (latitude 10 degrees N), of 88 vegan Buddhist nuns older than 50 showed 27 percent of these women to have vitamin D levels below 20 ng/ml and 73 percent to have levels below 30 ng/ml. At the same time, these women experienced no more bone fractures and had slightly less bone loss than nonvegetarians.¹⁰⁶

Vitamin D at the Beginning of Life

Cases of rickets have been documented where nursing mothers lived at northern latitudes and didn’t ensure that infants had a source of vitamin D. To avoid this, the IOM recommends 15 mcg (600 IU) per day during pregnancy and lactation; the German-Austrian-Swiss reference values increase recommended intakes to 20 mcg (800 IU). The American Academy of Pediatrics prescribes a daily intake of 10 mcg (400 IU) of vitamin D for infants, starting from the first few days of life.^17,85,113 Care must be taken to avoid excess amounts; seek physician advice regarding suitable intakes.

Vitamin D for Older Adults

Problems with Excess Vitamin D

Consuming excess amounts of vitamin D can cause too much calcium absorption. Taken over weeks or months, excess vitamin D can lead to unwanted calcification of the heart, kidneys, and blood vessels in adults and can harden children’s bones at too early an age. Adult intakes of vitamin D above 100 mcg (4,000 IU) per day may be helpful in certain cases but aren’t recommended without medical supervision. The ULs are lower for younger children.⁶⁶ Too much sun exposure doesn’t produce toxic levels of vitamin D, though overexposure to UV light carries the potential risks of premature wrinkling, loss of skin elasticity, sunburn, and skin cancer.⁸²

The Antioxidant Vitamins: A, C, and E

Atmospheric oxygen is necessary to survival. Yet oxygen’s undesirable effects are evident when food oil becomes rancid, apple slices brown, or metal rusts. In human bodies, damaging oxidation reactions can lead to chain reactions that create rampaging molecules called free radicals. During the body’s normal operating processes, moderate quantities of free radicals form and, propitiously, are inactivated by antioxidants. However, if a person smokes, consumes foods cooked at high temperatures, drinks alcohol, or is exposed to environmental pollutants, solvents, or radiation, the quantities of free radicals multiply, along with the damage they can inflict on cell membranes, genetic material (DNA), and essential proteins.

PROTECTION FROM FREE RADICAL DAMAGE

Vegan diets are outstanding sources of the diverse substances that protect against oxidative damage: antioxidants. These include certain phytochemicals (page 260); the minerals selenium, manganese, copper, and zinc (chapter 6) as part of specific enzymes; vitamins C and E; and the carotenoids that the body coverts to vitamin A (page 233). Antioxidants act synergistically. For example, vitamin C regenerates and revitalizes used vitamin E (page 237) for further action, and vitamin E protects beta-carotene from oxidation. The B vitamin riboflavin also plays a protective role against free radical damage.^{4,116–122,137}

The body relies on a steady supply of antioxidants; if antioxidant levels are depleted, the body’s cells are vulnerable to damage, disease, and aging. As people get older, an antioxidant-rich diet assumes even greater importance. A lively field of research explores the role of antioxidants in reducing the risk of cancer, cardiovascular disease, cataracts, macular degeneration, diseases of the nervous system (such as Alzheimer’s and Parkinson’s), and premature aging of skin due to UV light.^{4,116–122,137}

THE BODY’S DETOXIFICATION SYSTEM

The body eliminates some water-soluble toxins through urine or bile. Other toxins are sent to the liver, where a two-step Phase I and Phase II process renders them harmless. The enzyme activities of these two phases must be well coordinated, because intermediary compounds that form during Phase I can be even more troublesome than the original toxin. If these intermediary compounds aren’t quickly processed during Phase II, cell injury or the development of cancer can ensue.

A simplified summary of detoxification in the liver is shown in figure 7.1, with the nutrients required for the different steps listed below. During Phase I, detoxification enzymes give the toxin an electrical charge that creates a type of chemical handle that can attach to another molecule during Phase II. After receiving the charge, toxins can become highly reactive and potentially dangerous molecules. However, antioxidants can prevent such changes. If all is well—as is usually the case—the reactive molecule quickly passes into Phase II and becomes attached to a large water-soluble molecule. This process creates a water-soluble complex that the body can quickly and safely dispose of via urine or bile.

Nutrients Required for Detoxification

Diet, Lifestyle, and Detoxification

Clearly, diet and lifestyle choices can have a major protective effect against the potential damage the body’s cells face from oxygen and toxins. Knowing the nutrient interactions involved will illustrate why a varied diet of plant foods goes far beyond supplements in maintaining good health. Here are some examples.

• Phase I. The body’s first line of defense is a superfamily of enzymes—the cytochrome P-450 enzyme family—that the body builds from protein (including the sulfur-containing amino acid cysteine) and iron. These enzymes carry electrons or charges from one location to another, work in the presence of oxygen, and create a highly reactive form of oxygen that can rearrange the structure of toxic molecules. For Phase I to work properly, certain B vitamins (listed above) must be present and assisted by protective phytochemicals, such as flavonoids.^120,125,130

• Protection from highly reactive intermediary compounds. When reactive intermediary compounds and free radicals start to accumulate, the body relies on nutrients (listed above) to block destructive chain reactions, including antioxidant vitamins, enzymes (built from protein plus the minerals copper, manganese, selenium, or zinc), and phytochemicals.

• Phase II. For Phase II, the body needs a supply of large water-soluble molecules that can be attached to toxins, creating a soluble complex that can be excreted. An example of such a molecule is glutathione, a chain of three amino acids that works with selenium (found in Brazil nuts). Other suitable molecules are the amino acid cysteine or the mineral sulfur. Chewing cabbage, broccoli florets, Brussels sprouts, or broccoli sprouts activates sulforaphane, a sulfur-containing molecule that protects against cancer. Several amino acids and the B vitamins choline and riboflavin also have roles in Phase II detoxification. The fiber in plant foods is another helpful component; it binds toxins, which can then be excreted in feces so they’re not reabsorbed.^{120,125,131–133}

This remarkable defense sequence protects DNA, cell membranes, and proteins. Fortunately, the supply of necessary nutrients and phytochemicals is present in fruits, vegetables, legumes, nuts, seeds, and whole grains.^{119–121,125,126,133–137}

The Road to Disease

VITAMIN A (BETA-CAROTENE AND CAROTENOIDS)

Vitamin A in Perspective

In developing countries where diets are severely limited and centered on breads or rice, many children and adults become blind due to insufficient vitamin A. This tragic situation occurs in one-quarter- to one-half-million children each year and could be prevented if they had access to carotenoid-rich vegetables or fruits or to vitamin A. Millions more children and adults suffer lesser forms of visual impairment due to vitamin A deficiency. Because their immune systems also are weakened, deficient children also die from measles, diarrhea, or malaria.

Two categories of vitamin A exist in the food supply: preformed vitamin A from animal products and provitamin A carotenoids from plant foods. The body can convert certain carotenoids (beta-carotene, alpha-carotene, and beta-cryptoxanthin) to the active form of vitamin A known as retinol. These carotenoids are pigments that contribute to the orange, red, and yellow colors in fresh produce. Carotenoids also are present in green vegetables, though their color is overlaid by the green of magnesium-rich chlorophyll. Other carotenoids in plant foods (lycopene, lutein, and zeaxanthin) aren’t converted to vitamin A, though they have significant health benefits.^{4,116,117,141}

Function

Vitamin A has an important role in cell differentiation, enabling cells to become specialized and carry out specific tasks, so its effects are diverse. In the eye, vitamin A and certain carotenoids (lutein and zeaxanthin) improve night vision, prevent cataracts, and keep the cornea moist and healthy. Vitamin A is required for immune system function and to build and preserve the integrity of skin and mucous membranes so they form protective barriers against bacteria and viruses. Many carotenoids, such as the beta-carotene in carrots and the lycopene in tomatoes, are excellent antioxidants that protect against cancer and heart disease. (Preformed vitamin A has no antioxidant activity.) Vitamin A also is needed for the growth of bones and teeth, for reproduction, and for the building and regulation of hormones.^{4,116,117,137,141}

Recommended Intake

Vegan Intakes and Status

Vegan diets, with their abundance of colorful fruits and vegetables, can easily provide more than enough vitamin A. Average intakes by vegans have been estimated at 1,500 mcg RAE for women and 1,200 mcg RAE for men.¹⁷ However, intakes depend on the specific fruits and vegetables included. A study of plasma carotenoid levels in German vegans whose diets consisted of 95 percent raw foods (mainly fruits) showed those levels met or exceeded recommended intakes in 82 percent of the study participants. Important factors linked with good vitamin A status were the inclusion of yellow, orange, red, and green vegetables and of fat, which increases carotenoid absorption.^142,149,154

The understanding of how carotenoids are converted to retinol has evolved in recent decades. Although vegan intakes of carotenoids have been reported in the past, some studies significantly overestimated the conversion of these carotenoids to mcg RAE. Any comparisons with new studies would have to factor in these discrepancies; vegan intakes over the years can’t easily be compared in numerical tables.¹⁷

Vegan Food Sources of Vitamin A (Carotenoids)

Carotenoids are present in deep-orange vegetables and fruits (apricots, cantaloupes, carrots and carrot juice, mangoes, nectarines, papayas, peppers, persimmons, pumpkins, squash, sweet potatoes, tomatoes and tomato products, and yams), as well as broccoli, turnips, leafy greens, seaweeds, plantains, and prunes. (For other sources, see table 7.3 on page 252.) The recommended intake for the day can be derived from ½ cup (125 ml) of carrot juice, baked sweet potato, or canned pumpkin. About 470 mcg RAE is provided by ½ cup (125 ml) of cooked spinach or baked butternut squash, or half a cantaloupe.^44,45,137

Special Issues

Cooking allows increased absorption of some carotenoids, such as lycopene, so there are advantages in eating some colorful vegetables cooked, along with plenty of raw vegetables and fruits. Including a little fat (from seeds, olives, avocado, or in a dressing) as part of a meal also increases absorption of carotenoids and other fat-soluble nutrients. Juicing (for example, making carrot juice) also boosts carotenoid absorption.^{4,116,117,143}

A perspective from Harvard Medical School concludes, “We now know that supernutritional levels of vitamins taken as supplements do not emulate the apparent benefits of diets high in foods that contain those vitamins, and we now know that taking vitamins in supernutritional doses can cause serious harm.”^145–147 People should avoid high intakes of vitamin A (more than 3,000 mcg retinol) from supplements without medical supervision, especially during pregnancy, when such high intakes can lead to birth defects.^{4,116,117,145–148} If vitamin A supplements are used, no more than the recommended intakes should be taken. Unusually high intakes of carrot juice or other rich food sources of carotenoids aren’t harmful but may temporarily turn the skin yellow.^4,116

VITAMIN C (ASCORBIC ACID)

Vitamin C in Perspective

During the Age of Exploration in the fifteenth and sixteenth centuries, advances in naval technology by both the Europeans and Chinese made lengthy voyages possible. Yet, during these journeys, sailors developed scurvy, a condition that caused their bodies to weaken, their joints to become painful, their teeth to loosen, and their gums to swell to the extent that eating became impossible. The sailors could barely move and, often, death followed. North American Native cultures had known about scurvy and used effective remedies, such as pine needle extracts or cranberries, to cure the disease in winter, when fresh food was scarce. Even though a few European sailors successfully adopted these remedies to facilitate recovery from scurvy, at the time, the medical profession dismissed the concept that a potent cure could have originated from “savages.”

After a great deal of detective work, the exploration of numerous wrong leads, and eventual open-mindedness to new possibilities, naval commanders and physicians determined that the unhealthy factor in a sailor’s life responsible for scurvy was the lack of fresh fruits and vegetables. The Chinese began to grow bean sprouts to supplement diets at sea, and the British Royal Navy adopted the practice of adding lemon or lime juice to sailors’ grog. (The term “Limeys” came to refer to British seamen and, eventually, to all their countrymen.) By the time of the American Civil War, awareness had spread that citrus fruits, potatoes, or onions could prevent scurvy and save lives. A sign posted in Chicago during that period read, “Don’t send your sweetheart a love-letter. Send him an onion.”

The component in these fruits and vegetables responsible for preventing scurvy—vitamin C—was identified in 1912; its relationship to scurvy was established in 1932; and it was synthesized in 1935. As with other vitamins, exploration of its roles in the body continues.^4,116,151

Function

Vitamin C is a highly effective antioxidant; even small amounts can protect cells from damage. Vitamin C supports immune function, boosting the body’s ability to resist infection under stressful conditions. It also helps the body to synthesize thyroid hormone and regenerate vitamin E. Vitamin C from fruits and vegetables supports heart health, protects against chronic disease, and assists greatly in the absorption of iron from plant foods.^{4,116,137,152}

Laboratory Tests for Vitamin C

A diagnosis of vitamin C deficiency is generally based on symptoms, not blood tests. A deficiency isn’t likely in people whose diet regularly includes fruits and vegetables.

Recommended Intake

The RDA for vitamin C is 75 mg for women and 90 mg for men. Smokers are advised to get an additional 35 mg per day (or better yet, to quit smoking).¹¹⁶

Vegan Intakes and Status

Studies show that average vegan intakes of vitamin C range from 138 to 584 mg daily. Generally, these amounts reflect intakes from food rather than supplements.^17,42

Vegan Food Sources of Vitamin C

Good sources of vitamin C include blackberries, broccoli, Brussels sprouts, cantaloupes, citrus fruits and juices, green peas, guavas, kiwifruit, leafy greens (chard, collard greens, kale, sorrel, and spinach), mangoes, papayas, pineapples, raspberries, red peppers, strawberries, sweet potatoes, tomatoes, and vegetables in the cabbage family. Overall, five servings of fruits and vegetables per day should provide about 200 mg of vitamin C. (For additional food sources and vitamin C amounts, see table 7.3 on page 252.) Organic foods have been shown to provide significantly more vitamin C than foods treated with pesticides.¹⁵⁶

Special Issues

Vitamin C is the superstar that increases the body’s ability to absorb iron from natural and fortified plant foods, keeps iron in a soluble form, and overcomes factors (such as phytates) that inhibit iron absorption (page 188).^116,157,158

VITAMIN E (ALPHA-TOCOPHEROL)

Recommended Intake

Vegan Intakes and Status

Before 1993, studies showed that vegan vitamin E intakes averaged 11 to 14 mg per day; since then, average intakes have increased to between 14 and 33 mg per day.^17,42 Among the general American population, 90 percent fail to meet recommended intakes, with average intakes of 6.9 to 8.3 mg of vitamin E per day, less than is needed for optimal health.^4,116,162 People on low-fat diets are at increased risk for suboptimal intakes.

Vegan Food Sources of Vitamin E

Vitamin E can be found in avocados, broccoli, carrots, kiwifruit, leafy green vegetables, nuts, peanuts, seeds, whole grains, and wheat germ. (For additional sources and amounts of vitamin E, see table 7.3 on page 252). Though leafy greens don’t appear to be significant sources of fat, about 10 percent of their calories come from plant oils. For those on raw or high-raw diets, big salads provide plenty of vitamin E; for example, 8 cups (2 L) of raw spinach provides a third of the RDA. When half an avocado and 3 tablespoons (45 ml) of sunflower seeds are added, the salad contains the entire recommended intake for the day. Steamed spinach cooks down to a small volume while retaining this vitamin; so 1 cup (250 ml) of cooked spinach provides close to 4 mg vitamin E. Unrefined vegetable oils—especially olive, canola, safflower, sunflower, soybean, and wheat germ oils—contain vitamin E, which protects the oils from rancidity (oxidation). However, when oils are refined, the heat in the refining process destroys vitamin E; in some oils, vitamin E is added as a preservative.^{4,44,45,160,161}

Special Issues

What’s Special about Vitamin K?

VITAMIN K (PHYLLOQUINONE AND MENAQUINONE)

Vitamin K in Perspective

A relative newcomer to the vitamin hall of fame, vitamin K’s function wasn’t recognized until 1974 and still is being unraveled. The “K” is derived from the German word koagulation, which is related to the vitamin’s role in forming blood clots, an essential defense at times of injury. Symptoms of deficiency include defective blood clotting and hemorrhaging.

The first form discovered, vitamin K₁, or phylloquinone, is widely available in plant foods, especially greens. In addition, bacteria typically present in the intestine synthesize additional forms of this vitamin, known collectively as vitamin K₂, or the menaquinones. (There’s also a synthetic form known as vitamin K₃, or menadione, which can be toxic.)^4,117

The body absorbs plenty of vitamin K₂ from the intestine. However, with the use of antibiotics, this important source may temporarily be eliminated until the bacteria population in the intestine reestablishes itself. Vitamin K₂ of bacterial origin is stored in the flesh and tissues of humans and of other animals. Because production of vitamin K in infants’ intestines doesn’t start for five to seven days, babies are given a vitamin K shot at birth; their intestines are soon colonized with bacteria from their mother’s milk or general exposure to the environment.^4,117,163

Function

Vitamin K builds the proteins that allow blood to clot and regulates blood calcium levels. It has a role in bone growth and the maintenance of bone mineral density. Data from the 1998 Nurses’ Health Study showed that those who ate lettuce at least once a day had a significantly lower risk of hip fracture than those who ate lettuce once a week or less. Since then, studies have shown that 200 mcg of vitamin K—the amount present in 1½ cups (375 ml) of raw spinach, ¼ cup (60 ml) of cooked spinach, or ½ cup (125 ml) of raw kale—will reduce the risk of bone fracture.^{4,117,163–165,169}

Recommended Intake

Because there is inadequate scientific evidence upon which to base an RDA for vitamin K, an AI was set at 120 mcg of vitamin K per day for men and 90 mcg per day for women.^4,117

A few health advocates have suggested that the body doesn’t adequately convert vitamin K₁ to K₂ and that people require dietary sources of vitamin K₂. While vitamin K₁ serves blood-clotting processes and activities such as bone building, vitamin K₂ is needed for protection against heart disease, arthritis, and cancer.

Although vitamin K₂ has a wider range of biological activity, individuals with a healthy, normal supply of gut bacteria are well equipped to convert K₁ to K₂. Scientific evidence supporting a requirement for a direct source of vitamin K₂ is lacking, and the IOM doesn’t suggest that any direct intake of vitamin K₂ is necessary. However, people who’ve had significant antibiotic therapy and are concerned about a temporary loss of ability to convert K₁ to K₂ can obtain a vegan source of vitamin K₂ by taking a supplement or consuming natto. Natto (fermented soybeans) contains 23 mcg of vitamin K₁ plus 941 to 998 mcg of vitamin K₂ per 100 grams (a little more than ½ cup).45,167,168

Vegan Intakes and Status

The average intake of the US population has been estimated at 300 to 500 mcg per day. Vegan intakes are expected to be higher still, and adequate. Although no studies have assessed the vitamin K intakes of vegans, high levels would be expected due to the generous amounts of leafy greens and other vegetables consumed by this population. One investigation reported adequate blood clotting rates among vegans, which suggests adequate vitamin K status.^17,166

Vegan Food Sources of Vitamin K

Leafy greens (collard greens, dandelion greens, kale, spinach, Swiss chard, and turnip greens) are the vitamin K superstars. Other excellent sources are asparagus, avocados, broccoli, Brussels sprouts, cabbage, cauliflower, grapes, green powdered tea, kiwifruit, lentils, pumpkins, peas, soybean oil, soy foods, and nori and other seaweeds. (For other sources, see table 7.3 on page 252.) Natto, a fermented bacteria-rich soy food originating from Japan, is a unique and concentrated plant source of vitamin K₂.

A day’s recommended intake of vitamin K can be provided by 2 tablespoons (30 ml) of parsley or kale or 2 cups (500 ml) of romaine lettuce. Adding a little oil-containing dressing or avocado, olives, or tahini to salads increases absorption of this fat-soluble vitamin.^44,45,117 To minimize losses, avoid overcooking foods.

Special Issues

Production of Energy from Food: The Roles of the B Vitamins

The body uses carbohydrates, fats, and proteins from foods to produce energy, with enzymes and the B vitamins playing roles in releasing this energy. In complex sequences that resemble a busy factory’s production lines, each of the nine B vitamins assists specific enzymes. In fact, these enzymes can’t function without their particular vitamin assistant or coenzyme. For energy production, the body requires dietary sources of thiamine (vitamin B₁), riboflavin (vitamin B₂), niacin (vitamin B₃), pantothenic acid (vitamin B₅), pyridoxine (vitamin B₆), and biotin (vitamin B₇). Folate (vitamin B₉) and cobalamin (vitamin B₁₂) are required to form new cells that deliver oxygen and nutrients so energy production can proceed; choline assists this duo.

When the existence of vitamins was first recognized, fat-soluble vitamin A and water-soluble vitamin B were identified. Later, scientists realized that “vitamin B” consisted of a number of distinct compounds essential to life. The B vitamins build fats needed in cell membranes, genetic material, nerve-impulse transmitters, and certain hormones. Because B vitamins are water-soluble, they can be lost when soaking or cooking water is discarded; in addition, the body excretes excess B vitamins in urine.

When individuals restrict calories (for example, during a period of weight loss), vitamin intakes can drop below recommended levels, affecting energy levels and well-being. At such times, a supplement can top up intakes from food.

THIAMIN (VITAMIN B₁)

Thiamin in Perspective

Thiamin is sometimes known as the carbohydrate burner. Symptoms of its lack were described in China as early as 2600 B.C. Thiamin deficiency came to be known as beriberi, meaning “weak, weak” or “I cannot, I cannot.” Beriberi became a widespread cause of death in the poor, in prison inmates, among Asian laborers, and in the Japanese army after polished white rice became widely used in Asia during the 1870s; unfortunately the outer thiamin-containing bran layer was removed during the polishing process. Although more fortunate individuals could round out their nutrient intakes with other foods, many Asians relied on white rice—and little else—as their dietary staple.

At a time when such diseases were thought to be linked to infection or to other causes, three physicians (one of them Japanese and two Dutch), discovered the relationship between beriberi and a thiamin-deficient diet. Their insights played key roles in the discovery of vitamins in general and led to the eventual enrichment of white rice. In enriched rice, several—but not all—of the B vitamins, along with iron, are added back.^170,171

Function and Laboratory Tests for Thiamin

Recommended Intake

Vegan Intakes and Status

Studies show the average thiamin intake of vegans meets and generally exceeds recommended intakes by 50 to 100 percent.¹⁷

Vegan Food Sources

Thiamin is present in many plant foods in moderate amounts; it’s easily destroyed by cooking, though some remains. Whole and enriched grains, products made from these grains, legumes, nuts, seeds, and nutritional yeast are excellent sources. Among the many other good sources are avocados, carrot juice, corn, dried fruit, peas, and squash (see table 7.3 on page 252).^44,45

RIBOFLAVIN (VITAMIN B₂)

Riboflavin in Perspective

Part of this vitamin’s name is related to the Latin word flavius, meaning “blond.” Evidence of this vitamin’s color and water-soluble nature is often provided by the bright yellow color of an individual’s urine after ingestion of a multivitamin supplement. If the body doesn’t need all the riboflavin provided by the supplement, the excess is excreted in urine.

Function, Deficiency Symptoms, and Laboratory Tests for Riboflavin

Riboflavin helps to convert carbohydrates, fats, and proteins to useable energy. It interacts with and supports the action of other B vitamins (niacin, B₆, and folate) and iron, provides protection against free radicals and toxins, and participates in detoxification. Deficiency symptoms include sores or cracks radiating from the corners of the mouth and inflammation and redness of the tongue. Lab tests to check riboflavin levels can be done on blood and urine.^2,4

Recommended Intake

The RDA is 1.1 mg of riboflavin per day for women, and 1.3 mg per day for men.^2,4

Vegan Intakes

Vegan Food Sources

A day’s recommended riboflavin intake is provided by ½ tablespoon of nutritional yeast.³⁰ Soy foods, fortified cereals, and yeast extract are excellent riboflavin sources. Moderately good sources include almonds, avocados, bananas, broccoli, buckwheat, cashews, enriched wheat flour, green beans, leafy greens, mushrooms, peas, quinoa, sea vegetables, seeds, soybeans, sweet potatoes, and whole grains. Sprouting has been shown to increase the riboflavin content of alfalfa seeds and mung beans. For other sources and riboflavin amounts, see table 7.3 (page 252).^44,45

The sun’s UV rays or fluorescent light can destroy riboflavin. For this reason, nutritional yeast, which is high in riboflavin, should be stored in an opaque container or a dark cupboard.^30,172–174

NIACIN (VITAMIN B₃)

Niacin in Perspective

A deficiency of niacin causes the disease pellagra; the disease causes a worsening progression of the four “Ds”: dermatitis, diarrhea, dementia, and death. Niacin deficiency was recognized among poorer people in the southern United States and southern Europe, who subsisted mainly on corn. In contrast, many Latin Americans have diets centered on corn but have long avoided this devastating disease.

The corn (maize) used for tortillas and other dishes is first treated with lime to make it more flavorful and easier to grind. Because soaking corn in an alkaline solution releases bound niacin—making this vitamin more available for absorption—this treatment has proved to be an effective defense against pellagra (and also adds calcium to the diet). In time, scientific research led to the recognition that pellagra is a dietary problem. It occurs when corn isn’t treated in this manner or when corn-based diets aren’t supplemented with protein-rich foods (such as peanuts and other legumes) that provide the amino acid tryptophan, which the body can convert to niacin.^2,4,171

Function and Laboratory Tests for Niacin

Niacin is part of two coenzymes that are active in the production of energy. This vitamin supports the health of the skin, digestive tract, and nervous system. Deficiency can be detected by urine tests.^2,4

Recommended Intake

Because 60 mg of tryptophan can be converted to 1 mg of niacin, both this amino acid and the vitamin itself contribute to overall niacin intake. They’re measured in milligrams of Niacin Equivalents (NE mg). The RDA is 16 NE mg for men and 14 NE mg for women. Food tables may list only the milligrams of niacin or may list the NE mg (see table 7.3 on page 252).²

Vegan Food Sources

Excellent niacin sources include good protein providers: edamame, soybeans, peanuts, peanut butter, peas, tempeh, tofu, and other legumes. Good sources are avocados, buckwheat, cherimoyas, dried fruit, durians, enriched and whole grains, fortified cereals, mushrooms, nutritional yeast, nuts, quinoa, sea vegetables, seeds, tahini, wild rice, and yeast extract spread. (For other sources and niacin amounts, see table 7.3 on page 252.)^44,45 Seeds, nuts, legumes, and green vegetables are also high in tryptophan.

Special Issues

When intakes of riboflavin, vitamin B₆, or iron are low (as in very low-calorie diets), conversion of tryptophan to niacin can be impaired because these nutrients are involved in the conversion.^2,4

In supplements, the maximum tolerable upper intake level (UL) recommended is 35 mg. Pharmacological preparations of niacin are used as cholesterol-lowering agents in treating heart disease; these higher intakes may lead to uncomfortable flushing of the face, chest, and arms.

PANTOTHENIC ACID (VITAMIN B₅)

Pantothenic Acid in Perspective

The name of this vitamin hails from the Greek word pantothen, meaning “from everywhere.” It’s a component of coenzyme A, found in all living cells, so it’s present in all whole plant foods and not likely to be lacking in vegan diets. However, in vegan diets that are particularly low in calories, intakes can be insufficient.^2,4,17,153

Function

Recommended Intake

Insufficient evidence was available to set an RDA for pantothenic acid, so an AI was set for adults at 5 mg per day.^2,4

Vegan Intakes

Research shows the average pantothenic acid intakes of vegans to meet or exceed recommended levels.^17,42

Vegan Food Sources

All whole plant foods contribute this vitamin, at least in small amounts. Avocados, nutritional yeast, sunflower seeds, and sweet potatoes are particularly high in pantothenic acid; broccoli, legumes, mushrooms, nuts, seeds, and whole grains are also good sources of this vitamin. (For other sources and pantothenic acid amounts, see table 7.3 on page 252.) The body also may absorb some pantothenic acid produced by intestinal bacteria.^4,17,44,45

PYRIDOXINE (VITAMIN B₆)

Pyridoxine in Perspective

Can this vitamin help individuals to dream more vividly and recall dreams more often? Does getting enough pyridoxine decrease PMS symptoms in women and reduce nausea and vomiting in early pregnancy? Do deficiencies increase vulnerability to attention deficit hyperactivity disorder (ADHD) or autism? Can a little extra B₆ help older adults to retain memory or can it fight depression? The reputed effects of vitamin B₆ are subject to rumors, some true and many with no scientific backing.

Research has shown pyridoxine does help to alleviate morning sickness. High homocysteine levels are linked with depression, and vitamin B₆ may help to alleviate depressive symptoms by reducing homocysteine. When B₆ improves these conditions, its success occurs in those who were deficient in the vitamin in the first place. A diet rich in vitamin B₆ might brighten dreams and improve memory as individuals age, but these effects are not certain.^59,176–179

Function

Recommended Intake

To age 50, the adult RDA is 1.3 mg; above 50, it increases to 1.5 mg for women and 1.7 mg for men.^2,4

Vegan Intakes

Studies show the average vegan intakes of pyridoxine to exceed recommended levels.^17,42

Vegan Food Sources

Pyridoxine is well distributed among plant foods, especially fruits. For example, three bananas provide a day’s supply. Vegan diets generally include plenty of foods rich in vitamin B₆; some of the richest sources are avocados, bananas, chia seeds, soybeans, and sunflower seeds. Others are bell peppers, bok choy, cabbage, carrots, cauliflower, fortified breakfast cereals, guavas, kale, mangoes, navy beans and other legumes, okra, peas, pistachios, potatoes, spinach, squash, sunflower seeds, walnuts, water chestnuts, whole grains, yams, and zucchini. (For other sources and pyridoxine amounts, see table 7.3 on page 252.)^44,45

Special Issues

Pyridoxine is easily destroyed by cooking and is lost in soaking water or when foods are frozen or canned. It’s removed during the refining of grains and isn’t added back to enriched grains.^2,4,17

BIOTIN (VITAMIN B₇)

Biotin in Perspective

This vitamin doesn’t hit the headlines because deficiencies are rare; people on plant-based diets seem to fare well. Intakes of biotin are generally sufficient unless calorie intakes are particularly low.^17,29 Biotin also may help to strengthen fingernails.⁴

Function

In combination with other B vitamins, biotin is involved in the metabolism of amino acids, fats, and carbohydrates.^2,4

Vegan Intakes

Little data is available regarding the actual biotin intakes of vegans or of any dietary group or on the biotin content of foods. One study of Seventh-day Adventists found plasma levels of biotin to be higher in vegans than in lacto-ovo vegetarians or in nonvegetarians.^17,180

Vegan Food Sources

Almonds, avocados, bananas, carrots, cauliflower, corn, hazelnuts, legumes, nutritional yeast, peanut butter, raspberries, oatmeal, onions, tomatoes, walnuts, and whole grains are among the many sources of biotin. (For other sources and biotin amounts, see table 7.3 on page 252.)^44,45

Special Issues

Biotin is manufactured by many bacteria throughout the small and large intestine and absorbed from there, adding to the dietary supply. After a course of antibiotics, intestinal synthesis may be decreased, until friendly intestinal flora flourish again.^2,4

FOLATE (VITAMIN B₉, FOLIC ACID)

Folate in Perspective

Both the name for this vitamin and the word foliage come from the same Latin root, folium, meaning “leaf.” It’s not surprising, then, to learn that leafy greens are important folate contributors. Folate is the natural form of vitamin B₉ in foods. Folic acid is the more stable form used in supplements and fortified foods; it can be converted in the liver to folate.^2–4 Folate was first isolated from spinach in 1945. Since then, numerous green vegetables have been added to the list of excellent sources, along with oranges and legumes. In recent years, grain products have been fortified with folic acid.

Function

The synthetic form of this vitamin, folic acid, is chemically different, and scientists currently are exploring the similarities and differences in its action. While natural folate in foods is protective against cancer, the folic acid in supplements and fortified foods may actually increase the risk of breast, prostate, colorectal, and other types of cancer and of asthma, especially when total intake is greater than 1,000 mcg daily.^4,181,182

Laboratory Tests for Folate

High blood levels of homocysteine may indicate either deficiencies of folate (less likely in vegans) or of vitamin B₁₂ (likely in vegans who don’t supplement). Lack of these two B vitamins also can cause the failure of red blood cells to mature properly. Such cells become big enough to divide, but they don’t divide properly and can’t transport oxygen, creating a condition known as macrocytic (big cell) anemia. As a result, sufferers become weak, tired, and short of breath.^2,4

Recommended Intake

The body’s absorption of folate, folic acid from fortified food, or a folic acid supplement taken without food differs, with the latter showing highest absorption. These differences are reflected in the units, dietary folate equivalents (DFE), used to define recommended intakes for this vitamin.

The RDA for adults is 400 mcg (0.4 mg) of folate from food, equivalent to 400 mcg DFE per day (1 mcg DFE equals 1 mcg of food folate). A folic acid supplement of 240 mcg taken with food provides 400 mcg DFE (1 mcg DFE equals 0.6 mcg of folic acid from fortified foods or dietary supplements consumed with food). A folic acid supplement of 200 mcg taken on an empty stomach provides 400 mcg of DFE (1 mcg DFE equals 0.5 of mcg folic acid from dietary supplements taken on an empty stomach).

To protect a fetus against neural tube defects—and because more than half of pregnancies are unplanned—women who might become pregnant are advised to consume 400 mcg DFE of folic acid daily, and then 600 mg daily throughout pregnancy.^{2,4 17,183} See page 290 for details on getting 600 mg of folate from orange juice, black beans, quinoa, and lettuce.

Individuals don’t need higher levels than these recommended intakes.¹⁸² In fact, it’s important to be aware not only of the minimum requirement for folate but also of the UL for folic acid in fortified foods and supplements.2,185 The UL for adults (including pregnant women) is 1,000 mcg DFE per day from folic acid supplements or fortified foods, exclusive of food folate. No UL has been established for folate (the UL is for folic acid only), because no adverse effects have been associated with high intakes of natural folate in beans, greens, oranges, and other plant foods. An individual can easily exceed the UL by ingesting a supplement with 600 mcg of folic acid, a serving of fortified breakfast cereal that has 100 percent of the DV for folic acid (another 400 mcg), plus several slices of white bread made with folate-fortified flour (about 40 mcg each) or a cup of cooked enriched rice or spaghetti (each providing about 170 mcg DFE). Check labels for amounts to monitor intakes.^2,4,186

Vegan Intakes and Status

Studies show that vegan folate intakes meet and exceed recommended intake levels.¹⁷ A British study showed the average daily folate intake of vegans to be 420 mcg; a North American study reported average vegan intakes at 723 mcg daily.^40,42

Vegan Food Sources

Greens, beans, and oranges are folate champions. Other excellent sources of folate are almonds, asparagus, avocados, beets, cashews, fortified breakfast cereals, kelp, kiwifruit, legumes (beans, peas, lentils, and soy foods), mung bean sprouts, nutritional yeast, orange juice, quinoa, sunflower seeds, spinach, sprouted lentils, and yeasts. Folic acid is added to enriched flours, breads, cereals, pastas, rice, and corn meal in many countries. (For additional sources and folate amounts, see table 7.3 on page 252.)^44,45

Special Issues

Sprouting has been shown to more than double the folate content of seeds, such as rye.¹⁸⁷ To absorb folate, the body requires adequate intakes of vitamin C and iron. Folate is easily destroyed by boiling, but steaming causes little or no loss of folate from broccoli or spinach.¹⁸⁸

The mandatory addition of folic acid to enriched grain products is credited with reducing the incidence of neural tube defects by 30 to 70 percent in the United States, Canada, Australia, Chile, and many African and Middle Eastern countries. However, this practice hasn’t been adopted throughout the United Kingdom and Europe.¹⁷⁶

The folate naturally present in plant foods is safe, beneficial, and essential; meanwhile, safety concerns exist regarding folic acid. Even though fortification has also decreased other birth defects, it has perhaps increased the risk of colon cancer in later life. Because there are limits to the body’s conversion of the supplement form to folate, with high intakes from supplements, unconverted folic acid can remain in the blood, and this may increase cancer risk. High folic acid intakes also may provoke seizures in people who take anticonvulsant medications. As previously mentioned, folic acid can mask a B₁₂ deficiency, particularly when large amounts of folic acid are taken.

CHOLINE

Choline in Perspective

Choline is present in all the cell membranes of plants and animals, including those of humans. It’s present in the brain as part of a fatty compound known as lecithin. Although choline was officially recognized by the IOM as an essential nutrient in 1998, expert opinion has been divided on whether it’s a true vitamin (a dietary essential) or whether the body can synthesize enough to supply its needs. People seem to need significantly different amounts from food, depending on their genetics and the composition of their diet. When intakes of folate, vitamin B₁₂, and the amino acid methionine are low, the body’s choline synthesis can be limited.^2,4

Function

Choline helps transport fats and other nutrients through cell membranes. It’s used in the construction of an important neurotransmitter, so it’s crucial for the transmission of nerve impulses and it aids memory and muscle control. Choline also assists in clearing fat and cholesterol from the liver.^2,4,184

Recommended Intake

An RDA hasn’t been set for choline due to insufficient data; however, the AI is set at 425 mg per day for women and 500 mg per day for men. It may be beneficial for women who want to become pregnant to take a choline supplement to prevent infant neural tube defects.^2,4 When The Vegan Plate (page 434) is used as a guide, a diet can easily meet the AIs.

Vegan Food Sources

Because it’s a part of all cells, choline is widely distributed in plant foods, though data regarding exact amounts is limited. Soy foods, quinoa, and broccoli are particularly rich sources.¹⁸⁴ Other good sources are amaranth, artichokes, Brussels sprouts, buckwheat, corn, mushrooms, oats, wheat germ, and whole wheat products. For additional sources and choline amounts, see table 7.2 (page 250) and check online for the US Department of Agriculture (USDA) Database for the Choline Content of Common Foods.¹⁹⁰

Special Issues

Lecithin (which contains choline) is a common food additive that acts as an emulsifier. Lecithin also is found in nonstick cooking sprays. Most lecithin is vegan and is derived from soy or sunflower oil; however, a certain amount can be derived from egg yolks. Check labels: the source may be included, for example, as “soy lecithin.” For more information on whether ingredients are vegan, consult the online “Vegetarian Journal’s Guide to Food Ingredients” by Jeanne Yacoubou (see Resources on page 449).¹⁹¹

Vitamins in Vegan Foods

Table 7.3 (page 252) lists the vitamin content of a variety of foods, using typical portions, such as 1 cup (250 ml) or one unit (for example, one apple). The USDA website lists additional nutrient data.⁴⁵

Although tables and databases list exact numbers, nature is much more variable. For example, plants grown in plenty of sunlight contain much more vitamin C than those grown with less light.¹⁹³

**The RDA for vitamin B6 (pyridoxine) is 1.3 mg for adults to age 50; above 50, it increases to 1.5 mg for women and 1.7 mg for men.

FOOD (AMOUNT)	VITAMIN D CONTENT
Fortified breakfast cereal, 1 oz (30 g)	2.6 mcg (105 IU)
Fortified margarine, 1 tsp (5 ml)	0.5 mcg (20 IU)
Fortified soy milk, almond milk, rice milk, or fruit juice, 1 c (250 ml)	2.5–3 mcg (100–120 IU)

FOOD (SERVING SIZE)	CHOLINE (MG)
Al for women	425
Al for men	500
LEGUMES
Beans, cooked or canned (kidney, navy, pinto, vegetarian baked beans), ½ c (125 ml)	30–43
Edamame, ½ c (125 ml)	33
Peanut butter, 2 T (30 ml)	21
Peas, green, cooked, ½ c (125 ml)	23
Soy milk, ½ c (125 ml)	30
Tofu, firm, ½ c (125 ml)	35
SEEDS AND NUTS
Almonds, cashews, ground flaxseeds, or pistachios, ¼ c (60 ml)	20–22
Hazelnuts/filberts, ¼ c (60 ml)	16
Pecans, ¼ c (60 ml)	10
Sunflower seeds, ¼ c (60 ml)	18
VEGETABLES (RAW UNLESS STATED)
Asparagus, cauliflower, or spinach, cooked, ½ c (125 ml)	23–24
Avocado, medium	28
Broccoli, cooked, ½ c (125 ml)	31
Cabbage, red, ½ c (125 ml)	6
Carrot, medium	5
Corn kernels, ½ c (125 ml)	18
Pepper, bell, green or red, medium	7
Potato, baked, medium	26
Salsa, ½ c (125 ml)	16
Sweet potato, baked, medium	15
Tomato sauce, ½ c (125 ml)	12
FRUITS
Banana, medium	12
Blueberries, ½ c (125 ml)	4
Dates, medjool, 4	10
Orange, medium	16
Orange juice, ½ c (125ml)	8
Peach, medium	9
Raspberries, blackberries, ½ c (125 ml)	6–7
GRAINS
Bread, whole wheat, slice, 1 oz (30 g)	5
Corn tortilla, small, 24 g	3
Quinoa, raw, ½ c (125 ml)	60
Rice, or oatmeal, cooked, ½ c (125 ml)	9
Spaghetti, cooked, ½ c (125 ml)	4
OTHER
Baking chocolate, unsweetened, 1 oz (30 g)	13
Chili powder, 1 T (15 ml)	5
Mustard, prepared, 1 T (15 ml)	3
Turmeric or curry powder, 1 T (15 ml)	3–4

Vitamins: Vital for Life

Dodging Deficiencies

VITAMIN B12*

Vitamin B12 in Perspective

Function

Deficiency Symptoms

Laboratory Tests for Vitamin B12

Recommended Intake

B12 Recycling and Avoiding Deficiency

Vegan Intakes from Food and Supplements

Vitamin B12 Status of Vegans

Unreliable B12 Sources

Reliable B12 Sources

Unproven but Possible B12 Sources

Vitamin B12 at the Beginning of Life

Vitamin B12 for Older Adults

VITAMIN D

Vitamin D in Perspective

Function

The Body’s Production of Vitamin D

Vitamin D from Sun Exposure

Vitamin D Supplements

Vegan Food Sources of Vitamin D

Vegan Intakes from Food and Supplements

Laboratory Tests for Vitamin D

Vitamin D Status of Vegans

Vitamin D at the Beginning of Life

Vitamin D for Older Adults

Problems with Excess Vitamin D

The Antioxidant Vitamins: A, C, and E

PROTECTION FROM FREE RADICAL DAMAGE

THE BODY’S DETOXIFICATION SYSTEM

Diet, Lifestyle, and Detoxification

VITAMIN A (BETA-CAROTENE AND CAROTENOIDS)

Vitamin A in Perspective

Function

Vegan Intakes and Status

Vegan Food Sources of Vitamin A (Carotenoids)

Special Issues

VITAMIN C (ASCORBIC ACID)

Vitamin C in Perspective

Laboratory Tests for Vitamin C

Recommended Intake

Vegan Intakes and Status

Vegan Food Sources of Vitamin C

Special Issues

Vitamin E in Perspective

Function

Recommended Intake

Vegan Intakes and Status

Vegan Food Sources of Vitamin E

What’s Special about Vitamin K?

VITAMIN K (PHYLLOQUINONE AND MENAQUINONE)

Vitamin K in Perspective

Function

Recommended Intake

Vegan Intakes and Status

Vegan Food Sources of Vitamin K

Special Issues

Production of Energy from Food: The Roles of the B Vitamins

THIAMIN (VITAMIN B1)

Thiamin in Perspective

Recommended Intake

Vegan Intakes and Status

Vegan Food Sources

RIBOFLAVIN (VITAMIN B2)

Riboflavin in Perspective

Function, Deficiency Symptoms, and Laboratory Tests for Riboflavin

Recommended Intake

Vegan Food Sources

NIACIN (VITAMIN B3)

Niacin in Perspective

Function and Laboratory Tests for Niacin

Recommended Intake

Vegan Intakes and Status

Vegan Food Sources

Special Issues

PANTOTHENIC ACID (VITAMIN B5)

Pantothenic Acid in Perspective

Recommended Intake

VITAMIN B₁₂ *

Vitamin B₁₂ in Perspective

Laboratory Tests for Vitamin B₁₂

B₁₂ Recycling and Avoiding Deficiency

Vitamin B₁₂ Status of Vegans

Unreliable B₁₂ Sources

Reliable B₁₂ Sources

Unproven but Possible B₁₂ Sources

Vitamin B₁₂ at the Beginning of Life

Vitamin B₁₂ for Older Adults

THIAMIN (VITAMIN B₁)

RIBOFLAVIN (VITAMIN B₂)

NIACIN (VITAMIN B₃)

PANTOTHENIC ACID (VITAMIN B₅)

PYRIDOXINE (VITAMIN B₆)

BIOTIN (VITAMIN B₇)

FOLATE (VITAMIN B₉, FOLIC ACID)