Chapter 14

Appreciating Special Needs in Pregnant Women and the Elderly

In This Chapter

Understanding the link between vitamin D and age

Seeing the benefits of vitamin D for older people

Getting sufficient vitamin D for mother, fetus, and newborn

I define “elderly” as anyone older than I. Actually, the current definition of elderly is probably 70 and older. This group of people needs more vitamin D. Unfortunately, for several reasons, they are more likely to consume less vitamin D and have lower 25-hydroxyvitamin D levels.

There are other groups that may also need more vitamin D. A pregnant woman is meeting the needs of two people — herself and her baby. How will that affect her vitamin D requirements or the health of her baby?

This chapter discusses the special needs of these two groups and explains the role of vitamin D in fulfilling those needs.

Understanding Why Older Folks Need More Vitamin D

The U.S. government currently recommends that those 70 and older take 800 IU of vitamin D a day, which is 25 percent more than other adults.

As many as 70 percent of people older than age 70 have inadequate levels of 25-hydroxyvitamin D. They also tend to have low levels all year long; they don’t get the summer boost. Even among the 58 percent of men who reported taking supplements of vitamin D, levels were less than satisfactory. The elderly are deficient in vitamin D for these reasons:

Decreased ability to make vitamin D due to changes in their skin

Tendency to avoid the sun or live in places where they get less access to sun (such as nursing homes)

Diminished exposure to foods that contain vitamin D

Decreased memory, leading to failure to take vitamin D supplements

Some evidence that intestinal absorption of vitamin D is reduced in the elderly

Because the elderly are more likely to stay indoors and not get sunlight exposure, they may need to get their vitamin D from supplements.

There’s also good evidence that shows the elderly have a reduced ability to respond to calcitriol (active vitamin D). This problem has been shown to contribute to low intestinal calcium absorption in the elderly, but researchers haven’t yet learned whether this is also true for other aspects of vitamin D and health.

Although testing the blood level of 25-hydroxyvitamin D is the only way to know for certain if someone is getting enough vitamin D, the 800 IU per day recommended by the Institute of Medicine should be sufficient for most elderly (unless the person has a problem with intestinal absorption of vitamin D, due to a previous surgery, celiac disease, and so on). Correcting low vitamin D status is a simple and effective way to protect the health of your elderly friends and family members.

Seeing the Benefits of Vitamin D as You Age

With each passing day, more reports emerge suggesting that the elderly may benefit greatly from vitamin D. Researchers are discovering diseases that were previously never thought to be connected to vitamin D but which may benefit from increased vitamin D intake. Scientists are upping their recommendations on the amount of vitamin D that the elderly should be taking. I’m certain that more benefits will be discovered with time, but this is an introduction to the most prominent.

Avoiding falls and fractures

Osteoporosis is the brittle bone disease that affects a large number of elderly women (see Chapter 4 for more details). But people forget that weak bones are only half the story — elderly people often break a bone only after they fall. Improving balance and muscle strength is very important for preventing falls and fractures.

Unfortunately, falls and fractures are common among the elderly, and both can lead to death. Falls are the leading cause of death from injury among people age 65 and older. Forty percent of people over age 65 fall at least once a year; the elderly in nursing homes fall at least three times per year. It’s rare that a fall kills a person immediately. More likely it ruins their quality of life or puts them at risk of another illness. For example, an older person with a hip fracture will end up bed-ridden, and this increases the chance they could get pneumonia, blood clots, and congestive heart failure.

Three percent of all falls result in fractures, including fractures of the pelvis, the hip, the femur (upper leg), the vertebrae, the humerus (upper arm), the hand, the forearm, the lower leg, and the ankle.

In 2010, the elderly suffered about 290,000 hip fractures in the United States. Twenty percent of victims die within one year of the fracture, often as a result of blood clots that form in the immobilized person and travel to the lungs, cutting off the blood supply. Fifty percent never return home, but go to a nursing home for the rest of their life. Of the remainder, most do not return to their previous level of functioning and may require a cane or walker to get around. Fortunately, the rate of hip fractures in the United States is declining, but it’s still a serious problem.

Focusing on falls

Falls are a consequence of any or all of the following:

Environmental hazards

Impaired mobility

Impaired vision

Loss of balance

Side effects of medication

Weakness

It makes sense that vitamin D may lead to improved muscle strength and balance. Muscle expresses the vitamin D receptor and responds to calcitriol, and in extreme vitamin D deficiency, the muscles are weak, aching, and inflamed. But what about for the average, otherwise healthy, elderly person? Research studies hint that supplementing with vitamin D may lead to a reduced risk of falling. Additional analyses suggest that this results from improved strength and muscle function, as well as improved balance.

The first study to show there might be a benefit to muscle strength was from a large population study called the National Health and Nutrition Evaluation Survey, or NHANES. Researchers looked at 4,100 people who were 60 or older. They asked them to do two simple tests of leg muscle strength and balance and then related those results to serum 25-hydroxyvitamin D levels. They found that when people were vitamin D deficient (serum levels less than 15 ng/ml [37.5 nmol/L]) they didn’t perform well on these tests. Interestingly, the best performance on the test came when serum 25-hydroxyvitamin D levels were more than 30 ng/ml (75 nmol/L).

A recent study followed 625 people in an assisted living facility who had a mean age of 83 and whose starting levels of vitamin D were insufficient. They were given either 1,000 IU of vitamin D or a placebo every day for two years. Those who took the vitamin D had a significant reduction in falls; the more compliant they were in taking the vitamin D, thereby giving them higher blood levels of 25-hydroxyvitamin D, the less likely they were to fall.

Some people point to a recent review and meta analysis as firm proof for a relationship between vitamin D and falls. (A meta analysis combines a number of acceptable studies that may be too small on their own into one that has more power to see differences due to a treatment.) This analysis seemed to show that people benefit from high doses of vitamin D and get protection from falls. However, the Institute of Medicine expert committee re-ran this analysis and found that it wasn’t done correctly. I mention this because critics of the expert committee often use this study as proof that higher levels of vitamin D intake are needed to prevent falls. Unfortunately, the Institute of Medicine re-analysis doesn’t support that conclusion.

Moreover, there’s clear evidence that taking too much vitamin D at once may lead to more falls. A study was conducted on 2,256 community-dwelling women aged 70 or older. They were give a huge dose of vitamin D (500,000 IU) or placebo once per year. Rather alarmingly, the researchers found that use of vitamin D in this way significantly increased the risk of falls and fractures within the first several months after the annual dose. This suggests that taking too much vitamin D will increase falls instead of reducing them, and that infrequent large doses like those favored by the medical community may not be the way to go. Instead a lower, daily dose of vitamin D may be best.

Looking at fracture factors

Osteoporotic fractures of the spine happen in the home in response to lifting or pushing heavy loads (lifting a grandchild or heavy bags of groceries, pushing a mattress, shoveling, and so on). In contrast, the rest of the osteoporotic fractures result from falls in the person’s own home, usually during normal activity. This includes fractures of the hip, wrist, ankle, ribs, and so on. Women are three times more likely than men to have a fracture that results in hospitalization. Because of a fear of fractures, seniors tend to restrict their activity, which unfortunately worsens their risks by causing more muscle weakness, poor balance, reduced fitness, and thus more falls.

Several studies in the United States and the United Kingdom have examined small samples of bone from the fractured hips of the elderly and found that between one-third to one-half of hips had evidence of osteomalacia, a condition of poor bone mineralization that can be caused by poor vitamin D status. Consequently, many of what we think are osteoporotic hip fractures might actually be due to vitamin D deficiency-induced osteomalacia.

In Chapter 4, I explain how and why fractures develop. Fractures are a consequence of decreased bone. Thinner bone is more fragile and breaks more easily. We all start out with plenty of bone, but we lose bone as we age. The same level of trauma that we can ignore when we’re young may be responsible for fractures when we get older. For example, young football players can safely ignore most trauma to their legs, but the same trauma may cause a fracture in an elderly person.

A key to avoiding fractures is to build up bone and maintain it throughout life. These actions help safeguard bone health:

Taking vitamin D and calcium in sufficient quantities to strengthen bone throughout your life

Doing weight-bearing exercises to strengthen bone

Staying active to maintain balance and muscle strength

So what’s the evidence that taking more vitamin D reduces the chance that someone will suffer a fracture?

A study in England showed that elderly people with low vitamin D status who were given a large amount of vitamin D3 (100,000 IU) every four months for five years had fewer fractures than people who got a placebo. The vitamin D-treated group increased their serum 25-hydroxyvitamin D levels to more than 30 ng/ml (75 nmol/L). This group was mostly men. A later study repeated this approach in a group that was mostly elderly women, but they used vitamin D2 instead of vitamin D3 and they followed their volunteers for only three years instead of five. However, in that study they didn’t see a benefit. We don’t know why the vitamin D worked in one study but not another. Regardless, this is a medical approach where a person would have to go to the doctor’s office every four months to make sure their vitamin D levels stayed up.

Researchers working at University Hospital in Zurich, Switzerland, have shown that higher doses of both vitamin D and 25-hydroxyvitamin D increase antifracture activity significantly in elderly women. The positive effect was even independent of additional calcium supplementation.

An interesting study from Romania followed 45 nursing home residents who were given 5,000 IU of vitamin D3 by eating a piece of fortified bread daily. They were also given 320 mg of calcium. Their 25-hydroxyvitamin D levels started at 11 ng/ml (27.5 nmol/L) and rose to 50 ng/ml (125 nmol/L) after one year. No toxicity resulted from this treatment. Calcium levels remained normal. During the year, bone mineral density increased significantly, indicating harder bones that were less likely to fracture. However, the study was too small to prove that use of vitamin D in this way prevented fractures.

Right now the most important thing for the elderly to do is to make sure they aren’t vitamin D deficient. With very low vitamin D levels, our bodies just don’t use calcium efficiently.

Slowing muscle loss

Loss of muscle mass, called sarcopenia, is a well-known consequence of aging. It’s the muscle equivalent of osteoporosis, or a loss of bone. The general theory of the development of sarcopenia is as follows:

With increasing age, loss of appetite occurs.

The decline in food intake exceeds the decline in physical activity, resulting in weight loss.

With weight loss, muscle mass is lost.

The loss of muscle mass leads to adverse health outcomes, like falls and reduced physical function, and a compromised immune system.

Muscle quality and function decline as well.

Studies among nursing home residents show that the prevalence of sarcopenia is almost universal. The greater the degree of sarcopenia, the greater the individual must depend on other people. Sarcopenia also increases as the individual suffers from other medical conditions.

Without question, vitamin D is needed to keep blood calcium levels normal, and this is essential for the contraction of muscles. So the more vitamin D you have, the more likely you are to have strong muscles. Many epidemiological studies have shown that vitamin D insufficiency is associated with poor muscle performance. Muscle tissue has also been found to have receptors for vitamin D. When calcitriol goes to muscle, it activates the vitamin D receptor, which results in protein synthesis and the creation of new muscle tissue. We just don’t know if there’s value in raising serum 25-hydroxyvitamin D levels to more than 20 ng/ml (50 nmol/L).

Preventing pelvic floor disorders in women

Urinary and fecal incontinence, as well as pelvic organ prolapse (in which organs such as the uterus and the bladder bulge into the vagina), are a consequence of decreased muscle strength in the supporting muscles of the pelvis in women.

One in four women suffers from at least one of the three types of pelvic floor disorders. As women age, and with each completed pregnancy, their risk of pelvic floor problems increases.

A few things link vitamin D to this problem. Some women with pelvic floor disorders also have osteoporosis, which is aggravated in part by inadequate levels of vitamin D. Lack of vitamin D may cause pelvic flood disorders because of diminished functioning of the pelvic muscles that normally support the pelvic organs. This wouldn’t be a specific role for vitamin D in pelvic muscles, but just a consequence of when muscle strength was limited.

Recently, researchers checked vitamin D levels in 1,881 women from the NHANES study who weren’t pregnant. Twenty-three percent of the women with inadequate vitamin D had one or more pelvic floor disorders. The prevalence of pelvic floor disorders was lower in women with higher blood levels of vitamin D. In women older than 50, the risk of pelvic floor disorders was 45 percent less if the women had serum 25-hydroxyvitmain D levels of 32 ng/ml (80 nmol/L).

Improving memory and thinking

In Chapter 9, I explain some of the severe problems of diminished memory and thinking, such as Alzheimer’s disease. What about mild loss of memory and thinking ability? Is there an association with this condition and vitamin D deficiency? Will you remember where you put the keys or why you went upstairs if you take a dose of vitamin D?

Researchers have proposed roles for calcitriol in many parts of the brain, but especially the cerebellum and hippocampus, which are basically responsible for planning, developing, and creating new memories and impressions on the mind.

Several studies indicate an association between lower 25-hydroxyvitamin D levels and diminished memory and thinking ability. For example, 3,369 men age 40 to 79 had their cognitive (memory and thinking) function assessed and their 25-hydroxyvitamin D measured. High levels of 25-hydroxyvitamin D were associated with higher scores on tests of cognitive function.

In another study, 752 elderly women were divided into two groups, according to their vitamin D level. One group had 25-hydroxyvitamin D levels above 10 ng/ml (25 nmol/L) (deficient), and one group had 25-hydroxyvitamin D levels below 10 ng/ml (25 nmol/L). The group with the lower level had cognitive scores that were significantly lower than the group with the higher level. This is another good reason to avoid vitamin D deficiency.

Although these studies confirm a link between the loss of memory and thinking functions and very low vitamin D status, other studies don’t confirm the relationship, especially when they look at vitamin D levels that are closer to normal. In addition, we don’t know whether giving more vitamin D will restore cognitive function in these patients after they’ve lost it. We also don’t know how high the level of vitamin D must be for optimum mental performance.

As you’re reading this, studies are taking place to determine if there is an improvement in cognitive function when vitamin D raises the 25-hydroxyvitamin D to more than 30 ng/ml (75 nmol/L).

If you’re among the elderly with 70 years behind you, make sure you get your daily intake of vitamin D. In addition, keep doing activities that challenge your mind. Those mental challenges seem to help.

Getting Sufficient Vitamin D for Mother and Newborn

When a woman is pregnant, she’s really eating for two. The growing fetus gets its nutrition entirely from the mother. If she doesn’t have what it needs, she can’t give it to the fetus. The fetal needs occur when the key structures of the fetus are being formed. We know that extreme deficiencies of important nutrients can cause deformities in the fetus; for example, folate deficiency causes neural tube defects.

In Chapter 9, I discuss normal brain development for the fetus and newborn. Here I provide a few more details about vitamin D’s effect on a fetus and then emphasize the needs of the mother.

Both pregnant adult women and nursing mothers need 600 IU of vitamin D every day, and teen mothers need 800 IU per day.

Understanding how vitamin D influences a baby’s development

Scientists have long known that vitamin D’s greatest impact is on bone health. Keeping bones strong and healthy is especially important as infants and young children grow, but the foundation is established in the womb.

Evidence from animal models indicates that the fetal skeleton forms normally without vitamin D, the enzyme that makes calcitriol (active vitamin D) or the vitamin D receptor, and studies of babies born to severely vitamin D deficient mothers show that the skeletons of those babies were normal, too, in both lengths/shapes of the bones and the calcium content of them. A problem with calcium, bones, or vitamin D doesn’t occur until months after birth (and often into the second year). After birth, the baby becomes dependent on calcitriol to absorb calcium from the intestines, and if that baby is vitamin D-deficient, not enough calcium gets into the skeleton and the soft bones of rickets can develop (see Chapter 4 for more on rickets).

So the evidence suggests that the fetus doesn’t necessarily need vitamin D to have a normal skeleton by the time of birth, but that the newborn will get into trouble after birth if it’s vitamin D deficient. Getting enough vitamin D during pregnancy ensures that the baby is born with a good 25-hydroxyvitamin D level and is, therefore, well prepared to absorb needed calcium from breast milk or baby formula.

Whether vitamin D is important for other aspects of fetal development prior to birth is uncertain. Animals lacking vitamin D or the vitamin D receptor have babies that are apparently normal at birth. It’s not possible to determine whether subtle defects in development or immune function have occurred by birth. Other than for the skeleton, there have been no studies in humans comparing development at birth between severely vitamin D deficient versus normal babies.

Preparing for a pregnancy with vitamin D

Certain groups of women are at higher risk of having low levels of vitamin D:

Women with darker skin

Women who live in northern regions during the winter

Women who cover their skin for religious or cultural purposes

Even before a woman becomes pregnant, she must have a satisfactory level of vitamin D for a number of reasons:

In experimental animals, the onset of the reproductive cycle is delayed in females who are deficient in vitamin D because calcium metabolism is upset when vitamin D isn’t present. This is why fertility is lower when vitamin D is deficient.

Starting with healthy levels of vitamin D ensures that the fetus gets enough from the mother. Blood levels of 25-hydroxyvitamin D in the fetus are 75 to 100 percent of the mother’s value because that form of vitamin D passes readily across the placenta. But although the baby is taking 25-hydroxyvitamin D from the mother, the amount is quite small (given the size of the baby), and several studies have shown that the mother’s own blood level does not decrease significantly during pregnancy.

The following adverse health outcomes for the baby have been linked to severely low levels of vitamin D in the mother:

• Low birth weight

• Low blood calcium in the days after birth (but not at birth)

• Poor growth after birth

• Bone fragility developing after birth (but not at birth)

• Increased incidence of immune diseases like type 1 diabetes later in childhood

These adverse effects are probably due in part to the mother’s health before and during pregnancy: If her vitamin D intake is poor, her overall nutrition and socioeconomic status are likely not good, and she’s less likely to have access to prenatal care. All of these things contribute to the baby being born earlier, weighing less, and having a lower 25-hydroxyvitamin D level. If the mother has severe vitamin D deficiency with osteomalacia and inflamed or weakened muscles (myopathy), then those weak muscles mean she will have trouble with labor and delivery.

And the conditions that caused the mother to have low vitamin D status before and during pregnancy are likely to continue after the baby is born, such that the child shares low vitamin D status and is at higher risk for developing medical conditions that might be caused by low vitamin D.

Getting enough vitamin D for two during pregnancy

If a woman has enough vitamin D before pregnancy and she gets pregnant, she needs to continue to take sufficient vitamin D for her needs and those of the fetus. However, in some groups, like African Americans, 70 percent of women who are pregnant have low serum vitamin D levels.

Women who fail to get enough vitamin D during their pregnancy may develop complications. Some studies show that there are associations between serum vitamin D levels and diseases of pregnancy like preeclampsia (high blood pressure and protein in the urine) and gestational diabetes (diabetes that begins during the stresses of pregnancy).

Women with 25-hydroxyvitamin D less than 15 ng/ml (37.5 nmol/L) have Caesarean sections four times as often as women with a higher level. It just isn’t clear if low vitamin D levels are the cause or general markers of poor health.

If you’re pregnant, you can get your vitamin D from a combination of sun and supplements. Avoid fish with mercury (see Chapter 12), but enjoy other foods that contain some vitamin D like milk or fortified breakfast cereal.

Exposure to low levels of vitamin D in the womb may predispose the fetus to develop certain conditions later in childhood, such as lower bone mass/density, type 1 diabetes, and other autoimmune conditions. It’s clearly important for a pregnant woman to maintain 25-hydroxyvitamin D levels over 20 ng/ml (50 nmol/L) so the baby is born with a similar level, but we need clinical trials in which higher doses of vitamin D during pregnancy are tested to see if any outcomes for the mother or baby are improved.

For thousands of years, our maternal ancestors got up to 10,000 IU daily for themselves and their fetuses and newborns simply by running around in the sun before the advent of sunscreen. They generally didn’t live long enough to develop wrinkles, and they didn’t worry about it (don’t ask me how I know).

Paying special attention to preeclampsia

Preeclampsia is of special interest because the incidence is rising over time. Preeclampsia is a severe complication of pregnancy, with these major signs and symptoms:

Sudden onset of high blood pressure during pregnancy

More than 300 grams of protein present in a 24-hour urine collection

Swelling of the hands, feet, or face

Pain in the abdomen, which is related to liver involvement

Preeclampsia is more common in obese women (see Chapter 9) and women with twins. It’s also more common in pregnant women who already have high blood pressure (see Chapter 7 for more on how vitamin D affects the cardiovascular system); diabetes (see Chapter 8) or an autoimmune disease, like lupus erythematosis (see Chapter 5); or kidney disease (see Chapter 9). Because vitamin D may contribute to all of these conditions, low vitamin D status may indirectly lead to higher risk of preeclampsia. African Americans who have significantly lower levels of vitamin D than do whites face a higher risk of preeclampsia. Of course an alternative explanation for these relationships with low vitamin D is that being overweight or obese causes all of these problems (preeclampsia, diabetes, and so on) and that it also leads to low 25-hydroxyvitamin D levels. If this were true, vitamin D may not play any role in causing these diseases. For now, the role vitamin D plays in the prevention of preeclampsia is unclear.

Treatment for preeclampsia is to deliver the baby, but preeclampsia can occur up to six weeks after the baby is born.

Considering the scientific evidence

Several studies indicate that vitamin D levels are significantly lower in women with preeclampsia. A study in Norway compared the occurrence of preeclampsia between women who took vitamin D supplements and those who didn’t. The women who took more than 200 IU per day of vitamin D had significantly fewer episodes of preeclampsia than those who avoided vitamin D supplements.

Avoiding this severe complication of pregnancy should be enough to convince any woman to take her 600 IU of vitamin D each day.

A study was done of Arab women, who tend to have low levels of vitamin D because of their extensive body covering whenever they’re outside the home. They were given 400, 2,000, or 4,000 IU of vitamin D daily beginning at 12 weeks in their pregnancy. They were followed with measurements of 25-hydroxyvitamin D, calcium, and parathyroid hormone, with the following results:

The average 25-hydroxyvitamin D was 7 ng/ml (17.5 nmol/L) before vitamin D — they were severely deficient — and rose to 28 ng/ml (70 nmol/L) at delivery.

Parathyroid hormone levels fell throughout the pregnancy but rose by the time of delivery.

Calcium levels rose throughout the pregnancy but never into the abnormal range.

Giving vitamin D at any of the levels was associated with improved vitamin D status but no toxicity.

There are other small studies like this one that have given various doses of vitamin D to women beginning in the first trimester or later. All have shown that the maternal and fetal 25-hydroxyvitamin D levels are higher in response to the use of a supplement. Some of these studies also indicate that there is no effect on fetal blood calcium or the fetal skeleton, consistent with what was mentioned earlier. A few studies have suggested that hypocalcemia (low blood calcium) beginning 48 hours or later after birth is less likely in babies born of vitamin D-supplemented mothers. None of the studies published so far has shown any effect of vitamin D supplementation on preeclampsia/eclampsia or other obstetrical outcomes.

Making sure your newborn gets the right amount of vitamin D

Although a tiny newborn obviously doesn’t need as much vitamin D as required by the pregnant or nursing mother, she continues to need sufficient vitamin D. Bones, organs, and critical structures in the brain are developing, and sufficient vitamin D appears to be essential to all that growth and development. There’s no doubt that children born with a vitamin D deficiency won’t reach their full height or bone density because of the important role vitamin D plays in calcium metabolism — these conditions will affect them throughout their lives.

Breast milk contains almost no vitamin D. It’s possible that babies are supposed to get vitamin D through sunlight exposure, and getting it through milk at the same time could lead to vitamin D toxicity. But in our modern era of protecting the babies from sun, they’re left with no natural source of vitamin D.

Although we don’t know the exact vitamin D levels that are protective, association studies suggest that adequate vitamin D status may also provide

Resistance to asthma and upper-respiratory infections

Resistance to autoimmune diseases like type 1 diabetes

Possible avoidance of autism

Possible resistance to multiple sclerosis

Possible avoidance of cavities

Possible avoidance of newborn infant heart failure

Possible avoidance of schizophrenia later in life

These relationships still need to be established with careful clinical trials.

The American Academy of Pediatrics understood this need for vitamin D, and in 2008 the academy recommended that children get 400 IU of vitamin D each day. This beat the Institute of Medicine’s committee by two years.

Even after the American Academy of Pediatrics published its new recommendations, however, few children were getting the old level of vitamin D (200 IU per day), much less the new level (400 IU per day). When children were evaluated in 2010 to see if they met the 2008 new recommendations, only half of the infants met the old recommendations and fewer than a quarter met the new recommendations. I think the medical community needs to do a better job helping infants and parents meet these new requirements.

It’s especially important that breast-fed babies are looked after because the breast milk contains almost no vitamin D, and yet many women think that breast milk contains all the nutrition that babies need. For formula-fed babies it’s less of a concern because formulas are supplemented with vitamin D in amounts that should give about 400 IU per day.

Children should be treated on an individual basis. The baseline 25-hydroxyvitamin D can be measured if there is any doubt, and enough vitamin D should be given to bring the level to at least 20 ng/ml (50 nmol/L). When kids start walking and playing outside, this isn’t a hard standard to meet. The 400 IU recommended by the Institute of Medicine is more than enough to achieve this target level; in fact, in toddlers the 400 IU dose can lead to blood levels over 30 ng/ml (75 nmol/L).

Dermatologists worry that the skin of infants and young children is particularly sensitive to sunburns. By using 400 IU from a daily supplement, you can be fairly certain that your infant is getting enough vitamin D without worrying about too much sun.