Chapter 12

Getting Vitamin D from Food

In This Chapter

Selecting the best sources

Eating fortified foods

Adding more vitamins to your foods

Obtaining vitamin D if you have dietary restrictions

Animals and plants make vitamin D and use it just like you and I do. So it stands to reason that you should be able to get enough vitamin D by eating animals and plants; however, it’s not that simple.

In this chapter, I tell you about the foods that contain the highest levels of vitamin D, but as you’ll see, with rare exceptions, the vast majority of foods don’t have enough concentrated vitamin D to get you to 600 or 800 IU per day.

Scientists have tried to “fortify” certain foods by adding more vitamin D. But because of limits that the Food and Drug Administration has placed on the amount of supplemental vitamin D that can be added to foods, even that practice doesn’t produce a food that can supply your daily needs for vitamin D by itself.

So enjoy some foods with vitamin D in them. Many are D-licious foods that you want in your diet anyway. But depending on your vitamin D needs and your skin production of vitamin D, you may need more than your food will give you.

Selecting the Best Sources of Vitamin D

Vitamin D is a substance that dissolves in oil and not in water (nutritionists call it a fat-soluble vitamin). This means that oily foods like wild salmon or animal blubber are the best sources of vitamin D.

Table 12-1 lists the richest sources of vitamin D, from highest to lowest.

Although several of these foods have quite a lot of vitamin D, not many people eat fatty fish every day, and few consume the traditional vitamin D–rich diet of animal blubber seen in the far north of Canada. Many people know that milk is fortified with vitamin D, but few people drink the 5 to 6 cups of milk a day that would be needed to get all your vitamin D from milk.

You might have noticed that even though cheese is made from milk, it isn’t a great source of vitamin D because vitamin D is added only to fluid milk that’s going to consumers, and not to the milk being used for cheese.

It’s also important to realize that food fortification practices differ between the United States and Canada. For example, fortification of milk and margarine is optional in the United States but mandatory in Canada. Breakfast cereals can be fortified with vitamin D in the United States but not in Canada. The labeling of breakfast cereals will indicate whether vitamin D is added, but be careful of what it is telling you. In Canada it means that if the cereal is consumed with a cup of milk, you will obtain the specified amount of vitamin D, but not if you eat the cereal dry.

The recommended level of 25-hydroxyvitamin D in your blood is 20 ng/ml (50 nmol/L), and the new recommended dietary allowances say most healthy adults need 600 IU of vitamin D per day to reach this if you are getting no vitamin D from the sun.

In the following sections, I cover the best food sources of vitamin D. You’ll cook some of them before you enjoy them for dinner, but that doesn’t affect the amount of vitamin D they contain. Cooking foods that contain vitamin D doesn’t reduce the vitamin D content because vitamin D is heat stable.

Cod liver oil

Cod has a mild flavor and flaky white flesh. It’s often used in fish and chips. But that’s not where you get the vitamin D. Instead, most of the vitamin D in cod is in the liver; it’s extracted in the form of cod liver oil. Its liver is also a good source of vitamin A, vitamin E, and omega-3 fatty acids.

The old liquid form of cod liver oil tasted fishy, but cod liver oil now comes in capsule form, and you don’t have to taste it to take it. Just don’t burp. If you’re willing to take one of these capsules daily, this may be one way to get enough vitamin D, vitamin A, and omega-3 fish oils all at once. The amount of vitamin D in cod liver oil capsules varies from 400 to 1,200 IU. Cod liver oil is usually taken with meals and is probably best absorbed this way.

But don’t think of cod liver oil as necessarily being a natural source of vitamin D any more. The processing and purification process removes much of the vitamin D, and fish oil varies a lot in its natural content of vitamin D anyway. Because of this, vitamin D is artificially added back in to maintain the desired amount of vitamin D content, so modern cod liver oil is really a fortified source, much like milk.

Cod liver oil has ten times as much vitamin A as vitamin D per tablespoon. Some preparations can have more than the recommended upper limit of vitamin A in a tablespoon, so don’t take more than one tablespoon cod liver oil or the equivalent amount by capsule if you decide you want to get more vitamin D per day than this source can give you in a single dose. Taking more than 2 tablespoons of cod liver oil daily may cause vitamin A toxicity, which results in nausea, vomiting, headache, dizziness, and loss of muscle coordination.

Salmon

Salmon, like cod, is an oily fish. Many species of salmon exist, but one that has a lot of vitamin D is the sockeye salmon. It lives in the eastern and western Pacific Ocean and is found in Canada and California, among other places.

Salmon contains a fair amount of vitamin D; 3 ounces of salmon has about 800 IU of vitamin D. Many health organizations caution that you shouldn’t eat too much wild-caught salmon because it can accumulate toxins like pesticides and heavy metals. Still, nutritionists think you should eat fish twice a week for good health, so make salmon a part of at least one of those meals.

If you buy Atlantic salmon, chances are good that it will be a farmed salmon. These salmon are kept in pens and fed a diet of other fish. They’re also given coloring agents called astaxanthin and canthaxathnthin to match the color of wild salmon. Wild salmon get these substances in their food.

As a result of how they’re farmed, Atlantic salmon have less vitamin D (just 300 IU per 3-ounce serving) than wild salmon. To maximize the vitamin D you get from salmon, make sure the salmon you buy at the store or eat at a restaurant is wild salmon.

Pacific salmon are also farmed, but the vast majority (80 percent) are wild. They contain large quantities of vitamin D, omega-3 fatty acids, and protein, and are considered a very healthy fish.

Mushrooms

Of all the foods that are grown, mushrooms are the only crop that naturally contains vitamin D. This form is vitamin D2. As I’ve said previously, vitamin D3 is preferred, but if you’re a vegetarian and want to make sure you get your daily vitamin D without the sun and without supplements, this may be the way to go for you.

Ordinarily, mushrooms don’t contain a lot of vitamin D. For example, shiitake mushrooms have no more than 100 IU of vitamin D per 100 grams of mushroom. But when irradiated for 5 minutes or longer with UVB light, the levels rise significantly, up to 10,000 or more IU per 100 grams. Radiating the mushrooms doesn’t change the taste and is harmless for the person who eats it.

Much of the recent work has occurred in the Department of Food Science at Penn State University. Researchers there initially discovered that just one second of pulsed (very short duration, high intensity) UV light exposure doubled the vitamin D2 content of both white and brown mushrooms. Four seconds of UV light increased the content to as much as 7,000 IU. After four seconds, the increase leveled off. The shelf life of these irradiated mushrooms is also excellent: They lose little of their vitamin D content in two weeks. These scientists have basically created a tanning bed for mushrooms, although in this case the tanning is beneficial.

Given the current demand for vitamin D and the shortage of all things that contain large quantities of the vitamin in a small package, you can expect to see irradiated mushrooms on your grocer’s shelf soon. But remember, because mushrooms have low fat content, it may be best to eat them along with some other food containing fat to make sure the vitamin D is absorbed well.

Mackerel

Mackerel is another delicious oily fish that contains a significant amount of vitamin D, about 400 IU in 3 ounces. It’s found in the Atlantic Ocean on both the European and American coasts. Mackerel also contains high concentrations of vitamin B12, important for blood and the nervous system, and omega-3 fatty acids for heart health.

Mackerel tends to spoil quickly because of its high oil content, so it’s often salt-cured or eaten as sashimi immediately after it’s caught. The meat has a strong flavor, is red in color, and is low in mercury, so you can eat it more than once a week.

Tuna fish

Tuna is a fair source of vitamin D and omega-3 fatty acid, as well as high-quality protein. A 3-ounce serving contains about 150 IU of vitamin D.

A problem with tuna is the possibility of a high level of mercury. Chronic exposure leads to a buildup of mercury. Over time, mercury can damage the brain, the kidneys, and the lungs, resulting in visual and hearing disturbances and poor coordination. Mercury levels vary greatly among the various types of tuna; the largest tunas, such as bluefin and albacore, have the highest levels. The high mercury content makes it unwise for pregnant women to eat a lot of tuna.

Milk

Milk, whether nonfat, reduced fat, or whole, provides about 100 IU of vitamin D per 8-ounce glass. And that’s after it has been fortified with vitamin D — but if you get your milk direct from the cow, there will be no vitamin D in it. Three glasses of fortified milk can almost supply the vitamin D needs of a toddler, but an adult would need to drink six glasses to get 600 IU daily. You’d better love milk if that’s how you want to get your vitamin D!

Milk, whether mother’s milk or cow’s milk, tends to settle into an upper creamy layer that contains the fat and a lower, low-fat milk layer. To prevent this, milk is homogenized to break the fat particles into much smaller particles that remain suspended in the milk. Vitamin D is added to the milk during the homogenization process to bring it up to 100 IU per 8 ounces.

Cows’ milk is used to produce many cheeses that are a source of vitamin D as well. However, most cheese production uses milk before it’s been vitamin D-fortified. Scientists have studied whether vitamin D is lost during the pasteurization to eliminate bacteria. They’ve found no loss of vitamin D as a result of pasteurization.

Milk, pregnant women, and newborns

The first milk a newborn should drink is breast milk from the mother. The first milk from the mother, colostrum, contains protective anti-bodies. Unless the mother has built up her 25-hydroxyvitamin D to very high levels by taking about 6,000 IU per day of vitamin D, the baby gets little or no vitamin D in breast milk. Breast-fed babies must receive a vitamin D supplement until they begin taking vitamin D–fortified foods. Chapter 14 has more on this.

In addition to vitamin D (if the mother is taking enough), breast milk contains saturated fat, protein, and calcium, all needed by the baby.

Milk and people who are lactose intolerant

One major problem with drinking milk to get vitamin D, besides the relatively low content of vitamin D, is lactose intolerance in some people.

Lactose is the sugar in milk. Babies have an enzyme, lactase, that can break down lactose in the intestine and make it available for absorption. This enzyme declines in many people as they enter adulthood. This is especially true in African Americans. When people lose the ability to make the enzyme lactase but then eat dairy products, bacteria in the lower intestine use the lactose; the result is increased gas, bloating, and intestinal cramps.

Lactose intolerance affects about 50 million Americans, especially Native Americans, African Americans, and Asian Americans. They can get some relief from tablets that contain lactase. Alternatively, they can drink soy milk, which isn’t really milk, but a beverage made from soybeans that doesn’t have lactose. Vitamin D must be added to soy milk just as it is added to cows’ milk.

Orange juice

Orange juice, like milk, is often fortified with vitamin D to provide 100 IU per 8-ounce glass. Calcium may be added as well. Orange juice naturally contains vitamin C, potassium, thiamine, folic acid, and vitamin B6. It’s made simply by pressing the fresh fruit. Orange juice is very acidic, so few people will enjoy drinking six to eight cups of OJ a day to meet their vitamin D needs.

Other sources

After orange juice, the sources for vitamin D fall off rapidly in their content of vitamin D, meaning that you need to eat extremely large amounts of the food to get your daily 600 IU. For example, you’d have to eat 23 eggs. I don’t recommend that.

That’s not to say that you shouldn’t eat these sources in small quantities. Most of them, like ready-to-eat cereal, are quite tasty and help you meet your daily needs. But without balancing sun and diet to get enough vitamin D to keep your serum 25-hydroxyvitamin D levels to 20 ng/ml (50 nmol/L), you’ll need to take a vitamin D supplement (more on that in Chapter 13).

Obtaining Vitamin D If You Have Dietary Restrictions

If you’re a vegetarian or you have a condition that reduces your ability to absorb vitamin D, you can still get plenty of vitamin D. How, you ask? From the sun, of course. Just go back to Chapter 11 and figure out how much time you should spend in the sun.

But suppose that you live at the latitude of San Francisco (37 degrees north latitude) or above, and it’s winter. You can’t get enough vitamin D from the sun at that latitude in the winter. The next few sections tell you what to do.

If you’re a vegetarian

Other than fortified soy milk, fortified orange juice, and margarine, a vegetarian can’t eat much to get vitamin D. Be wary that although vitamin D2 has been described as “the plant vitamin D,” most plants contain almost none of it. Only certain yeasts and irradiated mushrooms have relevant amounts of vitamin D. Perhaps irradiated mushrooms are a choice, but they’re not yet being sold in stores. Vegetarians may have to take a supplement, discussed in Chapter 13.

In addition to tablets, vitamin D also comes packaged in gel capsules because vitamin D is fat soluble. These capsules come from animal bones, however, so you won’t want to take those. Instead, choose a vegetable-based capsule, a tablet, or vitamin D in liquid form. In addition, vitamin D2 is the form of vitamin D that comes from vegetable sources like mushrooms and yeast. You might want to make sure you’re getting that form of vitamin D and not vitamin D3, depending on how strict you are. (But the vitamin D2 in those supplements is actually chemically synthesized, and isn’t harvested from plants.)

If you can’t absorb fats

If you have a condition that reduces your ability to absorb fat, you may suffer from vitamin D deficiency even if you eat these foods. Because vitamin D is fat soluble, if you aren’t absorbing fat, you aren’t absorbing vitamin D.

Several diseases and other medical conditions can prevent you from absorbing fats normally. Because vitamin D is a fat-soluble substance, you can become deficient in vitamin D if you get no sun. Among the conditions are the following:

Use of antibiotics, especially neomycin.

Excessive use of alcohol.

Crohn’s disease, a form of inflammatory bowel disease that usually affects the intestines and results in crampy abdominal pain, loss of appetite, pain with bowel movements, watery diarrhea with blood, and weight loss.

Vitamin D may play an important role in controlling Crohn’s disease, so you want to be sure to get sufficient quantities of this vitamin.

Celiac disease, a digestive disease that occurs when you eat the protein gluten from bread, pasta, or other foods containing gluten. The result is a loss of ability to absorb many nutrients, with resultant vitamin deficiency. You may develop diarrhea, abdominal pain, and bloating. The disease can be controlled by avoiding anything with gluten in it.

Bacterial overgrowth or parasites in the intestine, which changes the environment of the intestine so the body absorbs food poorly.

Short bowel from intestinal resection or bariatric surgery, leaving an inadequate length of intestine to absorb nutrients.

Insufficient digestive agents. Pancreatic enzymes and liver enzymes are needed to digest foods. Any disease that blocks those enzymes results in malabsorption of fats. Examples are obstruction of the bile tubes that carry the enzymes, liver failure, cystic fibrosis, pancreatic cancer, pancreatitis, and removal of the pancreas.

If you have any of these conditions, obviously, you want to cure the condition to return to good health and normal uptake of nutrients. But get out in the sun for a few minutes a day. It won’t just raise your vitamin D; it will raise your spirits as well.

If you can’t get out in the sun and you can’t absorb vitamin D from food, you may have to get an injection of vitamin D, but this is a rare situation. Sometimes extremely high doses of oral vitamin D can work for conditions in which vitamin D is poorly absorbed (such as short bowel), but that approach needs to be done under the supervision of your doctor, with monitoring of the blood 25-hydroxyvitamin D levels to know that enough vitamin D is being absorbed and not too much. Dermatologists can also administer UVB light under controlled circumstances to enable vitamin D to be formed while minimizing the risk of skin damage and cancer.