A recent study published in the Archives of Internal Medicine (AIM) found that 3 out of 4 Americans suffer from Vitamin D deficiencies, and a 2008 AIM study showed that participants with the lowest levels of Vitamin D had double the risk of dying from heart disease. Vitamin D may also help prevent certain cancers, such as colon, breast and prostate cancer.
How much vitamin D is necessary? The government recommends 200 International Units (IUs) of vitamin D per day up to age 50, 400 IUs to age 70, and 600 IUs over 70. Many experts think these amounts are too low and they recommend exposure to short-term sunlight in the summer, in addition too "supplementation in the winter of about 2,000 IUs [of vitamin D] per day."
According to the 2008 AIM study, during the winter "it's impossible to produce vitamin D from the sun if you live north of Atlanta because the sun never gets high enough in the sky for its ultraviolet B rays to penetrate the atmosphere." However, it is possible to accumulate enough vitamin D in the summer months, which will last you throughout the winter. If you are light-skinned, experts recommend 10 minutes of outdoor sun exposure in shorts and a tank top with no sunscreen, which will yield about 10,000 IUs of vitamin D. People with darker skin and the elderly produce less vitamin D, which may mean you need more sun exposure and/or additional vitamin supplementation from sources like fortified milk* (if your body can handle it!) and fatty fish.
This is where the controversy begins. Clearly the Skin Cancer Foundation (SCF) is in the business of promoting limited exposure to the sun for fear you may develop skin cancer. Despite the studies' results, the Skin Cancer Foundation maintains its firm stance against all unprotected sun exposure. The SCF feels the studies supporting claims that some unprotected sun exposure is needed for sufficient vitamin D production "cannot directly correlate disease with individual sun exposure, and 'cannot establish that solar exposure decreases incidence or mortality from these cancers.'" The SCF claims that "when you wear sunscreen, some UV reaches the skin, and this may be plenty, at least for fair-skinned individuals." This type of "incidental protected exposure…to minimal UVB radiation three times weekly generates adequate vitamin D levels by classic criteria. Greater exposure adds nothing to vitamin D stores, while increasing DNA damage", thus increasing your chances for skin cancer. (Click HERE for the SCF's rebuttal.)
So, what is the average person supposed to make of all this information? Do we have to choose between risking skin cancer or risking heart and bone disease? I recommend MODERATION and a proper diet. A friend in medical school once told me that all you need to do is expose the back of your hand (with no sunscreen) to the sun for 5 minutes, and that will give you enough Vitamin D for about six months. I'm no expert, but it seems to me that everyone needs a little sunshine here and there, not only for some vitamin D, but getting out and taking in some fresh air is good for the soul. While this certainly isn't a license to go out and bake under the sun, I think most of us (not all) can handle a little bit of sunshine without risking too much. I still recommend using sunscreen all over your body and covering up at least your face, neck and shoulders. Unless you are head-to-toe in UV shielding armor, there is no way to 100% avoid UV rays. Incidentally, you will get some vitamin D production, perhaps not the recommended daily dosage, but that's where a proper diet comes in.**
Consult the table below for food sources providing vitamin D.
Table from the National Health Institute: Selected Food Sources of Vitamin D
| Food | IUs per serving | Percent Daily Value |
|---|---|---|
| Cod liver oil, 1 tablespoon | 1,360 | 340 |
| Salmon, cooked, 3.5 ounces | 360 | 90 |
| Mackerel, cooked, 3.5 ounces | 345 | 90 |
| Tuna fish, canned in oil, 3 ounces | 200 | 50 |
| Sardines, canned in oil, drained, 1.75 ounces | 250 | 70 |
| Milk, nonfat, reduced fat, and whole, vitamin D-fortified, 1 cup | 98 | 25 |
| Margarine, fortified, 1 tablespoon | 60 | 15 |
| Ready-to-eat cereal, fortified with 10% of the DV for vitamin D, 0.75-1 cup (more heavily fortified cereals might provide more of the DV) | 40 | 10 |
| Egg, 1 whole (vitamin D is found in yolk) | 20 | 6 |
| Liver, beef, cooked, 3.5 ounces | 15 | 4 |
| Cheese, Swiss, 1 ounce | 12 | 4 |
*More from the National Institute of Health: "In supplements and fortified foods, vitamin D is available in two forms, D2...and D3. The two forms have traditionally been regarded as equivalent based on their ability to cure rickets, but evidence has been offered that they are metabolized differently. Vitamin D3 could be more than three times as effective as vitamin D2 in raising serum 25(OH)D concentrations and maintaining those levels for a longer time, and its metabolites have superior affinity for vitamin D-binding proteins in plasma [6,32,33]. [Further] research is needed on the comparative physiological effects of both forms. Many supplements are being reformulated to contain vitamin D3 instead of vitamin D2 [33]. Both forms (as well as vitamin D in foods and from [sun exposure]) effectively raise serum 25(OH)D levels [6].
**From the National Institute of Health: "Sunscreens with a sun protection factor of 8 or more appear to block vitamin D-producing UV rays, although in practice people generally do not apply sufficient amounts, cover all sun-exposed skin, or reapply sunscreen regularly [31]. Skin likely synthesizes some vitamin D even when it is protected by sunscreen as typically applied."
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