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Issue 86: Vitamin 3D?

We all know about 3D movies, but maybe it’s time to view vitamin D in 3D. Put on your glasses.  

Your sunglasses, that is, because the first dimension of vitamin D we’re going to look at is prudent sun exposure. Vitamin D, incidentally, has two forms: vitamin D2 and vitamin D3. Vitamin D2 is made in plants and vitamin D3—a preferred form of vitamin D—is made when cholesterol in our skin cells reacts with sunlight.

Generally speaking, the sun’s where most people should be able to get their vitamin D requirements met. The reality, however, is that our world has nearly one billion people who are vitamin D deficient—including three-quarters of U.S. adults and teenagers—so we’re obviously not getting enough of this sunshine vitamin.

There are lots of reasons people don't get enough vitamin D, including age, melanin content, sunscreen use, geographic location and more. For example, those 70+ in age make one-third less vitamin D than a young adult does when exposed to the same amount of sunlight.

Likewise, dark-skinned individuals need 5-10 times longer sun exposure than light-skinned individuals to make the same amount of vitamin D. Even sunscreens get into the act. SPF 8+ sunscreens can reduce vitamin D production by 95%.

Where you live makes a difference, too. If you live north of an imaginary line that stretches from the northern border of California to Boston, then the ultraviolet (UV) energy is not enough for vitamin D synthesis from November through February. The more north you live, the worse it gets. Diminished UV energy can last for up to six months in those areas.

If you live south of an imaginary line between Los Angeles and Columbia, South Carolina, then UV energy is adequate for vitamin D synthesis all year long. But that’s only if you go out in it and there’s no cloud cover, smog or other inhibiting factors. Complete cloud cover can reduce UV energy by 50%, while shade, including manufactured “pollution” shade from smog, slows down UV energy by 60%.

For those who want to and can get their vitamin D levels from the sun, try 5-30 minutes in the sun between 10 a.m. and 3 p.m. at least two times a week to the face, arms, legs or back without sunscreen.

For many folks, however, consistent, year-round sun exposure isn’t possible because they live in areas where vitamin D synthesis can’t occur for four to six months out of the year. Add cold temps, cloud cover and other factors and it causes us to look for vitamin D from dietary sources or supplementation—the second and third vitamin D dimensions.

If you’re selecting more D-packed foods, choose wisely. Vitamin D content in milk, for example, is highly variable. Less than half of sampled milk contained the vitamin D content specified on the label, while about one-fifth of skim milk sampled had no detectable vitamin D. Fatty fish like salmon and mackerel are great sources of vitamin D, but farmed salmon provides only one-tenth to one-fourth of the vitamin D content compared with wild salmon.

Moving on to supplementation…how much vitamin D should we get? Current recommendations say kids from birth to their teen years and adults aged 51 to 70 should get at least 400IU daily, while those 71 and up should get at least 600IU daily. Emerging research, however, says we could require much more—to the tune of 2,000IU or more daily.

All in all, it’s good to know there’s more than one way to get your vitamin D, especially if you can’t get out in the sun regularly.

Oh…and you can take your glasses off now.


This information is intended for educational and informational purposes only. It should not be used in place of an individual consultation or examination or replace the advice of your health care professional and should not be relied upon to determine diagnosis or course of treatment.

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