Vitamin D: What’s the Big D, Anyway?

Cornflakes are often enriched with vitamin D.

You know something is going on with a vitamin if it has become so fashionable Vogue is featuring it on its cover (February 2009, in case you’re looking). Sure enough, the National Institute of Health (NIH) Office of Dietary Supplements is currently reviewing its recommendations for vitamin D intake for adults, and no wonder: it seems that approximately half of us in the northeast simply aren’t getting enough vitamin D. An editorial in The New England Journal of Medicine reports that 57% of 290 patients in one study were reported to have inadequate vitamin D levels. Another alarming 2007 study from the University of Pittsburgh found that approximately half of the pregnant women residing in the northeastern U.S. are “at high risk” for vitamin D insufficiencies and deficiencies, even when taking prenatal vitamins. Unfortunately, it does not seem those numbers are much different for non-pregnant patients in other northeastern cities.

In a 2004 review featured in the American Journal of Clinical Nutrition, renowned vitamin D expert Dr. Michael Holick explains the importance of vitamin D in “cancers, type 1 diabetes, heart disease, and osteoporosis.” Holick’s review cites one particularly alarming study by Dr. William B. Grant, Ph.D., in which “up to 25% of the deaths due to breast cancer in Europe could be [statistically] attributed to a lack of UVB from sunlight.” A similar study conducted by Dr. Grant in the U.S. found that cancer rates are approximately twice as high in the northeast compared with the southwest. The study, published in Cancer, supports this statement with a statistically significant inverse relationship between UVB exposure and bladder, esophageal, kidney, lung, pancreatic, rectal, stomach, and corpus uteri cancers. Holick’s review also definitively explains the exact physiology by which vitamin D deficiency leads to bone loss, which can be found here (page 366).

Further, vitamin D3 may keep you looking young. According to a 1985 study in The Journal of Clinical Investigation, the skin contains only about half as much vitamin D at age 80 than at 8-18, and vitamin D3 may fight aging by fighting inflammation and preserving telomere length. That’s where everything gets tricky: the sun is the leading cause of visible signs of aging, but we need the sun to produce vitamin D3!

But don’t toss your sunscreen out just yet: a 1995 Australian randomized clinical trial amongst 113 patients in Archives in Dermatology found that it was still possible to use broad-spectrum (UVA/UVB SPF 17) daily over the course of a summer and maintain healthy vitamin D levels. Even Dr. Holick, who strongly advocates getting adequate sun exposure, still recommends only “reasonable” exposure to sunlight (outside sunscreen-free between the hours of 10 A.M. and 4 P.M. for 15 minutes a day, three times a week. Expose your face, arms, hands, and back). Dr. Holick also recommends getting vitamin D3 through supplementation of 400 IU daily. I have personally never had any problems while taking Country Life Natural Vitamin D3 ($2.66, Amazon.com ).