Vitamin D: NEJM review article highlights importance to overall health

Key Points

National report - The importance of vitamin D to a wide range of health issues - from bone problems to cancer to infectious disease - is highlighted in a review article on vitamin D deficiency that appeared in the July 19 issue of the New England Journal of Medicine.

Research indicates that most tissues and cells express a vitamin D receptor and need adequate levels of active vitamin D for normal, healthy function. That understanding of basic science has been substantiated by epidemiological studies and controlled interventions.

"This message has so permeated the medical literature and lay press that the test for 25 hydroxyvitamin D (the measurement for vitamin D status) has become the most ordered test, more so than testosterone or estrogen," the paper's author, Michael F. Holick, M.D., Ph.D., a Boston University endocrinologist, tells Dermatology Times.

The second is "a study by Lappe et al (Am J Clin Nutr. 2007) that just came out, where women taking 1,100 units of vitamin D a day for five years reduced their risk of developing all cancers by 60 percent," Dr. Holick says.

Bone growth and replenishment is another area in which vitamin D is important.

Dr. Holick says, "In a vitamin-deficient state, you can't put in the (calcium hydroxyapatite) cement, so only the soft collagen matrix is laid down, and acts like Jell-O under the covering of your bone. The periosteum, which is heavily enervated with sensory fibers, is easily compressed with minimum pressure, often causing severe bone pain.

Sun and supplements

Dr. Holick says, "Sensible, moderate sun exposure has always been and continues to be the major source of vitamin D.

"Avoidance of all sun exposure runs a very high risk of (creating) vitamin D deficiency. We believe that everyone needs about 1,000 units of vitamin D a day - women, children and adults. There is good documentation that suggests raising your blood level of 25 hydroxyvitamin D above 30 ng/ml will decrease your risk of many serious chronic diseases, and maintain and improve bone health."

Diet seldom is sufficient to do the job, Dr. Holick says. There are about 100 IUs (1 IU = 25 ng) in a glass of milk, about 500 units in a serving of salmon.

"So if you ate salmon every day, then maybe you're getting enough," Dr. Holick says.

He adds there are limits to food supplementation, not the least of which are liability concerns that inhibit what companies are willing to add to their fortified foods.

But 10 to 15 minutes in a bathing suit on a beach, "and you get 50 percent of a minimal epidermal dose (MED: one MED is equivalent to taking about 20,000 units of vitamin D), equivalent to ingesting 5,000 to 10,000 IUs of vitamin D. I am a proponent of moderate sun exposure; I don't advocate tanning," Dr. Holick says.

He advises his patients to always protect their faces, and, "After moderate sun exposure, they should wear good sun protection."

A properly applied sunscreen of SPF 15 absorbs about 99 percent of solar UVB radiation, "and also decreases your ability to make vitamin D by 99 percent."