By Glenn S. Rothfeld, MD

In the alphabet soup of vitamins, one of the main players has gotten the short end of the tick for a long time.   Almost all of the vitamins have varied and sexy stories around them.  Vitamin A has two forms, vitamin A itself and “pro-vitamin A”, which we call carotene (beta carotene being the most famous).  It’s these carotenes that help to give the luscious orange and yellow colors to fruits and vegetables.  Vitamin A has long been known to strengthen the immune system, promote skin and mucous membrane healing, and help sharpen and sustain the vision.  And those of use who passed through medical school beyond a decade ago surely remember the ONE nutritional fact that was drummed into us, that if you eat too much polar bear liver, you will undoubtedly suffer from “hypervitaminosis A”, or vitamin A poisoning (I’m not making this up. Ask any doctor if they don’t remember this cautionary tale from medical school).B vitamins have all sorts of uses and stories, including the use of B1 (thiamin) for alcoholics, B2 (riboflavin) to prevent migraines (in addition to its traditional use to ward off beri-beri), and folic acid in a myriad of indications from preventing birth defects to lowering homocysteine and therefore lowering heart disease risk.  Vitamin C (ascorbic acid), of course, is the star of the vitamin family, having been promoted for anything from stress reduction to cold prevention to wound healing to cancer therapy.  And according to the recent book Napoleon’s Buttons, when Admiral Lind finally insisted that his sailors (later called Limeys) be given lime juice on their long sea voyages, therefore assuring that they would be hale and hardy and free of the scurvy that plagued all sea voyagers, he set the course of history, insuring the victory of the English fleet over the scurvy-ridden Spanish and Portuguese ships.  (It is suggested that the Spanish and Portuguese captains withheld citrus from their crew, preferring to keep them slightly weaker and sicker, and therefore less mutinous).

Vitamin E was, decades ago, known as the vitamin without a deficiency disease, is now known to play a very important role in protecting the lipid membranes of the brain, cardiovascular system and skin cells (for my comments on the recent vitamin E studies and the controversy that surrounds them, see my website http://www.wholehealthne.com/).  Vitamin K, of course, is mostly known in terms of clotting, and usually isn’t considered an issue unless it’s blocked by medications (although it has a poorly understood job in protecting antioxidants in the body).

Amongst all these well-known siblings, vitamin D has thus far been relegated to a second tier, mostly known for it’s association (when severely deficient) with rickets, a problem with bone growth leading to softening of bones.  The exact job of vitamin D in protecting bones has to do with its role in calcium metabolism.  Calcium is essential for proper muscle and nerve function, and the amount of calcium in the blood is a critical factor.  Vitamin D has the job of maintaining the proper amount of circulating calcium.  When calcium in the bloodstream gets too low, vitamin D boosts its absorption from the digestive tract.  So, it’s always been thought of as a vitamin with a fairly simple function.

But vitamin D is not so simple as that.  First of all, it is derived, not from food sources (although it can come from foods) but from sunlight.  Enzymes in our skin are altered by sunlight, resulting in vitamin D levels in the body.  The more sunlight, the more vitamin D.   And here’s where it gets interesting.  Studies of epidemiology have suggested that certain diseases, including some cancers and auto-immune associated diseases such as MS and ulcerative colitis, are more prevalent in northern climates than southern climates.  This led scientists to study a role for vitamin D in the immune system, and a fascinating thing has resulted.  We are now finding out that vitamin D is a controller of proper immune function.  In fact, it hardly acts like a vitamin at all (vitamins generally act by being co-factors in enzyme reactions, or by carrying electrons in oxidation-reduction reactions).  It acts more like a hormone for the immune system, and some scientists are suggesting that it be reclassified.

In any case, the research has been fascinating.  In animal models meant to mimic MS, vitamin D resulted in a profound decrease in inflammation of brain tissue, increase in proper immune system function, and a boost in the protective function of the blood-brain barrier.  Other studies have confirmed a crucial function of vitamin D in balanced immune function.

Meanwhile, the studies that associate vitamin D levels with certain disease prevention pile up.  Prevalence of MS is inversely correlated with the amount of sunlight; so is type I (insulin-dependent) diabetes and ulcerative colitis, among other auto-immune illnesses.  Several cancers are also inversely correlated with sunlight, particularly some lymphomas.  There is some suggestion that prostate cancer incidence can be lowered as much as 40% with high levels of vitamin D in the blood.  Many cancers have vitamin D receptors (VDRs) including breast, colon, skin, lung and bone cancer cells.  Cancers do their damage by rapid growth and lack of differentiation (that is, the cancer cells are more immature and not as well formed as normal cells.)   We know that vitamin D promotes cell differentiation and slows down proliferation (rapid growth).  Thus, there are clear mechanisms to explain vitamin D’s anticancer effects.

Another interesting thing that has come to light about vitamin D is the importance of adequate levels in the blood.  Currently, most labs have very broad range that is considered normal.  The lower limits of normal is usually around 9 ng/ml.  However, the risk of both cancer and auto-immune illnesses appears to increase when the blood levels are less than 35 ng/ml (around 80 nmol/L).  The recommended oral doses of vitamin D (currently 400 iu daily) are probably inadequate for most people to maintain these levels.  That’s where sunlight comes in: daily exposure to sunlight, particularly ultraviolet-B (UVB) radiation from sunlight, leads to synthesis of vitamin D in the skin.

But in fact, at latitudes like Boston’s, there is not nearly enough sunlight to provide adequate vitamin D to support immune system boosting levels.  For four months per year, there is no vitamin D produced in the skin of most Bostonians.  Furthermore, the successful public health campaign to cover up in the sunlight and wear heavy UVB blocking sunscreens can be helpful in lower skin cancer rates, but it clearly has a negative effect on vitamin D levels.

So, a more effective dose of vitamin D is about 1,000 iu per day, and should be in a form called D3, or cholecalciferol.  For people with cancer or autoimmune disease, including MS, 2,000 iu may be more appropriate.