Vitamin D has been getting a lot of press lately, and rightly so. If your read my blog you know that supplementing with some vitamins increases your chance of disease--specifically, supplemental vitamin C has been shown to increase cancer and cardiovascular death, vitamin E increases death rates in smokers, and vitamin A is toxic at high levels. Vitamin D, however, is coming out looking like a gem--supplementation boosts the immune system, builds bone, decreases cancer, gives resistance to the flu, and decreases death rates significantly (read this study).
Further, we now know that vitamin D requirements are higher than we once thought. New research shows that "the actual observations in both younger and older adults show that to ensure the goal of a vitamin D of 80 nmol/L in almost all adults, 100 mcg/d is required." This dosage in I.U. (which is how most vitamin D supplements are labled), is 4,000 I.U.
For these reasons I now carry an excellent vitamin D supplement in my office. In addition to a high dose of emulsified vitamin D, it contains Cod Liver oil, Genistein, and cofactors for absorption. Check it out!