The information in this article is from the November 2009 issue of the Nutrition Action Health Letter, published by the Center for Science in the Public interest.
While several different studies have linked higher blood levels of Vitamin D to lower levels of various cancers, some studies have shown no effect at all. Therefore, larger clinical trials with many more participants are needed to definitively show that Vitamin D decreases the risk of cancer.
The ability of Vitamin D to reduce heart attack and stroke risk is more firmly established. The vitamin works by suppressing potentially harmful hormones and reducing inflammation in the walls of arteries. It also appears to lower blood pressure. And because of its bone-building effects, Vitamin D (at least 700 IU per day) reduces the risk of bone fracture and has reduced the risk of falls by 20%, possibly by improving the ability of muscles to take preventive action when a fall in imminent. Another apparent benefit of Vitamin D is that, when taken with calcium, it slows the rise of blood sugar, thus reducing the risk of Type II diabetes.
Considering its apparent benefits, the Center recommendas 700 to 1,000 IU of vitamin D a day, which is much higher than the standard multivitamin dose of 400 IU. Supplements are particularly important for people living at northern latitudes as, in winter, the angle of the sun in cities north of Atlanta and Los Angeles is such that even direct sun exposure does not bring about the manufacture of appreciable amounts of Vitamin D.