Sunshine Vitamin In Short Supply

If you spend 10 to 15 minutes out in the sun two or three times a week, you make enough vitamin D to stay healthy. Our ancestors had little trouble getting that much sunshine. They walked and worked outside a lot more than we do.
Today, people go from their homes to their cars to their workplaces without spending more than a few minutes in sunshine. What’s more, Americans are so scared about sun and the risk of skin cancer that many don’t go out without sunscreen. A sunscreen of SPF 15 reduces the amount of vitamin D the skin makes by 99 percent.
Shunning the sun, however, can have serious consequences. Vitamin D deficiency is surprisingly common. A study in Boston found 42 percent of those studied were low in vitamin D. In Calgary, Canada, scientists found nearly all of the residents are deficient in vitamin D for part of the year.
It could be hard to get 10 minutes of sun exposure in Calgary in the wintertime: you’d probably risk frostbite. But even in New York or San Francisco, many people don’t get much sun during the winter.
What about foods fortified with vitamin D? This enrichment is not always enough. In the U.S., milk is fortified with 100 IU per 8 ounces, so an average person would need several cups a day just to meet current vitamin D recommendations, which may be too low.
Research is revealing that vitamin D (which is actually a hormone) may have many unsuspected benefits. People who have adequate levels are less likely to break bones as they age. Investigators thought that this was because vitamin D improves calcium absorption and utilization.
Researchers have recently found, however, that older women with adequate D have stronger muscles and are less likely to fall. The best protection is at 800 IU or more a day, quite a bit more than the current RDA of 400 IU (JAMA, April 28, 2004).
Other studies have shown that vitamin D can reduce the risk of multiple sclerosis (Neurology, Jan. 13, 2004). This nutrient may also prevent the development of type 2 diabetes. New research shows that vitamin D improves insulin sensitivity as well as or better than some diabetes drugs.
Perhaps the most intriguing role for vitamin D is against cancer. Epidemiologists have noted that a number of cancers are more common the further you go from the equator. One explanation is that people who live in tropical climates get more regular sunshine and have higher levels of protective vitamin D circulating in their bodies.
Studies have demonstrated that this nutrient helps maintain normal cell growth, especially in the breast, colon and prostate.
For those who would like to know more about the benefits of vitamin D and sensible sun exposure we offer a one-hour radio interview with Michael Holick, MD, PhD, an expert on this topic. For a CD of this session, please send $15 in check or money order to Graedons’ People’s Pharmacy, No. CD-502, P. O. Box 52027, Durham, NC 27717-2027.
There is growing recognition that vitamin D is crucial to good health and many people are deficient in this nutrient. Although excess vitamin D can be toxic, some nutrition experts believe it would be wise to raise the recommendations.