Winter is here, and that means less exposure to the sun. That’s good and bad—good in that you won’t get sunburned or expose your skin to harmful rays for long periods, bad because your body needs sunlight to produce vitamin D. New research suggests that one in three Americans is deficient in vitamin D, which is unfortunate because the healing vitamin not only builds bones but also helps prevent cardiovascular disease, arthritis, multiple sclerosis, colds, flu—even cancer.
For adequate production of vitamin D you need about 15 minutes of sun exposure twice a week—without sunscreen, which completely blocks vitamin D production. If you can’t get that amount in the winter—and not many people can—take vitamin D supplements. Another consideration is that people age 50 and older tend to have skin that loses some of its vitamin D conversion ability. Dark-skinned people don’t have as much ability to convert sunlight into vitamin D as light-skinned people do. Supplements may be necessary.
The optimal daily intake has been set at 400 international units per day for adults under age 70, but many researchers are suggesting 1,000 to 2,000 I.U. per day, especially in winter.