Vitamin D: Winter's Essential Wonder Vitamin
Raising the Bar
How much D should healthy people get? While the recommended dietary allowance (RDA) is still 200 International Units (IUs) a day for adults ages 19 to 50, many experts believe that's not nearly enough. Dr. Haden, for instance, advises her patients to take 800 to 1,200 IUs per day depending on their test results. Older people may need even more.
But getting enough D can be difficult. The problem is that the prime source of the nutrient is sunlight, and because women have become more conscientious about wearing sunscreen and staying out of the sun, they're getting less and less of the vitamin. (Obviously, being indoors cuts off the D supply, one reason that elderly people living in nursing homes are at high risk for D deficiency.)
If you live in a Northern state you face another challenge. The angle of the sun's rays in winter makes it impossible to get enough natural sunlight for you to reach your vitamin D quotient from October through April. The body can store extra vitamin D, but most Northerners don't stockpile enough during the summer to carry them through the winter.
Getting ample D in your diet is tough, too. One of the richest dietary sources of the nutrient is D fortified milk (regular, organic, and Lactaid milk all have D; soy milk may not) and D-fortified foods; oily fish, such as salmon, tuna, mackerel, and sardines naturally contain D. To get 1,000 IUs, however, you'd have to down 10 eight-ounce glasses of milk or eat three servings of salmon daily.
Finally, the darker your skin, the greater your risk for a deficiency. A 2002 study in the American Journal of Clinical Nutrition showed that 42 percent of African-American women were seriously D deficient. Because skin pigment keeps sunlight from being absorbed as quickly, dark-skinned people need up to six times as much daily sunlight exposure as do those with light skin.