Vitamin D is the most common vitamin deficiency in the United States. Present and future, this deficiency is a threat to your health span. In addition to keeping bones strong, vitamin D may play a role in preventing cancers of the breast, prostate, and colon. Low levels of D have been associated with risk for these diseases.
Vitamin D transports calcium from the intestine into your bloodstream. Without it, you would absorb a mere 10 percent of the calcium you ingest, which is why we now fortify milk with D.
Misnamed long ago, “vitamin” D is actually a hormone. Like other hormones, your body can manufacture D, but only with a little help from the sun.
Your skin contains a precursor to vitamin D. When the ultraviolet-B photons in sunlight penetrate the skin, they set off a series of chemical reactions that ends with the formation of the active form of vitamin D.
Quiz: Are you getting enough vitamin D?
Tabulate your points as the accumulate.
If you are 65 and older:
1 point: For each 5 minutes you spend each week outdoors in sunshine without sunscreen and with face, arms, and hands exposed.
1 point: For each hour you spend each week outdoors in sunshine with sunscreen and with face, arms, and hands exposed.
If you are 21 to 64:
4 points: For each 5 minutes you spend each week outdoors in sunshine without sunscreen and with face, arms, and hands exposed.
4 points: For each hour you spend each week outdoors in sunshine and with sunscreen and with face, arms, and hands exposed.
8 points: If you take daily supplements containing 1,000 vitamin D.
3 points: If you take a daily multivitamin or separate supplement containing 400 IU vitamin D.
1 point: For each glass of vitamin D-enriched milk you drink per day.
If you arrive at 8 or more points, your vitamin D is most likely adequate. But getting your vitamin D from the sun is the optimal way of receiving it.
Weekly Sun Exposure Recommendation for Vitamin D
This author’s recommendation is to get 1,000 IU of vitamin D a day from supplements and/or sun exposure. Do not exceed 1,000 IU a day from supplements.
Use these guidelines for getting your vitamin D from the sun. Weekly sun exposure should be without sunscreen, with face and arms exposed. Keep in mind that the sun isn’t strong enough to trigger vitamin D production during the winter at high latitudes.
Under 65: 3-5 minutes, 2-3 times a week.
65 and above: 5-15 minutes, 2-3 times a week.
How much vitamin D do you think you get from the sun?
Adapted from The Longevity Quotient by Edward L. Schneider, M.D. ( Rodale, 2003).