Vitamin D Deficiency Has Major Impact on Health
A nationwide survey published in the August Archives of Internal Medicine found that 41 percent of men and 53 percent of women in the United States are deficient in vitamin D, particularly postmenopausal women, African Americans and the elderly.
Because vitamin D plays a critical role in bone’s ability to absorb calcium, such a statistic sounds an ominous warning about America’s bone health. But researchers also are discovering that vitamin D—known as “the sunshine vitamin” because it is naturally produced in skin exposed to the sun’s ultraviolet (UV) rays—is important to immune function, cell growth and death, and keeping inflammation at bay. Those functions help explain how vitamin D may inhibit cancer’s run-amok cell division, prevent heart attacks and strokes, calm the pain of arthritis, preserve thinking and memory in the elderly, prevent hypertension during pregnancy, maintain insulin levels to prevent diabetes, increase muscle strength and coordination, and even prevent and help treat multiple sclerosis.
According to a separate study in the same issue of Archives of Internal Medicine, the sunshine vitamin is even tied to a lower risk for death. Researchers at the National Institutes of Health reported on a nine-year tracking study of more than 13,000 people in their 40s. Those with the lowest blood levels of vitamin D, less than about 18 nanograms per milliliter, had a 26 percent greater risk of dying during the follow-up period than did those in the top quarter of the vitamin D blood test results. Most of the deaths were related to heart attack and stroke.
What Is Vitamin D?
Did you know that vitamin D isn’t actually a vitamin? It’s not a hormone, either. It’s a prohormone, the chemical precursor to a hormone. Strictly speaking, vitamins are substances the human body can’t produce by itself. But when we expose our skin to sunlight, it makes fresh supplies of vitamin D for our bodies.
The ABCs of D
Foods rich in vitamin D are few and far between. The best sources of D when dining are:
- Salmon, tuna and fish liver oils, particularly cod liver oil
- Egg yolk
- Fortified foods, including milk, some yogurts, some ready-to-eat cereals and some calcium-fortified orange juice
Skim or reduced-fat milk may not be the best source. Some manufacturers put vitamin D into the milk before they skim off the excess fat. Bad idea. Vitamin D is fat-soluble, so when the skimmers take out that excess milk fat, they skim off most of the added vitamin D, too.
For supplements, cholecalciferol, or vitamin D3, is the best version.
Ask your doctor to check your vitamin D blood levels. Ask for the 25(OH)D3 test rather than the 1,25(OH)2D3 test. The first test is much more likely to give an accurate reading of overall vitamin D levels in the body.
Source: NIH Office of Dietary Supplements
Excerpted from a story that originally appeared in Cleveland Clinic Magazine, Winter 2009
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