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Importance
Why is Vitamin D important?
Getting enough vitamin D may be the most important variable in preventing osteoporosis. Vitamin D’s main function in the body is to aid calcium absorption. An analysis of data from the Nurses’ Health Study found that participants who consume 500 IU of vitamin D daily are 37% less likely to have broken a hip than women who consume 140 IU. (IU stands for International Units, a measure of biological activity.) Neither total calcium nor milk consumption was associated with a lower risk for hip fracture.
Studies have shown that up to 50% of older Americans don’t get enough vitamin D. There are several reasons for this. The vitamin’s biologically active form is metabolized when the skin is exposed to the ultraviolet radiation in sunlight. Theoretically, sun exposure can give you all the vitamin D you need. But north of about 40 degrees latitude — the latitude of Philadelphia, Indianapolis, and Denver — the winter sunlight is too weak to produce significant amounts of vitamin D. Even in sunnier climes and times of year, older people tend to spend a lot of time indoors. Moreover, older skin is less effective in making the vitamin even when it’s exposed to sunlight. Sunscreens are another problem: they filter out much of the ultraviolet radiation that produces vitamin D.
Theoretically, you could make up for a shortage of sunshine-generated vitamin D with diet. The problem is that precious few foods contain the vitamin. For practical purposes, it’s limited to several types of saltwater fish. So decades ago, health officials in many northern countries decided to fortify foods with vitamin D. In the United States, milk — but not other dairy foods — was chosen. An 8-ounce glass of milk is supposed to contain 100 IU, although surveys have shown that the actual amount can be a great deal less.
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Why Are America’s Bones Shrinking
by Thomas G. Kotronis, Rph |
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