For older men with normal levels of vitamin D, supplements of the vitamin do not appear to increase strength, according to a new study.
Researchers say that studies looking into the strength-building potential of vitamin D should focus on older adults with a deficiency in the nutrient. Elderly adults are at increased risk of vitamin D deficiency because their bodies are less able to synthesize the vitamin, and because they often get little sun, which triggers the synthesis of vitamin D in the skin. In addition, their dietary intake of the vitamin is typically inadequate.
Vitamin D aids in the absorption of calcium, and is best known for its benefits for bones. But there is also some evidence the vitamin might improve muscle strength; in one study, older men with low testosterone levels who took vitamin D and calcium for one year saw their leg strength improve.
In a study reported in the Journal of the American Geriatrics Society, 65 healthy older men were randomly assigned to take either 1,000 international units (IU) of vitamin D or a placebo each day for six months. All of the men, who were 76 years old on average, took a daily dose of 500 milligrams of calcium.
Those who took vitamin D showed higher levels of the nutrient in their blood, but their muscle strength, performance in physical tests and perception of their health were not appreciably changed. Both groups showed small increases in leg strength.
The findings suggest that additional vitamin D will not boost muscle strength or physical functioning in older men with adequate vitamin D stores. But the study does not negate the importance of adequate vitamin D intake among older adults.
In the U.S. an estimated 75% of older women consume less than half the recommended daily dose for vitamin D - which, after the age of 70, is 600 IU (15 micrograms). Besides sunlight and supplements, a small number of foods - including fatty fish such as salmon and mackerel, fortified milk and egg yolks - are good sources of the vitamin.
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