Vitamin D affects physical function in elderly

Older men and women who fail to get enough vitamin D -- either from their diets or exposure to the sun -- are at heightened risk for muscle weakness and poor physical performance, a study shows. This is troubling, researchers say, given the high numbers of older folks who are deficient in vitamin D.

In a sample of 976 adults who were 65 or older at the outset, nearly 29 percent of women and 14 percent of men had vitamin D deficiency, determined by measuring blood levels of 25-hydroxy-vitamin D, a frequently used and accurate measure of a person's vitamin D status.
Moreover, 75 percent of women and 51 percent of men had insufficient vitamin D levels.

The researchers tested the participants' physical performance by timing their walking speed, as well as their ability to get up from a sitting position and keep their balance while standing in increasingly more challenging positions. They also measured handgrip strength, a predictor of future disability.

Dr. Denise K. Houston of the Wake Forest University of Medicine in Winston-Salem, North Carolina, and colleagues found that physical performance and grip strength were 5 to 10 percent lower in people with low blood levels of vitamin D levels, compared with those with normal levels.

The finding held up after they took into account factors that could potentially influence the results such as a person's weight, level of physical activity, the season of the year, mental abilities, overall health condition and anemia (a deficiency of oxygen-carrying red blood cells that frequently causes fatigue).

Vitamin D plays an important role not only in bone health -- research suggests it may also help protect against diabetes, cancer, colds, and tuberculosis.

People get vitamin D from the sun's ultraviolet rays and from certain foods such as fortified milk, juice and cereals. However, it is hard to get sufficient amounts of the vitamin through diet alone. Older adults are prone to low vitamin D levels because of reduced exposure to the sun and because their skin is less able to produce vitamin D from sun exposure compared with younger adults.

It's estimated that 1 in 4 people over age 60 have low vitamin D levels.

Current guidelines recommend that people between the ages of 50 and 69 get 400 international units (IUs) of vitamin D per day and for those over age 70 to get 600 IUs.

Houston contends that "higher amounts of vitamin D may be needed for the preservation of muscle strength and physical function as well as other conditions such as cancer prevention."

"The current recommendations," she added, "are based primarily on vitamin D's effects on bone health."