NEW YORK (Reuters Health) — 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.