LOS ANGELES, April 23 (Xinhua) -- Low vitamin D levels may increase the risk of poor physical performance and disability for older adults, according to a new research.

"With a growing older population, we need to identify better ways to reduce the risk of disability," said Ph. D. Denise Houston at the Wake Forest University School of Medicine.

The researchers found that lower levels of vitamin D may result from diets or insufficient exposure to the sun.

The study involved 976 people who were 65 years and older from two towns in the Chianti area of Italy. The mean age of participants was 74.8 years. Data were collected from September 1998 through March 2000.

Participants completed a short physical performance which measured their walking speed, ability to stand from a chair and ability to maintain their balance in progressively more challenging positions. A hand-held dynamometer was used to measure handgrip strength, a predictor of future disability.

The researchers found that physical performance and grip strength were about five percent to 10 percent lower in those who had low levels of vitamin D.

The results held true after looking at other variables that could influence the results, such as body mass index, physical activity, the season of the year, mental abilities, health conditions and anemia.

"Our study showed a significant relationship between low vitamin D levels in older adults and poorer physical performance," said Houston.

According to the research, about one-fourth of people over age 60 had low vitamin D levels.

Previous research showed that vitamin D not only plays a role in bone health, but possibly also in protecting people against diabetes, cancer, colds and tuberculosis.

"Recent findings showing the importance of vitamin D status on multiple health outcomes underscore the need for more research on the effects of low vitamin D levels in elderly populations," said Houston, an instructor in internal medicine - gerontology.

Vitamin D is produced when skin is exposed to the sun's ultraviolet rays. Foods such as fortified milk, juice and cereals also contain vitamin D, but it is difficult to get enough through diet alone, said Houston.

Older adults are particularly prone to low vitamin D levels because they may get less exposure to sunlight and because their skin is less efficient in producing vitamin D from exposure to the sun. Older adults also may not get enough vitamin D from dietary sources.

"There is a growing awareness that the prevalence of low vitamin D levels is common among the elderly," said Houston.

Current recommendations call for people from age 50 to 69 to get 400 international units (IUs) of vitamin D per day and for those over 70 to get 600 IUs. Many researchers, however, suggest that a higher amount may be needed.

The results were reported in the April issue of the Journal of Gerontology: Medical Sciences.