Researchers have linked vitamin D concentrations greater than 40 nmol/L with improved lower extremity function in ambulatory patients age 60 and older, regardless of calcium intake, activity level, sex, age, race or ethnicity.

In the past, vitamin D has been shown to maintain calcium homeostasis and improve bone density, lowering the risk of fractures. Results of this published survey suggest vitamin D bolsters muscle strength and function, therefore decreasing the chance for falls that may lead to fractures.

Researchers examined the relationship between vitamin D levels and muscles strength and function in 4,100 subjects, about half men and half women, age 60 and older, with the mean age being about 71.

Vitamin D -- also known as 25-hydroxyvitamin D or 25(OH)D -- concentrations were measured in all participants, who were then classified into five groups, or quintiles, according to their vitamin D level. Participants also were classified by activity level. About 75 percent of them were active, meaning they had walked one mile without stopping, swam, jogged, bicycled, danced, exercised or gardened in the previous month. Those that had not, about one in four, were considered inactive. Researchers also controlled for calcium intake, sex, age, race or ethnicity.

Using a timed 8-foot walk test and a repeated sit-to-stand test, investigators assessed each subject's lower extremity functionality. Those who performed the tests in a shorter amount of time were judged as having better muscle strength and functionality.

Subjects in the highest quintile of vitamin D concentration had a mean 5 percent decrease in time of 0.27 second in the 8-foot walk test compared to those in the lowest quintile. For the sit-to-stand test the highest quintile of participants had a mean 3.9 percent decrease of 0.67 seconds compared to the lowest group.

Therefore, researchers associated higher vitamin D concentration with improved lower extremity function. The best results were seen in subjects with levels from 22.5 to 40 nmol/L. Positive results were also seen in the 40-90 nmol/L range.

Researchers summarized that in both active and inactive subjects, those with higher concentrations have better musculoskeletal function. They noted that while concentrations of 40 nmol/L or greater are desirable for optimal function, concentrations as high as 100 nmol/L appear advantageous.

They went on to conclude that vitamin D supplementation may offer a way to improve lower-extremity function in both active and inactive elderly subjects.

American Journal of Clinical Nutrition
September 2004 80(3):752-758
Posted September 21, 2004

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