New research suggests that both low and high vitamin D levels may be associated with an increased likelihood of frailty in older women.
Scientists at the University of Minnesota set out to study the links between vitamin D levels and frailty, which becomes more common as people age and increases the risk of falls and fractures.
They were keen to find out whether experts' advice to prescribe high doses of vitamin D in older adults with low levels of the vitamin was likely to be effective.
The researchers measured vitamin D levels of 6,307 women, aged 69 and older, and assessed their degree of frailty.
Of these women, 4,551 who were not frail at the start of the study had their vitamin D levels reassessed about 4.5 years later.
Researchers found that older women with vitamin D levels less than 20 ng/ml and those with levels in excess of 30 ng/ml had higher levels of frailty at the start of the study.
Those who were not frail but had low vitamin D at the start of the study were also more likely to become more frail over the next few years.
Commenting on the findings, which are published in the Journal of Clinical Endocrinology & Metabolism, lead author Dr Kristine Ensrud said that the association between vitamin D status and risk of adverse health outcomes was uncertain.
"Our study did not find that higher vitamin D status was associated with lower subsequent risks of frailty or death. In fact, higher levels of vitamin D were associated with increased likelihood of frailty," the professor of medicine and epidemiology revealed.
"Our results indicate that well-designed large randomised trials of sufficient duration are needed to accurately quantify health effects of vitamin D supplementation, including whether or not supplementation reduces the incidence or progression of frailty in older adults."
However, a spokeswoman from Arthritis Research UK said that vitamin D had its place as a treatment for older women. It was recommended for women over the age of 60 to counter the risk of developing osteoporosis, as a lack of the vitamin prevents the body from absorbing calcium, she added.
Source Arthritis Assoc