Are You Getting Enough Vitamin D to Prevent Disability?


You already know that vitamin D, the sunshine vitamin, is important to help your body use calcium for strong bones. But vitamin Ds role in boosting muscles is also emerging in scientific studies, with implications for disability and the capacity to perform daily chores with aging. As the days get shorter and it becomes more difficult for your body to synthesize vitamin D from sun exposure on the skin, you may not be getting enough for long-term healthy aging.

Patients with severe vitamin D deficiency develop extreme muscle weakness, most severe in the proximal region of the extremities, says Bess Dawson-Hughes, MD, director of Tufts HNRCA Bone Metabolism Laboratory. It appears that mild insufficiency also has harmful effects on muscle performance and may affect balance as well. Adults with low blood levels of vitamin D have a higher risk of falling and many intervention trials have demonstrated reduced risk of falling with supplementation.

Vitamin D levels in the body are measured by blood tests, and expressed in nanograms per milliliter, abbreviated ng/mL (a nanogram is one-billionth of a gram). The Institute of Medicine (IOM) recently recommended a minimum blood level of vitamin D of 20 ng/mL for older people. Another scientific group, the Endocrine Society, sets the level higher, at 30 ng/mL.

EVERYDAY TASKS: A new Dutch study, using the 20 ng/mL standard, reports that people ages 55 and older who are deficient in vitamin D are at increased risk of developing limitations in performing everyday tasks. The study looked at 725 people ages 55-65 and 1,237 people ages 65-88, all participants in the ongoing Longitudinal Aging Study Amsterdam. Participants were asked about their ability to perform six common tasks:

– Walking up and down 15 stairs without a rest
– Dressing and undressing
– Sitting down in and rising from a chair
– Cutting their toenails
– Walking outside five minutes withoutresting
– Using personal or public transportation.

Those with levels below 20 ng/mL-41% of the younger group and 48% of the older group-were significantly more likely to report limitation in at least one activity from the list. Over six years follow-up for the younger group and three for the older participants, those low in vitamin D were more likely to develop at least two limitations.

GETTING ENOUGH: Publishing their findingsin the Journal of Endocrinology & Metabolism, Natasja van Schoor, PhD, of VU University Medical Center, and colleagues THINKSTOCKcommented, Although the current study is not designed to determine the direction of the relationship, the results of the longitudinal analyses, the known presence of vitamin D receptors on muscle cells, and the positive effects of vitamin D supplementation on muscle function… suggest a potential positive effect of vitamin D on functional performance.

Tufts Dr. Dawson-Hughes comments, The National Institute on Aging recognizes the importance of this issue and has recently requested applications for dose finding studies to identify the precise amount of vitamin D needed to maximally improve muscle performance and minimize risk of falling.

Healthy adults need 600-800 International Units (IU) daily of vitamin D to avoid deficiency, she adds, and high-risk groups such as the obese and those with limited sun exposure need more. That can be difficult to obtain from food alone, so vitamin D is one nutrient where experts often recommend supplements.


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