Vitamin D supplementation does not have beneficial effects on muscle function, strength, or mass, according to a new meta-analysis, and may even have detrimental effects on muscle strength in people with normal levels of the vitamin.
Vitamin D deficiency, causes a generalised decrease in bone mineral density, resulting in osteopenia and osteoporosis. In young children who have little mineral in their skeleton, this defect results in a variety of skeletal deformities classically known as rickets. It is also believed to cause muscle weakness; affected children have difficulty in standing and walking, whereas the elderly have increasing sway and more frequent falls,thereby increasing their risk of fracture.
The analysis, which is published in the Journal of Bone and Mineral Research, included 54 trials involving 8747 individuals. Overall, no benefits of vitamin D over placebo were observed for improving muscle health. On the contrary, vitamin D appeared to have detrimental effects in terms of increased time spent performing what’s called the Timed Up and Go test, a decrease in maximum strength at knee flexion, and a tendency towards a reduced score of the Short Physical Performance Battery.
“Care should be taken recommending vitamin D supplementation to improve muscle strength and function in people with normal or only slightly impaired vitamin D status,” said lead author Lise Sofie Bislev, MD, PhD, of Aarhus University Hospital, in Denmark. “We need to study further whether it may benefit muscles in those with severe vitamin D deficiency, however.”