Doses of vitamin D between 700 and 1,000 International Units (IU) may reduce the risk of falling by about 20 per cent, said the results of the meta-analysis published in the British Medical Journal (BMJ). However, doses less than 700 IU had no benefits.
Current recommendations for vitamin D intake, like the Food and Drug Administration’s (FDA) Reference Daily Intake (RDI), are for 400 IU for most adults, and 600 IU for the over 70s.
The researchers, led by Professor Heike Bischoff-Ferrari from the University of Zurich, reviewed double-blind, randomised controlled trials of 2,426 older individuals. Eight trials were included, and the doses used varied greatly, from 200 to 1,000 IU per day.
According to their findings, “high dose supplemental vitamin D reduced fall risk by 19 per cent”, stated Bischoff-Ferrari and her co-workers.
Furthermore, blood levels of 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form of the vitamin in the body, above 60 nanomoles per litre were associated with a 23 per cent reduction in falls.
On the other hand, lower vitamin D doses, and 25(OH)D levels less than 60 nanomoles per litre, were not associated with any decrease in falls.
Two of the studies included in the study had data for supplements with the active form, 1,25-dihydroxyvitamin D (1,25(OH)2D), and the risk of falls by 22 per cent.
“An important risk factor for falls is muscle weakness, which is a prominent feature of the clinical syndrome of vitamin D deficiency and could plausibly mediate fracture risk through increasing susceptibility to falls,” explained the researchers. “Binding of vitamin D to its nuclear receptor in muscle tissue may lead to de novo protein synthesis, a benefit that appears to precede the effect of vitamin D on bone.”
The results are inline with findings presented at a recent symposium “Nutrition and Functionality” held at the 19th IAGG World Congress of Gerontology and Geriatrics in Paris, and sponsored by the Nestlé Nutrition Institute. During the symposium Prof Bischoff-Ferrari highlighted the direct effect of the vitamin on muscle strength resulting in fall and fracture reduction.
In addition to the newest meta-analysis, a previous analysis published in the Archives of Internal Medicine (Vol 169, pp. 551-561) Prof Bischoff-Ferrari reported that a daily dose of 400 international units may reduce hip fractures by 18 per cent, and non-vertebral fractures by 20 per cent.
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320 nm), is said to be more bioactive.
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
“Vitamin D supplementation also reduced falls in several trials of institutionalized and community dwelling elderly. This additional benefit is important as falls are a great burden to functionality at old age and are the primary cause of hip fractures,” said Prof Bischoff-Ferrari.
Source: British Medical Journal
Published online ahead of print, doi:10.1136/bmj.b3692
“Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials”
Authors: H.A. Bischoff-Ferrari, B. Dawson-Hughes, H.B. Staehelin, J.E. Orav, A.E. Stuck, R. Theiler, J.B. Wong, A. Egli, D.P. Kiel, J. Henschkowski,