Recent studies have shown that older adults can reduce the risk of non-vertebral (non-spinal) bone fractures by as much as 20% and that of hip fractures by up to 18% by taking vitamin D supplements. Although there have been several clinical trials around this possibility in the past, it is only a recent meta-analysis that has provided conclusive evidence of the link. (A meta-analysis is where the results of several studies on a related topic are combined.)
Up until now, a number of factors have hindered acceptable findings, namely: participants not following the required treatment program, the use of a different form of the vitamin (ergocalciferol, or vitamin D2) which is weaker, or the use of doses that are too low to be effective.
The meta-analysis was based on previous studies which had looked at the benefits of oral supplements of the vitamin in adults upwards of 65 years old. There were 12 studies with a total of 42,279 subjects where the average age was 78 years. 40,886 of these were considered specifically for hip fractures. In each case neither the participants nor the researchers were aware of who formed part of the control group and who was in the experimental group i.e. they were double-blind studies.
Clinical Trials Yield Significant Results
Dr Heike A. Bischoff-Ferrari of the University of Zurich, University Hospital, led a team of colleagues through this work and the results were published in a JAMA/Archives journal: Archives of Internal Medicine, March 23 issue.
The group determined that the critical amount of the vitamin in the diets of older adults is 400 international units per day. This amount or lower will have no effect on reducing the risk of fractures, whilst more than this intake will have a marked impact.
Looking at the combined results of all of the 12 studies, the risk of non-vertebral fractures was decreased by 14 percent and that of hip fractures by 9 percent. This was exciting in itself, but when the researchers concentrated on only the studies where participants were given doses of above 400 international units per day (9 of the trials), the real significance was revealed, with risk reductions of 20 and 18 percent respectively.
Besides considering the quantity of supplement ingested, the studies also included measuring the participant’s blood levels of the vitamin. The amount of 25-hydroxyvitamin D in the blood provides a measure of the levels of the vitamin. It was found that a higher blood content of this chemical is associated with even more of a drop in risk of fracture.
Calcium is typically associated with assisting in reducing the likelihood of bone fracture; therefore they also investigated whether adding calcium supplements could increase benefits even more. However, it seems not to be the case. Researchers suggest that this is because the vitamin increases calcium absorption and makes the process more efficient; thereby eliminating the need for additional calcium. The effects of low doses of the vitamin combined with calcium have not been investigated.
The team now proposes investigating the use of even higher doses of the vitamin in order to maximise results. Another avenue of thought is that taking the supplement earlier in life and for longer may improve results even further.