An international study of older adults has found that mass, untargeted provision of vitamin D supplements provides little clinical benefit to many when it comes to the common bone disease, osteoporosis. Instead, the study recommends targeting vitamin D supplements at individuals whose levels of this vitamin are markedly reduced.
The results of the study - carried out by researchers at the University of Auckland, New Zealand, and Harvard Medical School, Boston, MA - were announced today by Professor Ian R. Reid at ECTS 2017, the 44th European Calcified Tissue Society Congress being held in Salzburg, Austria.
Professor Reid said: "We know that severe vitamin D deficiency causes osteomalacia, yet trials in the community have not consistently shown that vitamin D supplements improve older adults' bone density or reduce the risk of fracture. So we set out to determine whether a higher dose of vitamin D influences bone density or whether benefit is dependent on the level of vitamin D already present in the individual.
"The study was part of a bigger trial among community-resident adults aged 50-84 years and followed 418 participants for two years, who were randomized to receive, monthly, either high oral doses of vitamin D or a placebo. We were looking at changes over time to bone density in their lower spines, primarily, and in other commonly tested sites on the body.
"We were also testing thresholds in the levels of vitamin D already present in the participants and found that that level was significant when it came to the effect of the vitamin D treatment. There was a certain threshold (of 30 nmol 25-hydroxyvitamin D per litre) where, for those above the threshold, there was no real change in bone density for those receiving the treatment, compared to those receiving the placebo, while for those at or below the threshold, the change in bone density was around 2%."
Professor Reid concluded: "It was clear to us that future trials of vitamin D supplements in older adults should focus on those who have baseline vitamin D levels equal to or below 30 nmol per litre and that the findings represent a significant step towards defining vitamin D deficiency for bone health in older adults."