But the Harvard Medical School researchers call for further investigation into the effect of different types of the vitamin and dosages, the role of calcium supplementation, and the impact of vitamin D in men.

Falls among elderly individuals occur frequently, increase with age, and lead to substantial morbidity and mortality, but not all trials had shown benefits of taking vitamin D to prevent falls.

The conclusions of the meta-analysis will however be valuable for increasingly ageing populations around the world, at significant risk of the brittle bone disease osteoporosis. This disease has been classified the world's second biggest public healthcare problem by the World Health Organisation.

Dr Heike A. Bischoff-Ferrari and colleagues analysed data from 10 randomized controlled trials that looked at the association between risk of falls and the vitamin in elderly populations.

They only included studies on patients in stable health.Based on five trials involving 1237 participants, vitamin D reduced the risk of falling by 22 per cent compared with patients receiving calcium or placebo, write the researchers in today's issue of the Journal of the American Medical Association (291:1999-2006).

Five additional studies, involving 10 001 participants, in a sensitivity analysis resulted in a smaller but still significant effect size, they said.

The research also showed that this effect was independent of calcium supplementation, type of vitamin D, duration of therapy, and sex.However the reduced sample sizes made the results statistically nonsignificant for calcium supplementation, cholecalciferol, and among men.