Several earlier studies have linked vitamin D and calcium supplements to fewer falls, as well as lower risk of osteoporosis and osteoporotic fractures.
The new double-blind, randomised, placebo-controlled study, published in the Archives of Internal Medicine (Vol. 166, pp.424-430) supplemented the diets of 199 men and 246 women with 700 IU of cholocalciferol (vitamin D3) plus 500 mg of calcium in the form of calcium citrate malate, or placebo.
The study population was analysed in terms of sub-groups for men, women, active and inactive, and serum levels of 25-hydroxyvitamin D (the non-active 'storage' form).
After three years of supplementation the researchers observed: "Long-term dietary cholocalciferol-calcium supplementation reduces the odds of falling in ambulatory (mobile) older women by 46 per cent, and especially in non-active women by 65 per cent."
The same level of supplementation had no effect on men, regardless of how active they were.
Interestingly, there was no significant difference in the serum 25-hydroxyvitamin D levels in the supplemented or placebo women (28 versus 25 nanograms per millilitre) or men (33.2 versus 32.8 nanograms per millilitre).
The difference between the sexes was rationalised in terms of women have lower muscle strength than men and are thus more likely to fall.
It could also be argued that the difference between the number of falls of active and less-active women is not due to the supplements but is in fact due to the fact that more active people put themselves at increased risk simply by being more active, a point the researchers admit.
Another limitation is that the main findings are linked to subgroups of the sample population, but the original study design was not powered to specifically detect the effect of sex, activity and serum 25-hydroxyvitamin D levels.
Despite these limitations, the double-blind, randomised, placebo-controlled design is a big strength, and the researchers argue that the results have clinical significance.
"We show a significant reduction in the odds of falling in ambulatory older women with a very inexpensive, well-tolerated, and simple supplementation with cholocalciferol-calcium," wrote lead author Heike Bischoff-Ferrari from the University Hospital Zurich.
These results support a previous study by the same group, which reported a 60 per cent reduction of fractures from supplements.
The recent WHI study also supports these results, despite some misrepresentation by the mainstream media. For those women who actually adhered to the supplementation program, taking a daily supplement of 1000 mg of elemental calcium in the carbonate form and 400 IU of vitamin D3 was linked to a 29 per cent reduction in fractures.
The combination of vitamin D and calcium has long been recommended to reduce the risk of bone fracture for older people, particularly those at risk or suffering from osteoporosis, estimated to affect about 75 million people in Europe, the USA and Japan.
This use of the supplements is widely accepted by the general public, with calcium supplements reported to be the biggest seller in the US supplements industry, with annual sales of about $993 (€836) million in 2004, according to the Nutrition Business Journal.