Older people who take vitamin D and calcium supplements may live a bit longer than their peers, according to an international review of several studies covering more than 70,000 people.
Researchers writing in the Journal of Clinical Endocrinology found that older people who were given the supplements were 9 percent less likely to die over three years than those given placebo pills. Vitamin D alone had no impact on death rates.
A 9 percent dip in death risk over a three year period might sound small, but lead researcher Lars Rejnmark said that effect is "at least as pronounced" as the benefits linked to cholesterol-lowering statins and blood pressure drugs.
"In my view, a 9 percent reduced mortality in the general population of elderly is of major importance," Rejnmark, an associate professor at Aarhus University in Denmark, told Reuters Health by email.
"Except for stopping smoking, there are not many other known interventions that are capable (of) such a reduction in the risk of death."
Rejnmark and his colleagues combined the results from eight clinical trials that involved more than 70,000 older adults, mostly women.
In each trial, people were randomly assigned to take vitamin D or a placebo. Some studies used a combination of vitamin D and calcium.
The doses varied, but most trials used a daily vitamin D dose of 10 to 20 micrograms. In the United States, health officials suggest that most adults get 15 micrograms (or 600 IU) of vitamin D per day, while people older than 70 should aim to get 20 micrograms (or 800 IU).
In trials that used calcium, the dose was 1,000 milligrams per day. In general, women older than 50, and everyone over 70, are told to get 1,200 milligrams of calcium each day.
Vitamin D and calcium are probably best know as bone-builders. Older women often take the supplements to ward off the bone-thinning disease osteoporosis - and some trials have found that the supplement combination can prevent falls and bone fractures in the elderly.
But that probably does not explain the lower death risk in this study. When the researchers factored in hip and spine fractures, they did not account for the dip in death risk.
Another possibility is that supplements curbed people's risk of dying from cancer. Rejnmark said there's some evidence that calcium and vitamin D may lower the odds of colon cancer, but the evidence is not yet "firm".
For now, he said, the findings supported getting the recommended amounts of vitamin D and calcium.
Some members of Rejnmark's team had connections to supplement makers that market vitamin D and calcium products.