Researchers found that older adults who were given vitamin D and calcium supplements were 9 percent less likely to die over three years than those given placebo pills. Vitamin D on its own, however, showed no effect on death rates.
The findings are based on data from eight past clinical trials — where people were randomly assigned to take vitamin D (with or without calcium) or get inactive placebos for comparison.
Those types of studies offer the strongest kind of evidence on whether the supplements have health effects or not, said Dr. Lars Rejnmark, the lead researcher on the review.
A 9 percent dip in death risk over a three-year period might sound small. To put it in context, Rejnmark’s team — some of whom have connections to supplement makers that market vitamin D and calcium products — estimates that to prevent one death, 151 older adults would have to take vitamin D and calcium for three years.