After following up on individuals who took vitamin D supplements for six years, researchers have concluded that it does lower one’s risk of death from any cause. The researchers looked at 18 previously published articles and wrote a report which appears in Archives of Internal Medicine (JAMA/Archives), September 10 issue.

Previous studies had indicated that there is a link between a higher risk of death from heart disease, cancer and diabetes for people with vitamin D deficiencies. In developed countries, these illnesses make up 60-70% of all deaths due to illness, the writers explain. They write “If the associations made between vitamin D and these conditions were consistent, then interventions effectively strengthening vitamin D status should result in reduced total mortality.”

In this study, Philippe Autier, M.D., International Agency for Research on Cancer, Lyon, France, and Sara Gandini, Ph.D., European Institute of Oncology, Milano, Italy, looked at randomized controlled vitamin D supplement trials published prior to November 2006. This led them to 18 different trials involving 57,311 participants. They evaluated the doses of vitamin D – this ranged from 300 to 2,000 international units, the average dose being 528 international units. Most supplements one buys in the high street are around 400-600 international units.

4,777 of the participants died during an average follow-up of 5.7 years. The authors wrote that those who took vitamin D had a 7% lower risk of dying compared to those who did not. Blood samples were taken in nine of the trials that the researchers examined. They found that people who took vitamin D supplements had 1.4 to 5.2 times the level of vitamin D in their blood compared to those who did not.

The authors explained that the mechanisms by which vitamin D supplementation would decrease all-cause mortality are not clear. Vitamin D may undermine some mechanisms which help cancer cells proliferate, on the one hand, or it could boost the function of blood vessels or the immune system, they added.

The authors concluded that “..the intake of ordinary doses of vitamin D supplements seems to be associated with decreases in total mortality rates. The relationship between baseline vitamin D status, dose of vitamin D supplements and total mortality rates remains to be investigated. Population-based, placebo-controlled randomized trials in people 50 years or older for at least six years with total mortality as the main end point should be organized to confirm these findings.”

Arch Intern Med. 2007;167(16):1730-1737

Written by: Christian Nordqvist