Individuals who take vitamin D supplements appear to have a lower risk of death from any cause over an average follow-up time of six-years, according to a meta-analysis of 18 previously published studies in the September 10 issue of Archives of Internal Medicine, one of the JAMA/Archives journals1.
Past studies have suggested that deficiencies in vitamin D might be associated with a higher risk of death from cancer, heart disease and diabetes—illnesses that account for 60 percent to 70 percent of deaths in high-income nations, according to background information in the article. “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,” the authors write.
Philippe Autier, M.D., of the International Agency for Research on Cancer,
Over an average follow-up period of 5.7 years, 4,777 of the participants died. Individuals who took vitamin D had a 7 percent lower risk of death than those who did not. In the nine trials that collected blood samples, those who took supplements had an average 1.4- to 5.2-fold higher blood level of vitamin D than those who did not.
“Mechanisms by which vitamin D supplementation would decrease all-cause mortality are not clear,” the authors write. Vitamin D could inhibit some mechanisms by which cancer cells proliferate, or it may boost the function of blood vessels or the immune system, they note.
“In conclusion, the intake of ordinary doses of vitamin D supplements seems to be associated with decreases in total mortality rates,” the authors write. “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.”
The meta-analysis “adds a new chapter in the accumulating evidence for a beneficial role of vitamin D on health,” writes Edward Giovannucci, M.D., Sc.D., of the Harvard School of Public Health,
“Research on vitamin D should be continued to clearly elucidate the specific benefits and optimal intakes and levels of vitamin D,” Dr. Giovannucci writes. “Nonetheless, based on the total body of evidence of health conditions associated with vitamin D deficiency, abetted with the results from this meta-analysis, a more proactive attitude to identify, prevent and treat vitamin D deficiency should be part of standard medical care. From a broader public health perspective, the roles of moderate sun exposure, food fortification with vitamin D and higher-dose vitamin D supplements for adults need to be debated.”
1. Arch Intern Med. 2007; 167(16):1730-1737.
2. Arch Intern Med. 2007; 167(16):1709-1710.