Vitamin D May Increase Survival in Elderly Women
Elderly women appear to enjoy increased survival from taking vitamin D, according to a new meta-analysis of 50 randomized trials. Researchers found that vitamin D supplementation decreased mortality, but only one type of the nutrient showed significant results.
And the winner is…vitamin D3
Vitamin D supplements are available in several forms. Vitamin D 3 (cholecalciferol) is the same substance produced by the skin when it is exposed to sunlight. According to the Vitamin D Council, it is “the only form of vitamin D that should be used to treat vitamin D deficiency.”
Vitamin D2 (ergocalciferol) is derived from fungal sources and is not naturally present in the human body. It is used in supplements. A metabolite of the vitamin D formed in the skin, 1,25-dihydroxyvitamin D (calcitriol), is referred to as “activated vitamin D.” A fourth form, alfacalcidol, is used to treat low calcium levels in the blood. It is not available in the United States.
In this latest study, a team of eight international researchers analyzed the data from 94,148 participants who had been randomly assigned to take either vitamin D, no treatment, or placebo. The mean age of the participants was 74 years, 79 percent were women, and the average duration of vitamin D supplementation was two years.
Overall, taking any vitamin D was associated with a reduction in mortality, but when the individual forms of vitamin D were evaluated, only one had a significant impact on survival: vitamin D3. Dr. Goran Bjelakovic, of the University of Nis and The Cochrane Hepato-Biliary Group at The Copenhagen Trial Unit, noted that “our analyses suggest that vitamin D3 reduces mortality by about 6%.”
This finding translates into about 200 people taking vitamin D3 for around two years to save one additional life, explained Bjelakovic. The researchers cautioned, however, that although they saw no significant benefits from taking the other forms of vitamin D, there was much less data available on them, so more trials are needed.
In terms of adverse effects, however, the researchers did observe a significantly increased risk of high blood calcium levels (hypercalcemia) associated with alfacalcidol and calcitriol. In addition, a combination of vitamin D3 and calcium was found to significantly increase the risk of kidney stones.
The results of another meta-analysis published in 2010 looked at 28 studies that included nearly 100,000 middle-aged and elderly participants. That analysis showed a significant association between high levels of vitamin D and a reduced risk of developing cardiovascular disease (33% compared with low levels), type 2 diabetes (55%), and metabolic syndrome (51%).
The authors of the latest meta-analysis concluded that vitamin D3 seems to reduce mortality, mainly in elderly women who are in institutions and dependent care environments.
Bjelakovic G et al. Cochrane Database of Systematic Reviews 2011; issue 7, art CD007470. DOI: 10.1002/14651858.CD007470.pub2
Parker J et al. Maturitis 2010; 65(3) 225-36; DOI: 10.1016/j.maturitas.2009.12.013
Vitamin D Council