Mounting evidence suggests routine vitamin D supplementation reduces all-cause mortality.
“We may finally have a vitamin that translates into greater longevity,” declared Dr. Robert A. Vogel, professor of medicine at the University of Maryland, Baltimore, at a conference sponsored by the Society for Cardiovascular Angiography and Interventions.
Given the high likelihood that vitamin D supplementation provides a survival benefit, its demonstrated lack of harm, and the pervasiveness of vitamin D deficiency, it's now reasonable for physicians to routinely recommend taking a daily 400- to 1,000-IU vitamin D3 supplement, he said at the conference, which was cosponsored by the American College of Cardiology.
He pointed to a recent meta-analysis by investigators at the International Agency for Research on Cancer in Lyon, France, as a key piece of evidence in the evolving vitamin D story. The French investigators identified and analyzed 18 randomized trials of vitamin D supplementation with 57,311 generally healthy participants that included total mortality as a secondary end point; the primary end point was typically fracture risk.
All-cause mortality during a mean 5.7 years of follow-up was reduced by a statistically significant 7% in subjects randomized to vitamin D. In studies in which the intervention lasted at least 3 years, the reduction in mortality from any cause was 8% (Arch. Intern. Med. 2007;167:1730-7).
In an accompanying editorial, Dr. Edward Giovannucci called the meta-analysis “skillfully done” and the findings “remarkable,” adding that the results probably underestimate the true benefit in reducing mortality if vitamin D is important in influencing the development of cancer, cardiovascular disease, and other chronic diseases.
“Based upon 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,” said Dr. Giovannucci, professor of nutrition and epidemiology at Harvard University, Boston.
Dr. Vogel noted that beyond vitamin D's well-established effects upon calcium and bone, the hormone vitamin also functions in gene regulation, regulation of cell proliferation and differentiation, production of antibiotic peptides, and innate immunity.
Most foods contain very little vitamin D; it's a vitamin that is dependent upon UVB exposure. Coronary heart disease events are more frequent in the winter and in cooler climates, where there is less sun exposure.
What constitutes an adequate serum vitamin D concentration is a topic of debate. Many nutrition experts say a 25-hydroxyvitamin D level of 30-35 ng/mL is a reasonable target; others argue that is two- or threefold too low.
Dr. Vogel said a recent British twin study offers a glimpse of the magnitude of the possible longevity-promoting impact of vitamin D supplementation. The investigators measured serum vitamin D concentrations and leukocyte telomere length in 2,160 members of female twin pairs aged 18-79 years.
The investigators at St. Thomas' Hospital, London, found that serum vitamin D level was positively correlated with leukocyte telomere length after adjustment for age, menopausal status, physical activity, and other factors. The difference in mean telomere length between women in the lowest tertile, who had a mean serum vitamin D of 41 ng/mL, and those in the top tertile, where serum vitamin D averaged 124 ng/mL, was 107 base pairs. That's the equivalent of 5 years of telomeric aging (Am. J. Clin. Nutr. 2007;86:1420-5).
The ability to turn back the clock on the basic biology of human aging by a full 5 years via vitamin D supplementation is particularly impressive in light of the more modest—albeit certainly worthwhile—longevity gains to be had from lifestyle modification, Dr. Vogel observed.
He cited the Harvard Alumni Study, which he considers the best data available on the longevity impact of lifestyle change. In nearly 91,000 person-years of follow-up of 10,269 middle-aged men, remaining thin throughout life conferred roughly an additional half-year survival. Becoming physically active or taking up a moderately vigorous sport was associated with a similar increase in longevity (N. Engl. J. Med. 1993;328:538-45).
Of course, a dose of humility is appropriate. “We were wrong on vitamin A. We were wrong on vitamin B. We were wrong on vitamin C. We were wrong on vitamin E. Except for K, there's only one letter left—and that's D,” Dr. Vogel quipped.
Yeah for vitamin D!