It was no April Fool’s joke when, on the first day of this month, two significant studies were published that link low levels of vitamin D with a greater likelihood of dying of heart disease and cancer, and of becoming ill with other illnesses as well. Correlation may not imply causation; a low level of the sunshine vitamin may reflect other lifestyle/diet factors that contribute to disease, rather than itself cause disease.
The two studies, both of which appeared in the journal BMJ, are meta-analyses, including data on more than a million people. They include observational findings as well as evidence from randomized controlled trials.
One study, conducted by Harvard and Oxford University researchers, along with members of other institutions, finds that adults with lower levels of vitamin D have a 35% greater chance of dying of heart disease and a 14% higher risk of dying of cancer. The researchers report that ingesting supplements of vitamin D2 confers no benefit, but that, for adults, supplementing diet with vitamin D3 is associated with an 11% reduction in death from all causes. The researchers conclude that Vitamin D deficiencies contribute to 13% of deaths in the United States.
The other study, conducted by researchers from Stanford and several European universities, is somewhat more conservative in its conclusions. While acknowledging “suggestive evidence” that high vitamin D levels have a protective effect against hypertension, diabetes, and other diseases, they assert that “highly convincing” evidence is lacking for the value of vitamin D supplementation. Addressing the widespread belief that such supplements are useful as a tool against osteoporosis, they say, “vitamin D may not be as essential as previously thought in maintaining bone mineral density.” Read more in a New York Times article.