Study questions benefit of extra Vitamin D
Although some observational studies have suggested that supplements of Vitamin D reduce the risk of vascular disease and mortality, a new placebo-controlled, randomised trial has found that the supplements have no effect on the most common blood markers for cardiovascular risk and death.
Researchers randomly assigned 305 healthy postmenopausal British women to a placebo or to 400 or 1,000 units of Vitamin D. They all started their regimens at the same time of year to assure they all got the same amount of sunlight, which also affects Vitamin D levels.
The study, in the October issue of The Journal of Clinical Endocrinology & Metabolism, found no significant differences between the placebo and treatment groups in blood levels of total cholesterol, LDL, HDL, triglycerides or C-reactive protein, all known risks for heart disease.
Nor were there any differences in insulin resistance or blood pressure. Blood pressure went down in summer and up in winter in all groups — seasonal changes that earlier studies may have mistakenly attributed to Vitamin D supplementation, the authors said.
"The study actually shows that Vitamin D does not protect you against heart disease," said Helen M Macdonald, a senior lecturer at the University of Aberdeen in Scotland, who led the study. "That's not what people want to hear, but it's true."
Nicolas Bakalar