there was a time when everybody was taking vitamin d to prevent everything from heart disease to cancer. but as one editorialist recently put it, “then came the randomized trials.” in fact, 2019 has not been a good year for vitamin d. a lot of the trials that came out this year have been negative.
firstly, a meta-analysis in jama cardiology of 83,000 individuals from 21 randomized trials found that vitamin d did not help reduce the risk of cardiovascular disease, heart attack stroke or death.
in terms of cancer risk, in january the large vital study was published in the new england journal of medicine and showed that vitamin d did not prevent breast, prostate or colon cancer, nor did it prevent cancer deaths overall. in april the amaterasu randomized trial studied 417 patients with gi cancer and found that giving them vitamin d did not improve five-year survival.
come summer, the publication of the d2d study showed that vitamin d did not reduce the risk of developing diabetes in patients who were pre-diabetic. also, a research letter provided data on the six-year follow-up of a danish study looking at whether giving vitamin d to pregnant women reduced the probability that their children would develop asthma. it did not. finally, the recently published vital-dkd found that vitamin d did not help preserve kidney function in people with diabetes.
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christopher labos is a montreal doctor and an associate with the mcgill office for science and society. he also co-hosts a podcast called the body of evidence.