There has been a lot of interest and a lot of controversy about the need for vitamins and supplements. Part of the problem is that there is very little good research on the subject.

Research is costly, as it requires many subjects who have to be followed over a long period of time, in order to establish whether or not the substance actually prevents the conditions it is purported to. The participants need to be matched with a control group and variables such as age, sex, weight, ethnic background, other diseases and risks all are taken into account.

The most accurate type of trials are called “double-blind” experiments. That means that neither the doctor nor the patient knows if they are taking the drug or vitamin that’s being studied, or a placebo. They’re also randomized, which means that each subject has an equal chance of being in one group or the other, and there is an understanding that the groups are evenly balanced for all the possible variables that may impact the outcome.

If a trial is able to follow these principles and is supported for enough time to see if the vitamin in question makes a difference, then the outcome will be regarded as important by the medical community.

Dr. JoAnn Manson and her colleagues recently published an article in the New England Journal of Medicine (arguably the most prestigious medical journal in the world), after they conducted a trial, called the VITAL study, which looked at whether vitamin D reduces the risk of cancer or cardiovascular disease.

The trial followed rigorous standards, was randomized and had more than 25,800 participants who were followed for more than five years. They showed that adequate doses of vitamin D did not result in a lower incidence of invasive cancers or cardiovascular events, such as strokes and heart attacks.

We do know that vitamin D is important for bone-related diseases, such as osteoporosis. But we cannot advise patients to take vitamin D to prevent cancer or heart disease.

READ: HEALTHY AGING: CANADA’S NEW FOOD GUIDE HAS EVOLVED WITH TIME

I appreciate this study, because I think prevention is a serious and important medical tool. We need to be clear when we discuss prevention, such as quitting smoking or getting more exercise, so that we all have trust in our choices. So if there is no evidence that vitamin D supplements reduce the risk of cancer and heart disease, that gives me confidence as a physician and as a patient that I will make the right choices and not be misled by false claims.

Yes, we need vitamin D for our bones. Yes, we need it even in the summer, as sunblock hampers the absorption of vitamin D. Yes, we need to take it with, or after, food, as it is a fat-soluble vitamin. But no, as this excellent study concludes, it does not decrease our risk of cancer or cardiovascular disease.

The results are certainly disappointing, but we should be grateful for the exemplary quality of the research.