Almost half of all Canadians take at least one dietary supplement regularly such as vitamins, minerals, fiber supplements, antacids and fish oils. Many of these people are in good health and hope to improve their general well-being or prevent chronic disease.
However, scientific evidence suggests that certain high-dose nutritional supplements – such as beta-carotene, vitamin E and vitamin A – have little role to play in preventing chronic disease in healthy individuals, unless there is a diagnosed deficiency in specific micronutrients. Research suggests that these supplements may actually do more harm than good.
As a physician and public health specialist, I have participated in several studies and clinical trials examining the benefits and risks of micronutrients and nutritional supplements, such as selenium, in several populations in North America and Europe.
In a recent study, my colleagues and I found no evidence that selenium supplements help prevent chronic diseases – in this case diabetes – even in areas where the amounts of selenium in the natural diet are relatively weak.
Our study used data from a randomized clinical trial conducted in Denmark and recently published in Diabetes, obesity and metabolism.
There is, on the other hand, a great deal of scientific evidence supporting the effectiveness of other lifestyle modifications for healthy aging and the prevention of major chronic diseases. These include improving overall diet quality, increasing physical activity, abstaining from smoking, maintaining healthy sleep habits and minimizing stress.
Supplements increase the risk of diabetes
In a previous randomized clinical trial conducted in the United States, we observed that relatively high doses of selenium supplements in areas where it is already abundant in the diet (such as the United States) increased risk of type 2 diabetes.
This problem has potential implications for public health for several reasons. First, in the United States and many other Western countries, the use of selenium-fortified foods and nutritional supplements has increased dramatically in recent years. This is due to the perception that selenium and other antioxidant supplements can potentially reduce the risk of chronic diseases.
It is essential to ensure that selenium supplementation does not exacerbate the existing high incidence of newly diagnosed diabetes or cardiovascular disease.
Second, most previous research in this area has been conducted in North American populations where baseline selenium status is considerably higher than in Europe. Dietary selenium intakes vary greatly between countries and regions largely due to the variability in selenium content of plant foods (and therefore animal forage) from one part of the world to another.
Finally, there have been disappointing results from several expensive clinical trials of antioxidant supplements showing not only no health benefits but even a potential danger.
Eat plants, sleep well, exercise more
As stated in a previous editorial published in the Annals of Internal Medicineevidence from current trials is insufficient to recommend routine dietary supplementation in the general population of healthy individuals.
The message is simple: most supplements do not prevent chronic disease or death. Their widespread use is unwarranted and should be avoided.
This message is especially true for the general population without clear evidence of micronutrient deficiencies, who make up the majority of supplement users in the United States, Canada, and other countries.
From a public health perspective, funding should be allocated to policies, campaigns and interventions that improve the dietary habits of the general public and disadvantaged population subgroups – interventions that increase the consumption of plant foods containing the vitamins and minerals needed for optimal health.