by Saverio Stranges
Almost
half of all Canadians regularly take at least one nutritional supplement such
as vitamins, minerals, fibre supplements, antacids and fish oils. Many of these
individuals are healthy and hoping to improve general well-being or prevent
chronic disease.
Scientific
evidence, however, suggests that some high-dose nutritional supplements — such
as beta carotene, vitamin E and vitamin A — have little role to play in the
prevention of chronic disease among healthy individuals, unless there is a
diagnosed deficiency of specific micronutrients. Research suggests these
supplements might actually do more harm than good.
As
a medical doctor and public health specialist, I have been involved in several
studies and clinical trials examining the benefits and risks of micronutrients
and nutritional supplements, such as selenium, across several populations in
North America and Europe.
In
a recent study, my colleagues and I found no evidence that selenium supplements
help prevent chronic disease — in this instance diabetes — even in regions
where there are relatively low amounts of selenium in the natural diet.
Our
study used data from a randomized clinical trial conducted in Denmark and was
recently published in Diabetes, Obesity and Metabolism.
There
is, on the other hand, ample scientific evidence supporting the effectiveness
of other lifestyle modifications for healthy aging and the prevention of major
chronic disease. These include: improving the overall quality of diet,
increasing physical activity, refraining from smoking, maintaining healthy
sleep patterns and minimizing stress.
Supplements increase 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 plentiful in the diet (such as the U.S.) actually increased the risk of Type 2 diabetes.
This
issue has potential public health implications for several reasons. First, in
the U.S. and many other Western countries, use of selenium-enriched foods and
nutritional supplements has increased markedly in recent years. This is because
of a perception that selenium and other anti-oxidant 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 substantially higher than in
Europe. Dietary intakes of selenium vary considerably between countries and
regions largely due to the variability of the selenium content of plant foods
(and hence of animal forage) from one part of the world to another.
Lastly,
there have been disappointing findings from several costly clinical trials of
antioxidant supplements showing not only no
health benefits but even potential harm.
Eat plants, sleep well, exercise more
As
reported in a previous editorial published in the Annals of Internal Medicine,
the current trial evidence is insufficient to advise routine dietary
supplementation in the general population of healthy individuals.
The
message is simple: most supplements do not prevent chronic disease or
mortality. Their widespread use is not justified, and they should be avoided.
This
message is especially true for the general population with no clear evidence of
micronutrient deficiencies, who represent the majority of supplement users in
the U.S., Canada and other countries.
From
a public health perspective, funding should be allocated to policies, campaigns
and interventions that improve dietary patterns in the general public and
disadvantaged population subgroups — interventions that increase consumption of
plant foods containing the required vitamins and minerals for optimal health.
Saverio Stranges is currently Professor and Chair of the Department of Epidemiology & Biostatistics within the Schulich School of Medicine & Dentistry, at Western University, in London, Ontario, Canada. This article originally appeared in The Conversation
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