Antioxidants: hype or… hazard?

Vitamin and mineral supplements are big business. So although the manufacturers make a lot of claims, can you really believe what they say?

Multivitamins complete a to z, 250 tablets (click to embiggen)
Bottle of multivitamin supplements, complete a to z (Photo by Mike1024, via Wikimedia Commons)
For that matter, how do you know whether to believe any claims about medical products? With the amount of money involved in the health industry, there’s, well, a bit of a temptation to shape the truth.

In mid-2009, an entire scientific journal, the Australasian Journal of Bone and Joint Medicine – put out by the prestigious publisher Elsevier – was found to be basically an advertising brochure for the pharmaceutical company Merck. It claimed to cover reviews of research, but all the reviews were all suspiciously favourable to Merck’s products.

(Shortly after, Elsevier revealed that another 5 Australian journals were also sponsored by pharmaceutical companies.)

So where do you turn for real, reliable medical research?

Logo of the Cochrane Collaboration

Me, I like the Cochrane Collaboration – an independent, international organisation of over 28,000 volunteers who do systematic reviews of medical research.

What this means is they add together all the trials that have been done on a particular topic, to find the patterns in the pooled data. Because science never rests on one single study that overturns everything: it’s replication (or not) of the research by other scientists that eventually builds a consensus.

In these reviews, preference is given to randomised controlled trials, which are studies where you randomly choose which patients get a certain treatment and which are given a control, or placebo, to compare what would happen without the treatment. The best trials try to remove all bias by blinding the patients, the people giving out the treatments and the people measuring the results – that is, none of them know in advance who’s given the treatment and who’s given the control.

Their reviews are then published online in The Cochrane Library. Since 2002, the Australian Government has paid for a subscription that gives all Australians free access to the Cochrane Library. You can search on any topic, and each review includes a plain language summary so that anyone can understand it.

This is free access to the best summaries of research on hundreds of health-related topics, so it’s worth taking advantage of.

Okay, so what do the Cochrane Library have to say about vitamin and mineral supplements? Well, let’s look at one recent review that examined antioxidants.

As the name suggests, antioxidants are chemicals that help prevent oxidation, which is a type of chemical reaction. One example of an oxidative reaction is combustion, i.e. good old burning, like the burning of energy in the human body. But oxidation can cause damage as well, like deterioration to proteins and DNA (as an example of damaging oxidation, see rust).

For this reason, our bodies use a whole lot of natural antioxidants to control these reactions. So the theory is that if you consume more antioxidants, you protect yourself against damaging oxidation.

Unfortunately, clinical trials performed on real people in the real world show a different result. These trials were last reviewed by the Cochrane Collaboration in January 2010: Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C, “Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases”, Cochrane Database of Systematic Reviews 2008, Issue 2 (By “prevention of mortality” they simply mean, do supplements reduce your chances of dying, which is probably the simplest way to measure if a medicine helps.)

This review looked at 67 randomised trials with 232,550 participants, examining the effects of antioxidant supplements like beta-carotene, vitamin A, vitamin C, vitamin E and selenium. What they found was that, putting all these studies together, there was no evidence to say that taking supplements reduces your chance of dying.

In fact, there were indications that vitamin A, beta-carotene and vitamin E may actually increase your chances of dying. This wasn’t found in all the trials, but it did happen more in the larger and better quality trials.

So further research is needed, but overall there’s no good reason to take antioxidant supplements.

But remember, we’re talking about supplements here. Eating a balanced diet of fruits and vegetables does still seem to be good for you – just don’t assume the benefits are due to antioxidants.

So, as is often the case with these sorts of things, once you clear away the hype it’s the same old, simple recommendations: eat a balanced diet, get plenty of exercise – and listen to your doctor.

But when you hear about medical research, and you want to check how reliable it is, try the Cochrane Library: go to


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