Antioxidants‑those wonderful nutrients that you find in blueberries, or green tea, or high dose capsules from the health food shop. The ones that can prevent cancer, cure the common cold, make your hair shiny and help you lose weight‑or so the food and supplement industries would have us believe. They’re added to everything from breakfast cereals and sports drinks to shampoo, alongside prominent claims about their health benefits.
 
We hear about them so often, it’s easy to get carried along with the idea that antioxidants must be good for us. Let’s take a closer look at the claims, though, and see what the research actually says.
 
What are antioxidants, and why are they supposed to be good for us?
 
Oxidation is a chemical process that takes place all around us, as well as inside us. It’s what happens when substances combine with oxygen from the air‑when something burns, for example, or iron rusts. (The formal definition is more technical than this, but it’ll do for our purposes).
 
We need oxidation in order to stay alive. It allows us to break down food and use it for energy, for example. These oxidation reactions often create a type of molecule called a “free radical,” and free radicals, left unchecked, can cause chains of chemical reactions that have the potential to damage cells. If free radicals are the “bad guys” of biochemistry, then antioxidants are often presented as the superheroes‑substances that can help to neutralize free radicals and prevent them from causing cellular damage.
 
Vitamin C, vitamin E, beta-carotene, coenzyme Q10 and selenium are examples of antioxidants; between them they’ve been touted as miracle cures for just about every disease under the sun. Megadoses of these substances are available in health food shops, and they’re routinely used to promote “healthy” products and “superfoods”.
 
Excellent. So how do I get more antioxidants in my diet? What are the best supplements to buy?
 
Not so fast. It’s an easy story to get sucked in by‑free radicals cause cellular damage and antioxidants mop up free radicals, so they must be good for us‑but as is so often the case, reality turns out to be more complicated than that.
 
First of all, not all antioxidants are the same. Antioxidants occur naturally in many of the foods we eat, such as fruit and vegetables. It’ll come as no surprise to discover that a diet high in fruit and vegetables turns out to be good for you. People who eat more fruit and vegetables are less likely to suffer from cardiovascular disease, some cancers and type 2 diabetes, amongst other conditions. When we look more closely, though, it’s unclear whether it’s the antioxidants that give us the benefit, or something else about the fruit and vegetables. Some research suggests that the health benefits are due to the complicated mix of different phytochemicals, rather than any isolated substance. Suggesting that one food is better than another because it contains “more antioxidants” is overly simplistic marketing hype that’s been dressed up to sound reassuringly scientific. It’s even difficult to separate the benefits of fruit and vegetables themselves from the fact that people who eat more fruit and vegetables are likely to benefit from having a lifestyle that’s healthier in lots of other ways.

Evidence for the benefits of antioxidant supplements‑high doses of vitamin C, vitamin E, beta-carotene, coenzyme Q10 or selenium, for example‑is even murkier. While a few studies have shown that in some circumstances, supplementation may have certain very specific benefits; other studies have shown it to be no better than placebo. Worse still, there have been trials that have concluded that people taking antioxidant supplements were at a higher risk of some conditions.

The most recent Cochrane Review of the evidence (2012)concludes that there is no evidence to support the health benefits of antioxidant supplementation, and that in particular beta-carotene and vitamin E may be associated with an increased mortality rate.

The theory that antioxidants might improve athletic performance by protecting our bodies from free radicals also appears to fall flat on its face when the evidence is examined carefully. In fact, there’s a real possibility that supplementation might be counterproductive and actually reduce some of the beneficial effects of exercise.

There are a few theories as to why antioxidant supplements may not be all that great for you after all. Firstly, there’s the problem we mentioned above - fruit and vegetables appear to be good for you, but we don’t know whether that’s got anything to do with antioxidants. But even if antioxidant containing foods are good, that doesn’t mean that taking the antioxidants out of the foods and selling them to you in high dose capsules will have the same effect: just because a little of something is good, it doesn’t mean that more of it is better.

Secondly, the idea that “free radicals” are the bad guys and antioxidants have the power to stop them in their tracks isn’t the whole story. Free radicals may contribute to some problems, but they also have an important role to play in the body. For example, oxidation may help to inhibit the metastasis of some cancer cells and recent research suggests that antioxidants may help certain cancers to spread faster. We should always beware of simplistic ideas in biology, and this is a good example of why that’s the case.

Finally, there’s also the danger that people diagnosed with a serious disease might buy into the hype and take supplements instead of seeking proper medical treatment. Among those who take supplements alongside regular medical care, many don’t tell their doctors what they’re taking and run the risk that they might interfere with prescribed medicines.

Verdict: at least partially false.

Keep eating a varied diet rich in different types of fruits and vegetables, because we’re pretty sure that’s good for you. As we mentioned last month when we talked about organic food, though, there’s no real evidence that foods with higher levels of antioxidants are better than those with lower levels, so by all means pick the vegetables that you like (and can afford) rather than paying over the odds for the latest “antioxidant rich superfood”.

Although it’s possible that more research in future will discover that supplements containing particular antioxidants are helpful for some specific conditions, at the moment there’s no reason to think there are any general health benefits, and there’s a very real possibility that supplementation actually does more harm than good.