Dr David Stevenson, a senior scientist with Plant & Food Research, explains that recent research into the activity of polyphenolic antioxidants has shown that they have more of a pro-oxidant effect rather than an antioxidant effect. This generates a mild oxidative stress, which the body responds to by up-regulating its own antioxidant defences. It is thought to be similar to the response the body makes to exercise.
Point of interest
Could eating a daily dose of fruit and vegetables have the same beneficial effect on the body as engaging in a bout of mild exercise?
DR DAVID STEVENSON
The reason we are interested in understanding how polyphenolic antioxidants work is that it used to be thought that the antioxidants in the body functioned the same way as they do in the chemical assay – they are just neutralised free radicals.
We now know that does happen but it’s a very minor effect, because our bodies have all sorts of antioxidant defences. And on top of that, the polyphenols maybe make 1 or 2% difference, and that can’t really explain all the apparent health benefits of consuming polyphenols in fruit and vegetables.
The new theory of how antioxidants work is actually that they are what they call pro-oxidants, which actually generate a mild oxidative stress, and that then up-regulates or stimulates the body’s own antioxidant defences. And so you get a huge effect from a small amount of what you might call an antioxidant.
So we now think antioxidants actually have a similar effect to exercise. We know that exercise generates oxidative stress and that then signals all the beneficial adaptations so that we can exercise better.
We now think that some of the polyphenols can actually get into the mitochondria and cause a mild disruption to their metabolic pathways and generate an oxidative stress which, to the cells looks exactly the same as exercise, like a vaccine stimulating the immune system – it’s the same principle.
Eating fruit and vegetables may well have a similar effect to doing exercise. It doesn’t mean we can give up exercise, because there are lots of things that exercise does which simply stimulating oxidative stress won’t do, like strengthening bones and muscles and things like that.