Cranberry capsules. Green tea extract. Effervescent vitamin C. Pomegranate concentrate. Beta carotene. Selenium. Grape seed extract. High-dose vitamin E. Pine bark extract. Bee spit.
You name it, if it's an antioxidant, we'll swallow it by the bucket-load. According to some estimates around half the adults in the US take antioxidant pills daily in the belief they promote good health and stave off disease. We have become antioxidant devotees. But are they doing us any good? Evidence gathered over the past few years shows that at best, antioxidant supplements do little or nothing to benefit our health. At worst, they may even have the opposite effect, promoting the very problems they are supposed to stamp out.
It's little surprise that antioxidants have acquired a reputation as miracle health supplements. As long ago as the 1950s, scientists discovered that many diseases - including heart disease, strokes, cancer, diabetes, cataracts, arthritis and neurodegenerative disorders such as Parkinson's and Alzheimer's - were linked to damage caused by highly destructive chemicals called free radicals.
Free radicals are compounds with unpaired electrons that stabilise themselves by oxidising other molecules - including proteins, carbohydrates, lipids and DNA. In the process they often create more free radicals, sparking off a chain of destruction. Oxidative damage accompanies most, if not all, diseases and has even been proposed as a direct cause of some including lung cancer, atherosclerosis and Alzheimer's.
Free radicals are an unavoidable hazard of being alive. We live in an oxygen-rich atmosphere, and radicals, particularly reactive oxygen species (ROS), are natural by-products of respiration. "One per cent of the oxygen we consume turns into ROS," says biochemist Barry Halliwell from the National University of Singapore. "It doesn't sound like much but humans are big animals and we breathe a lot. Over a year a human body makes 1.7 kilograms of ROS." Exposure to X-rays, ozone, tobacco smoke, air pollutants, microbial infections, industrial chemicals and intensive exercise also trigger free radical production.
In the 1980s, however, a potential weapon against free radical damage appeared on the horizon. Scientists had known for a long time that people whose diets are rich in fruits and vegetables have a lower incidence of heart disease, diabetes, dementia, stroke and certain types of cancer - the very diseases that are associated with free radical damage. Now there was an explanation. Fruits and vegetables are a rich source of antioxidants that can neutralise free radicals by donating electrons to them.
Green plants are full of antioxidants for good reason. They are especially vulnerable to oxidative stress since they produce pure oxygen during photosynthesis. To protect themselves they manufacture an assortment of potent antioxidants.
