How food helps

Antioxidants

Much of the focus on healthy foods concerns the way they combat harmful substances called "free radicals".

Free radicals are made in the body during normal metabolism and during exposure to infection, UV light, pollution, radiation and even exercise. The body has "antioxidant" enzymes and other defence mechanisms to neutralise the free radicals, but when more free radicals are produced than are neutralised, they can damage the cells of the body.

This is where food comes in. Many of the phytochemicals in fruit, vegetables and other plant foods have an antioxidant action and will mop up the free radicals so they are no longer harmful. Numerous studies have demonstrated an association between high intakes of antioxidants, especially from fruit and vegetables, and a lower risk of cancers and cardiovascular disease.

Get it in a pill?

But individual substances in foods don't always work on their own. Studies have shown when substances are isolated out of food and concentrated as supplements, they don't seem to confer the same benefits. Studies of beta-carotene and vitamin E, for example, have failed to produce anticipated benefits.

In fact, completely opposite negative effects have occurred, producing increased cancer and /or cardiovascular risk in some people.

Current advice, therefore, recommends avoiding high doses of antioxidant supplements.

"I'll have a beer and a chocolate fish, thanks"

Though poor diet has a big effect on poor health, science is struggling to pin down exactly which ingredients in a good diet make the biggest difference to health. Alcohol, fish and chocolate have all been found to have positive effects, but fruit and vegetables seem to be emerging as the biggest heroes.

It seems increasingly likely that regular, generous servings of fruit and vegetables offer the most protection against the ravages of degenerative disease. Their magic comes not only from the vitamins, minerals and fibre they contain but also from phytochemicals. Thousands of these chemicals, many present in only tiny amounts, are thought to have protective effects on our health.

More than diet

It's worth remembering that diet isn't everything. Failure to get enough exercise, being overweight, smoking and a genetic predisposition to certain diseases are also important.

Good food isn't a cure for or a guarantee against degenerative disease, but a good diet overall does reduce the risk. If your family medical history increases your chances of getting heart disease or cancer, a good diet may slow the process or take you from high to moderate or low risk.

Other dietary factors can also make a difference. Saturated (animal) fats contribute to heart disease and some cancers. Charred and smoked meats, and those preserved with nitrates (bacon and corned meats), are known to be carcinogenic if consumed in quantity. Nuts and grains contaminated with the mould that produces aflatoxin are also known to cause cancer.