Dr Alan Crozier on why flavonols are healthy

Flavonols are antioxidants which can protect against cancer, heart disease, degenerative illnesses and the effects of ageing.

The research could be a factor in why people who eat a Mediterranean diet live longer.

Scientists from Glasgow University have found that some fruits and vegetables have more flavonols than others.

Tiny cherry tomatoes have many more of the chemicals than bigger tomatoes, for example.

Red onions are full of flavonols while the white version has almost none.

Red-coloured Lollo Rosso lettuce has 100 times more flavonols than ordinary lettuce.

Wines whose grapes are left to ripen for a long time in the sun, such as Chilean Cabernet Sauvignon and some French red wines, are also more flavanol rich.

Top healthy wines include Cabernet and Merlot, while Beaujolais has a relatively low level of the chemicals.

Wide variation

Dr Alan Crozier, reader in plant biochemistry from the Institute of Biomedical and Life Sciences at Glasgow University, said: "What our data shows is there is a surprisingly wide variation of flavonol levels in very similar products.

Supermarkets may seek to promote flavonol-rich produce

"A tomato is not just a tomato - there are different types. You can select a different variety and your flavonol content will increase dramatically."

He added that the research showed that people could increase their flavonol levels and their health with a relatively simple change in diet.

Flavonols work by mopping up free radicals in the body.

These are by-products of the body's chemistry and destroy cells and their DNA.

Scientists are only just beginning to understand the role of flavonols.

And unlike many vitamins, the chemicals are not destroyed by cooking.

They even remain after boiling, although in lower levels.

"You can fry the hell out of your tomatoes and still get 75% of your flavonols present," said Dr Crozier.

He and his team are working with supermarket chain Safeway to develop a comprehensive list of flavonol-rich food.

Beneficial

A spokeswoman from the British Nutrition Foundation said the research was further proof of the benefits of eating fruit and vegetables.

It recommends five portions a day.

"Fruit and vegetables have an enormous benefit for the diet. You cannot go far wrong with them," said the spokeswoman.

As well as flavonols, fruit and vegetables contain other antioxidants, including vitamins A, C and E.

And tomatoes - particularly processed tomatoes - contain lycopene.

The spokeswoman, however, said it would be worrying if interest in antioxidants led to people rushing to buy the chemicals in pill form.

"The dietary approach is best as we do not know what concentrations are in fruit and vegetables and which is the most beneficial," she said.