A naturally occurring chemical that protects against heart disease could be added to certain foods in an attempt to improve the nation's health, a conference hears today.

Because the substance is not artificial, adding it to food products could be done without having to penetrate complicated legislation, the Biochemical Society was told at Queen Mary and Westfield College.

The call follows the discovery that eating unripe or cider apples could cut the risk of heart attacks.

The apples contain a type of oestrogens known as phyto-oestrogens. These not only protect against disease in the way that several chemicals, known as anti-oxidants, discovered in fruit and vegetables have been found to do, but also by a mechanism unique to oestrogens.

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Tim Ridgway, a researcher at Nottingham University, painted a picture of such apples, selected to produce higher levels of phyto-oestrogens, being grown en masse and the extract added to some processed foods.

The use of artificially increased but naturally occurring phyto-oestrogens circumvents the complex legislation associated with the use of new food additives. The phyto-oestrogen in question, phloridzin, could be produced at low cost and on a large scale from apples grown specifically for their phloridzin content.

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Mr Ridgway said: "The western diet is unlikely to change radically to include foods with cardioprotective properties." Instead, he said, "small changes, for example the inclusion of extracts from early harvested or cider apples, in some foods could markedly increase the phtyo-oestrogen content of the western diet".

Despite recent adverse publicity about oestrogens, which have been blamed for problems such as decreasing male sperm count, phyto-oestrogens have shone through as beneficial chemicals. High levels in soy protein, an ingredient in chinese and eastern food, have already been linked to reduced heart disease and breast cancer.

But Mr Ridgway warned that the additive should be restricted to adults.

Richard Sharpe at the Medical Research Council's Human Reproductive Biology Unit, Edinburgh said: "The evidence for the benefits of phyto-oestrogens in reducing prostate and breast cancer and heart disease in adults is fairly good. But it is equally likely that they may have very adverse effects on children."

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No such harmful effects have been seen in orientals who have eaten phyto-oestrogens throughout their lives. But, he said, "they have had hundreds of years to adapt to their diet".