So'(y) ... what's new? News reports make it sound more like a drug than a simple bean--how good is the evidence and is soy's safety in question? (Nutrition: soy).

Publication: Choice (Chippendale, Australia)

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COPYRIGHT 2003 Australian Consumers' Association

It's the new yoghurt: as yoghurt was to the seventies, soy is now--just the mention of it smacks of cutting-edge healthy eating.

You might not be a big tofu eater, but there are many foods that contain soy, some whose whole being centres around it: breads, cereals, drinks, 'nondairy' products, juices, noodles and burgers can all be found with soy as a selling point.

But how good is the evidence that soy is something special? Here we look at the claims made for it and the scientific reality behind them, plus weigh up the evidence about claims that soy isn't safe.

A SOY GLOSSARY

Before we go any further, a brief rundown of the soy vocabulary will help:

* Phytochemicals are substances that occur natually in plants (from the Greekphyton).

* Phytoestrogens are a group of phytochemicals that have a similar structure to the hormone oestrogen. Because of this similarity, they may be able to affect the systems and processes in the body where oestrogen acts. They're found in legumes such as soy and seeds (especially linseed), but also in whole grains, nuts and many fruits and vegetables.

* The two main types of phytoestrogen are isoflavones and lignans. Soy is rich in isoflavones and these may have a role to play in the effects of soy on health.

HEART DISEASE

The claim: Soy can lower high cholesterol and reduce the risk of heart disease.

The reality: It can, but you've got to eat a lot to reduce high cholesterol--though smaller amounts may be useful to prevent it developing.

Scientific studies support the idea that soy can reduce high cholesterol levels and so the risk of heart disease, but we're not talking a little soy once in a while--rather a concerted effort to get at least 25 grams of soy protein a day into your diet. That's the amount that both the us and UK governments have settled on as helping to reduce cholesterol. There are no Australian recommendations at this stage.

The US government allows foods that contain one quarter of this amount (6.25 g) in a serve to make a cholesterol-lowering claim, suggesting people with a cholesterol problem would need to eat four serves per day. But experts have suggested that even most Asians (who traditionally eat a lot of soy and have a lower risk of heart disease) wouldn't eat that much: it amounts to around three cups of soy milk or 200-300 g of tofu a day.

In fact, reducing already high cholesterol levels isn't the whole picture. Many experts consider the real value of soy may lie in its ability to prevent...

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