But there have been suggestions that soya could interfere with a woman's hormone levels, and encourage the growth of some breast tumours.

This is because soya contains plant sex hormones called phytoestrogens, which mimic the action of human sex hormones.

But the finding, at the University of Toronto's department of nutritional sciences, also suggests that women who believe that soya-rich diets could have a similar effect to hormone replacement therapy may be mistaken.

The hormone examined by the researchers was the female sex hormone oestrogen.

Some breast cancers are sensitive to this hormone, meaning that their rate of growth can be influenced by the levels of the hormone in the body.

Researchers took urine samples from women put on a low fat diet over two one-month periods.

Half were also given soya products in their meals.

The urine was tested on human breast cancer cells. The presence of oestrogen stimulates them to produce a particular protein, so levels of this were then measured.

They found the women eating soya actually appeared to have less oestrogen in their urine than those eating a normal low-fat diet.

Some breast cancer cells are sensitive to hormones

Professor David Jenkins, who led the study, said: "The concerns have been whether soy oestrogen might lead to hormone dependent breast cancer, or abnormal sexual development in children, yet we found no evidence of this.

"It suggests that soy may not have the oestrogenic effects that were thought to alleviate menopausal symptoms - but it refutes claims about its purported hormone risks."

The heart health benefits of soya are well-established.

It reduces the amount of so-called "bad" low density lipoprotein cholesterol in the body, while maintaining the amount of "good" high density lipoprotein cholesterol.

Research from Professor Jenkins also shows that soya reduces the amount of a type of cholesterol which is more likely to clog up arteries.