Many women swear by chemicals found in soy to relieve the effects of the menopause - but research has undermined evidence of some benefits.

The research found that there was no difference in the hormone levels of women taking the supplements compared with other women.

Soy is said to work because it contains plant hormones called phyto-estrogens - which are similar in structure to a sex hormone produced by women.

When the menopause diminishes the production of female sex hormones, it is claimed the phyto-estrogens can partially mimic them and relieve symptoms such as hot flushes and night sweats.

Proponents of soy claim they can also reduce cholesterol levels in the blood stream, perhaps extending the protection against heart disease enjoyed by pre-menopausal women. However, a team of researchers from the University of Illinois School of Public Health in Chicago carried out tests on 73 postmenopausal women, none of whom was taking HRT.

They were given diets including either low or high doses of soy chemicals, or one containing a milk protein. Blood samples were collected at the beginning of the study and after three and six months on the diets. However, over time, there was no significant difference in the levels of several hormones between the three groups.

The researchers concluded that there was no evidence that soy intake was having any effect on levels of key sex hormones in the blood, which might bring relief from menopausal symptoms. 'More research needed'

American Journal of Clinical Nutrition January 2002