Soy isoflavones show no impact on health in older women

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The increasingly popular supplements of soy isoflavones do not seem
to help lower cholesterol, improve bone mineral density or benefit
brain function after menopause, new research suggests.

Isoflavones, compounds found in soybeans that are similar to the female hormone oestrogen, have been increasingly researched in recent years for their potential as an alternative to hormone replacement therapy, to counter the changes that often accompany the loss of estrogen in menopause.

They are thought to help reduce hot flushes and other symptoms of the onset of menopause. There is also some research showing that they could help protect bone mineral density, of particular concern to postmenopausal women as the lower levels of oestrogen have a negative impact on bone health.

This has prompted significant sales increases over 2003 for isoflavone suppliers, with both Israeli firm Solbar and the Netherlands-based Acatris reporting 30 per cent rises.

But a new study in today's issue of the Journal of the American Medical Association​ (292:65-74) appears to counter much of the suggested benefits of soy isoflavones for postmenopausal women.

Researchers from the University Medical Center in Utrecht, the Netherlands, followed 202 healthy women between the ages of 60 and 75 for one year. The participants were randomly assigned to receive either 25.6 g of soy protein containing 99 mg of isoflavones (52 mg genistein, 41 mg daidzein, and 6 mg glycetein) or a milk protein powder, as control, everyday for a year.

None of the outcomes - cognitive function, bone mineral density, or plasma lipids - differed significantly between the soy and placebo groups at the end of the study, said the researchers.

They write: "This double-blind randomized trial does not support the hypothesis that the use of soy protein supplement containing isoflavones improves cognitive function, bone mineral density, or plasma lipids in healthy postmenopausal women when started at the age of 60 years or later."

The authors noted that the isoflavone supplement may not have worked because the women featured in the study were very healthy. Also, both bone density and cognitive function decline relatively slowly and a one-year intervention may not have been long enough to detect an effect.

Related topics: Dairy Health Check, Ingredients