Beans' benefits brought back down to earth
Two new studies on soya shed light on the cognitive and cardiovascular benefits of the ancient Asian dietary staple for older women. The first study, published today in Neurology, the medical journal of the American Academy of Neurology, suggests that soya protein may not preserve overall thinking abilities in post-menopausal women, contrary to earlier reports. However, a high soya protein diet did not appear to harm thinking skills either.
'Our study found long-term use of soya protein neither improved nor impaired overall cognition,' says study author Dr Victor W. Henderson, with Stanford University in Palo Alto, California.
More than 300 healthy women between the ages of 45 and 92 were given 25 grams of soya protein daily - a dose comparable to that of traditional Asian diets - or a milk protein-matched placebo. Participants were also given tests that measured memory and other thinking abilities at the start of the study and 2 1/2 years later.
The study found no significant change in test scores in both groups. There was, however, a small improvement in visual memory, or facial recognition, in the soya protein group compared to the milk protein group, by about 13 per cent.
In the other study, published last week in The American Journal of Clinical Nutrition, researchers from Baylor College of Medicine in Houston examined whether soya isoflavone supplements provided cardiovascular benefits, such as cutting blood pressure or cholesterol levels.
Previous research had shown that Asian populations with soya-rich diets have lower rates of heart disease than people who eat Western diets. But the researchers found that soya supplements alone may not do anything for older women's blood pressure.
Twenty-four menopausal women, all with moderately elevated blood pressure, were randomly assigned to take either 80mg of soya isoflavones or placebo tablets daily for six weeks. Those taking the soya supplement were found to fare no better than those on the placebo (that is, on the upper threshold of 'normal').
Special blood tests were also done to see whether the soya supplement affected the production of nitric oxide, a chemical that dilates blood vessels. No effect was found.