EATING soya for just a few weeks makes you smarter, by improving your memory and allowing you to think more flexibly. So says the author of a small new study, but other experts dispute the findings.
Soya is rich in chemicals that resemble human oestrogen. Some claim that these 鈥減lant oestrogens鈥� have many benefits, from preventing breast and prostate cancer to easing the symptoms of the menopause. Other studies have revealed potential health risks (New Scientist, 11 May, p 16). But do plant oestrogens also affect our mental abilities?
To find out, Sandra File and her team at King鈥檚 College London put 27 students and 33 post-menopausal women on a diet that was either high or low in soya. After 10 weeks on the high-soya diet, both male and female students showed improvements in memory and mental flexibility, File told a conference in London last month. For example, on average they recalled 14 pictures out of 22 instead 12. 鈥淭hat鈥檚 a figure that would make a difference to your life,鈥� she says. The post-menopausal women also showed marked improvements in their mental flexibility and ability to plan ahead. They were better at remembering pictures, though other forms of memory didn鈥檛 improve.
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But Sanne Kreijkamp-Kaspers at the University of Utrecht in the Netherlands thinks the improvements occurred because the diet relieved post-menopausal depression, rather than affecting memory directly. She also points out that the number of participants was small. 鈥淚 do not attach much confidence to this study,鈥� she says.
In a larger, longer-term study of 115 post-menopausal women, Kreijkamp-Kaspers found no evidence that plant oestrogens improve brain function. But File says this study did not test the skills that showed the greatest improvements in her study.