If you're a fan of tofu, here's some bad news. A new study has suggested that consuming high levels of some soy products - including tofu - may increase the risk of dementia.
Dementia is the progressive decline in cognitive function due to damage or disease in the brain beyond what might be expected from normal aging.
AdvertisementThe Loughborough University-led study focused on 719 elderly Indonesians living in urban and rural regions of Java, reports BBC.
It showed that high tofu consumption - at least once a day - was linked to worse memory, particularly among the over-68s.
Soy products are a major alternative protein source to meat for many people in the developing world.
However, in recent years, soy consumption has gone up in the West where it is often promoted as a 'superfood'.
Soy products are rich in micronutrients called phytoestrogens, which mimic the impact of the female sex hormone oestrogen.
There is some evidence that they may protect the brains of younger and middle-aged people from damage - but their effect on the ageing brain is less clear.
The new study suggests that high levels of phytoestrogens may actually raise the risk of dementia.
Lead author Professor Eef Hogervorst said that previous study had associated oestrogen therapy to a doubling of dementia risk in the over-65s.
She said that oestrogens and probably phytoestrogens tended to promote growth among cells, not necessarily a good thing in the ageing brain.
Alternatively, high doses of oestrogens might promote the damage caused to cells by particles known as free radicals.
A third theory is that damage is caused not by the tofu, but by formaldehyde, which is sometimes used in Indonesia as a preservative.
According to Professor David Smith, of the University of Oxford, tofu was a complex food with many ingredients, which might have an impact.
However, he said: "There seems to be something happening in the brain as we age which makes it react to oestrogens in the opposite way to what we would expect."
Hogervorst stressed that there was no suggestion that eating tofu in moderation posed a problem.
Rebecca Wood, of the Alzheimer's Research Trust, which funded the study, said more research was needed to pin down the potential risks and benefits of so-called superfoods.
However, she said: "This kind of research into the causes of Alzheimer's could lead scientists to new ways of preventing this devastating disease.
The study is published in the journal Dementias and Geriatric Cognitive Disorders.