Eating tofu and other soy foods may lead to memory loss, but one soy product may have the reverse effect, a British study has found.
The study by researchers at Loughborough University and the University of Oxford examined the effects of soy consumption in 719 Indonesian people, between the ages of 52 and 98, and found that those who ate large amounts of tofu experienced higher rates of memory loss.
Researchers point to phytoestrogens in soy as a possible cause. The micronutrient may have a negative effect on patients older than 65, "for whom it could heighten risk of dementia and lower memory function," lead researcher Eef Hogervorst said in a statement.
While phytoestrogens in some soy products are thought by researchers to be linked to memory loss, tempeh - another type of fermented soy product - was found to do exactly the opposite. Tempeh soy products contain folate, known to reduce dementia risk, and may not have the same suspected degenerative effects as other soy products. The full study is to be published later this month.
A 1999 study by the University of Hawaii first discovered the suspected link. It studied Japanese men and found those eating more than two servings of tofu each week noticed "accelerated brain aging" about 30 years later in life. But it found no increased Alzheimer's rate, and the effects were thought to be minimal.
"Most of the people were not demented, and the differences between average cognitive function test scores [were]definite but not dramatic," Hawaii researcher Lon White saidin an e-mail, adding that he questioned the methodology of the new study.
A full conclusion would require a study that is "very unusual, very costly and very well carried out," he said.
In Canada, growers say soy has a range of health benefits, and, like anything, should be eaten in moderation.
"There have been studies on both sides of the issue," said Dale Petrie, general manager of the Ontario Soybean Growers. "I'm not sure we can extrapolate from a study that was done in Indonesia, with a totally different diet and different environment."