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Soy and cognitive function

. There's only one study that found a negative effect of soy. The Honolulu Heart Program (a study of the health of Japanese-American men living in Hawaii) showed that those who consumed the most tofu during their lives showed the most signs of mental decline in later years. This study showed only a statistical association, but other factors also associated with high tofu consumption may be responsible for the cognitive decline.

This Honolulu Heart Program study has never been confirmed in any other study. On the contrary, other studies even suggest that soy isoflavones may protect against cognitive decline. Estrogen therapy may help maintain cognitive function in postmenopausal women and may even protect against Alzheimer's disease. Japanese men living in Hawaii have more dementia and Alzheimer's disease than those living in Japan. Japanese women living in Western countries have better cognitive function when they consume their traditional soy-rich diet.

A two-year study of Japanese-American women living in Seattle, USA, found no association between tofu consumption and cognitive decline.

Until we have more results from new clinical and epidemiologic studies, it's not possible to draw conclusions about the relationship between soy intake and cognitive function.