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 life showed the most signs of mental deterioration in later years. This study only showed a statistical relationship but other factors which are also linked to high tofu consumption could be responsible for the cognitive decline.

This Honolulu Heart Program study has never been confirmed in any other study. To the contrary, other studies even suggest that soy isoflavones may protect against cognitive decline. Estrogen therapy may help to maintain cognitive function in postmenopausal women and it 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 if they consume their traditional soyfood rich diet.

One two-year study of Japanese-American women living in Seattle (USA) did not find any relationship between tofu consumption and cognitive function decline.

Until we have more results of new clinical and epidemiological studies, it’s not possible to make conclusions about the relationship between soy intake and cognitive function.