The invention is directed to a method of preventing or ameliorating a neuropsychiatric or neurodegenerative disease or disorder in a subject. The method includes administering a composition comprising equol in an amount sufficient to prevent or ameliorate the neuropsychiatric or neurodegenerative disease or disorder. The equol may be a racemic mixture of R-equol and S-equol. The equol may be enantiomerically enriched with R-equol or enantiomerically enriched with Sequol.