The study, published in April and based on data from the Honolulu-Asia Aging Study, got lots of media attention, since the accused was no ordinary food. Soy is supposed to keep people healthy. Only a few months earlier the FDA had begun to allow many soy products to carry a health label stating that they may help prevent heart disease. And, according to its many advocates, soy can also ease symptoms of menopause and protect against osteoporosis and cancer, though the evidence for all this is either inconclusive or minimal.
Soy foods are a staple for much of the world's population.
Tofu does contain estrogen-like substances called isoflavones, which, animal studies suggest, might affect brain activity. But little is known about their effect in the human brain. These researchers did not measure isoflavones in the men's blood or in the food they ate. One problem with observational studies like this is that it's impossible to know whether tofu somehow causes this slight premature aging of the brain, or if there's something else about men who eat tofu that's responsible. On balance, soy is good food.