Soy

I'm seeing more soy-based products in the marketplace.  In my opinion, this is an unfortunate event.  From an evolutionary viewpoint, soybeans are legumes(beans) and were not part of the diets of hunter-gatherers.

The clues that soy is unhealthy are everywhere.  There's suggestive evidence in animal studies that soy consumed during infancy has effects on puberty development and adult hormone levels.  There's also evidence soy can harm the reproductive system in animals. 

As for research with humans, here's a paper showing that midlife tofu/soy consumption can lead to "brain aging".  Some also think that women consuming soy are reducing their odds of becoming pregnant.

There are other sides to this issue.  Soy may help slow prostate cancer - but this is primarily because it acts like estrogen in men and reduces testosterone levels.

The medical research on soy and its dangers is just beginning.  In the coming years, I predict researchers will show that soy is detrimental to men, women, and especially infants.  But why wait until all the research is in?  The eating practices of hunter-gatherers show us the diet we are meant for.  Soy was not a part of their diet, and it shouldn't be a part of yours.