Fermented vs. Unfermented
Unfermented soy is not the health food it's purported to be. In fact, in 2002, the British government's expert committee on the toxicity of food (CoT) published the results of its inquiry into the safety of plant oestrogens (or phyto-estrogens), mainly from soya proteins, in modern food.
Their experiments and other studies have found that soy contains toxins and plant oestrogens that could disrupt women's menstrual cycles, stimulate the progression of breast cancer, damage the thyroid, lower testosterone levels and have uncertain effects on the prostate.
From a digestive perspective, soy beans, like other legumes, consist of protein and starch, making them difficult to disgest, especially when stomach acid is low. Fermenting soyfoods can reduce their harmful effects.