During the last few years we have seen on the market a great increase of soya derived products: soya milk and yoghurts, tofu, miso, natto, tempeh, tamari, etc.
Photo by Baltar. Creative Commons license
The high level of proteins (soya contains all the essential amino acids) is probably one of the reasons explaining why this plant is so interesting from a nutritional point of view. Indeed, it is considered a good alternative to animal food, such as meat, fish and milk, and is especially appreciated by people following a vegetarian or vegan diet.
In addition, several studies suggest that some substances present in soya (such as isoflavones) might help to prevent some cancers and other diseases.
However, the success story of soya has started to decline because there are doubts about the effective benefits on human health. The results of several studies seem to show that the regular and abundant consumption of soya food might be deleterious in the long term. This would be true even for products derived from OGM (organisms genetically modified) free and organic plants.
The negative effects would be reduced or eliminated by the lacto-fermentation process. Therefore, there would be no risk in eating miso, tempeh, natto and tamari, obtained by fermented soya beans. It is probably not by chance that Asian people tend to prefer these latter products to the non-fermented ones, usually accompanied by large amounts of fresh vegetables.
It is true that some diseases have a smaller incidence in some Asian countries (for instance breast cancer and osteoporosis in women). However, this does not only depend on the presence of soya products in their diet, but most likely on a lifestyle which is very different, and probably healthier, than the western way of living.
From what I have read so far, it seems that there are not enough elements to exclude any risk linked to the regular and abundant consumption of soya food.
Here are a few articles explaining good and bad sides of eating these beans.
The following article offers a different, more optimistic point of view.