Health: Soy beans prevent heart disease by lowering LDL (the “bad” cholesterol), and may protect against breast cancer. They are a good source of good source of protein, while being low in fat, with zero cholesterol.
Harm: Soy contains phytoestrogen (=plant estrogens), and rumours are constantly reappearing that eating too much soy is bad for men. However a meta-analysis (a study that combines the results of many studies) found no affect of soy on the reproductive hormone concentrations of men. There is concern that soy disrupts thyroid function – but studies show that this isn’t the case, unless you are deficient in iodine or have a thyroid condition.
In terms of the environmental impact of soy, some argue that drinking soy milk may be less harmful for the environment than drinking milk but this is outside my realm of expertise.
If you want to include soy in your diet, (like all foods) choose less processed variety, and if it’s fermented, even better. Avoid soy supplements (e.g. isoflavones). Try slowly introducing foods like edamame, tofu, soymilk, miso, and tempeh into your diet, to up to 3 servings per day.
Photo by Trey Ratcliff on Flickr