An article in the journal Nutrients reviewed more than 200 scientific papers on soya published in recent years with regard to specific soya bean constituents, especially isoflavones. The article highlighted the role that soya foods have in reducing risk of heart disease, osteoporosis and certain forms of cancer and concluded that concerns about adverse effects of soya consumption were not scientifically supported. The authors also searched data from population studies and clinical trials - on the optimal intake of soya or soya derived products in adults - which suggested that it would appear to be between two and four servings per day.
Messina M. and Messina V. (2010). The Role of Soy in Vegetarian Diets. Nutrients. 2 (8) 855-888.