The evidence that phytoestrogens (plant oestrogens) and soy products in the diet are associated with breast cancer risk is inconclusive. Only a small number of studies have been performed and the evidence is inconsistent; however, analyses of higher quality cohort studies show no association with breast cancer risk for intake of any specific group of dietary oestrogens, including ‘isoflavones’ (a type of phytoestrogen found in soybeans and soy products) and soy and soy products.