Consumption of soy foods such as tofu is not associated with weight gain. In fact, many studies have found that vegetarian or plant-based diets, which include soy foods, are more effective for weight management. Soy does contain phytoestrogens, which are plant-based estrogen-like compounds that can exert weak estrogenic effects. Most research has found that soy foods do not raise estrogen levels in the body.
What about the estrogen in green tea and soy for increasing breast lumps? My GP has told me not to drink green tea.
Green tea does not contain any estrogen. In fact, some research has suggested that it may actually help in estrogen metabolism and reduce reduce risk of breast cancer.
Soy contains isoflavones which are known as phytoestrogens because they can bind to estrogen receptors and exert weak estrogenic effects. Soy foods have been shown in studies to offer many health benefits including providing protection against osteoporosis (increasing bone density), reducing risk of heart disease with beneficial effects on cholesterol, platelets and blood vessels, and relieving menopause symptoms.
According to most human research, eating whole soy foods does not increase risk of breast or endometrial cancer in postmenopausal women, and may even be protective. There is also some evidence that soy may be beneficial for cyclic breast pain and improve fibrocystic breast conditions.
However, consuming purified soy products and supplements is a different matter. A study published in Carcinogenesis suggests that not only is the cancer-preventive ability of soy foods markedly reduced in highly purified soy products and supplements, but that such processed foods can stimulate the growth of pre-existing estrogen-dependent breast tumors.