Women
A 2001 literature review suggested that women with current or past breast cancer should be aware of the risks of potential tumor growth when taking soy products, based on the effect of phytoestrogens on breast cancer cell growth in animals.[45]

A 2006 commentary reviewed the relationship with soy and breast cancer. They stated that soy may prevent breast cancer, but cautioned that the impact of isoflavones on breast tissue needs to be evaluated at the cellular level in women at high risk for breast cancer.[46]

Infant formula
There are some studies that state that phytoestrogen in soy can lead to alterations in the proliferation and migration of intestinal cells. The effects of these alterations are unknown.[47] However, some studies conclude there are no adverse effects in human growth, development, or reproduction as a result of the consumption of soy-based infant formula.[48] Other reviews agree, but state that more research is needed to answer the question of what effect phytoestrogens have on infants.[49][50] Soy formula has also been linked to autoimmune disorders of the thyroid gland.[51]

Allergens
Main article: Soy allergy
About 8% of children in the USA are allergic to soybean proteins.[citation needed] The major soy allergen has been identified by scientists at USDA.[citation needed] Both transgenic and conventional soybean varieties without the allergenic protein have been prepared.[citation needed] Soy allergy, typically, will manifest itself approximately a day after consumption of the beans. Common symptoms are urticaria, rash, itching, and redness of the skin.[52][53]

Promotion as health food
Soy consumption has been promoted by natural food companies and the soy industry’s aggressive marketing campaign in various magazines, television ads and in health food markets. Research has been conducted examining the validity of the beneficial health claims with regard to the increase in consumption of soybeans which mimic hormonal activity. A practice guideline published in the journal Circulation questions the efficacy and safety of soy isoflavones for preventing or treating cancer of the breast, endometrium, and prostate (although the same study also concludes that soy in some foods should be beneficial to cardiovascular and overall health) and does not recommend usage of isoflavone supplements in food or pills.[54] A review of the available studies by the United States’ Health and Human Services’ Agency for Healthcare Research and Quality (AHRQ) found little evidence of substantial health improvements and no adverse effects, but also noted that there was no long-term safety data on soy consumption.[55]

Brain
Estrogen helps protect and repair the brain during and after injury.[56] The mimicry of estrogen by the phytoestrogens in soy has introduced a controversy over whether such a replacement is harmful or helpful to the brain. Several studies have found soy to be harmful for rats.[57][58][59][60] One study followed over 3000 Japanese men between 1965 and 1999, and that showed a positive correlation between brain atrophy and consumption of tofu.[61] The study was rejected as not credible by the Food and Drug Administration when it issued its health claim for soy: “25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.”[62]

Carcinogen
Raw soy flour is known to cause pancreatic cancer in rats.[63] Whether this is also true in humans is unknown because no studies comparing cases of pancreatic cancer and soy intake in humans have yet been conducted, and the doses used to induce pancreatic cancer in rats are said to be larger than humans would normally consume. Heated soy flour may not be carcinogenic in rats.[64][65]

JUST FACTS