Soy, the bean of an Asian legume, is a major source of vegetable protein and oil. Soy protein contains all nine of the essential amino acids that your body cannot manufacture on its own, thus making it a complete protein. In addition to its high nutritional value, soy is also studied for its health-promoting properties. However, soy products might not be safe for everyone. If you have health problems, consult with your health-care provider before making the switch to soy products.
Breast Cancer
Soy's role in breast cancer isn't clear. There is some concern that soy-based products could increase breast cancer risk in women who are at high risk. Soy products contain plant-based sources of estrogen, called phytoestrogens. Estrogen is a reproductive hormone. Researchers believe that high estrogen levels promote the development of estrogen-dependent tumors in the breast via cell proliferation in the mammary gland tissues. It is possible that soy phytoestrogens strengthen the effects of the body's own estrogen and therefore further stimulate breast tumor growth, according to the Sprecher Institute at Cornell University.
Soy Allergy
Soy allergy, a type of food allergy, occurs when the body's immune system reacts to proteins found in soy foods. The release of antibodies, such as histamine, may lead to a variety of symptoms that can range from harmless skin reactions to gastrointestinal problems, difficulty breathing, difficulty swallowing, indigestion, diarrhea and lowered blood pressure. Normally, infants and young children are at higher risk of developing a soy allergy than are adults.
Thyroid Disease
People with an underactive thyroid gland should not consume soy products without talking to a doctor, because soy isoflavones, molecules with antioxidant and estrogenic properties, can interfere with thyroid hormone synthesis. Two main soy isoflavones, genistein and daidzein, have been found to reduce the effectiveness of thyroid peroxidase, the key enzyme involved in thyroid hormone synthesis. The decreased levels of thyroid hormones are linked to many health problems, including malaise, sleepiness, lethargy, indigestion, hair loss, weight gain, dry and flaky skin and an enlargement of the thyroid gland called goiter.
Gout
Excessive intake of soy-based products is associated with an increase in serum urate, a metabolite of purines. Purines are substances found naturally in your body and in certain foods, including meats, poultry, fish and soy. High levels of urate can lead to a condition called gout. It occurs when needle-like urate crystals accumulate in joint spaces and the surrounding tissue, causing pain, inflammation and swelling.
References
- UMMC: Soy
- University of California: eScholarship: "Nutrition Noteworthy"; Soy and the Thyroid: Can This Miracle Food Be Unsafe?; Monica Ralli; 2003
- "The Anti-Estrogenic Diet: How Estrogenic Foods and Chemicals Are Making You Fat and Sick"; Ori Hofmekler and Rick Osborn; 2007
- The University of Mississippi; Food Intolerance and Allergies; Spring 2003
- Sprecher Institute for Comparative Cancer Research, Cornell University: Phytoestrogens and Breast Cancer
- University of Hawaii; College of Tropical Agriculture and Human Resources: Food Allergies; Alfonso Tirado; 2005
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