Soy is an important crop in the world in terms of its extensive use in human food and its high protein content. It also provides health benefits relative to chronic diseases such as cardiovascular diseases, osteoporosis, diabetes and cancer. However, you should exercise caution in eating soy because its estrogenic components may have some negative side effects.
Breast Cancer
Soy contains phytochemicals called isoflavones, which mimic the activity of the body's own estrogen hormone. Estrogen is essential to normal human health, but high levels can raise the risk of breast cancer. Therefore, women who consume phytoestrogen-filled soy foods are susceptible to breast cancer, although this issue needs more research, the Sprecher Institute at Cornell University notes.
Thyroid Disease
People with an underactive thyroid gland should avoid all thyroid inhibitors in their diet, including soy. Slow thyroid foods can compromise with your thyroid function. Insufficient production of thyroid hormones leads to underfunctioning of the thyroid gland, a condition known as hypothyroidism. People with hypothyroidism often complain of lethargy, sleepiness, fatigue, depression, weight gain, hair loss, poor memory, menstrual irregularities and goiter. It has been found that genistein and daidzen, major isoflavones in soy, inhibit the utilization of iodine by the thyroid gland. Your thyroid gland needs iodine for a healthy production of thyroid hormones.
Soy-Based Infant Formulas
Commercial soy infant formulas are lifesaving alternatives for infants who are lactose intolerant. However, there have been persistent concerns regarding the safety levels of isoflavones, especially when taken in relatively pure form as a food supplement. Soy isoflavone concentrations in soy-based infant formulas are so high that they can exert negative consequences on growth, development, reproductive and immune system in infants, according to the Linus Pauling Institute at Oregon State University.
Drug Interactions
Soy isoflavones may also reduce the effectiveness of some prescription drugs. For examples, isoflavones, often in high doses, can lower blood concentrations of anticoagulant drugs such as warfarin, making them less effective. There is also some concern that soy might inhibit tamoxifen effects on breast cancer progression due to its potential estrogenic effects. So, patients taking warfarin or tamoxifen should avoid all foods that contain soy.
References
- University of Maryland Medical Center; Soy; Dec. 14, 2009
- Cornell University: Sprecher Institute; Phytoestrogens and Breast Cancer;Barbour S. Warren, et al.; Jul. 1, 2002
- "The Anti-Estrogenic Diet"; Ori Hofmekler and Rick Osborn; 2007
- Linus Pauling Institute: Oregon State University: Soy Isoflavones; Jane Higdon; January, 2006
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