Soy – a protein made from the soybean plant - has gained a lot of attention in the food and health industry as a nutritiously edible bean with numerous uses. It is rich in omega-3 fats, B-vitamins, zinc, iron, polyunsaturated fat, fiber, phytochemicals and antioxidants. Most popular within the vegetarian community, soy protein is a replacement for animal protein - one cup contains 23 grams of protein (about half the daily requirement). Soy is found in popular foods including tofu, edamame, tempeh and soy milk.
Soy contains isoflavones, which are changed in the body to phytoestrogens. Phytoestrogens are similar to the hormone estrogen. Women often use soy as a hormone replacement therapy to relieve menopause-related symptoms. It has also been linked to the prevention and control heart disease and cancer.
However, the effects of soy are controversial. Human cells, including cancer cells, have protein receptors that are extremely particular about the molecules they bind to. The fit between the two determines how that cell is going to behave - they will either trigger a cell’s activity or block it. Soy can do both. Because human estrogen and soy-derived phytoestrogen are so similar, human cells cannot distinguish between the two. Some believe that soy’s phytoestrogen may cause breast cancer growth due to its similarity to human estrogen. On the other hand, some believe it may prevent breast cancer by taking human estrogen’s place within the protein receptors.
Soy’s controversy begins with the two different types: fermented and unfermented. Fermented soy is native to East Asia where it is consumed in small amounts. Fermented soy is an excellent source of vitamin K2. When combined with vitamin D, K2 can help prevent heart disease, dementia, osteoporosis, and some cancers. This is different from the type of soy consumed by Americans, which is unfermented and processed. Ninety percent of soybeans grown in the United States are genetically modified. Unfermented soy contains high amounts of anti-nutrients which block your body from absorbing its nutrients.
In order to get the benefits from soy, consuming only fermented soy products – such as miso, tempeh, natto and most soy sauces – in small amounts, is the way to do it. Soy protein is still a good alternative for animal protein and dairy – both of which are high in saturated fat.
Tips for eating soy:
- Avoid processed soy products such as soy ice cream, canned tuna, soy chips, soymilk, soy burgers, soy infant formula, soy nuts and some tofu.
- Avoid soy supplements made from isoflavones.
- Eat only fermented soy products such as miso, tempeh, natto, and some soy sauces.
- Consume no more than one serving of soy daily (30 mg).
Dr. Samadi is a board-certified urologic oncologist trained in open and traditional and laparoscopic surgery and is an expert in robotic prostate surgery. He is chairman of urology, chief of robotic surgery at Lenox Hill Hospital and professor of urology at Hofstra North Shore-LIJ School of Medicine. He is a medical correspondent for the Fox News Channel's Medical A-Team and the chief medical correspondent for am970 in New York City. Learn more at roboticoncology.com. Visit Dr. Samadi's blog at SamadiMD.com. Follow Dr. Samadi on Twitter and Facebook.