Protein is an essential nutrient for building muscle, maintaining the structural integrity of cells and helping to break down toxins. Soybeans are an excellent source of protein, but, unlike meat, they don't contain all of the amino acids that make up the proteins we need to keep our bodies healthy. Vegetarians should eat a variety of protein-containing foods to make up the difference. While health-care professionals generally regard soy protein as safe, more research is underway to examine both its benefits and possible side effects.
Benefits of Soy Protein
Scientists are examining the benefit of soy protein in the treatment or prevention of cardiovascular disease, some cancers and osteoporosis. Most studies have had mixed or negative results, but the American Heart Association still thinks soy is a good meat substitute, because it has lots of fiber, polyunsaturated fats, vitamins and minerals, which help keep bad LDL cholesterol from building up in your arteries.
Common Mild Side Effects
Like other dried beans, peas and legumes, soybeans increase gas production in your intestines. You may get a stomach ache or have constipation or diarrhea if you eat excessive amounts of soy protein foods. Harvard School of Public Health recommends starting by eating soy foods no more than two to four times per week if you didn't grown up using soy as a dietary staple. Although rare, some people have an allergy to soy protein, so if you get a rash or have trouble breathing after eating soy products, seek medical advice.
Purines and Zinc
Purines are a compound that, if eaten in excess, can worsen gout, a painful rheumatoid condition. Soy contains purines, though in a moderate amount. Most studies have not shown a relationship between soy consumption and gout, but if you have gout, talk to your doctor or a dietitian about soy protein in your diet.
People who eat lots of soy protein and other unrefined grains have also been found to have trouble absorbing zinc, due to the presence in grains of a compound called phytate. Your body is likely to adapt, however, so eventually your zinc absorption should improve.
Phytoestrogens in Soy
Much of the soy protein found in supplements is made up of soy isoflavones, a type of phytoestrogen, or plant-based, estrogen-producing substance. While a large percentage of the isoflavones may be lost during soybean processing, all soy protein products contain at least some of this phytoestrogen. These micronutrients may affect how the estrogen hormone functions in your body, including the possibility of reducing risk for certain types of cancer and osteoporosis, according to the Linus Pauling Institute. On the other hand, at least one study seemed to indicate that consumption of tofu is related to earlier cognitive decline in a group of middle-aged men.
One Harvard School of Public Health study in 2008 found that men who consumed soy food products every day had lower sperm counts compared to men who did not eat soy. This was especially true of overweight men. The lead researcher, Dr. Jorge Chavarro, added that further research would help determine the clinical significance of these findings.
Soy Protein in Your Daily Diet
If you're like most Americans, about 12 to 18 percent of your daily diet is made up of protein, which is plenty to meet your body's needs. Protein supplements of any sort, including soy protein, are not generally needed. People over 70, however, tend to eat less protein. At the same time, older adults have a harder time maintaining muscle mass, so soy protein supplements may be of benefit, as they would be if you have a disease that causes malnourishment. Vegans and vegetarians need to be sure to include a variety of protein sources in their daily diet, and not to rely solely on soy protein. Talk to your doctor or a registered dietitian if you have concerns about protein, including soy protein, in your daily diet.
References
- National Center for Complementary and Alternative Medicine; Soy; July 2010
- "Circulation"; Soy protein, isoflavones, and cardiovascular health: an AHA Science Advisory; F.M. Sacks et al.; February 21, 2006
- Harvard School of Public Health: Protein: Moving Closer to Center Stage
- The Nutrition Place: Debunking Myths about Soy
- Medline Plus; Zinc; February 24, 2011
- Linus Pauling Institute; Soy Isoflavones; Jan Higdon, Ph.D.; January 2006
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