Soy has become a common part of the American diet, particular among people who are vegetarian or vegan. About 40 percent of the calories in soy come from protein, making it one of the richest sources of protein available. Research suggests that soy foods can be a valuable part of a weight loss plan for obesity. However, under certain circumstances, you should consult a doctor before taking soy protein.
What is Soy Protein?
Soy protein is available in whole soy foods, such as soybeans and soy beverages. However, it can also be separated from soy oil when soybeans are crushed to create various soy products. Plant estrogens called isoflavones, such as genistein and daidzein, remain in the soy protein. Isoflavones are linked to various health benefits, including lowering bad cholesterol and reducing the risk of some cancers, such as breast cancer. However, the levels of isoflavones in soy foods vary depending on how the soy is processed. For instance, while soy protein isolates are richer sources of protein than other soy protein products, they contain lower levels of isoflavones. Soy isolates are the main constituents in products such as soy milk, ice cream and cheese.
How Soy Benefits Weight Loss
A rat-model study by the University of Illinois presented at the 2007 Experimental Biology meeting gives some insight into how consumption of soy promotes weight loss. Researchers found that injections of soy protein and soy peptides three times a week for two weeks significantly boosted weight loss. Soy protein may help increase metabolism, and soy peptides may help signal your brain when you're feeling full.
Adding Soy to Your Diet
When you're trying to lose weight, low-fat sources of soy protein are your best options. These include low-fat or fat-free soy milk or reduced-fat tofu. Whole soy foods such as soybeans or soy nuts are also good sources of soy. Reducing foods rich in saturated fat and cholesterol, such as meat, can aid weight loss. Tempeh and tofu are popular meat substitutes. Also, eat a handful of soy nuts as a snack instead of fatty or sugary snacks.
Precautions
Although soy protein may help you lose weight, it's still important not to consume too much of it. Excess calories in any form can cause you to gain weight. Also, too much soy protein boosts your isoflavones intake, which might increase your risk of cancer. Fifty grams of soy protein daily is considered safe, according to the UC Davis Department of Nutrition. If you experience symptoms such as itching, diarrhea or nausea from eating soy, you may have a soy allergy and need to avoid foods or supplements with soy protein. If you've had breast cancer, kidney disease or hyperthyroidism, or you're taking medication, consult your doctor before taking soy protein and other soy foods to manage obesity.
References
- College of Agricultural Sciences: Soy Protein and Soy Isoflavones
- National Soybean Research Laboratory: Nutritional and Health Benefits of Soybeans
- Illinois College of ACES: Report on Research: How Does Soy Promote Weight Loss? U of I Scientist Finds Another Clue
- University of Maryland Medical Center: Soy
- UC Davis Department of Nutrition: Nutrition and Health Info Sheet: Some Facts About Soy; Karrie Henneman, Ph.D. et al.
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