The Soybean – A Nutritional Powerhouse!*

31 August 2010 by Aaron Tabor

Soybeans are rich in macronutrients like protein, fat, and carbohydrates and contain a variety of micronutrients such as calcium, iron, zinc, riboflavin, and folate [1].  Some of these are discussed briefly below.

Protein. Soybeans are best known as a rich source of non-animal protein.  In fact, about 37% of the raw soybean consists of protein according to the USDA National Nutrient Database for Standard Reference, Release 22 [2]. The amino acid pattern of soy protein provides adequate levels of each indispensable amino acid for normal growth and development. The high digestibility of properly processed soy protein and the bioavailability of its amino acids and nitrogen content make soy protein a high quality protein.  The Protein Digestibility Corrected Amino Acid Score (PDCAAS) of soy protein is 1.0, the highest possible score and similar to other high quality proteins.   Therefore, the addition of soy to the diet is a great way to meet all of one’s protein nutritional requirements.

Fat. Soybeans typically contain more dietary fat than other legumes; however, the fats in soybeans are mainly of the healthier varieties.  According to the USDA National Nutrient Database for Standard Reference, Release 22, raw, mature soybeans contain approximately 20 grams of fat in a 100-gram portion [2].  Of the fat present in soybeans, ~15% is saturated, ~24% is monounsaturated, and ~60% is polyunsaturated; therefore, over 80% of the fat in soy is of the healthier, unsaturated kind.  The predominant unsaturated fats found in soy include linoleic acid and alpha-linolenic acid, two essential fatty acids. Alpha-linolenic acid is an essential omega-3 fatty acid that is metabolized in the body to form eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in small amounts.

Carbohydrates. Carbohydrates in soy, while present in only low levels, consist primarily of fiber and the oligosaccharides raffinose and stachyose [1]. The low level of carbohydrates in soybeans and the poor digestibility of these carbohydrates is responsible for the low glycemic index of soybeans and many soy products [3].

Vitamins & Minerals. Soybeans are a quality source of several vitamins and minerals including folate, calcium, zinc, and iron [1].  Folate, an essential B-vitamin, is present in raw, mature soybeans at a level of 375 mcg/100 grams of soybeans according to the USDA National Nutrient Database for Standard Reference, Release 22.  A 100-gram portion of raw soybeans also contains 277 mg calcium (~28% of the daily value), 15.7 mg iron (~80–100% of the daily value for most adults), and 4.9 mg zinc (~40–50% of the daily value).  The bioavailability of these minerals from soy is an area of increasing research interest.   Recent studies indicate that calcium-fortified soymilk is an excellent source of calcium [4] and that soybean ferritin, a source of iron, is readily bioavailable [5].  Additionally, zinc absorption has been reported to be similar between meat and soy proteins [6, 7].  There has been some concern about the presence of phytate (or phytic acid) in soy.  Phytate is considered to be a strong binder of minerals and thus it has been suggested that the phytate in soy could limit mineral availability.  However, recent research suggests that this is only a concern when very high levels of phytate are consumed in combination with a nutrient-poor diet [8].

The nutritional profile of soybeans makes them an excellent choice as part of a healthy diet.  Like many other foods, cooking will alter their nutritional profile; however, soybeans and other soy products can be a excellent source of high quality protein and a good source of many other nutrients when consumed as part of a healthy, well-balanced diet.

Start enjoying the nutritional benefits of soy with Dr. Tabor’s Revival® soy protein shakes, bars, snacks, and other delicious products.*

References

1.  Choi MS, Rhee KC.  Production and processing of soybeans and nutrition and safety of isoflavone and other soy products for human health.  J Med Food 2006; 9:1-10.
2.  U.S. Department of Agriculture, Agricultural Research Service.  2009.  USDA Nutrient Database for Standard Reference, Release 22.  Nutrient Data Laboratory Home Page, http://www.ars.usda.gov/nutrientdata.  Note:  Release numbers change as new versions are released.
3.  Foster-Powell K, Holt SHA, Brand-Miller JC.  International table of glycemic index and glycemic load values: 2002.  Am J Clin Nutr 2002; 76:5-56.
4.  Zhao Y, Martin BR, Weaver CM.  Calcium bioavailability of calcium carbonate fortified soymilk is equivalent to cow’s milk in young women.  J Nutr 2005; 135:2379-2382.
5.  Lönnerdal B, Bryant A, Liu X, Theil EC.  Iron absorption from soybean ferritin in nonanemic women.  Am J Clin Nutr 2006; 83:103-107.
6.  Sandstrom B, Kivisto B, Cederblad A. Absorption of zinc from soy protein meals in humans.  J Nutr 1987; 117:321-327.
7.  Davidsson L, Almgren A, Sandstrom B, Hurrell RF. Zinc absorption in adult humans: the effect of protein sources added to liquid test meals. Br J Nutr 1996; 75:607–613.
8.  Kang J, Badger TM, Ronis MJJ, Wu X.  Non-isoflavone phytochemicals in soy and their health effects.  J Agric Food Chem 2010; 58:8119-8133.

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*DISCLAIMER: Individual results vary. These statements have not been evaluated by the Food and Drug Administration. Revival foods and dietary supplements are not intended to diagnose, treat, cure or prevent any disease. Typical hot flash reduction was nearly 40% in a 12-week study funded by Physicians Laboratories. Typical weight loss was 26 - 29 pounds for dieters in a 16 week study. Studies were funded in part or in whole by Physicians Laboratories. The information presented on this web site is not intended to take the place of your personal physician's advice. Discuss this information with your own physician or healthcare provider to determine what is right for you. Revival is not a substitute for prescription medication, surgery, chemotherapy, radiation therapy, or any other medical treatment. Revival is not a substitute for the care of your own physician. The FDA states that 25g of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce risk of heart disease. Each Revival protein shake and protein bar provides 20g of soy protein. All information is intended for your general knowledge only and is not a substitute for medical advice or treatment for specific medical conditions. We can not and do not give you medical advice. You should seek prompt medical care for any specific health issues and consult your physician before starting a new fitness or nutrition regimen. The information contained in this online site and emails is presented in summary form only and intended to provide broad consumer understanding and knowledge. The information should not be considered complete and should not be used in place of a visit, call, consultation or advice of your physician or other healthcare provider. We do not recommend the self-management of health problems. Should you have any healthcare-related questions, please call or see your physician or other healthcare provider promptly. You should never disregard medical advice or delay in seeking it because of something you have read here.