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.
