Soybeans and the U.S. Food Supply
By Mark Messina, PhD, Executive Director, Soy Nutrition Institute
Soybeans play a critical role in the U.S. food supply but not in a way that is often thought. Some soyfoods are consumed directly. But mostly Americans consume soy-derived ingredients that are found in hundreds of commonly-consumed foods. Soybeans also are important in the diets of livestock on American farms.
Soybeans are classified as oilseeds rather than pulses by the UN Food and Agriculture Organization (FAO). (Pulses are part of the legume family, but the term “pulse” refers only to the dried seed). This is because in contrast to most pulses about 40% of the calories in soybeans are derived from fat.
The most commonly consumed cooking oil in the United States is soybean oil, which is typically labeled as vegetable oil, and which is an ingredient in a wide range of products. It is estimated that about 7% of the calories consumed by Americans come from soybean oil; it accounts for over 40% of the intake of both essential fatty acids, the omega-6 fatty acid linoleic acid and the omega-3 fatty acid, alpha-linolenic acid.1
The United States produces about one-third of all soybeans in the world followed closely by Brazil and then Argentina. The U.S. Department of Agriculture estimates that global soybean production this year will be approximately 320 million metric tons. However, only about 6% of soybeans are consumed as whole soyfoods, mostly in Asia.
In contrast, soy protein is widely used as an ingredient by the US food industry where it is found in everything from bread to tomato soup. Despite its extensive use, the total amount of soy protein consumed by Americans is far less than commonly believed.
Soy protein is primarily used by the food industry for functional purposes (such as moisture retention) rather than for nutritional reasons. In the vast majority of cases, the soy protein added to foods makes a negligible contribution to the nutritional value of the product because it is present in such small amounts. U.S. daily per capita soy protein intake is estimated to be less than 2 grams per day which is a small percentage of total protein intake among Americans. Total protein consumption among men and women in the United States is approximately 80 and 65 grams per day, respectively.
Not surprisingly, soy protein also contributes only negligible amounts of isoflavones, the phytoestrogens found in soybeans, to American diets. This is because of the small amount of soy protein consumed and because in many cases as a result of processing, the concentration of isoflavones in the protein used by the food industry is quite low. Estimates are that U.S. per capita intake is less than 2½ milligrams per day.2 In comparison, one cup of soymilk made from whole soybeans contains about 25 mg isoflavones.
Extensive use of soy protein by the food industry does present problems for individuals with soy allergies. Fortunately, soy protein allergy is relatively rare among adults3 and most children outgrow soy allergy but age 10.4 Soy protein is required to be listed on food labels making it easier for those with allergies to avoid soy.
Additional soy-based products routinely found in the food supply include soy lecithin (an emulsifier), soy sauce and hydrolyzed soy protein or hydrolyzed vegetable protein (HVP). HVP, which is used as a flavoring agent or taste enhancer, is also produced from gluten from maize or wheat. Lecithin extracts, which are also derived from egg yolks, contain phosphatidylcholine and other phospholipids, and are a significant source of choline in American diets.5 6
In summary, soybeans play a huge role in the US food supply although the amount of soy protein and isoflavones consumed by most Americans is limited.