Your body requires 20 different amino acids to function optimally. As food is the only way to obtain nine of these, they are called essential amino acids. Complete proteins provide a good source of all essential amino acids. Although meat, poultry, fish, seafood and animal by-products are the best natural sources of complete proteins, there also are numerous ways to obtain all essential amino acids on a vegan diet.
Soybeans and Legumes
Legumes are a group of plants that include some of the only vegan sources of complete proteins. All legumes are a source of all essential amino acids. Of these, soybeans and soy products are the best vegan complete proteins. For example, you can meet all of your essential amino acid needs by stir-frying four servings of tempeh with vegetables or snacking on six servings of dry-roasted peanuts each day, which amounts to 2 cups of either food. To ensure that you eat a balanced diet with a variety of protein sources, however, you should not rely solely on legumes for all of your essential amino acids.
Non-animal protein sources typically lack the essential amino acid lysine. In general, grains are no exception to this rule. Although a serving of buckwheat provides a higher-than-average amount of lysine, the only complete grain protein is quinoa. You can meet all of your daily amino acid needs by eating 5 1/2, 1-cup servings of cooked quinoa per day. As quinoa is a flexible grain that can be eaten in salads or as a replacement for pasta or rice, this complete grain-protein can fit into most diets.
Aside from quinoa, soy products and some other legumes, vegan foods typically lack at least one essential amino acid. Combining foods is a good way to get around this problem. For example, grains are typically high in methionine but low in lysine, nuts are good sources of all but these two amino acids and seaweed primarily lacks histidine. Although your vegan diet should regularly include legumes, soy products or quinoa, you can combine complementary proteins to obtain all essential amino acids.
The federal 2010 Dietary Guidelines for Americans recommends eating a balanced diet with a variety of fruits, vegetables, grains and proteins, all of which contain some essential amino acids. Although eating complete and complementary proteins is the easiest way to obtain all essential amino acids, this is not necessary. Your body stores essential amino acids, so you do not need to obtain a source of complete protein every day. As long as you eat a balanced, varied and nutritious diet that regularly includes a source of lysine, you can easily meet your body's essential amino acid needs on a vegan diet.
Matthew Lee has been writing professionally since 2007. Past and current research projects have explored the effect of a diagnosis of breast cancer on lifestyle and mental health and adherence to lifestyle-based (i.e. nutrition and exercise) and drug therapy treatment programs. He holds a Master of Arts in psychology from Carleton University and is working toward his doctorate in health psychology.