Proteins are formed of chains of 20 types of amino acids. Some are considered indispensable amino acids (IAAs) or essential amino acids because they must be consumed in food. Others, known as dispensable amino acids, can be synthesized in the body by the IAAs. Research has established that all plant foods contain all of the IAAs in varying proportions.
The amino acid lysine is of particular importance in vegan diets. Peas, beans and lentils are excellent sources of this amino acid in both cooked and raw sprouted forms. Quinoa, amaranth and pumpkin seeds are also good sources. A prudent diet should contain about three servings daily of high lysine-containing foods along with a mix of low-lysine foods.1
Soybeans are very high in lysine and have a protein profile similar to that of animal flesh. Soy products such as tofu, tempeh, soymilk and soy veggie burgers are commonly recommended sources of plant protein, and while they are excellent sources, there is no need to eat a diet high in soy products in order to meet protein needs.2
Current recommendations are that vegan adults should consume 0,4 grams/lb. (0.9 grams/kg) of protein for each pound of healthy body weight. With a varied vegan diet one can obtain all the indispensable amino acids.
Norris, J. & Messina, V. (2011) Vegan for life, Philadelphia: Da Capo.
2 Yáñez, E.; Uauy, R.; Zacarías, I. & Barrera, G. (1986) “Long-term validation of 1 g of protein per kilogram body weight from a predominantly vegetable mixed diet to meet the requirements of young adult males”, Journal Nutrition, 116, pp. 865-872. Young, V. R.; Pellett, P. L. (1994) “Plan proteins in relation to human protein and amino acid nutrition”, The American Journal of Clinical Nutrition, 59, pp. S1203-S1212. Haddad, E. H.; Berk, L. S.; Kettering, J. D.; Hubbard, R. W. & Peters, W. R. (1999) “Dietary intake and biochemical, hematologic, and immune status of vegans compared with non-vegetarians”, The American Journal of Clinical Nutrition, 70, pp. 586S-593S [accessed on 23 April 2017]. Caso, G. (2000) “Albumin synthesis is diminished in men consuming a predominantly vegetarian diet”, Journal Nutrition, 130, pp. 528-533. Elango, R.; Humayun, M. A.; Ball, R. O. & Pencharz, P. B. (2010) “Evidence that protein requirements have been significantly underestimated”, Current Opinion in Clinical Nutrition and Metabolic Care, 13, pp. 52-57.