Legumes are an excellent source of plant-based protein for several reasons:

Legumes are high in protein. A single cup of cooked beans, lentils, or peas contains around 15 grams of protein[2], which is nearly a quarter of the daily protein requirement for an average adult. This makes legumes one of the most protein-dense plant foods.

Legumes contain all the essential amino acids. While they are considered "incomplete" proteins because they lack sufficient amounts of certain amino acids like methionine and cystine, this can be easily remedied by combining legumes with other incomplete proteins like grains[1]. This complementary pairing creates a complete protein profile.

Legumes are a sustainable protein source. When legume plants die, the nitrogen in their amino acids is released back into the soil, serving as a natural fertilizer for future crops[5]. This makes legumes an environmentally-friendly protein compared to animal-based sources.

Legumes provide additional health benefits. Beyond just protein, legumes are rich in fiber, complex carbohydrates, vitamins, and minerals[2][3][4]. Studies show that regularly consuming legumes can help lower cholesterol, control blood sugar, and reduce the risk of chronic diseases like diabetes and heart disease.

In summary, legumes are an optimal plant-based protein due to their high protein content, complete amino acid profile when combined with other foods, sustainability, and additional nutritional benefits[1][2][3][4][5].

Citations: [1] https://www.reddit.com/r/IsItBullshit/comments/wsqnhe/isitbullshit_protein_from_legumes_is_almost/ [2] https://www.nytimes.com/2024/01/17/well/eat/mediterranean-diet-protein-fiber.html [3] https://www.hsph.harvard.edu/nutritionsource/2015/11/16/ask-the-expert-legumes-and-resistant-starch/ [4] https://www.webmd.com/food-recipes/health-benefits-legumes [5] https://en.wikipedia.org/wiki/Legume