As a source of dietary fiber and plant-based protein, beans have a ton of bang for the buck. But if you’re subsisting on beans as your sole source of protein, then you’re likely missing out on some key essential amino acids. Let’s get to know beans a little better, including the amino acid profile of beans with the highest protein content.
Protein in Beans
Dietary protein, whether it comes from animal or plant foods, is made up of 20 amino acids linked together in different combinations, which is why amino acids are referred to as the building blocks of protein. Eleven of these are nonessential amino acids that the body can synthesize on its own. Nonessential amino acids become conditionally essential in times of stress and illness. The other nine are essential amino acids, and the body cannot make them. These in-demand aminos must be obtained from a food source.
The nine essential amino acids are:
When dietary protein is digested, it’s broken down into its component amino acids, which get to work performing various functions in the body—building and repairing tissue, producing neurotransmitters and hormones, boosting mental and physical performance, improving mood, and strengthening the immune system.
A complete protein contains sufficient amounts of all nine of the essential amino acids. Most beans are incomplete proteins, as they tend to be too low in certain essential amino acids, particularly the sulfur-containing amino acid methionine.
That’s the case for most plant-based sources of protein. They are limited in certain essential amino acids (EAAs), including lysine and leucine. Even if they are considered complete by some accounts, they don’t have the anabolic, or muscle building, capacity that high-quality animal-based proteins do, such as meat and eggs.
That doesn’t mean they aren’t an important part of your diet, but knowing the essential amino acid profile of beans can help you get a more complete essential amino acid makeup in your diet.
Amino Acid Composition of Common Legumes
Many of the most popular types of beans come from the edible ripe fruit or dry seeds of the Phaseolus vulgaris plant, or the common bean. Types of common beans include kidney beans, pinto beans, navy beans, and black beans. One cup of each of these cooked beans renders approximately 15 grams of protein. Soybeans, chickpeas, mung beans, adzuki beans, and lentils are common varieties of nutrient-dense legumes that are high in protein and fiber.
Essential Amino Acid Content of Kidney Beans
A 2018 study in the journal Nutrients determined that household-cooked kidney beans are the highest in protein of five beans studied: kidney beans, white beans, chickpeas, brown and green lentils, and flageolets. In all the beans lysine, leucine, and valine were the most plentiful EAAs, but methionine levels were inadequate (1).
One cup of boiled kidney beans has the following essential amino acid profile.
|Histidine||421 mg||66% RDI|
|Isoleucine||726 mg||52% RDI|
|Leucine||1303 mg||48% RDI|
|Lysine||1074 mg||51% RDI|
|Methionine||200 mg||27% RDI|
|Phenylalanine||904 mg||103% RDI|
|Threonine||565 mg||54% RDI|
|Tryptophan||84 mg||66% RDI|
|Valine||885 mg||49% RDI|
Essential Amino Acid Content of Navy Beans
Given the name navy beans when they became a staple of the U.S. Naval diet in the second half of the 19th century, these small white beans have the following essential amino acid content in 1 cup:
|Histidine||375 mg||54% RDI|
|Isoleucine||704 mg||50% RDI|
|Leucine||1274 mg||47% RDI|
|Lysine||946 mg||45% RDI|
|Methionine||202 mg||28% RDI|
|Phenylalanine||857 mg||98% RDI|
|Threonine||526 mg||50% RDI|
|Tryptophan||182 mg||65% RDI|
|Valine||917 mg||50% RDI|
Essential Amino Acid Content of Black Beans
Also known as turtle beans, black beans are a featured bean of Latin cuisine. Here’s the essential amino acid breakdown of black beans:
|Histidine||425 mg||61% RDI|
|Isoleucine||673 mg||48% RDI|
|Leucine||1218 mg||45% RDI|
|Lysine||1046 mg||50% RDI|
|Methionine||229 mg||31% RDI|
|Phenylalanine||824 mg||94% RDI|
|Threonine||642 mg||61% RDI|
|Tryptophan||181 mg||65% RDI|
|Valine||798 mg||44% RDI|
Essential Amino Acid Content of Pinto Beans
When you dig into a serving of refried beans, you’re eating pinto beans and getting these proportions of essential amino acids:
|Histidine||422 mg||60% RDI|
|Isoleucine||728 mg||52% RDI|
|Leucine||1308 mg||48% RDI|
|Lysine||1077 mg||51% RDI|
|Methionine||200 mg||27% RDI|
|Phenylalanine||908 mg||98% RDI|
|Threonine||566 mg||54% RDI|
|Tryptophan||185 mg||66% RDI|
|Valine||887 mg||49% RDI|
Essential Amino Acid Content of Chickpeas
Otherwise known as garbanzo beans, chickpeas are used in salads and soups and bring us everyone’s favorite pita dipper—hummus! Here’s the EAA composition of chickpeas:
|Histidine||400 mg||57% RDI|
|Isoleucine||623 mg||45% RDI|
|Leucine||1035 mg||38% RDI|
|Lysine||973 mg||46% RDI|
|Methionine||190 mg||26% RDI|
|Phenylalanine||779 mg||89% RDI|
|Threonine||540 mg||51% RDI|
|Tryptophan||139 mg||50% RDI|
|Valine||610 mg||34% RDI|
Essential Amino Acid Content of Mung Beans
Although lower in methionine and valine then some of the other popular beans, mung beans can be enjoyed sprouted or dried and are a versatile cooking staple. Here’s what you get in 1 cup of mung beans:
|Histidine||414 mg||59% RDI|
|Isoleucine||600 mg||43% RDI|
|Leucine||1099 mg||40% RDI|
|Lysine||990 mg||47% RDI|
|Methionine||170 mg||23% RDI|
|Phenylalanine||859 mg||98% RDI|
|Threonine||465 mg||44% RDI|
|Tryptophan||154 mg||55% RDI|
|Valine||735 mg||40% RDI|
Essential Amino Acid Content of Soybeans
When it comes to plant-based protein sources, soybeans are a shining star. You can enjoy them as edamame or turn them into soy milk, soy protein powder, tofu, and tempeh. One cup of cooked green soybeans has an impressive essential amino acid profile, but is still lacking in methionine.
|Histidine||598 mg||85% RDI|
|Isoleucine||977 mg||70% RDI|
|Leucine||1589 mg||58% RDI|
|Lysine||1330 mg||63% RDI|
|Methionine||270 mg||37% RDI|
|Phenylalanine||1006 mg||115% RDI|
|Threonine||886 mg||84% RDI|
|Tryptophan||270 mg||96% RDI|
|Valine||988 mg||85% RDI|
Essential Amino Acid Content of Adzuki Beans
Adzuki beans are fitting for bean bowls, pastes, and even flour! And they can hold their own in terms of beans with admirable EAA compositions. One cup of adzuki beans delivers the following EAAs:
|Histidine||455 mg||65% RDI|
|Isoleucine||690 mg||49% RDI|
|Leucine||1454 mg||53% RDI|
|Lysine||1404 mg||62% RDI|
|Methionine||182 mg||25% RDI|
|Phenylalanine||915 mg||105% RDI|
|Threonine||587 mg||56% RDI|
|Tryptophan||166 mg||59% RDI|
|Valine||890 mg||49% RDI|
Essential Amino Acid Content of Lentils
Lentils offer up an impressive 18 grams of protein in 1 cup and are a terrific source of iron. Protein and iron are two nutrients that can be lacking in vegetarian diets, which make lentils a nutrient-dense ally for plant-based eaters.
|Histidine||503 mg||72% RDI|
|Isoleucine||772 mg||55% RDI|
|Leucine||1295 mg||47% RDI|
|Lysine||1247 mg||59% RDI|
|Methionine||152 mg||21% RDI|
|Phenylalanine||881 mg||108% RDI|
|Threonine||640 mg||61% RDI|
|Tryptophan||160 mg||67% RDI|
|Valine||887 mg||49% RDI|
Don’t Miss Out on the Essentials
As mentioned at the beginning of this article, the protein quality of beans, even soybeans, isn’t as high as that of animal food sources. Beans also contain phytates, which are anti-nutrients that can impair protein digestibility. While beans confer many health benefits—antioxidants, heart health, cancer protection, and appetite control to name a few—it’s important to complement your protein intake with other plant-based foods, such as quinoa, in addition to animal foods.
If you are vegan or vegetarian, you can get your essential amino acids from a vegetarian or vegan essential amino acid supplement rather than from dietary protein from meat or animal byproducts.
All Amino Co blends are vegetarian approved, gluten-free, non-GMO, halal, and free of additives and artificial sweeteners, and our Life blend is also vegan. You can supplement your diet with the essentials here.