Legumes & Amino Acids

Legumes are a class of vegetables and a good source of protein. Legumes, which include peas, beans, lentils, soybeans and peanuts, are also an excellent source of fiber and naturally low in cholesterol and fat. While most legumes are not complete proteins, they do provide most of the essential amino acids.

Essential Amino Acids

Amino acids are the building blocks of protein. Proteins are part of every cell and tissue in your body. Protein in the foods you consume is digested into amino acids, which are later used to replace proteins. Humans can produce 10 of the 20 amino acids, which means, you do not have to obtain these non-essential amino acids through your diet. However, the other 10 -- the essential amino acids -- must come from the food you eat. Amino acids are not stored, so you must consume essential amino acids regularly to prevent degradation of body protein.

Limiting Amino Acids

Not all essential amino acids are provided by legumes, with the exception of soybeans. A limiting amino acid is the essential amino acid that is missing, or that is present in a lower amount than is needed by the body. Methionine is the limiting amino acid in legumes. Soybeans provide a greater amount of methionine than other legumes and are considered a complete protein. If you ate no other protein, the limiting amino acid could be an issue for proper protein synthesis. However, if you consume eggs, meat, soy, milk or whole grains throughout the day, the methionine is provided and no longer a concern.

Suggested Intake

You can consider legumes either a vegetable or protein source when planning your daily menu. One-half cup is considered 1 vegetable serving and 1/4 cup of cooked beans is equivalent to a 1 oz. serving of meat protein. If you consume animal protein, you should count beans, peas and lentils toward your recommended daily intake of 2 to 3 cups of vegetables.

Cooking Suggestions

Canned beans are a quick way to get your veggies and protein. Check labels and choose the low-sodium varieties if sodium is a concern for you. Using dried beans in your recipes takes a little more time to cook, from 2 to 10 hours, but they are less expensive. Dried forms, with the exception of lentils and black-eyed peas, require soaking in water for proper rehydration and softening, so plan ahead.