The pinto bean, part of the Phaseolus vulgaris bean family, has been cultivated for thousands of years, mainly in the region now known as Mexico. "Pinto" is the Spanish word for "painted" and refers to the beans' mottled skin, which is similar to the pinto horse. While the pinto bean is an excellent source of protein, it is not considered complete, which is why indigenous peoples combined it with rice and corn.
Protein and Amino Acids
Protein consists of chains of amino acids. Protein is digested in the gut to yield up to 20 different amino acids, which are used as building blocks to make connective tissue, muscle fiber, fingernails, hair, enzymes and other substances. Of the 20 amino acids used in humans, nine are considered essential because they can't be synthesized internally. These essential amino acids must be obtained from dietary sources. and they include leucine, isoleucine, valine, lysine, threonine, tryptophan, methionine, phenylalanine and histidine. Most animal-based sources of protein are complete and contain all the amino acids in proper proportions. Vegetable-based sources of protein, such as legumes, rarely contain all the amino acids and are traditionally eaten with carbohydrates to avoid any deficiencies.
Pinto Bean Nutritional Facts
In general, legumes, such as pinto beans, are excellent sources of protein, fiber, B-vitamins and various minerals. In fact, according to the "American Dietetic Association Complete Food and Nutrition Guide," one cup of pinto beans contains 236 calories and 14g of protein, which is 28 percent of the U.S. Recommended Daily Allowance of protein for adults. However, with the exception of soy beans, all legumes are incomplete protein sources. In particular, pinto beans lack the essential amino acid methionine. Pinto beans can be combined with methionine-rich foods to avoid deficiency.
Combining Strategies
In general, legumes contain either no or very low levels of methionine, but are usually rich in lysine. Vegetarians often compensate by mixing legumes with grains, which are high in methionine and low in lysine. The native Indians of Mexico traditionally ate pinto beans with corn tortillas, especially during the winter months when meat was hard to come by. Combining pinto beans with some meat, dairy products, whole-wheat pasta or brown rice will also provide all the essential amino acids. According to "Contemporary Nutrition: Functional Approach," mixing two parts corn and one part pinto beans is almost equal in protein quality to fresh milk.
Pinto Bean Types and Preparation
There are various types of pinto beans, which include the Burke, Othello, Maverick and Sierra types. The pinto bean is most often eaten whole in broth or mashed and refried. Pinto beans are the most commonly used for refried beans and often used for filling in burritos. The young bean pods can also be harvested and cooked as green pinto beans.
References
- "Advanced Nutrition: Macronutrients, Micronutrients, and Metabolism"; Carolyn D. Berdanier; 2009
- "American Dietetic Association Complete Food and Nutrition Guide"; American Dietetic Association; 2006
- "Biochemistry of Human Nutrition"; George Gropper; 2000
- "Contemporary Nutrition: Functional Approach"; Gordon M. Wardlaw; 2009
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