Protein's structure is built from various combinations of amino acids -- the building blocks of protein. Of the 22 amino acids, 9 are considered essential because they cannot be created from parts of other amino acids. The human body is able to make up for any shortfall of the other 13 amino acids by rearranging chemical bonds to convert one amino acid to another.
Complementary Proteins
The conventional nutrition wisdom of 10 more years ago said that protein had to be "complete." Animal products like meat and eggs contain all the essential amino acids, so they could be eaten on their own, but foods that did not contain all the essential amino acids had to be combined with complementary proteins and eaten at the same meal to be utilized. The medical community has since come to understand that combining proteins is not necessary.
Beans and Rice
Beans contain adequate amounts of eight of the nine amino acids, but, with the notable exception of soybeans, they tend to be low in methionine. Rice also contains adequate amounts of eight of the nine amino acids -- including methionine -- but it is low in lysine. By combining rice and beans, you get a dish that is a "complete" protein that contains adequate levels of all nine essential amino acids.
Cholesterol, Fat and Saturated Fat
In addition to being an excellent source of protein, beans and rice also provide a wealth of nutrients including thiamin, riboflavin, magnesium, B-6, niacin, potassium and manganese. And unlike many animal proteins, rice and beans have little total fat, no saturated fat and no cholesterol.
Fiber
Beans have an average of 8 g of fiber per ½ cup serving and whole grains have 2 g per ½ cup serving. Animal sources of protein do not have fiber, so by replacing your steak or chicken with beans and rice, you will raise your fiber intake by 10 g. The 2010 "Dietary Guidelines for Americans" recommends that you eat a minimum of 14 g of protein for every 1,000 calories in your diet, and higher fiber intakes are associated with lower body weight and lower incidence of heart disease and cancer.
References
- USDA National Nutrient Database for Standard Reference: Beans, Black, Boiled
- USDA National Nutrient Database for Standard Reference: Rice, Brown, Boiled
- "Krause's Food and Nutrition Therapy: 12th Edition"; L. Kathleen Mahan and Sylvia Escott-Stump; 2008
- "Nutrition and Wellness"; Winston J. Craig; 1999
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