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United States Department of Agriculture

Agricultural Research Service

Spillin' the Beans on Good Nutrition
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By Philip Reeves

Dry beans are good for your health! The 2005 Dietary Guidelines for Americans issued by the U.S. Department of Health and Human Services and the U.S. Department of Agriculture recommends eating at least three cups of cooked dry beans per week. One cup of beans per day will give you a high percentage of the RDA (Recommended Daily Allowance) for protein, copper, zinc, iron, potassium, and the vitamin folate. One cup of beans also contains high fiber, good carbohydrates, very low fat, and only about 250 calories.

Dry beans were a staple food for native peoples of the Americas more than 6,000 years ago. Today, dry beans are used sparingly in the American diet - about a half cup per person per week. However, because of their high nutritional value, probably more should be consumed. The U.S. Food and Drug Administration recently approved the statement, "Diets including beans may reduce your risk of heart disease and certain cancers", to be placed on packages of dry beans.

North Dakota ranks first among the states in dry bean production of all classes. For the 2003/2004 crop, North Dakota produced more than twice as many beans as the next highest state, Nebraska. Of the many varieties of edible dry beans, pinto beans make up about half of those consumed in the U.S.

The good nutritional value and health benefits of dry beans have been known for many years, but only recently have nutritionists begun to publicize those benefits. One cup of cooked beans will provide about 25% of your protein needs. However, as with most plant proteins, bean protein does not contain enough of what we call the sulfur amino acids, and the amino acid tryptophan. These must be obtained from other food proteins such as eggs, meat, and dairy products.

Beans also are an excellent source of copper, with one cup providing 40 to 50% of the RDA, and of iron, with 20% of the RDA for women of childbearing age and 40% for men. Beans also contain essential vitamins, including folate at about 70% of the RDA in one cup. Folate is important in the diet of pregnant women to help prevent birth defects.

As with most food derived from plant seeds, beans contain a complex collection of compounds, some of which tend to reduce the absorption of nutrients such as iron and zinc. However, preliminary results from a recent study at the Grand Forks Human Nutrition Research Center by Dr. Jack Saari and myself show that the nutrient copper is almost 100% available for absorption from cooked dry beans.

Dry beans also contain the so-called "good carbohydrates", those that have a low glycemic index. This means that they are slowly digested and do not raise blood sugar and blood insulin levels as fast or as high as the more refined carbohydrates such as starches and sugars.

Beans are high in soluble fibers, which have been shown to reduce serum cholesterol. In addition, beans contain "resistant starches" that are not readily digested in the small intestine. Instead, they are passed on to the colon where bacteria break them down and form short chain fatty acids, such as butyric acid. In studies with laboratory animals, this compound has been shown to promote colon health by preventing pre-cancerous lesions in the lower bowel.

To learn whether beans can benefit the colon health of humans, an upcoming study at the Grand Forks Human Nutrition Research Center will determine the effects of including a half cup serving of beans in the daily diet of free-living volunteers. We will evaluate the effects on the production of short chain fatty acids, and on changes in populations of specific bacteria in the colon, particularly those associated with colon health. For this study, the Center is accepting applications from men and women, ages 18 to 55 years.

Last Modified: 10/23/2006
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