Nutritional Profile

Energy value (calories per serving): Moderate

Protein: High Fat: Low

Saturated fat: Low

Cholesterol: None

Carbohydrates: High

Fiber: Very high Sodium: Low

Major vitamin contribution: Vitamin B6, folate

Major mineral contribution: Iron, magnesium, zinc

About the Nutrients in This Food

Beans are seeds, high in complex carbohydrates including starch and dietary fiber. They have indigestible sugars (stachyose and raffinose), plus insoluble cellulose and lignin in the seed covering and soluble gums and pectins in the bean. The proteins in beans are limited in the essential amino acids methionine and cystine." All beans are a good source of the B vitamin folate, and iron.

One-half cup canned kidney beans has 7.5 g dietary fiber, 65 mcg folate (32.5 percent of the RDA for a man, 36 percent of the RDA for a woman), and 1.6 mg iron (10.6 percent of the RDA for a woman of childbearing age).

Raw beans contain antinutrient chemicals that inactivate enzymes required to digest proteins and carbohydrates. They also contain factors that inactivate vitamin A and also hemaglutinins, substances that make red blood cells clump together. Cooking beans disarms the enzyme inhibitors and the anti-vitamin A factors, but not the hemaglutinins. However, the amount of hemaglutinins in the beans is so small that it has no measurable effect in your body.

The Most Nutritious Way to Serve This Food

Cooked, to destroy antinutrients.

With grains. The proteins in grains are deficient in the essential amino acids lysine and isoleucine but contain sufficient tryptophan, methionine, and cystine; the proteins in beans are exactly the opposite. Together, these foods provide "complete" proteins.

With an iron-rich food (meat) or with a vitamin C—rich food (tomatoes). Both enhance your body's ability to use the iron in the beans. The meat makes your stomach more acid (acid favors iron absorption); the vitamin C may convert the ferric iron in beans into ferrous iron, which is more easily absorbed by the body.

Diets That May Restrict or Exclude This Food

Low-calcium diet

Low-fiber diet

Low-purine (antigout) diet

Buying This Food

Look for: Smooth-skinned, uniformly sized, evenly colored beans that are free of stones and debris. The good news about beans sold in plastic bags is that the transparent material gives you a chance to see the beans inside; the bad news is that pyridoxine and pyridoxal, the natural forms of vitamin B₆, are very sensitive to light.

Avoid: Beans sold in bulk. Some B vitamins, such as vitamin B6 (pyridoxine and pyridoxal), are very sensitive to light. In addition, open bins allow insects into the beans, indicated by tiny holes showing where the bug has burrowed into or through the bean. If you choose to buy in bulk, be sure to check for smooth skinned, uniformly sized, evenly colored beans free of holes, stones, and other debris.

Storing This Food

Store beans in air and moisture proof containers in a cool, dark cabinet where they are protected from heat, light, and insects.

Preparing This Food

Wash dried beans and pick them over carefully, discarding damaged or withered beans and any that float. (Only withered beans are light enough to float in water.)

Cover the beans with water, bring them to a boil, and then set them aside to soak. When you are ready to use the beans, discard the water in which beans have been soaked. Some of the indigestible sugars in the beans that cause intestinal gas when you eat the beans will leach out into the water, making the beans less "gassy."

What Happens When You Cook This Food

When beans are cooked in liquid, their cells absorb water, swell, and eventually rupture, releasing the pectins and gums and nutrients inside. In addition, cooking destroys anti nutrients in beans, making them more nutritious and safe to eat.

How Other Kinds of Processing Affect This Food

Canning. The heat of canning destroys some of the B vitamins in the beans. Vitamin B is water-soluble. You can recover all the lost B vitamins simply by using the liquid in the can, but the liquid also contains the indigestible sugars that cause intestinal gas when you eat beans.

Preprocessing. Preprocessed dried beans have already been soaked. They take less time to cook but are lower in B vitamins.

Medical Uses and/or Benefits

Lower risk of some birth defects. As many as two of every 1,000 babies born in the United States each year may have cleft palate or a neural tube (spinal cord) defect due to their mothers' not having gotten adequate amounts of folate during pregnancy. The current RDA for folate is 180 mcg for a woman and 200 mcg for a man, but the FDA now recommends 400 mcg for a woman who is or may become pregnant. Taking a folate supplement before becoming pregnant and continuing through the first two months of pregnancy reduces the risk of cleft palate; taking folate through the entire pregnancy reduces the risk of neural tube defects.

Lower risk of heart attack. In the spring of 1998, an analysis of data from the records for more than 80,000 women enrolled in the long-running Nurses Health Study at Harvard School of Public Health/Brigham and Woman's Hospital in Boston demonstrated that a diet providing more than 400 mcg folate and 3 mg vitamin B6 a day from either food or supplements, more than twice the current RDA for each, may reduce a woman's risk of heart attack by almost 50 percent. Although men were not included in the analysis, the results are assumed to apply to them as well. NOTE: Beans are high in B6 as well as folate. Fruit, green leafy vegetables, whole grains, meat, fish, poultry, and shellfish are good sources of vitamin B6.

To reduce the levels of serum cholesterol. The gums and pectins in dried beans and peas appear to lower blood levels of cholesterol. Currently there are two theories to explain how this may happen. The first theory is that the pectins in the beans form a gel in your stomach that sops up fats and keeps them from being absorbed by your body. The second is that bacteria in the gut feed on the bean fiber, producing short-chain fatty acids that inhibit the production of cholesterol in your liver.

As a source of carbohydrates for people with diabetes. Beans are digested very slowly, producing only a gradual rise in blood-sugar levels. As a result, the body needs less insulin to control blood sugar after eating beans than after eating some other high-carbohydrate foods (such as bread or potato). In studies at the University of Kentucky, a bean, whole-grain, vegetable, and fruit-rich diet developed at the University of Toronto enabled patients with Type I diabetes (who do not produce any insulin themselves) to cut their daily insulin intake by 38 percent. Patients with Type II diabetes (who can produce some insulin) were able to reduce their insulin injections by 98 percent. This diet is in line with the nutritional guidelines of the American Diabetes Association, but people with diabetes should always consult with their doctors and/or dietitians before altering their diet.

As a diet aid. Although beans are high in calories, they are also high in bulk (fiber); even a small serving can make you feel full. And, because they are insulin-sparing, they delay the rise in insulin levels that makes us feel hungry again soon after eating. Research at the University of Toronto suggests the insulin-sparing effect may last for several hours after you eat the beans, perhaps until after the next meal.

Adverse Effects Associated with This Food

Intestinal gas. All legumes (beans and peas) contain raffinose and stachyose, complex sugars that human beings cannot digest. The sugars sit in the gut and are fermented by intestinal bacteria which then produce gas that distends the intestines and makes us uncomfortable. You can lessen this effect by covering the beans with water, bringing them to a boil for three to five minutes, and then setting them aside to soak for four to six hours so that the indigestible sugars leach out in the soaking water, which can be discarded. Alternatively, you may soak the beans for four hours in 9 cups of water for every cup of beans, discard the soaking water, and add new water as your recipe directs. Then cook the beans; drain them before serving.

Production of uric acid. Purines are the natural metabolic by-products of protein metabolism in the body. They eventually break down into uric acid, sharp crystals that may concentrate in joints, a condition known as gout. If uric acid crystals collect in the urine, the result may be kidney stones. Eating dried beans, which are rich in proteins, may raise the concentration of purines in your body. Although controlling the amount of purines in the diet does not significantly affect the course of gout (which is treated with allopurinol, a drug that prevents the formation of uric acid crystals), limiting these foods is still part of many gout regimens.

Food/Drug Interactions

Monoamine oxidase (MAO) inhibitors. Monoamine oxidase (MAO) inhibitors are drugs used to treat depression. They inactivate naturally occurring enzymes in your body that metabolize tyramine, a substance found in many fermented or aged foods. Tyramine constricts blood vessels and increases blood pressure. If you eat a food containing tyramine while you are taking an MAO inhibitor, you cannot effectively eliminate the tyramine from your body. The result may be a hypertensive crisis. Some nutrition guides list dried beans as a food to avoid while using MAO inhibitors.