By Dr. Michael T. Murray
Michael T. Murray, N.D., is widely regarded as one of world's leading authorities on natural medicine. A prolific author, Dr. Murray has written over 20 books on health and nutrition including the best-selling Encyclopedia of Natural Medicine and his latest book The Encyclopedia of Healing Foods. Dr. Murray is also Director of Product Development and Education for Natural Factors one of the leading manufacturers of natural products.
Legumes (beans) are among the oldest cultivated plants. In fact, fossil records demonstrate that prehistoric people domesticated and cultivated legumes for food. Today, this extremely large category of vegetables contains over 13,000 species and is second only to grains in supplying calories and protein to the world's population. Compared to grains, legumes supply about the same number of total calories, but usually provide 2-to-4 times as much protein.
Legumes are often called "the poor people's meat," however, they might be better known as the "healthy people's meat." Many legumes, especially soybeans, are demonstrating impressive health benefits. Diets rich in legumes are being used to lower cholesterol levels, improve blood glucose control in diabetics, and reduce the risk of many cancers. Legumes contain many important nutrients and phytochemicals, and when combined with grains, they form a complete protein. According to studies conducted by the United States Department of Agriculture, richly colored dried beans offer a high degree of antioxidant protection (see below). In fact, small red kidney beans rated the highest just ahead of blueberries.
The soybean, thanks largely to the United States is now the most widely grown and utilized legume, accounting for well over 50% of the world's total legume production. In terms of dollar value, the soybean is the United States' most important crop, ranking above corn, wheat, and cotton.
A QUICK PRIMER ON COMMON BEANS
Common beans are variants of Phaseolus vulgaris and include black, kidney, lima, mung, navy, pinto, and string (or snap) beans. All of the varieties of Phaseolus vulgaris originated in Peru over 7,000 years ago, and were then spread by migrating bands of Native Americans into Latin and North America. The early explorers and settlers of the 15th, 16th, and 17th centuries were introduced to these beans by the natives. In fact, the basic recipes for Boston baked beans and succotash were derived from those used by Native Americans. Common beans were then introduced into Europe in the 15th century by Spanish explorers returning from their voyages to the New World. They were subsequently spread to Africa and Asia by Spanish and Portuguese traders.
As common beans are a very inexpensive form of good protein, they have become popular in many cultures throughout the world. However, their use as a health promoting food today seems to have been eclipsed by the growing popularity of soybeans and soy foods. Nonetheless, there is an emerging appreciation on the benefits of consumption of beans based upon the results of recent scientific investigations. One of the big differences between the common bean and the soybean is the absence of phytoestrogens and goitrogens in common beans.
The key nutritional benefits of common beans are quite similar to those discussed above for soybeans except that they are much lower in fat content—usually only 1-to-2%. Their protein content and quality is quite similar though. Common beans also offer an excellent source of complex carbohydrate and fiber. They are a very good source of folic acid and molybdenum. Common beans are also a good source of phosphorus, iron, protein, magnesium, manganese, and potassium.
The major health benefit of common beans is their rich source of cholesterol-lowering fiber. In addition to lowering cholesterol, the high fiber content of beans prevents blood sugar levels from rising too rapidly after a meal, making these beans an especially good choice for individuals with diabetes, insulin resistance, or hypoglycemia.
The common beans’ contribution to heart health lies not just in their fiber, but in the significant amounts of antioxidants, folic acid, vitamin B6, and magnesium these beans supply. Folic acid and B6 help lower levels of homocysteine, an amino acid that is an intermediate product in an important metabolic process called the methylation cycle. Elevated blood levels of homocysteine are an independent risk factor for heart attack, stroke, or peripheral vascular disease, and are found in between 20-to-40 percent of patients with heart disease.
Intake of common beans is also protective against cancer. In one analysis of dietary data collected by validated food frequency questionnaires in 1991 and 1995 from 90,630 women in the Nurses Health Study II researchers found a significant reduced frequency of breast cancer in those women who consumed a higher intake of common beans or lentils. That was not surprising, what was surprising was that only beans and lentils seemed to offer protection. Intake of tea, onions, apples, string beans, broccoli, green pepper, or blueberries had not protective effct. Eating beans or lentils two or more times per week was associated with a 24% reduced risk of breast cancer.
The largest USDA study of food antioxidants reveals common beans are amoung the best sources. Researchers with the United States Department of Agriculture analyzed antioxidant levels in over 100 different foods. Each food was measured for antioxidant concentration as well as antioxidant capacity per serving size. Base upon the results, the USDA has provided a list of the top 20 ranking of foods by antioxidant capacity. Several common beans appear within the list including small red beans at the top.
USDA Ranking of Foods by Antioxidant Capacity
1 Small Red Bean (dried) Half cup: 13727
2 Wild blueberry 1 cup: 13427
3 Red kidney bean (dried) Half cup: 13259
4 Pinto bean Half cup: 11864
5 Blueberry (cultivated) 1 cup: 9019
6 Cranberry 1 cup (whole): 8983
7 Artichoke (cooked) 1 cup (hearts): 7904
8 Blackberry 1 cup: 7701
9 Prune Half cup: 7291
10 Raspberry 1 cup: 6058
11 Strawberry 1 cup: 5938
12 Red Delicious apple One: 5900
13 Granny Smith apple One: 5381
14 Pecan 1 ounce: 5095
15 Sweet cherry 1 cup: 4873
16 Black plum One: 4844
17 Russet potato (cooked) One: 4649
18 Black bean (dried) Half cup: 4181
19 Plum One: 4118
20 Gala apple One: 3903
LEGUMES AND FLATULENCE
One of the problems with legumes is increased intestinal flatulence (gas) or intestinal discomfort. Most humans pass gas a total of 14 times per day, with a total of 1 pint. About half of the gas is swallowed air and another 40% is carbon dioxide given off by bacteria in the intestines. The remaining 10% is a mixture of hydrogen, methane, sulfur compounds, and by-products of bacteria, such as indoles, skatoles, ammonia, and hydrogen sulfide. It is this last fraction that is responsible for the offensive odors.
The flatulence causing compounds in legumes are primarily oligosaccharides, which are composed of 3-to-5 sugar molecules linked together in such a way that the body cannot digest or absorb them. Because the body cannot absorb or digest these oligosaccharides, they pass into the intestines where bacteria break them down. Gas is produced by the bacteria as they digest the oligosaccharides. Navy and lima beans are generally the most offensive.
The amount of oligosaccharides in legumes can be significantly reduced by properly cooking or sprouting them. In other words, the amount of flatulence produced by legumes can be dramatically reduced by proper cooking. If you still experience increased flatulence when you eat legumes even if they are cooked properly, you may wish to try a commercial enzyme preparation such as MultiEnzyme from Natural Factors or Beano.
COOKING COMMON BEANS
Although most beans can be purchased precooked in cans, cooking your own offers significant economical, as well as possibly health, benefits. Cooking your own will produce 3 times the amount compared to canned products.
Dried beans are best prepared by first soaking them overnight in an appropriate amount of water in the refrigerator to prevent fermentation. Soaking will usually cut the cooking time dramatically. If soaking overnight is not possible, here is an alternate method: place the dried legumes in an appropriate amount of water in a pot, for each cup of dried legumes add 1/4 teaspoon of baking soda, bring to boil for at least 2 minutes, and then set aside to soak for at least 1 hour. The baking soda will soften the legumes and help breakdown the troublesome oligosaccharides. The baking soda will also help reduce the amount of cooking time. Be forewarned, however, beans cooked using the quick soak and no soak methods may split or develop a slightly mushy consistency. For beans that retain an even shape, ideal texture, and tender, creamy bite without mushiness, overnight soaking is the optimal method. Also beans that have not been presoaked may need some additional water, about ¼ to ½ cup per cup of beans, to replace the water that evaporates as steam during their longer cooking process.
Before cooking presoaked beans, regardless of soaking method, skim off any skins that floated to the surface, drain the soaking liquid, and then rinse them with clean water. The beans should be brought to a gentle boil and then simmered with a minimum of stirring to keep them firm and unbroken. A pressure cooker or crock pot can also be used for convenience. Regardless of cooking method, do not add any seasonings that are salty or acidic, such as vinegar, wine, tomatoes, or citrus fruits and their juices, until after the beans have been cooked since adding them earlier will make the beans tough and greatly increase the cooking time. Whenever possible, use the cooking liquid as well as the beans. About 35% of the B vitamins and 50% of the folic acid will leach into the liquid when beans are cooked for 1 hour and 15 minutes.
If you are running short on time, you can always use canned beans in your recipes. If the beans have been packaged with salt or other additives, simply rinse them after opening the can to remove these unnecessary additions. Canned beans need to only be heated briefly for hot recipes, while they can be used as is for salads or prepared cold dishes.
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