A convenient way to increase legume intake

By Mark Messina and Virginia Messina

In This Section

February 2009

Until about 15 years ago, soyfoods were popular only with vegetarians and other health-conscious individuals. But with a growing body of research on the health benefits of these foods, mainstream consumers are now embracing them as well. And in response to demand, conventional grocery stores are just as likely as food co-operatives and health food markets to offer these foods.

But even those who do not have an interest in soy are likely to consume it-whether they realize it or not. A wide range of foods, including baked goods and convenience products, contain soy protein as a functional ingredient. Soy protein is added to foods for moisture retention, whitening, gel formation, oxidation inhibition, and emulsification, all of which can serve to improve product shelf life and organoleptic properties. More recently, it has been added to a variety of products such as cereals and protein bars to boost protein content of foods, particularly foods aimed at weight control. Technological advances have produced soy protein products that fit the needs of a wide range of food manufactures. As a result, the soybean is one of the few legumes to which Americans are regularly exposed.

But while interest in soyfoods and exposure to soy protein have increased, Americans have a limited relationship with other legumes. The Dietary Guidelines for Americans recommends consuming 3 cups (6 servings) of legumes per week, but few Americans meet that goal. Average daily intake of beans is less than 1 cup per week, and less than one-third of Americans report eating beans on any given day. Even vegetarians consume only about one-half cup of beans per day according to one survey.

Bean consumption in the United States is similar to that in most European countries. However, beans play a much more important role in diets in Asia, Central and South America, and Mexico. For example, although US residents get less than 2% of their protein from beans, Japanese and Brazilians get more than 10% of their protein from legumes.

There is good reason to encourage greater bean consumption. Replacing animal foods in the diet with legumes reduces saturated fat intake without compromising overall protein intake. Beans are also superior sources of fiber, folate, and potassium, among other nutrients. Because many Americans meet less than half the Dietary Reference Intake for potassium, identifying good sources of this nutrient is a public health issue. Beans are higher in potassium than most other foods, and equal to dairy in that regard.

Although they are high in carbohydrate, beans have a low glycemic index, attributable in part to their high contents of both fiber and resistant starch. As a result, the glycemic load of beans is actually quite modest. Resistant starch is the sum of starch and products of starch degradation that are not absorbed in the small intestine of healthy individuals. Foods with a high concentration of  resistant starch may improve digestive health and glycemic control and possibly reduce colon cancer risk and increase calcium absorption. One-half cup of beans provides about 3 grams of resistant starch, which is equal to at least half of the estimated 4 to 6 grams of resistant starch consumed daily by the typical US resident. Evidence suggests the consumption of at least twice that amount is closer to the ideal.

Even moderate bean consumption can make a significant contribution to fiber intake. One serving of beans provides about 7 grams of fiber, which is half the average daily intake of US residents and about 25% of the recommended intake. Substituting just 1 cup of beans for animal food or refined grains could double fiber intake and help Americans meet recommendations. Finally, beans are high in antioxidants, providing amounts that are equal to those found in foods such as strawberries and blueberries, both much touted for their antioxidant content.

Antioxidants protect against the oxidative damage to biological molecules such as protein, lipids, and DNA that is thought to increase risk of certain forms of cancer, heart disease, and possibly even diseases such as Alzheimer's and to contribute to the aging process. Exposure to free radicals that cause this damage comes in many forms such as environmental pollutants, but they are also generated endogenously. Although the human body has an elaborate system to defend against free radicals, it is not 100% successful. Therefore, consuming foods that are high in antioxidants is thought to reduce risk of a variety of diseases. The major emphasis on increasing fruit and vegetable intake that has taken place in recent years can be attributed in part to their antioxidant content.

In recent years, the ORAC (Oxygen Radical Absorbance Capacity) has emerged as the most commonly used method of measuring the antioxidant capacities of different foods. It was developed by the scientists at the National Institute on Aging. In a recent analysis of a wide range of foods conducted by the US Department of Agriculture, the total antioxidant content of beans on a per serving basis exceeded that of many fruits and vegetables as shown in Table 1. The antioxidant activity of beans combined with their phytochemical (phenolic acids, saponins, etc.), fiber, and resistant starch contents may individually or collectively account for the reduced risks of heart disease and cancer associated with bean intake shown in many epidemiologic studies. The oligosaccharides in beans, which are responsible for the gas production sometimes associated with these foods, are also prebiotics and may improve intestinal health.

Bean consumption also addresses two concerns of growing interest to many consumers. First, agricultural production of beans has a low environmental impact compared with animal foods and even some plant foods. They require less water than crops such as corn and wheat, and their symbiotic growth with rhizobia adds nitrogen back to the soil. Second, beans are a highly economical food.

But despite the many benefits of beans, and the important role they have played in the cuisines of populations throughout the world, US residents have largely ignored this food category. There are psychological barriers against legume consumption since beans are often perceived as bland, uninteresting, and difficult to prepare

A recently developed line of bean products marketed under the brand name VegeFullTM (www.admworld.com/vegefull ) by the Archer Daniels Midland Co. addresses many concerns about bean consumption. These cooked ground bean powders and dehydrated, cooked black, red, navy, and pinto beans provide convenient ways for food processors to incorporate beans into meals and individual products. VegeFull is marketed to manufacturers who are looking for ways to increase the protein, fiber, and antioxidant content of a wide variety of foods. Applications include pizza crusts, bagels, cookies, extruded snacks, dips, spreads, salads, and soups, utilizing whole and cut beans in a variety of ways. Whole precooked dehydrated beans can be incorporated into recipes in the same way that prepared beans are used. Replacing flour with bean powder (one-for-one in most batters or doughs) is a new way to incorporate vegetables into products. VegeFull powders can add a natural color to give a new look to existing products; for example red bean powders can be added to a flour tortilla to make a nutritious and appealing red tortilla. As the public and the food industry learn more about the nutritious and healthful properties of beans, one can expect that products such as VegeFull will be part of an increasing number of commonly consumed foods.

Mark Messina owns his own consulting company, Nutrition Matters, Inc., and is an adjunct associate professor in the Department of Nutrition, School of Public Health, at Loma Linda University (Loma Linda, California, USA). He has organized and chaired all eight international symposia on the role of soy in preventing and treating chronic disease and is the chairperson of the editorial board of The Soy Connection, a quarterly newsletter on soy that is distributed to more than 125,000 dietitians and other health professionals. He can be contacted at: markm@olympus.net .

Virginia Messina is a dietitian and public health nutritionist specializing in vegetarian diets. She is a former co-author of the American Dietetic Association's Position on Vegetarian Diets and is co-author of six books on vegetarian diet and cooking. She works as a consultant and writer for a variety of publications and organizations, and provides information through her website www.vegnutrition.com  and her blog www.veggiedietitian.blogspot.com . She can be contacted at messina@olympus.net .