Beans, Beans...

by Jeff Novick, M.S., R.D., L.D./N.

We keep hearing that Americans have become more health conscious, but have they really?

Perhaps you have heard that we consume more beans. That we eat almost 8 pounds per person each year. However, what you probably didn't hear is that pinto and navy beans account for 5 of those pounds, and those are eaten mostly as refried beans (pintos) or as canned pork and beans (navy).

In all, U.S. growers harvested over 3 billion pounds of edible dried beans in 1998, worth over $600 million. But despite beans' familiarity and popularity, few of us are aware of the surprising amount of convenience, nutrition and health that can be found in an inexpensive can of beans.

One of the beans that has gotten the most attention lately has been the soybean. Many soy products, like tofu, soy milk, and soy cheese, have been flooding the market. Recently, the FDA approved a health claim for some soy products ruling that foods containing 6.25 grams/serving or more of soy protein, as part of a diet low in saturated fat and cholesterol, may reduce the risk for coronary heart disease. The FDA ruling approved soy protein, not the whole bean, as heart healthy. Sources of soy protein identified in the ruling include foods composed of or derived from whole soybeans and foods that contain processed soy protein ingredients, including isolated soy protein, soy protein concentrate, soy flour, texturized soy protein, or texturized vegetable protein.

It is still not clear which components of soy are beneficial in lowering cardiovascular disease risk factors. Soy isoflavones may also be a component involved. Many of you may be familiar with isoflavones as they are also the component of soy that are thought to be responsible for the beneficial effect of soy on hot flashes.

Soy has been shown in several studies to reduce certain risk factors for cardiovascular disease, including total cholesterol, LDL, and triglycerides.

But does soy have any real advantage over other beans?

Soy beans are high in fat containing a fat to protein ratio about 10 times higher then most other beans. Could other beans, which have much lower fat to protein ratios be as good, if not better, than soybeans for hypercholesterolemia?

A closer look at some other beans.

Soy is neither unique in protein nor isoflavone content. One comment received by the FDA noted that soy protein's cholesterol lowering effects may be due in part to its amino acid composition, specifically its high arginine and low methionine content. Other vegetable proteins, such as pea proteins, have a similar amino acid profile. The FDA responded that it had not reviewed any data on other vegetable protein and that virtually all prospective studies have examined only soy protein.

The primary isoflavones in soy are genistein and daidzein. If these are the active component, then, like protein, are other beans as good a source, if not better, than soybeans?

One study found that anasazi, brown, black, navy, pinto and turtle beans contain about as much as or more genistein than soybeans (J Altern Compl Med. 1997;3:7-12).

When considering the fat to protein ratio (without moisture), there are many other beans that are better sources of isoflavones like the kidney bean, lima bean and mung bean.

Most beans are about 1% fat, while the soybean is about 18-20% fat, of which 15% is saturated, 23% monounsaturated, and 58% polyunsaturated. Of the 58% polyunsaturated, 51% is omega 6 and 7% is omega 3. As we know, not all fats are created equal. Omega 3 fats have been shown to be beneficial. Omega 6 fats have effects on lipid oxidation and blood clotting, but it is still not clear whether this is beneficial or not. Saturated fat should be avoided.

The only other bean that is high in fat is the peanut. Dried peanuts are 33-50% fat including about 31% polyunsaturated, and about 13% saturated fat.

And there are even more benefits to other beans...

We have all heard about the benefit of eating more red grapes, oranges, pink grapefruit, strawberries, blueberries — all foods that contain colored pigments with nutritious cancer- and heart-disease-fighting compounds called flavonoids. They are the anti-aging antioxidants. Flavonoids are also known to be in many other fruits and vegetables, as well as in green and black teas and soy protein.

Now, Agricultural Research Service food quality geneticist and plant breeder George L. Hosfield has found these flavonoids in bean seed coats, which is where bean colors are also found. And beans come in a mosaic of colors that can rival the colors of fruits and vegetables.

The seed coat, which is 10 percent of the bean, is not only high in antioxidants for some beans, but is also where the high fiber content of beans comes from.

It was Hosfield who found the antioxidants in the bean coat. He and colleagues removed the coating and made it into an extract, which they freeze-dried. Then, they analyzed the constituents. They found eight flavonoids, six of which were particularly strong antioxidants. They also found a genetic link between bean color and the flavonoids. His work is published in the September 2000 issue of Agricultural Research magazine.

Beans could claim a place among colorful fruits, berries and vegetables as nutritious cancer- and heart disease-fighting foods, U.S. Department of Agriculture research has shown. Beans are great sources of not only fiber, but also soluble fiber.

Beans are excellent sources of protein and amino acids. Beans are also great sources of isoflavones and phytochemicals. However, there is no real magic to the soybean, and like the peanut, they are also fairly high in fat.

You can get all these benefits without the fat by choosing other healthy and colorful beans, along with a diet high in fruits and vegetables.