Beans Against Cancer?

“… and let them give us pulse to eat and water to drink.” -Daniel 1.12

Beans are among our most ancient foods. The major problem in discussing Phaseolus vulgaris is, well, its vulgarity. No other kind of food elicits as much low humor as “the musical fruit.” Benjamin Franklin, a vegetarian who knew his beans, once wrote a whole essay on this most unlikely of topics. He proposed a scientific prize for the inventor who could come up with “some drug, wholesome and not disagreeable, to be mixed with our common food, or sauces, that shall render the natural discharges of Wind from our bodies not only inoffensive, but agreeable as perfumes.” Like many utopian dreams of the Enlightenment, this one came to naught. That mighty Wind is, alas, still with us.

However, we should not allow a little intestinal rumbling to come between us and a truly beneficial food. Happily, beans received a major boost from the Bean Research Unit of the Department of Agriculture (USDA). The US Midwest produces much of the world’s bean supply, so it is perhaps understandable that these Michigan scientists are unabashedly partisan toward beans. However, the facts speak for themselves: the common dry bean turns out to be an outstanding source of antioxidants. When these USDA scientists analyzed the colored seed coats of twelve different types of beans they found that these legumes contained many of the same antioxidants (such as anthocyanins) that are also found in pricier berries and fruits, and also in wine. “Although these polyphenols can cause problems in digestibility,” they admitted, “they may be important dietary supplements with beneficial health effects.”

Most of the antioxidant benefit of fruits and vegetables comes from the component that gives them their color. Just as with the beta-carotene that makes the carrot orange and the lycopene that turns the tomato and the watermelon their gorgeous shades of red, so it is with beans: the darker the hue, the more abundant the supply of valuable micronutrients. According to another recent study, the amount of antioxidants varies greatly in kidney beans, but in general the greatest amount is found in red and black varieties (Choung 2003). In shopping, therefore, shun the pale cannellini and Great Northern and go for the more colorful varieties.

Taking the Pulse of the Pulses

At various times, scientists have tried to agree upon the ideal anti-cancer diet. These consensus statements by large groups of experts have generally spoken in positive tones about peas, beans and lentils (the group collectively known as pulses or legumes) and cowpeas (a related category that includes black-eyed peas). For example, the World Cancer Relief Fund/American Institute for Cancer Research (WCRF/AICR) committee included general recommendations concerning legume consumption. The opinion of the committee was that, in order to minimize the risk of developing cancer, 45-60% of dietary calories should come from starchy or protein-rich foods of plant origin. Pulses are included in this category. The World Health Organization (WHO) has also recommended a daily consumption of 30 grams (about an ounce) of pulses, including nuts and seeds, to reduce the risk of heart disease and some types of cancer.

A breakthrough in nutritional thinking came three years ago when scientists showed that people who ate legumes four times per week had a 22% lower risk of heart disease compared with people who consumed legumes less than once per week (Bazzano 2001). This finally gave empirical justification to the childhood jingle that beans are “good for the heart.” And although beans are high in carbohydrates they have a low-glycemic index (i.e., they are slowly digested), and therefore “provide a sustained source of energy that curbs caloric intake and helps to maintain weight” (Smith 2003). Because of this, beans can help people with diabetes to maintain healthy blood sugar levels.

Research over the past 20 years has in general, supported the health-promoting properties of beans. One older survey found that people who ate lots of beans enjoyed a measure of protection against breast, prostate and colon cancer (Correa 1981). Another study found an inverse trend between legume consumption and the incidence of prostate cancer (Kolonel 2000). Two experimental studies showed that feeding rodents navy, black and pinto beans inhibited the incidence of colon cancer by 52 to 57% (Hangen 2002 and Hughes 1997).

However, in most Western countries, beans get little respect and therefore little research interest. In cancer circles, it’s genes, not beans, that attract the big bucks. Questions on surveys about food consumption typically lump together all pulses, a category that generally includes nuts, seeds, lentils, peas, soy beans as well as all types of dry beans. There has been a tendency to look on beans as a source of cheap calories, but nothing more.

Beaneaters

Culturally, one cannot think of beans without thinking of Boston. At one time the local baseball team was even called the “Beaneaters.” Boston has since become a home of haute cuisine, but here in rural New England we still adhere to the old ways. The Bean Supper is a prominent feature of the social calendar, whether at the local clapboard church, Town House or Odd Fellows’ Hall. But, as a general rule, bean consumption declines as one’s socioeconomic standing improves. (The exceptions being the health-food conscious and the Tex-Mex crazed.) Consumption in Western countries tends to be quite low–a few pounds per head per year.