The Color of Beans

Allison J. Cleary

Black magic

Black is in. And we’re not talking urban fashion here, we’re talking beans. Researchers in Michigan have found that the darker the skin of a bean, the higher its level of antioxidants, the protective compounds that can work against cancers and cardiovascular disease.

In painstaking work that involved identifying and comparing the chemical components in the skins of a large number of different varieties of beans, from pintos to navy beans, geneticist George Hosfield and a team of researchers at the USDA Agricultural Research Service at Michigan State University found that the most potent levels of antioxidants, in the form of flavonols, anthocyanins and tannins, were found in black beans, followed by red, brown, then yellow and finally white, in order of descending power.

“If you have a choice, go for the darker bean,” Hosfield advises. But he’s quick to explain that regardless of color, all beans are healthful. “I’ve been working with beans for 28 years, and you can’t find a better plant food for its proteins, energy, zinc, iron, folic acid and fiber. And the glycemic index of beans is low, so it doesn’t cause surges in blood sugar.” On days when he eats white beans, in Michigan’s traditional Navy Bean Soup, for example, he makes sure to drink a glass of red wine, also full of antioxidants.

In a country where per capita consumption of sugar and related sweeteners has reached 149 pounds, but bean consumption is less than eight pounds, Hosfield says people would benefit from eating more beans. “My wife and I eat beans at least twice a week. I probably eat close to 50 pounds a year.” Although the study examined dry beans, Hosfield suggests also eating the broth that the beans cook in because antioxidants, such as anthocyanins, the same pigments that give flowers their color, are water-soluble and can leach during cooking.