Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338
December 12, 2003
Beans rich source of healthy antioxidants, finds U of G researcher
A University of Guelph researcher has found that beans, particularly black ones, are a rich but overlooked source of antioxidants and may provide health benefits similar to some common fruits. It's the first study to link bean colour to antioxidant activity.
"Black beans are really loaded with antioxidant compounds. We didn't know they were that potent until now," said Clifford Beninger, an environmental biology researcher who led the study. "It's maybe a bit of a wake up call that we should be eating more beans."
The results will appear in the Dec. 31 issue of the Journal of Agricultural and Food Chemistry, a peer-reviewed publication of the American Chemical Society, the world's largest scientific society.
Beninger and George Hosfield of the U.S. Department of Agriculture tested the antioxidant activity of flavonoids — plant pigments — found in the skin of 12 common varieties of dry beans. Antioxidants destroy free radicals, which are highly active chemicals whose excess has been linked to heart disease, cancer and aging.
Black beans came out on top, having more antioxidant activity, gram for gram, than other beans, followed by red, brown, yellow and white beans, in that order. In general, darker coloured seed coats were associated with higher levels of flavonoids, and therefore higher antioxidant activity, said Beninger.
The study found that one class of flavonoid pigments in particular, anthocyanins, were the most active antioxidants in the beans. Based on a previously published study of the anthocyanin content of black beans, Beninger found that the levels of anthocyanins per 100 gm serving size of black beans was about 10 times the amount of overall antioxidants in an equivalent serving size of oranges and similar to the amount found in an equivalent serving size of grapes, apples and cranberries.
"We don't know if the cooking process alters the amount of antioxidants in the beans," said Beninger. Although dry beans were used in this study, frozen or canned beans may have similar antioxidant activity, he said.
"Human studies are still needed to confirm the link between bean antioxidants and health and until then, no one knows how many beans one must eat to obtain maximum health benefits," said Beninger.
The finding adds antioxidants to a growing list of healthy chemicals found in the widely available and inexpensive legume, which is also rich in protein, carbohydrates, folate, calcium and fiber. The researchers hope to use information gleaned from this study to help develop new varieties of beans that pack even more disease-fighting power.
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