Antioxidant Superstars: Vegetables and Beans

The lowly bean has been boosted to star status. A ground-breaking study that looked at numerous foods says beans -- red, black, pinto, kidney -- are high-octane sources of antioxidants.

Antioxidants are the disease-fighting compounds that Mother Nature puts in foods to help our bodies stay healthy, explains researcher Jeffrey Blumberg, PhD, professor of nutrition at Tufts University in Boston. "Our job is to take advantage of those antioxidants."

The USDA guidelines recommend eating a variety of fruits and vegetables each day, selecting from all five vegetable subgroups: dark green vegetables, legumes (beans), starchy vegetables, orange vegetables, and other vegetables. They also suggest eating at least two and a half cups of vegetables daily for people eating 2,000 calories.

Which of these are the best antioxidant foods? Researchers used advanced technology to study 100 fruits, vegetables, and other food sources to measure the levels of antioxidants. Beans were the clear winners, but so was a quirky mix of other veggies -- artichoke hearts, russet potatoes, sweet potatoes, spinach, and eggplant.

Knowing which foods have the most antioxidants is important, because in today's polluted world, the human body needs all the help it can get to fight disease-causing free radicals. That's what antioxidants do -- stop free radicals from damaging other cells in your body.

The biggest class of antioxidants is flavonoids. Researchers have identified some 5,000 different flavonoids fruits and vegetables, explains Ronald Prior, PhD, a chemist and nutritionist with the USDA's Arkansas Children's Nutrition Center in Little Rock, Ark. He authored the groundbreaking antioxidant measure study.

Yet the body simply doesn't absorb all flavonoids equally well - that is, not all are as bioavailable as others. "Bioavailability has to do with absorption or metabolism in the gut, a process we know very little about," Prior says.

Here's the science behind it: An antioxidant attached to a fiber or sugar molecule may require certain enzymes in the gut to help absorption, he explains. If those enzymes are there, the flavonoid is absorbed. Some flavonoids simply don't seem to get absorbed. It's still relatively a mystery what happens in the gut, Prior notes.

Cooking some vegetables even slightly can help boost bioavailability, Prior says. "Tomatoes are a classic example. Flavonoids in cooked tomatoes are better absorbed than raw tomatoes. We don't know for sure what's happening in the gut, but we do know this is true."

However, cooking is not always good. It kills antioxidants in some foods, he says. Until researchers figure it out, "aim to eat those at the higher end of the antioxidant chart," says Prior.

The Antioxidant Winner: Beans

Prior's study found beans to be clear winners - one-half cup of red beans yields 13,727 antioxidants; red kidney beans have 13,259; pinto beans, 11,864; and black beans, 4,191. Beans are inexpensive and filling. Classic meals such as beans and rice, beans in a burrito, split pea soup, and a peanut butter sandwich are bean naturals. (Peanuts are not nuts; they are in the same family of plants as beans and peas.)