Antioxidant research

The largest and most advanced analysis of the antioxidant content of common foods to date shows that disease-fighting antioxidants may be found in unexpected fruits and vegetables, such as beans, artichokes, and even the Russet potato.

Researchers found that small red beans contain more disease-fighting antioxidants than both wild and cultivated blueberries, which have been heralded in recent years for their high antioxidant content. In fact, three of the top five antioxidant-rich foods studied were beans.

The study also shows that nuts and spices, such as ground cloves, cinnamon, and oregano, are rich in antioxidants, although they are generally consumed in much smaller amounts than fruits and vegetables.

Antioxidants are believed to help prevent and repair oxidative stress, a process that damages cells within the body and has been linked to the development of cancer, heart disease, Alzheimer's disease, and Parkinson's disease.

The study, which appears in the Journal of Agricultural and Food Chemistry, used updated technology to assess the antioxidant content of more than 100 foods, including fruits, vegetables, cereals, breads, nuts, and spices.

Each food was analyzed for antioxidant concentration and ranked according to antioxidant capacity per serving size. But researchers note that the total antioxidant capacity of a food does not necessarily reflect their potential health benefit.

"A big factor in all of this is what happens in the digestion and absorption process," says Researcher Ronald Prior, PhD, a chemist and nutritionist with the USDA's Arkansas Children's Nutrition Center in Little Rock, Ark. "With some of these compounds, it appears that even though they have a high antioxidant capacity, they may not be absorbed."

It's important to remember that there are many different ways to measure antioxidants. And nobody is sure which one is most accurate.

"Right now, it's difficult to compare the antioxidant content of a can of blueberries to a fruit smoothie," said John W. Finley, Ph.D., associate editor of the Journal of Agricultural and Food Chemistry.

"There's no uniformity in the way antioxidants are evaluated. You don't know what you're getting, and that's not fair to consumers." One of the most heated issues at the meeting concerned the identification of the most reliable values for antioxidant measurements.

Finley estimates that there are currently between 25 and 100 different methods used to measure antioxidants. "A little difference in methodology can make a huge difference in results," cautioned Finley. "We need to identify the four or five best methods and make them consistent."

Cranberries, blueberries, and blackberries were ranked highest among the fruits studied. Beans, artichokes, and Russet potatoes were tops among the vegetables.

Pecans, walnuts, and hazelnuts were the winners in the nut category, and ground cloves, cinnamon, and oregano were the top three antioxidant-rich spices.

Here's the list of the top 20 food sources of antioxidants, based on their total antioxidant capacity per serving size:

Researchers also found that cooking method also had a significant effect on the antioxidant content of the foods tested, but those effects were not consistent.

For example, cooked Russet and red potatoes had much lower antioxidant levels than those found in raw potatoes. Boiling also decreased antioxidant levels in carrots, but cooking tomatoes increased their antioxidant content.

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References
Wu X, Beecher GR, Holden JM, Haytowitz DB, Gebhardt SE, Prior RL. (2004). Lipophilic and hydrophilic antioxidant capacities of common foods in the United States. Journal of Agricultural and Food Chemistry, 52, 4206-4037