America's most common apple also may be its most potent. Just don't skimp on the skin.

A Canadian government study that measured the levels of antioxidants (search) in eight varieties of apples found that Red Delicious (search) contain the highest concentrations of the health enhancing chemicals.

And to get the most bang for your bite, be sure to eat the peel.

The skin of Red Delicious apples — the most common variety grown in the United States — contains over six times more antioxidant activity than the flesh, according to researchers at Agriculture and Agri-Food Canada.

But don't swear off other varieties just yet.

Though antioxidants are believed to help ward off certain diseases, more research is needed to determine whether quantity alone counts. The study did not consider whether antioxidants in some apples may be better absorbed than others.

Until that is known, food scientist Rong Tsao says his study — which also identified the chemicals responsible for antioxidant activity in apples — probably is most useful to horticulturists breeding new, antioxidant-rich varieties.

The information also could lead to the development of techniques for harvesting antioxidants from the waste products of the apple processing industry, the bulk of which is peel, Tsao said during a recent telephone interview.

The study, to be published in the June 29 issue of Journal of Agricultural and Food Chemistry, compared apple varieties popular in Canada, some of which are available only regionally in the United States.

Red Delicious, which account for 27 percent of U.S. apple production, has more than six times the antioxidants as the bottom-ranked Empire variety. Northern Spy was No. 2, followed by Cortland, Ida Red, Golden Delicious, McIntosh and Mutsu.

And in every variety tested, the skins of the apples contained substantially higher levels of antioxidants than the flesh.

But if you simply can't bear to eat the peel, the sweet-tart Northern Spy ranks No. 1 for antioxidants in flesh alone. Cortland was second, followed by Red Delicious.

Tsao attributed the variations to differences in growing seasons, geography and genetic predispositions.

Though apples have significantly lower concentrations of antioxidants than other fruits, especially many berries, researchers say year-round availability and greater popularity might make them a better source for many people.

In the United States, apples are second only to bananas among popular fruits. The average adult ate about 16 pounds of fresh apples in 2003, according to the U.S. Department of Agriculture.

Jeffrey Blumberg, a professor of nutrition and antioxidant expert at the Friedman School of Nutrition (search) at Tufts, praised the research, saying analyzing and ranking foods in this manner is key to understanding disease.

"This is the tool that epidemiologists need to look at diet-health relationships," he said. "One can ask a question such as, 'How many apples do you need to eat a day to prevent heart disease or keep the doctor away?'"