It's no secret that an apple a day—along with other fruits, vegetables, and nuts—will help keep the doctor away. These foods are loaded with antioxidants, substances that fight free radicals, disease-causing compounds that have been linked to heart disease, cancer, and Alzheimer's. But just how many antioxidants these foods contain has been a mystery—until now. The U.S. Department of Agriculture (USDA) recently analyzed the antioxidant content of more than 100 foods, including fruits, vegetables, nuts, dried fruits, spices, and cereals.

The big surprise: Even though they're consumed in small amounts, herbs and spices, such as oregano, cinnamon, and cloves, showed higher amounts of antioxidants than researchers had previously thought.

A high antioxidant level doesn't equate to a superfood, however. "There's still a lot we don't understand about how the body uses antioxidants," says Ronald L. Prior, Ph.D., nutritionist and research chemist with the USDA. The body absorbs some antioxidants better than others, he notes, and cooking may also alter the content. But most antioxidant-rich foods also have other benefits, such as low fat and calorie levels, and helpful vitamins and minerals. For optimal health, aim for at least five to nine servings of fruits and vegetables a day.

Antioxidant Breakdown
The U.S. Department of Agriculture ranked the following foods among the highest in antioxidant content. The number after each food denotes its total antioxidant capacity (TAC). Foods with TACs of 2,000 or higher, like these, are considered high in antioxidants.

Fruits one-cup serving
Dried Plums: 14,582
Cultivated blueberries: 9,019
Blackberries: 7,701
Sweet cherries: 4,873

Vegetables one-cup serving, cooked
Artichoke hearts: 7,904
Red cabbage: 4,718
Russet potato: 4,649

Nuts one-ounce serving
Pecans: 5,095
Walnuts: 3,846
Hazelnuts: 2,739