A Ranking of Antioxidant Values of Foods
Research Shows Antioxidant Concentrations Are Surprisingly Varied
Oct 8, 2009
“Reactive oxygen species” such as free radicals are molecules that can cause damage when they come in contact with cells. Antioxidants, which are naturally attracted to radicals, circulate throughout the body and help improve overall health and well being by seeking out and neutralizing or destroying free radicals before they can damage cells.
Although the supplements Vitamin C (ascorbic acid), alpha-tocopherol (Vitamin E),or beta-carotene (Vitamin A) contain antioxidants, most randomized trials indicate they do not protect against oxidative stress-related diseases as well as foods from natural plants.
By far the largest published systematic screening of antioxidants in fresh fruits, vegetables and processed items is a study titled "Content of redox-active compounds (ie, antioxidants) in foods consumed in the United States," that appeared in the July 2006, American Journal of Clinical Nutrition. Researchers measured the total antioxidant concentration of 1113 food samples obtained from the US Department of Agriculture National Food and Nutrient Analysis Program.
An Overview of the Study's Findings
- Among 22 ranked food groups, these had the highest antioxidant contents, in the following category order: (1) spices and herbs; (2) nuts and seeds; (3) chocolates and sweets; (4) vegetables; (5) ready-to-eat cereals; (6) desserts and cakes; (7) berries; (8) fruits; (9) beverages; (10) soups, sauces, gravies and dressings; (11) fast foods.
- Grains and dairy products have only modest concentrations.
- Several food categories contained products almost devoid of antioxidants: fats and oils; meat, poultry, seafood and eggs.
- Of the 50 food products highest in antioxidant concentrations, 13 were spices, 8 were fruits and vegetables, 5 were berries, 5 were chocolate-based, 5 were breakfast cereals, and 4 were nuts or seeds.
- On the basis of typical serving sizes, blackberries, walnuts, strawberries, artichokes, cranberries, brewed coffee, raspberries, pecans, blueberries, ground cloves, grape juice, and unsweetened baking chocolate were at the top of the ranked list.
- Never-smokers with the highest antioxidant intake had the lowest risk of cancer (odds ratio: 0.44) and a high antioxidant intake is inversely related to lung cancer risk.
Some Surprising Findings
- Among 1,113 foods tested, ground cloves ranked first. The spice had by far (three times) the antioxidant content of its nearest competitor, oregano. A single gram (about 1/2 teaspoon) of cloves has more antioxidants than a 1/2-cup serving of blueberries or cranberries. And 1/2 teaspoon dried oregano had the same amount of antioxidant activity as 1/2 cup of sweet potatoes.
- Besides cloves and oregano, these spices and herbs ranked among the top 20 antioxidant-rich foods: ginger, cinnamon, turmeric, basil, mustard seed, curry, paprika, chili, parsley and pepper. Spices and herbs typically are a more concentrated source of dietary antioxidants than many other food groups, and used more sparingly.
- In spite of the widespread belief that green and black tea are packed with health benefits, fresh brewed coffee, on a per-serving basis, ranks sixth in antioxidant potency, closely behind only blackberries, walnuts, strawberries, artichokes and cranberries. The researchers calculated that a typical cup of Joe from Wendy's or Burger King has roughly three times more antioxidant value than an equal-size serving of tea from the same restaurants.
- Processed foods such as lasagna, pudding mix, and chocolate chip cookies were among the 50 foods with the highest antioxidant contents, and chocolate ice cream had a higher antioxidant value than did some fruits such as honeydew melons and green grapes.
- Many plant foods, especially walnuts, containing high amounts of unsaturated fatty acids had high antioxidant values, whereas fish that also contain high levels of unsaturated fatty acids lacked significant antioxidant values.
- Unsweetened baker's chocolate, ounce-for-ounce, has more antioxidant content than most berries, red wine and grape juice.
Some researchers hypothesize that antioxidants in foods may work in combination to produce synergistic effects. Plant foods, which are rich in flavonoids, have many different antioxidant compounds. In one study, when spices and herbs were added to salad dressing, the antioxidant values of some salad vegetables increased.*
The researchers did not measure the antioxidant value of Nopal (Prickley Pear) cactus, which contains betalains, a rare class of potent healing anti-inflammatory antioxidants.
*Ninfali P, Mea G, Giorgini S, Rocchi M, Bacchiocca M. "Antioxidant capacity of vegetables, spices and dressings relevant to nutrition." Br J Nutr. 2005 Feb;93(2):257-66.
*Baghurst K., "Herbs and spices: An integral part of the daily diet." Position paper, November 2006. National Centre of Excellence in Functional Foods, Australia.
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