Holy cacao: cocoa is a food high in antioxidants. It has been found to have nearly twice the antioxidant content of red wine and up to three times that of green tea. But it needs to be consumed dark to get the antioxidant punch. Look for dark chocolate with a cacao content of 70% or greater, preferably 85%. Photo by Radek Bayek | SXC.

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June 2006
Updated May 2008

Product Reviews / NutriNibbles

A Guide To High-Antioxidant Food

A Little Biochemistry, A Grocery Checklist For Antioxidant-Rich Foods

• What Exactly Are Antioxidants
• Antioxidant Glossary: Terms & Definitions
• High-Antioxidant Foods
• What About Açaí?

What Exactly Are Antioxidants

One cup of green tea provides 10 to 40mg of polyphenols and has antioxidant effects greater than a serving of broccoli, an antioxidant-rich food. The high antioxidant activity of green tea makes it beneficial for protecting the body from damage due to free radicals. Research shows that the EGCG in green tea may help the arterial wall by reducing lipids; green tea can protect against experimentally induced DNA damage, and much more. A 2006 study* showed that elderly Japanese people who drank more than 2 cups of green tea a day had a 50% lower chance of cognitive impairment than those who drank less green tea, or who consumed other tested beverages. The high amount of catechins in green tea are believed to be responsible.

*The American Journal of Clinical Nutrition, Vol. 83, pp. 355-361.

Sounds good, but how much of that was truly comprehensible? The media is full of news about antioxidants...free radicals...EGCG...catechins. But what do these terms mean? Much of the “antioxidant” chatter flies over most people’s heads. Don’t worry—we’ve provided a glossary of antioxidant terms and definitions. Here’s an overview of how it all works for a popular antioxidant foods, green tea and white tea:

There are many antioxidants with different degrees of strength. Green tea and white tea contain a particularly strong antioxidant, the catechin EGCG. Catechins are flavonoids, a subgroup of polyphenols, which are substances found in plants. Green and white teas have different catechins from black tea and oolong tea, due to lesser processing (green and white teas are not oxidized; oxidation inactivates the catechins). To look at the relationship visually:

With this basic introduction, you can plunge into the glossary of antioxidant terms and definitions, or skip ahead to look at foods that are high in antioxidants.

Glossary

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• Antioxidant: An enzyme or other organic molecule that reduces the rate of particular oxidation reactions and can counteract the damaging effects of oxygen in tissues. Although the term technically applies to molecules reacting with oxygen, it is often applied to molecules that provide protection from any free radical (i.e., a molecule with an unpaired electron). While new foods seem to appear every day touting higher levels of antioxidants (the latest is the açaí berry from the rainforests of Brazil), the highest level of antioxidant foods generally found in supermarkets are, in order of strength: undutched cocoa powder; bittersweet chocolate (particularly that which has 85% or more in cocoa solids); white tea; green rooibos tea; green tea; red rooibos tea; oolong tea; and black tea. Some studies claim that the blueberry (especially wild blueberry, a.k.a. bilberry) contains more antioxidants than any other mainstream fruit or vegetable, when compared on the basis of equal calories. Others give the top award to Montmorency cherry juice—which does have more calories than blueberries, but is accessible year-round. Other fruits and berries that are high in antioxidants include the blackberry, raspberry, cranberry, cherry (especially the Montmorency, also known as the tart or sour cherry), dried plum (prune), dark grapes (including raisins, purple grape juice and red wine), crowberry (a North American berry that looks similar to a blueberry), kiwi, pomegranate, papaya (a source of vitamin E, lycopene and beta-carotene, three very powerful antioxidants), citrus fruit such as orange and grapefruit (the highest concentration of antioxidants are in the pulp, where the pectin is found); and leafy, dark green cruciferous vegetables (broccoli, brussels sprouts, cabbage, cauliflower, daikon radish, kale, kohlrabi, mustard/chard greens, parsnip, rutabaga, turnip and watercress). See the chart below for a more extensive list.
  Photo of blueberries courtesy U.S. Agricultural Research Service.
  
• Catechin: Biochemically, catechins are monomers (molecules that can be chemically bound as a unit of a polymer) of flavanol, a subclass of flavonoids, which are themselves a subclass of polyphenols. Catechins make up some 25% of the dry weight of a fresh tea leaf. The concentration of catechins is higher in green and white tea†; in black and oolong teas the oxidation process inactivates the catechins. Tea contains four main catechin substances: EC, EG, EGC and ECGC, all of which are inclusively called “catechin.” Epigallocatechin gallate (EGCG) is the one most abundant in tea. EGCG as an antioxidant is about 25 to 100 times more potent than the antioxidant vitamins C and E. (Tea flavor, color and astringency are in part due to the condensation of the catechins to form the bright orange-red pigment thalami.) Researchers believe that catechin is effective because it easily sticks to proteins, blocking bacteria from adhering to cell walls and disrupting their ability to destroy them. Viruses have hooks on their surfaces and can attach to cell walls. The catechin in green tea prevents viruses from adhering and causing harm. Catechin reacts with toxins created by harmful bacteria and harmful metals such as lead, mercury, chrome and cadmium.
  †White tea is substantially more expensive than green tea, and has a few more catechins per serving.
• EGCG: Epigallocatechin gallate, a specific antioxidant compound found in green tea and elsewhere, is a key biological and biochemical driver for many health benefits, for reasons noted in the “Catechin” definition. It can reduce cancers and tumors, prevent cancer cells from growing, lower cholesterol, help digest excess fat and even protect against the common cold virus. Worldwide studies are ongoing and reports regularly discover new health benefits.
• Flavonoids: A large group of water-soluble plant pigments, commonly referred to as bioflavonoids in the media. All flavonoids are biological in origin, so the two terms are interchangeable. Flavonoids are most commonly known as powerful antioxidants, protecting against oxidative and free radical damage. They have been referred to as “nature’s biological response modifiers” because of strong experimental evidence of their ability to modify the body’s reaction to allergens, viruses and carcinogens. They show anti-allergic, anti-inflammatory, anti-microbial and anti-cancer activity. As a result, consumers and food manufacturers have become interested in flavonoids for their medicinal properties, especially their potential role in the prevention of cancers and cardiovascular disease. The beneficial effects of fruit, vegetables, tea and red wine have been attributed to flavonoid compounds. Cocoa is loaded with the flavonoid epicatechin; cocoa has been found to have nearly twice the antioxidant content of red wine and up to three times that of green tea (dark chocolate should be consumed with a cocoa content of 70% or greater). Other good sources of flavonoids include all citrus fruits, berries, onions, parsley and legumes, plus green tea and red wine.
• Free Radicals: Highly unstable and reactive molecules that attack, infiltrate and injure vital cell structures. They are constantly formed as a natural by-product of body chemistry. Free radicals are highly toxic and can damage important cellular molecules such as DNA, lipids or other parts of the cell, impairing the brain and other tissue. They are believed to accelerate the progression of age-related conditions and other diseases.
• Green Tea. All tea comes from the leaves of the Camellia sinensis plant (referred to as the tea tree, tea plant or tea bush); the difference in the many varieties of tea lies in the processing and the terroir (e.g. the difference in Indian versus Chinese versus Japanese growing environments, and different regional environments within countries). Unlike black and oolong teas, green tea is made from leaves that are not fermented before they are dried. Thus, the antioxidant levels of green tea are five times higher than black tea. Green tea is also high in vitamin C. Green tea is produced by panning freshly picked tea leaves at a high temperature for a short period of time to stop oxidation before it starts, which also preserves most of the polyphenols. (Note: See also white tea. White tea is also not fermented and is even higher in antioxidants.)
• ORAC: An acronym for Oxygen Radical Absorbance Capacity, ORAC is a test tube analysis that measures the total antioxidant power of foods. Findings to date suggest that eating plenty of high-ORAC foods (i.e., high antioxidant fruits, nuts and vegetables) may help fight disease and slow the aging processes in both the body and the brain.
• Polyphenols: Polyphenols are a group of chemical substances found in plants. Research indicates that the flavonoids, a class of polyphenols, has antioxidant characteristics with potential health benefits that may reduce the risk of cardiovascular disease and cancer. Polyphenols are potent antioxidant compounds that have demonstrated greater antioxidant protection than vitamins C and E. Green tea may also increase the activity of antioxidant enzymes. Green tea polyphenols may inhibit cancer by blocking the formation of cancer-causing compounds and suppressing the activation of carcinogens. The major polyphenols in green tea are flavonoids: catechin, epicatechin, epicatechin gallate, epigallocatechin gallate (EGCG) and proanthocyanidins. Though both green tea and black tea are derived from the same plant (Camellia sinensis), they contain different antioxidants. In producing black tea, the leaves are allowed to oxidize; during the process, enzymes present in the tea convert many polyphenols to larger molecules with different biological effects. However, green tea is produced by lightly steaming the fresh-cut leaf, which inactivates these enzymes, and oxidation does not occur. Sources of polyphenols include peanuts, green tea, white tea, red wine, olive oil, dark chocolate, pomegranates and other fruits and vegetables. Chocolate or cocoa that has been processed with alkali (“dutched” cocoa) will not contain any polyphenols or antioxidants.
• White Tea. White tea is made mostly from the buds of the tea plant. White tea is not oxidized: The tea leaves are subject only to withering (wilting) and firing. The buds are withered in the shade while subjected to cool circulating air, to allow the moisture to evaporate, then are gently dried in natural sunlight. The most delicate-tasting of teas, white tea also has the highest concentration of antioxidants. The color of the dried tea is actually pale green; the curled-up white tea buds have a silvery/white appearance from the fine, silvery white hairs, or down, that cover the buds and young leaves. The taste is similar to the green tea, but sweeter and milder.

Antioxidant-Rich Foods

Aside from açaí (see below), cacao is king...but like cocoa and chocolate, it’s tough to consume enough to reap antioxidant benefits without ingesting a lot of sugar in the process. The beauty of tea over all other foods is that you can enjoy it calorie-free and relatively effortlessly, wherever you are. But to eat a well-rounded, antioxidant-rich diet, there’s a broad shopping list below.

Note, though, that it isn’t easy getting an accurate read on ORAC values: Measurements are made using different scales, making it difficult to compare. Some evaluations compare units per grams of dry weight, others use wet weight, others use units per serving. Thus, if one picks and chooses numbers from different reports, different foods can appear to have comparatively higher or lower ORAC values than they actually do. Thus, for example:

• A raisin has no more antioxidant potential than the grape from which it was dried, yet raisins have a much higher ORAC value per gram wet weight than grapes, due to their reduced water content.
• Similarly, fruits with high water content can appear to be very low in antioxidants.
• Higher-quality produce can yield higher ORAC levels.
• No one is yet comparing the ORAC value per calorie. Montmorency cherries have much higher ORAC values, as well as many more calories per serving than blueberries (Montmorency cherry juice has 12,800 ORAC units per 100 grams).

Hopefully, manufacturers will begin stating ORAC values along with other information on on food nutrition labels. In the interim, please use this chart as a relative guide—3-1/2 ounces of chocolate, for example, is three portions.

‡ORAC numbers from Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.

Generally, the deeper and richer the color of fruits and vegetables, the higher the quantity of antioxidants. Many fruits and vegetables are also high in fiber, minerals and vitamins.

• Fruit juice contains antioxidants, but not as much as the fruits from which they are made, since the antioxidants are concentrated in the skins and pulps.
• The color rule of thumb does not apply to varieties of tea. The darker the variety of tea, the lower its antioxidant concentration, because it has been oxidized.

What About Açaí?

The açaí berry (pronounced ah-sigh-EE) from the Brazilian rainforest has been trumpeted as the next important food, a true superfruit. It may in fact be one of the most nutritious fruits on the planet: Açaí’s antioxidants are significantly higher than green tea, chocolate or blueberries and 10 times higher than red grapes. It has 10 to 30 times more anthocyanins (flavonoids that bind free radicals) than red wine. Açaí also has a synergy of omega 6 and 9 essential fatty acids (healthy fats), fiber, amino acids and vitamins A and C.
Photo of açaí berries by Ronaldo Salame.

Great—however açaí is not one of the most palatable fruits. The plain berries are very tart; like eating plain cranberries, very few people enjoy them straight. Brazilians drink açaí in sweetened juices, which are now in U.S. supermarkets in a variety of blends with more familiar fruits (banana, raspberry, etc.).** But not everyone who is health-and-wellness focused wants to add all that sweetened juice to their daily intake (the same is true with cocoa and chocolate, even at 70% cacao). So, tea still looks like a winner: You can drink all you want for zero calories, and even a heaping teaspoon of sugar adds just 25. Note, though, that you can’t add milk: the milk proteins counter the effect of the catechins.

**Naked Juice and Bossa Nova are two brands that offer açaí mixed with other fruit juices; Bossa Nova has a pure açaí sweetened with agave, a honey-like sweetener from the Mexican plant that also is the source of tequila.

Some information in this article is courtesy of Wikipedia and Tzu Thé.

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