Antioxidants are molecules that have the unique ability to neutralize free radicals, which are unstable molecules produced by the body during normal metabolic processes. Free radicals damage normal molecules, including proteins, fats and DNA. This could lead to an increased risk of cancer development, heart disease or premature aging. One way to prevent this is to consume foods that contain antioxidants. There are several groups of antioxidants; each one is chemically different, but they have similar effects on free radicals.
Some of the vitamins that have antioxidant properties include vitamin C and vitamin E. Vitamin C, or ascorbic acid, is a water soluble molecule found in a variety of food sources including oranges, grapefruit, limes and broccoli. It protects several types of molecules from free radical damage, including lipoproteins. Vitamin E consists of several fat-soluble molecules including tocopherols and tocotrienols. Turnip greens, sunflower seeds, almonds, and spinach contain vitamin E. This antioxidant protects the skin from ultraviolet light, and it works with a group of molecules to protect cells from oxidative stress.
Another group of antioxidants with beneficial properties is the carotenoids. Beta-carotene and lycopene are two carotenoids that protect cells from free radicals. Beta-carotene protects the skin, and it is commonly used in topical creams. It is found in a variety of foods including mango, carrots, sweet potatoes and spinach. Lycopene has anti-cancer effects against several types of cancer cells, and it reduces clumping of platelets. Tomatoes, guava, pink grapefruit and watermelons contain lycopene.
Phenolic acid is a group of molecules consisting of tannins, which are primarily astringent compounds, meaning they constrict tissue. Tannic acid is one example in this group. It is found in tea, nettle, oak wood and berries. In addition to its antioxidant properties, tannic acid is an anti-bacterial and anti-mutagenic compound. Another molecule in this group is ellagic acid. It is effective at combating certain types of cancer cells. It is abundant in raspberries, blackberries, strawberries and pecans.
The largest family of antioxidants is the flavonoids. This group consists of several types of antioxidants that are divided based on their properties. Anthocyanins is a subset within the flavonoid group, and it contains several compounds including cyanidin and malvidin. Cyanidin is a particularly strong antioxidant found in several foods including bilberries, cherries, cranberries and elderberry. It has been the focus of research in diabetes prevention, and its anti-inflammatory properties have been established in lab tests.
The isoflavones is another subset of molecules classified within the flavonoid family. Daidzein is a molecule in this group that is particularly effective at preventing DNA damage caused by oxidative stress. This compound is also effective against some types of cancer cells. Daidzein is present in soy beans, red clover, and the kudzu vine. Another antioxidant classified as a isoflavone is genistein. This compound is known for its estrogenic activity, which is beneficial in the prevention of osteoporosis and symptoms of menopause, including hot flashes. As an antioxidant, it reduces lipid peroxidation and increases the activity of glutathione peroxidase and superoxide dismutase. It is found in soy beans and chickpeas.
Stylbenes are another group of antioxidants under the umbrella of flavonoid compounds. Pterostillbene is one member of this subset, and it is found in blueberries, grapes, and peanuts. It is effective at lowering cholesterol and improving cognitive function. Other properties of this compound include anti-cancer and anti-inflammatory effects. Specifically, it inhibits the production of prostaglandin E2. Another stylbene with antioxidant properties is resveratrol. Some of the foods that contain this compound include red grapes, euclayptus, mulberries and peanuts. It is also in red wine. It is effective at reducing damage to cells that line the interior walls of blood vessels caused by nitrite radicals. It also protects skin cells from UV damage.
There are several more groups of flavonoids that have antioxidant properties. Epcatechin is classified as a flavonol, and it is found in cocoa, tea, and grapes. It reduces lipid peroxidation and inhibits clumping of platelets. Hesperidin is classified as a flavanone and lemons and oranges are its food sources. It improves the integrity of capillary walls and reduces symptoms of allergies. The flavones is another type of flavonoid and tangeretin is classified in this group. This compound is primarily found in citrus peels, but it may be present in small quantities in orange juice. Laboratory tests with this compound show cholesterol lowering effects and anti-tumor effects.
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