Antioxidants have the ability to neutralize and reduce free radical damage. To deeply comprehend the power of antioxidants, you must first understand what free radicals are and how they react in the body. Free radicals are harmful compounds that have an unpaired electron, an aspect of their structure that makes them highly unstable. Their instability causes them to wreak havoc on cells, fatty acids, and other structures in your body. Free radicals also act as catalysts for diseases, many diseases.
Normal metabolic processes in our bodies promote oxidation, a stage of metabolism where free radicals are produced. Eating, breathing, physical activity all play a part in the oxidation process and the formation of free radicals. Cell, organ, bone, joints, and immune system damage results from excessive free radicals. The damage is over the long haul. In fact, free radicals and oxidation are actually what cause the visible signs of aging and contribute to the aging process.
The Best Dietary Antioxidants
Antioxidants are available in many forms and are present in virtually all foods, whether they are of plant or animal origin. Generally, natural plant foods are the best source of antioxidants and also offer many other nutritional benefits. Although antioxidants in supplement form are beneficial, food-based antioxidants are thought to be better absorbed.
Here are 9 of the best dietary antioxidants readily available in natural, whole foods:
Plant pigments are the main source of anthocyanidins. The anthocyanidins in blueberries, for example, may be protective against DNA damage from UV radiation.  One study on the anthocyanidins in the Hibiscus flower suggested antidepressant effects from its naturally-occurring pigments.  Anthocyanidins have also been shown to offer certain benefits against lung and colorectal cancer, cognitive decline, and even gluten intolerance.    
Food sources include: oranges, cherries, berries, eggplant, radishes, red grapes, and even red wine.
2. Beta Carotene
Beta carotene is in many fruits, grains, oils, and vegetables. A member of the carotenoids family, it’s recognized by its orange-red color. It is a precursor to vitamin A, a fat-soluble vitamin that requires the presence of dietary fat for proper absorption. Beta carotene's antioxidant effects are plentiful, with eyesight being its most popular benefit. Data from the Age-Related Disease Study suggests that beta carotene is a key nutrient for preventing age-related macular degeneration. 
Food sources of beta carotene include: carrots, broccoli, spinach, kale, cantaloupe, mangoes, apricots, goji berries, squash, pumpkin greens, and sweet potatoes.
3. Caffeic and Ferulic Acid
Ferulic acid is derived from the biosynthesis of caffeic acid, and both have mighty antioxidant effects. Isolated caffeic acid has been shown to play a role in fighting inflammatory diseases.  Ferulic acid, on the other hand, may be a potential therapy for mood disorders, according to some research. 
Foods containing caffeic and ferulic acids include: apples, pears, oranges, pineapple, artichoke, coffee, peanuts, oregano, turmeric, steel-cut oats, rice, kale, basil, thyme, and rosemary.
Flavonols are found in a range of fruits, vegetables, tea, spices, and herbs. The well-known antioxidants quercetin and kaempferol are a type of flavonols. These flavonol antioxidants show potential for fighting inflammatory conditions. 
Kaempferol, specifically, has been shown to be beneficial for blood sugar and skin health. Studies have also shown that kaempferol positively affects metabolism and thyroid hormone production.  Along with quercetin, kaempferol has also been shown to promote a calm mood. Interestingly enough, these effects occur only when the flavonols are broken down during digestion by intestinal microflora.  That being said, it may be important to maintain a healthy, probiotic-supported digestive tract to see the benefits from these antioxidants!
Foods high in flavonols include: apples, apricots, raspberries, cocoa, chocolate, blackberries, onions, red wine, and green and black teas.
Also in the flavonoid family are flavanones, compounds with potent anti-inflammatory activity. Humans and animal studies indicate neuroprotective effects from this antioxidant. Researchers have discovered that flavanones support the digestion and absorption of carotenoids found in foods like carrots and bell pepper, further improving the nutrient's effect in the body. 
Foods containing flavanones include: oranges, lemons, limes, grapefruit, and milk thistle.
Similar to beta carotene, lutein belongs to the carotenoid plant pigments responsible for promoting retina health. Lutein occurs naturally in green vegetables, fruits, and even some animal products. Lutein may potentially lower your risk for developing cataracts and age-related macular degeneration. 
Foods containing lutein include: spinach, kale, collard greens, broccoli, parsley, green peas, carrots, celery, squash, okra, egg yolks, and pumpkin.
Another member of the carotenoid family, lycopene typically makes up the red pigment in vegetables and fruits. Its best source in the human diet comes from tomatoes, although it can also be found in red bell peppers and various red-colored fruits and vegetables. A highly-potent antioxidant, lycopene may be helpful in the fight against cancer.  Lycopene has also been shown to increase HDL cholesterol levels ("good" cholesterol), possibly reducing the risk for heart disease. 
Foods containing lycopene include: spinach, pumpkin, squash, papaya, watermelon, red bell peppers, red (pink) grapefruit, and sweet potatoes.
It is widely believed that proanthocyanidin, a type of flavanols, may support the blood vessels. It also offers benefits to the cardiovascular system. High amounts of this antioxidant are found in cacao (chocolate) – it's responsible for the food’s health benefits.  Some studies indicate that proanthocyanidins are ten times more powerful than vitamin C and may even act as an internal sunscreen that protects the skin against UV radiation! 
Foods containing proanthocyanidins include: apples, red grapes and red wine, cranberries, strawberries, cinnamon, peanuts, chokeberry, and black and green tea.
Sulforaphane is a sulfur-based antioxidant found in cruciferous vegetables. Some findings suggest it discourages breast cancer tumors.  Another study reported positive effects against colon cancer. Other studies have linked it to normal blood pressure, heart health, and cholesterol. It also appears to activate mechanisms which maintain balanced blood glucose levels. 
Foods containing sulforaphane include: broccoli, cabbage, cauliflower, kale, turnip, brussel sprouts, radish, collard greens, and watercress.
One Final Thought
When it comes to protecting your health, you can never go wrong with incorporating more antioxidants into your diet. Do remember that although antioxidants are good nutrition, they're not pharmaceutical medicine and shouldn't be thought of as such. Vegetables, fruits, nuts, and seeds are an extraordinary source of dietary antioxidants, so a diet comprised of at least half to three quarters of these foods should be a great source of antioxidants.
What are your favorite antioxidant-rich foods? Let us know in the comments!
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†Results may vary. Information and statements made are for education purposes and are not intended to replace the advice of your doctor. If you have a severe medical condition or health concern, see your physician.