What Are Antioxidants? Health Benefits, Best Sources, Side Effects, and More Everyday Health MenuNewslettersSearch Diet & Nutrition A Detailed Guide to Antioxidants Why They re Beneficial and the Best Sources By Angela Lemond, RDNMedically Reviewed by Kelly Kennedy, RDNReviewed: June 12, 2019Medically ReviewedTo reap the benefits of antioxidants, reach for a handful of fresh, juicy berries.Florian Kunde/500pxYou’ve probably heard the word antioxidant before — maybe in a health magazine, a story headline online, or even in your doctor’s office. But how much do you know about these important nutrients? Here, we explain what antioxidants are, how they function in the body, how to increase your intake, and more. What Is an Antioxidant and Why Is It Important In order to understand what an antioxidant is, we must remember some basics from science class. Atoms are made up of protons, electrons, and neutrons. Molecules are made of two or more atoms. In order for a molecule to remain stable, it must contain the right number of electrons; otherwise it will turn into a “free radical.” Free radicals are dangerous molecules that attack good molecules that promote essential body functions. These “pro-oxidants” are produced by internal and external exposures. Antioxidants combat free radicals that cause various diseases such as cancer, diabetes, and heart disease. (1) Free radicals are a natural part of human metabolism, but problems happen when the balance of free radicals and antioxidants is thrown off. This imbalance is called oxidative stress. (1,2) Antioxidants are considered free radical scavengers. Exposure to air pollution, heavy metals, and cigarette smoke can cause free radical damage, increasing the risk of autoimmune diseases, diabetes, heart disease, Parkinson’s disease, Alzheimer’s disease, and cancer. (1) Types of Antioxidants and the Top Food Sources According to the U.S. Department of Agriculture's MyPlate guidelines, there are various types of antioxidants – each of which may play an important role in your health. Phytonutrients These are chemical compounds found in plants, and they have a variety of possible health benefits for the body, including antioxidant activity. Scientists estimate there are more than 4,000 phytonutrients, though only a small fraction have been closely studied. (3) Some of the more studied phytonutrients include: Anthocyanins These are found in blue and purple fruits and veggies, such as berries, eggplant, purple potatoes, carrots, and asparagus. These antioxidants help promote blood vessel health. Resveratrol This type of antioxidant is found dark chocolate, red wine, peanuts, and grapes. They have been shown to help promote heart and lung health, help prevent certain types of cancer, and reduce inflammation overall.More on Vitamins You Need 3 Key Nutrients for Better Brainpower IsoflavonesThey’re found in soybeans. They may help promote bone health, decrease joint inflammation, ease menopause symptoms, and help protect against breast cancer. Lycopene This is found in tomatoes and tomato products, pink grapefruit, watermelon, and red peppers. These help promote prostate and heart health. Lutein This antioxidant is found in spinach, Brussels sprouts, broccoli, lettuce, kale, artichokes, and collard greens. This antioxidant can help promote eye and heart health and may play a role in preventing some cancers. This one is the precursor to vitamin A and this antioxidant is high in orange produce items such as carrots, apricots, sweet potatoes, and pumpkin. It is also found in dark leafy greens such as spinach, collard greens and kale. Beta-carotene plays a role in healthy vision, immunity, and bone health. Most Recent in Diet and Nutrition Later Meals Increase Hunger Decrease Calories Burned Zinc 101 Uses Dosage Foods Supplements Risks and More 6 Bugs You Can Eat and Their Health Benefits Whole Grains 101 Health Benefits Nutrition Facts Recipes and More Vitamin and Mineral Sources of AntioxidantsVitamins and minerals can also perform antioxidant activity. Here are some examples. (4) Vitamin E This vitamin is found in eight various chemical forms in food, but alpha-tocopherol is the only form that meets human vitamin E needs. (5) In addition to helping the body carry out its normal functions, vitamin E limits the production of free radicals. Foods high in vitamin E, along with their daily values (DVs), include: (5)Wheat germ oil (1 tablespoon [tbsp]), 100 percent DVSunflower seeds, dry roasted (1 ounce [oz]), 37 percent DVAlmonds, dry roasted (1 oz), 34 percent DVSunflower or safflower oil (1 tbsp), 25–28 percent DVHazelnuts, dry roasted (1 oz), 22 percent DV Vitamin C If you see ascorbic acid listed on your food labels, your eats contain vitamin C. This nutrient is naturally occurring in many plant-based foods, and it not only acts as an antioxidant, but it revives other antioxidants attacked by free radicals such as vitamin E. (6) Research suggests vitamin C may help protect against various diseases, including certain types of cancers, and heart disease. (7) Foods high in vitamin C include: (7)Red bell pepper, raw (½ cup), 158 percent DVOrange juice (¾ cup), 155 percent DVOrange (1 medium), 117 percent DVGrapefruit juice (¾ cup), 117 percent DVKiwi (1 medium), 107 percent DV Selenium This vitamin exists in two forms: inorganic (selenate and selenite) and organic (selenomethionine and selenocysteine). (8) The body can use both forms of this vitamin, which you can get from various plants and animals. Selenium is a powerful antioxidant that may help protect the heart and body from developing certain types of cancer. (9,10) Foods high in selenium include: (11)Brazil nuts (1 oz), 777 percent DVYellowfin tuna (3 oz), 131 percent DVHalibut (3 oz), 67 percent DVSardines, in oil with bones (3 oz), 64 percent DVHam, roasted (3 oz), 60 percent DV Copper This vitamin is both a pro-oxidant (meaning it causes free radical damage) and an antioxidant. (12) Copper is composed of a powerful antioxidant enzyme and ceruloplasmin, a protein responsible for transporting iron to your tissues. Balance of copper is the key — too much makes it destructive to the body and not enough doesn’t provide ample protection. (12) Not getting enough copper affects the levels of selenium, iron, catalase, and glutathione — all powerful antioxidants. (12) Foods high in copper include: (13)Oysters (3 oz), 539 percent DVBlack beans (1 cup), 181 percent DVSoy protein powder (1 scoop), 131 percent DVGranola (1 cup), 88 percent DVTomato puree (1 cup), 80 percent DV ManganeseMore on Essential Nutrients 7 Common Nutrient Deficiencies and Their SignsLike copper, manganese is a powerful antioxidant. Manganese superoxide dismutase (MnSOD) is the main antioxidant enzyme in the mitochondria of every cell in the body. (14) As you may remember from high school chemistry, the mitochondria are considered the “powerhouses” of the cell because they are responsible for the production of energy. (14) Foods highest in manganese include: (14)Pecans (1 oz), 57 percent DVBrown rice (½ cup cooked), 48 percent DVPineapple (½ cup), 33 percent DVAlmonds (1 oz), 28 percent DVPineapple juice (½ cup), 27 percent DV Zinc This vitamin is instrumental in the activity of about 100 enzymes in the body. (15) Among its known anti-inflammatory powers is protection of the arteries. (16) Zinc also helps maximize the immune system. (16) Foods high in zinc include: (15)Oysters (3 oz), 607 percent DVBeef roast (3 oz), 47 percent DVAlaskan King crab (3 oz), 43 percent DVBeef patty (3 oz), 35 percent DVBreakfast cereal, fortified with 25 percent DV (¾ cup), 25 percent DV total Iron This nutrient helps protect the cell membrane from damage (oxidation). (17) It’s found in two forms: iron connected to a special protein that helps with absorption (heme) and one without the attached protein (nonheme). Nonheme iron is found in plant foods and fortified foods, while meat, seafood, and poultry contain both nonheme and heme iron. (18) Foods high in iron include: (18)Breakfast cereal, fortified with 100 percent DV (¾ cup), 100 percent DV totalOysters (3 oz), 44 percent DVWhite beans, canned (1 cup), 44 percent DVDark chocolate, 44–69 percent cacao solids (3 oz), 39 percent DVBeef liver (3 oz), 28 percent DV Editor s Picks on Sources of Antioxidants 11 Vitamin-Packed Superfoods for Type 2 Diabetes 7 Top Antioxidant-Rich Foods for Osteoarthritis 10 Foods That May Help Prevent Cancer 6 Superfoods You Should Be Eating Today — and Why Enzymes Are Another Type of Antioxidant That Fight Against Free RadicalsEnzymes convert free radicals to hydrogen peroxide and then water using a process that includes copper, zinc, manganese, and iron. (19) Examples of enzymatic antioxidants include: Superoxide dismutases (SODs) These are the major antioxidant defense system against free radicals. Formed in the body, they do require copper and manganese to make them work. (20) There are three forms: two varieties of copper-zinc superoxide dismutase (CuZnSOD) with one being in the cell and one located outside the cell, as well as manganese superoxide dismutase (MnSOD). (20) Oysters and black beans are good sources of copper. (13) Oysters also contain zinc, but zinc is also abundant in various seafood and beef cuts. (15) Glutathione peroxidase (GSHPx) This is a cell antioxidant enzyme that reduces hydrogen peroxide to water. (21) Selenium is part of the regulation and translation which means it is a required mineral for this enzyme to activate. (21) Selenium is highest in Brazil nuts and yellowfin tuna. (11) Catalase (CAT) This is also responsible for changing hydrogen peroxide to water using iron as its assistant (called a cofactor). (22) Breakfast cereals, oysters, and white beans are high in iron. (18) Don’t let these scientific names confuse you. The upshot is how important it is to eat foods rich in these minerals. All antioxidants are directly or indirectly influenced by the body’s supply of vitamins and minerals. Any deficiencies could mean a reduction in antioxidant activity that can increase the oxidative stress you may be under. 5 Tricks for Getting Enough Fruits and Veggies It’s not always easy to incorporate produce into your diet, but if you’re an older adult, the effort is worthy. Follow these tips for upping your intake.Article Other Food Sources of Antioxidants to Know AboutHerbs and spices contain compounds that have antioxidant effects on the body. In particular, research has zeroed in on the contents of phytonutrients (flavonoids). (23) Although there are no specific intake recommendations, consider incorporating them as a part of healthy eating as functional food ingredients. (23) Spices with the highest flavonoids, from highest to lowest, are: (23)ParsleyMexican oreganoCelery seedsCapersSaffronDillThymeFennelCoriander, leavesWormwoodRosemaryGingerMustardSageRed onionChile pepperYellow pepperTasmanian pepperGarlic Most Popular in Diet and Nutrition The 10 Best and Worst Oils for Your Health 5 Reasons You Should Eat Oatmeal Every Day 7 Healthiest Salad Dressings for Weight Loss 10 Healthy Foods That Are Great Sources of Iron Essential Oils May Also Offer Antioxidant BenefitsThese natural oils contain antioxidant and anti-inflammatory properties. Several factors can influence their effects — including harvesting time, mode of intake (skin, ingestion, or inhalation), temperature and weather, and growth and oil extraction methods. (26,23) Be sure to check the U.S. Food and Drug Administration (FDA) for a list that is generally recognized as safe (GRAS). (24) Top-Selling Essential Oils on AmazonArtizen Aromatherapy Top 14 Essential Oil Set, $19.99, AmazonRadha Beauty Aromatherapy Top 8 Essential Oils, $14.95, AmazonArtNaturals Aromatherapy Top 8 Essential Oils, $14.95, AmazonNatrogix Bliss Essential Oils – Top 9, $14.99, AmazonHealing Solutions Best Blends Essential Oil Set, $19.99, Amazon You Can Increase Your Intake of Antioxidants With Supplements Supplementing your diet is another way you can up your antioxidant intake. Supplements often come with a variety of the necessary forms of vitamins E and C and selenium. But with antioxidant supplements, balance is key. Some studies suggest that certain antioxidants, such as beta-carotene and vitamin E, may increase mortality, with a possible similar outcome with vitamin C and selenium (but more studies are needed). (26) For people with cancer, antioxidant supplements may be counterproductive, causing cancer cells to grow rather than die in some cases. Additionally, supplements may interact with cancer treatment or medications and should be avoided. (27) Be sure to talk to your doctor before taking any supplements, regardless of whether you’re on medication or have a preexisting health condition such as cancer. It’s always best to get your nutrients from nutritious, whole foods rather than supplements. And remember, supplements fall under the Dietary Supplement Health Education Act (DSHEA), but are not regulated for safety or efficacy by the FDA. (28) Top-Selling Antioxidant Supplements on AmazonNOW Super Antioxidants, $20.37, AmazonVimerson Health: Turmeric Curcumin With Bioperine, $21.97, AmazonaSquared Nutrition Resveratrol Maximum Strength, $29.99, AmazonSolgar Advanced Antioxidant Formula, $31.35, AmazonHealths Harmony Super Antioxidants, $17.86, Amazon The Bottom Line on Antioxidants and Their Health Benefits Antioxidants are powerful components that may help protect your body from disease. When possible, enjoy foods rich in a variety of antioxidants to reap all their possible health benefits. If you choose to supplement or use essential oils to get your fix, consult your healthcare team to see if this is the right fit for you. NEWSLETTERS Sign up for our Diet and Nutrition Newsletter SubscribeBy subscribing you agree to the Terms of Use and Privacy Policy. Editorial Sources and Fact-Checking Phaniendra A, Jestadi DB, Periyasamy L. Free Radicals: Properties, Sources, and Their Implication in Various Diseases. Indian Journal of Clinical Biochemistry. January 2015.Betteridge DJ. What Is Oxidative Stress? Metabolism: Clinical and Experimental. February 2000.What Are Phytonutrients? Produce for Better Health Foundation. March 19, 2012.Jeeva JS, Sunitha J, Ananthalakshmi R, et al. Enzymatic Antioxidants and Its Role in Oral Diseases. Journal of Pharmacology Bioallied Sciences. August 2015.Vitamin E: Fact Sheet for Health Professionals. National Institutes of Health. March 2, 2018.Jacob R, Sotoudeh G. Vitamin C Function and Status in Chronic Disease. Nutrition in Clinical Care. March–April 2002.Vitamin C: Fact Sheet for Health Professionals. National Institutes of Health. September 18, 2018.Sunde R. Selenium. In Bowman B, Russell RM. Present Knowledge in Nutrition 9th Edition. 2006.Terry E, Diamond A. Selenium. In Erdman JW, Macdonald IA, Zeisel SH. Present Knowledge in Nutrition 10th Edition. 2012.Tinqqi U. Selenium: Its Role as Antioxidant in Human Health. Environmental Health and Preventive Medicine. March 2008.Selenium: Fact Sheet for Health Professionals. National Institutes of Health. September 26, 2018.Johnson MA, Fischer JG, Kays SE. Is Copper an Antioxidant Nutrient? Critical Reviews in Food Science and Nutrition. September 2009.Copper Content of Foods. USDA Food Composition Database. September 23, 2018.Manganese. Oregon State University.Zinc: Fact Sheet for Health Professionals. National Institutes of Health. September 26, 2018.Prasad AS. Zinc: An Antioxidant and Anti-Inflammatory Agent: Role of Zinc in Degenerative Disorders of Aging. Journal of Trace Elements in Medicine and Biology. October 2014.Zago MP, Oteiza PI. The Antioxidant Properties of Zinc: Interactions With Iron and Antioxidants. Free Radical Biology and Medicine. July 2001.Iron: Fact Sheet for Health Professionals. National Institutes of Health. December 7, 2018.Nimse SB, Pal D. Free Radicals, Natural Antioxidants, and Their Reaction Mechanisms. Royal Society of Chemistry. March 2015.Fukai T, Ushio-Fukai M. Superoxide Dismutases: Role in Redox Signaling, Vascular Function, and Diseases. Antioxidants and Redox Signaling. September 2011.Lubos E, Loscalzo J, Handy DE. Glutathione Peroxidase-1 in Health and Disease: From Molecular Mechanisms to Therapeutic Opportunities. Antioxidants and Redox Signaling. October 2011.Heck DE, Shakarjian M, Kim HD, et al. Mechanisms of Oxidant Generation by Catalase. Annalsof the New York Academy of Sciences. August 2010.Yashin A, Yashin Y, Xia X, et al. Antioxidant Activity of Spices and Their Impact on Human Health: A Review. Antioxidants. September 2017.Code of Federal Regulations Title 21: Food for Human Consumption: Essential Oils, Oleoresins (Solvent-Free), and Natural Extractives (Including Distillates). U.S. Food and Drug Administration. April 2018.Sacchetti G, Maietti S, Muzzoli M, et al. Comparative Evaluation of 11 Essential Oils of Different Origin as Functional Antioxidants, Antiradicals, and Antimicrobials in Foods. Food Chemistry. June 2004.Bjelakovic G, Nikolova D, Gluud LL, et al. Mortality in Randomized Trials of Antioxidant Supplements for Primary and Secondary Prevention: Systematic Review and Meta-Analysis. American Medical Association. February 27, 2007.Ozben T. Antioxidant Supplementation on Cancer Risk and During Cancer Therapy: An Update. 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