Last updated: February 14, 2020

The term “antioxidant” is everywhere these days. It’s linked to superfoods, skincare, dark chocolate, and even red wine. Antioxidants are marketed to combat chronic disease, reverse aging, and boost overall wellbeing – but what exactly are antioxidants, where can you find them, and how are they beneficial to your health?

Let us explain.

What is an antioxidant?

“Antioxidant” is not so much the name of a substance or compound, but a description for what a range of substances can do – neutralize free radicals and help protect cells from damage.

Free radicals contain an unpaired electron in their chemical structure making them highly unstable and reactive in the body. Left unaddressed, excess free radicals in the body can contribute to oxidative stress and numerous health conditions. Antioxidants, however, have the ability neutralize free radicals by acting as stable electron donors. (7)(12)

Glasses of water infused with pomegranate

Infusing water with different fruits such as lemon and pomegranate seeds is a simple (& sweet!) way to get an extra boost of antioxidants into your diet.

The connection between oxidative stress and chronic illness

Although free radicals are produced in the body, lifestyle and environmental factors can accelerate their production. Examples of these factors include pesticides, tobacco, alcohol, stress, air pollution, insufficient sleep, UV rays, radiation, certain prescription medications, and substances found in fried foods. (16)

When free radicals accumulate and go unchecked, they often cause a cascade of reactions leading to oxidative stress. Oxidative stress increases your risk of atherosclerosis, cancer, diabetes, rheumatoid arthritis, and other chronic conditions. (7)

The good news is, we’re not defenceless against free radicals. Along with the antioxidants produced by your body, consuming antioxidant-rich foods may help lower free radical levels. (7) Eating a diet rich in exogenous antioxidants has been shown to help neutralize free radicals, reduce the risk of chronic disease, and boost overall health. (12)

Did you know?
The body makes its own antioxidants, called endogenous antioxidants. Antioxidants from outside the body are known as exogenous. (14)

A woman's hands holding a bowl of colourful fruits and vegetables including avocado, blood oranges, pomegranate, clover leaves, and more over top of a cutting board.

You can increase your intake of antioxidants by eating a more colorful variety of fruits, vegetables, nuts, seeds, and legumes.

Different types of dietary antioxidants

Antioxidants found in food can be grouped into two general categories: water-soluble and fat-soluble antioxidants. Fat-soluble antioxidants perform their actions in cell membranes, while water-soluble antioxidants act primarily in the fluid inside and outside of cells.

Furthermore, antioxidants may be categorized as nutrient or non-nutrient antioxidants. Vitamins A, C, and E, and the minerals copper, zinc and selenium are examples of micronutrients with antioxidant effects. Other dietary food compounds known as the non-nutrient antioxidants, such as lycopene, a phytochemical found in tomatoes, may have an even greater antioxidative effect. (5)(15)

A common misconception is that all antioxidants are interchangeable. They are not! Each antioxidant has unique biological properties and chemical behaviors. (11) Different antioxidants provide a diverse range of health benefits, beyond neutralizing free radicals. For example, lutein, which is found in spinach, has been linked to a lower incidence of eye lens degeneration and associated blindness in the elderly. This is one reason why it’s so important to incorporate a variety of foods in your diet. (10)

Man wearing a chef apron slicing a tomato on a cutting board for his salad

Men who eat plenty of the antioxidant lycopene (which is found in tomatoes) may be less likely to develop prostate cancer. (8)

Did you know?
Flavonoids, such as the tea catechins found in green tea, are believed to contribute to the low rates of heart disease in Japan. (3)

Measuring and testing antioxidant levels

Scientists have used different methods to measure the antioxidant power of foods and dietary supplements.

ORAC score

ORAC, which stands for oxygen radical absorbance capacity, was a lab test once used that measured the ability of a food or supplement to neutralize oxygen-free radicals. The higher the score, the higher the antioxidant power.

However, the USDA pulled its ORAC database off their public website, citing two main reasons: it was routinely misused by advertisers, and more human clinical trials are needed to support its health claims. (4)

FRAP analysis

A more current testing method used for antioxidant levels is the ferric reducing ability of plasma (FRAP) analysis method. This test measures the antioxidant content of foods by how well the food was shown to neutralize a specific free radical. (1)

Fresh blueberries in a small wooden bowl

Blueberries are one of the best natural sources for antioxidants and superfoods. Testing has shown they are packed with anthocyanins and other antioxidants.

Foods highest in antioxidants

Interested in learning about more foods that are high in antioxidants?

A 2010 report published in the Nutrition Journal analyzed the antioxidant content of over 3100 foods, beverages, spices, herbs, and supplements, providing an excellent guide to antioxidant-rich foods by food group.

The plant-based foods listed below were found to offer the most abundant source of antioxidants.


Acai berries, cranberries, red grapes, peaches, raspberries, strawberries, red currants, figs, cherries, pears, guava, oranges, apricots, mango, red grapes, cantaloupe, watermelon, papaya, and tomatoes.


Broccoli, spinach, carrots, and potatoes are all high in antioxidants, and so are artichokes, cabbage, asparagus, avocados, beetroot, radish, lettuce, sweet potatoes, squash, pumpkin, collard greens, and kale. (2)

Did you know?
To reap the benefits of antioxidants, vegetables are best consumed raw, microwaved, or lightly steamed. It’s not a good idea to heavily bake, pressure cook, or boil them. (9)


Cinnamon, oregano, turmeric, cumin, parsley, basil, curry powder, mustard seed, ginger, pepper, chili powder, paprika, garlic, coriander, onion, and cardamom.


Sage, thyme, marjoram, tarragon, peppermint, oregano, savory, basil, Indian Winter cherry, and dill weed.

Cereals and nuts

Oatmeal, walnuts, hazelnuts, pistachio nuts, almonds, cashews, macadamia nuts, and even peanut butter.


Espresso, red wine, pomegranate juice, apple juice, grape juice, prune juice, tomato juice, pink grapefruit juice, as well as green, black, and plain tea. (2)

A glass of juice next to blood oranges

A study on blood orange juice found it had significantly higher antioxidant power than sugar water with the same amount of vitamin C. (6)

The bottom line

As a general rule of thumb, focus on eating more colorful vegetables and fruits. Research has shown that the best strategy to ensure you are getting all the antioxidants you need to promote optimal health is to consume more natural nutrients found in whole foods. (13)

And remember, when it comes to adding antioxidants to your diet, no one food, food group, or antioxidant should be your sole focus. Try to incorporate a variety of plant-based nutrients into your diet.

Interested in some of the health benefits associated with antioxidants and want to know more about specific antioxidants? Talk to a trusted healthcare provider about ideas to add in more antioxidant-rich foods to your diet.

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  1. Benzie, I. F. F., & Strain, J. J. (1996). The ferric reducing ability of plasma (FRAP) as a measure of “Antioxidant Power”: The FRAP assay. Analytical Biochemistry, 239(1), 70–76.
  2. Carlsen, M. H., Halvorsen, B. L., Holte, K., Bøhn, S. K., Dragland, S., Sampson, L., … Blomhoff, R. (2010). The total antioxidant content of more than 3100 foods, beverages, spices, herbs and supplements used worldwide. Nutrition Journal, 9(1).
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  5. Crichton, G. E., Bryan, J., & Murphy, K. J. (2013). Dietary antioxidants, cognitive function and dementia: A systematic review. Plant Foods for Human Nutrition, 68(3), 279–292.
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  9. Jiménez-Monreal, A. M., García-Diz, L., Martínez-Tomé, M., Mariscal, M., & Murcia, M. A. (2009). Influence of cooking methods on antioxidant activity of vegetables. Journal of Food Science, 74(3), H97–H103.
  10. Lobo, V., Patil, A., Phatak, A., & Chandra, N. (2010). Free radicals, antioxidants and functional foods: Impact on human health. Pharmacognosy Reviews, 4(8).
  11. Lü, J. M., Lin, P. H., Yao, Q., & Chen, C. (2010). Chemical and molecular mechanisms of antioxidants: Experimental approaches and model systems. Journal of Cellular and Molecular Medicine, 14(4), 840–860.
  12. National Center for Complementary and Integrative Health. (2010). Antioxidants and health. Retrieved from
  13. National Center for Complementary and Integrative Health. (2013). Antioxidants: In depth. Retrieved from
  14. Roehrs, M., Valentini, J., Paniz, C., Moro, A., Charão, M., Bulcão, R., … Garcia, S. C. (2011). The relationships between exogenous and endogenous antioxidants with the lipid profile and oxidative damage in hemodialysis patients. BMC Nephrology, 12, 59.
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  16. Turpeinen, A.M., Basu, S., & Mutanen, M. (1998). A high linoleic acid diet increases oxidative stress in vivo and affects nitric oxide metabolism in humans. Prostaglandins, Leukotrienes & Essential Fatty Acids, 59(3), 229-33.