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What Are Antioxidants? | Mark’s Daily Apple

What Are Antioxidants? | Mark’s Daily Apple

Gold pill capsule bursting open with a variety of fruits and vegetables shooting out of it and up out of the photo.You’ve undoubtedly heard that you should consume certain foods like berries and wine because they contain antioxidants (as if you needed a reason). Maybe you’ve been persuaded to grab a bottle of pricy supplements off the shelf because of their big antioxidant claims. But what are antioxidants, and what do antioxidants actually do? 

As long as you’re a living, breathing person moving through the world, your cells are fighting a constant battle against free radical damage. Free radicals are molecules like reactive oxygen species (ROS) and reactive nitrogen species (RNS) that cause oxidation, DNA damage, protein modification, and, worst case scenario, cell death. And they’re impossible to avoid. Free radicals are normal byproducts of cellular metabolism and exercise. You also accumulate free radicals from exposure to radiation, smoke, and everyday environmental pollutants. 

If your body didn’t have a way to deal with these marauders, you’d be in a world of trouble. Luckily, though, nature has an answer: antioxidants.  

What Do Antioxidants Do?

Antioxidants serve as a powerful first line of defense against free radicals, preventing their formation and neutralizing their effects. 

Free radicals are complicated little molecules. On the one hand, they cause oxidative damage, or oxidative stress, in the body. Too much oxidative stress contributes to aging and probably every chronic disease. That’s the bad news. 

At the same time, oxidative stress is beneficial—necessary even—in the right amounts. In fact, the body is naturally happiest in a state of mild oxidative stress. Mild oxidative stress is hormetic, meaning it prompts beneficial adaptations that make you stronger, healthier, and more resilient to future stressors. The trick is to maintain the appropriate balance. That’s where antioxidants come in.

Antioxidants are responsible for maintaining the right level of free radicals in the body (also known as redox homeostasis). For decades, scientists have believed that antioxidants work primarily by donating electrons to free radicals, which makes them less reactive and less destructive. More recently, researchers have also hypothesized that they could exert their effects in other ways, such as by acting on the microbiome or epigenome.

Types of Antioxidants and Where to Find Them

Your body makes some antioxidants on its own. Glutathione and uric acid are two endogenous antioxidants you’ve probably heard of. Melatonin, too, has powerful antioxidant properties. The majority, though, come from food. Colorful plant foods get the lion’s share of the credit for being antioxidant-rich, but as you’ll see, nutrient-dense animal foods also contribute here.  

Antioxidants found in food include vitamins, minerals, and the various -noids detailed below. 

Antioxidant vitamins and minerals

Vitamin A (retinol), vitamin C (ascorbic acid, ascorbate), and vitamin E (tocopherols, tocotrienols) have all been identified as antioxidant nutrients. Animal products—eggs, fish, offal, dairy—are the best food sources of vitamin A. Fruits and vegetables, especially red bell pepper, citrus fruits, and guava, deliver the vitamin C you need, while nuts and seeds are best for vitamin E. 

Certain minerals are also lauded for their antioxidant properties, acting directly as antioxidants or as cofactors for enzymatic reactions that buffer free radical damage. They include copper, zinc, selenium, iron, and manganese. To get more of these trace minerals from your diet, focus on seafood, nuts and seeds, and organ meats. 


Flavonoids (also called bioflavonoids) are polyphenol pigment compounds that are present in most flowering plants. They are commonly grouped under anthocyanidins, proanthocyanins, and phenolics. Research links flavonoids to many important health benefits, including being anti-inflammatory and protecting against diseases like cancer, cardiovascular disease, and diabetes. These effects are likely due at least in part to their antioxidant effects and their ability to chelate (bind to) metals that can increase free radicals. Flavonoid antioxidants also offer a double-punch because they improve vitamin C’s antioxidant capabilities.

Find flavonoids in fruits and vegetables, tea, and cacao (a good reason to eat more dark chocolate).


Carotenoids are another type of polyphenol pigment. Beta-carotene is the most studied, but there are dozens more in the human diet, including lutein, zeaxanthin, and lycopene. Certain carotenoids, including beta-carotene, can also convert to vitamin A.

Colorful fruits and vegetables contain carotenoids, especially those of the red, yellow, and orange persuasions. Skip the egg white omelets and eat egg yolks for lutein as well. 

Antioxidant enzymes

The antioxidant enzymes are superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). (The latter is not the same as glutathione, although their activities are closely related. (Glutathione is also an important antioxidant—the so-called master antioxidant.) 

Like the other antioxidants, these enzymes are found widely in Primal foods like dark leafy greens and cruciferous vegetables. Importantly, antioxidant enzymes work in tandem with the mineral cofactors listed above, so don’t neglect those trace minerals. 

How Many Antioxidants Do You Need?

You can’t really measure the amount of antioxidants you’re getting in a day. A better approach is to focus on eating a variety of nutrient-dense foods like oysters, organ meats, and egg yolks, plus dark leafy greens and cruciferous vegetables. Throw in a Brazil nut or two for selenium (don’t go overboard). Add other produce for color. 

If it sounds like I’m describing the Primal Blueprint Food Pyramid, you’re right. And that’s not a coincidence. When you eat as nature intended, you get the right balance of nutrients and enzymes without a lot of fuss. If you’re into food tracking, it certainly doesn’t hurt to watch your intake of the antioxidant vitamins and minerals discussed here. Make sure you’re hitting the RDA more often than not. 

Picky eaters can also consider supplementing with antioxidants, although that strategy is surprisingly controversial. In any case, it’s preferable to get your nutrients packaged in their whole food matrices when you can. You can’t overdo antioxidants from whole foods, and you get all the other good stuff—other nutrients, fermentable fiber for your gut microbes, amino acids, and healthy fats—that come along with them.


About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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