6 Antioxidants for Immune Health

By Molly Knudsen, MS, RDN

There’s no doubt that antioxidants are good for health. Antioxidants have been in the public spotlight since the 1990s and have only gained attention over the years, basically reaching celebrity status. And that status has not wavered, especially as their role in immune health becomes increasingly known. Antioxidants and antioxidant-rich foods continue to trend and make headlines, most recently in the forms of matcha/green tea drinks, acai bowls, golden milk, or just good ol’ fashioned fresh fruits and vegetables. Antioxidants are here to stay not only because they’re found in delicious foods, but they also play a vital role in health by protecting the body against oxidative stress.1

What is oxidative stress?

Everyone’s heard of oxidative stress, but what exactly does that refer to? Oxidative stress occurs from damage caused by free radicals. Free radicals are unstable molecules that have lost an electron from either normal body processes like metabolism, reactions due to exercise, or from external sources like cigarette smoke, pollutants, or radiation.1

Now electrons don’t like to be alone. They like to be in pairs.

So do free radicals suck it up and leave one of their electrons unpaired?

Nope. They steal an electron from another healthy molecule, turning that molecule into another free radical and, if excessive, wreak havoc in the body and its defense system.

Immune cells are particularly vulnerable to oxidative stress because of the type of fat (polyunsaturated) that they have in their membrane.2 So high amounts of oxidative stress over time can be especially detrimental to immune system.

What are antioxidants?

Antioxidants are the heroes that can break this cycle. And there’s not just one antioxidant. Antioxidants refer to a whole class of molecules (including certain vitamins, minerals, compounds found in plants, and some compounds formed in the body) that share the same goal of protecting the body and the immune system against oxidative stress.2 But different foods contain different antioxidants, and each antioxidant has its own unique way of supporting that goal.  

6 antioxidants for oxidative stress protection + immune health

  1. Vitamin C

Vitamin C is a powerful antioxidant that also contributes to immunity. It works by readily giving up one of its electrons to free radicals, thereby protecting important molecules like proteins, fats, and carbohydrates from damage.3 Vitamin C is a water-soluble vitamin, which means storage in the body is limited, and consistent intake of this nutrient is vital. Research shows that not getting enough vitamin C can impact immunity by weakening the body’s defense system.3 Vitamin C is found in many fruits and vegetables, including strawberries, bell peppers, citrus, kiwi, and broccoli. The benefits of vitamin C’s antioxidant capabilities are more than just internal. Benefits are also seen when a concentrated source of this antioxidant is applied to the skin. For example, topical vitamin C serums are often recommended by dermatologists and estheticians to help protect the skin from sunlight and address hyperpigmentation.4

  1. Epigallocatechin 3-gallate (EGCG)

Green tea is easily, and unofficially, considered one of the world's healthiest foods, and the presence of EGCG is one reason for this drink’s reputation. EGCG is the most abundant, potent, and researched polyphenolic antioxidant found in green tea leaves.5 It has been shown to protect against damage caused by free radicals.5 Drinking green tea is a great way to reap the benefits of EGCG and other nutrients found in tea leaves, or it’s also available as an extract in nutritional supplements. If you choose to drink green tea, it’s important to remember that water preparation matters. Using hot water to steep green tea not only preserves, but it also encourages more antioxidant activity compared to using cold water, as hot water may be better at extracting polyphenols from the leaves.5

  1. Glutathione

Glutathione is a powerful antioxidant that the body actually makes internally from three amino acids (AKA building blocks of protein): cysteine, glutamate, and glycine.6 Not only does this antioxidant protect the body against oxidative stress, it also supports healthy liver detoxification processes.7 Glutathione levels naturally decrease with age, and lower glutathione levels in the body are associated with poorer health.8 Since it takes all three of those amino acids to form glutathione, ensuring that the body has adequate levels of all three is vital. Cysteine is the difficult one. It’s considered the “rate-limiting” step in this equation, since it’s usually the one in short supply, and glutathione can’t be formed without it.6 Cysteine contains sulfur, so foods like unprocessed meat, garlic, and asparagus are great choices to support cysteine levels. Like cysteine, the compound N-acetylcysteine (found in supplements and often labeled NAC) can also be used to support the body’s glutathione levels.6

  1. Curcumin

Curcumin is the yellow pigment and considered the active ingredient in the spice turmeric. In the culinary world, turmeric is best known for playing the leading role in curries as well as in golden milk. Studies show that curcumin has been shown to improve markers of oxidative stress, act as a free radical scavenger, and assist with other antioxidant processes in the body.9 Curcumin isn’t very bioavailable, so your body isn’t able to fully capture the benefits when consumed on its own or just as turmeric.9 But adding other spices or herbs like black pepper or fenugreek can significantly increase your body’s ability to utilize curcumin.9

  1. Vitamin E

Vitamin E is a fat-soluble vitamin, meaning it’s best absorbed with fat. It acts as an antioxidant by stopping the production of free radicals from forming when fat is oxidized, or burned.10 Vitamin E is found in nuts and seeds (almonds, sunflower seeds, and hazelnuts) as well as green leafy vegetables. Vitamin E also plays a role in heart, eye, and cognitive health.10 

  1. Quercetin

Quercetin is one of the most well-studied flavonoids, or plant compounds, typically found in onions, kale, broccoli, apples, and tea. Quercetin acts as a free radical-scavenging antioxidant, helps inhibit oxidative stress, and supports a healthy immune response.11

What’s the bottom line?

Antioxidants are a crucial part to any healthful diet. They help protect the body from damage caused by oxidative stress and support immune function. There are many more antioxidants that are beneficial to health than those listed here. The best way to ensure that you’re getting enough antioxidants from the diet and supporting the antioxidants the body makes on its own is to consume a diet high in plants like fruits, vegetables, nuts, seeds, and legumes.


  1. Pizzino G et al. Oxid Med Cell Longev. 2017;2017:8416763. 
  2. Knight JA. Ann Clin Lab Sci. 2000;30(2):145-158.
  3. Carr AC et al. Nutrients. 2017;9:1211.
  4. Al-Niaimi F et al. J Clin Aesthet Dermatol. 2017;10(7):14-17.
  5. Forester SC et al. Mol Nutr Food Res. 2011;55(6):844-854.
  6. Minich DM et al. Nutrients. 2019;11:2073.
  7. Pizzorno J. Integr Med (Encinitas). 2014;13(1):8-12.
  8. Glutathione. Webmd.com. https://www.webmd.com/vitamins-and-supplements/glutathione-uses-risks. Accessed August 19, 2020.
  9. Hewlings SJ et al. Foods. 2017;6(10):92.
  10. Vitamin E fact sheet for health professionals. Ods.od.nih.gov. https://ods.od.nih.gov/factsheets/VitaminE-HealthProfessional/. Accessed August 25, 2020.
  11. D’Andrea G. Fitoterapia. 2015;106:256-271.

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