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The Truth About Antioxidants

by , | April 18, 2023

The Truth About Antioxidants

Written by Jonah Udall; Select sections of article written by and article reviewed by Dr. Bojana Jankovic Weatherly.

Walk into any natural health store, and you’re bound to see products labeled with claims like “cellular protection antioxidants,” or “antioxidant-rich for optimal health.” Antioxidants are popularly lauded for anti-aging effects, cancer-fighting abilities, and all kinds of health benefits, but what are they, really? We’re going to dive into the research about what antioxidants are – and are not – and how to harness their natural power to support your health.

Antioxidants are compounds that quench highly reactive molecules known as free radicals. Free radicals can damage DNA and interfere with cellular function by stealing electrons in a process called ‘oxidation.’ Antioxidants are martyrs, sacrificing themselves to become oxidized in order to spare our cells. Free radicals, and the wider category of reactive species, are normal byproducts of energy production and other cellular processes. These include reactive oxygen species (ROS) as well as reactive nitrogen species (RNS). It has often been suggested that aging itself results from the cumulative effects of this ‘oxidative stress’ over a lifetime.1 Oxidative stress is also driven up by toxic exposures, radiation, infections, and imbalances in energy production such as insulin resistance and liver diseases. Sounds like a bad thing, right?

But before you go binge on the latest superfood antioxidant, this is not the whole story. As it turns out, normal levels of oxidative stress are actually beneficial and even necessary for optimal health. Say what?

MYTH #1: All oxidative stress is bad

For example, the thyroid gland requires the pro-oxidant hydrogen peroxide to produce thyroid hormone, the master metabolic regulator in the body.2 Furthermore, some of the oxidative stress in an infection is intentional – free radicals are vital to the immune system’s defense against viruses and bacteria.3 And while excess free radicals may damage cells, free radicals are also important signaling molecules that regulate healthy bodily functions.4

Like many things, it’s about balance – not too much, or too little. Indeed, most research has found no benefit, and sometimes even harm in long-term supplementation with many nutritional antioxidants.5 This may also have to do with the second myth about how antioxidants work.

MYTH #2: Antioxidants you consume scavenge free radicals in the body

The popular belief about dietary and supplemental antioxidants is that they are beneficial because they go around the body quenching free radicals. However, research strongly suggests this is not true.6 Nutritional antioxidants are inert, they float around the bloodstream and into body tissues just like other nutrients. In order to quench free radicals, an antioxidant molecule would have to get lucky and bump into one before it oxidizes some part of a cell. And this can only happen once – after an antioxidant has become oxidized to neutralize a free radical, it cannot be oxidized a second time. Given the speed at which free radicals are created and move inside a cell, it is nearly impossible that free-floating antioxidants have any benefit in this way.6

But don’t fret, we don’t need to rely on random chance to buffer the damaging effects of excess oxidative stress. The body is much smarter than that!

MYTH #3: The most powerful antioxidants are the ones we consume

While nutritional antioxidants are not enough on their own, some can be powerfully therapeutic in certain conditions.7 This is most likely because, rather than scavenging free radicals themselves, they are helping to support and stimulate the body’s innate antioxidant defense systems.6 Yes, the most powerful antioxidants are made by the body itself. Instead of passively waiting to bump into a free radical by chance, these body-made antioxidants use targeted enzymes to seek out and rapidly eliminate free radicals and ROS in the most vulnerable places. Complementary enzymes rapidly regenerate these martyred antioxidants so they can continue to combat oxidative stress repeatedly. Because these enzyme systems are tightly controlled, the body can tightly regulate oxidative stress on its own terms when they’re functioning optimally – allowing just enough where it’s needed to support health, and reducing the rest.

To make matters more complex, some nutritional antioxidants, including the rich purple anthocyanins in dark berries, may stimulate our innate antioxidant systems by acting instead as pro-oxidant stressors.6,8 This concept is called ‘hormesis,’ the idea that low levels of stress strengthen cellular responses, much in the way that lifting weights makes your muscles stronger. Indeed, exercise itself is a powerful hormetic stressor, which can become overt and damaging oxidative stress when overexercising.9

So, where does this leave us? In summary, oxidative stress needs to be balanced, not eliminated, for optimal health, and nutritional antioxidants can’t do it alone. The most powerful antioxidants are enzyme systems in the body, which can be trained in part by low-level pro-oxidant stimuli including some so-called ‘antioxidants’ and healthy exercise. Fortunately, there are more ways to support a healthy antioxidant balance.

Supporting the body’s master antioxidant system

The master of our body-made cellular antioxidants is glutathione, which may play a vital role in health and disease.10 Dementia, cancer, liver diseases, diabetes, hypertension, infertility, cystic fibrosis, multiple sclerosis, systemic lupus erythematosus, HIV, and Parkinson’s disease, just to name a few, have all been associated with depleted glutathione.11 Whether or not this relationship is causal, supporting the body’s glutathione system can be a helpful component of promoting optimal health. But not only is glutathione an important antioxidant, it is also crucial for detoxifying some of the most pervasive and insidious environmental toxins, including pesticides, mold, mercury, and air pollution.12–15

How can we support this powerful glutathione antioxidant and detox system? It’s not just about the molecule glutathione, which has become a popular supplement in recent years, but more importantly about supporting the enzymes that are responsible for its rapid and regenerating effects.11 This means three things: supporting glutathione synthesis, antioxidant activity, and detoxification function. Supporting these three facets of the glutathione system can allow the body to optimally regulate oxidative stress and detoxification. While specialized nutraceuticals can be powerful in the right context, you can do a lot to bolster glutathione with food alone. Speak with a functional medicine doctor about whether therapeutic doses of antioxidants may be indicated in your condition, such as N-acetyl cysteine which has been shown to support glutathione status and mitochondrial function.16 We’ll leave you here with a few of the most powerful foods you can incorporate into your routine today to help optimize glutathione naturally!

Glutathione superfoods (supporting all three functions):

  • Purple and blue polyphenols:17–19 red grapes, blackberries, chokeberries, black currants, cranberries, sour cherries, blueberries, raspberries, pomegranate, boysenberries
  • Rooibos and honeybush infusions20,21
  • Green and white tea22–24

Synthesis supports:

  • Whey protein25,26
  • Magnesium-rich foods (or supplements):27,28 Seeds (pumpkin, flax, chia, sesame, sunflower); Nuts (Brazil, cashews, almonds); Grains (brown rice, oats, buckwheat, amaranth, wheat germ, quinoa); Legumes (edamame, black beans, peanuts); Greens (seaweed, kale, basil); avocado
  • Cacao29,30

Antioxidant supports:

  • Extra virgin olive oil31
  • Salmon32
  • Vitamin C-rich foods (or supplements):33,34 bell peppers, chili peppers, acerola cherries, rosehips, guava, cantaloupe, parsley, kale, kiwi, broccoli, cauliflower, brussels sprouts, lemons, oranges, strawberry

Detox supports:

  • Cruciferous vegetables:15,35,36 particularly brussels sprouts, broccoli sprouts, red cabbage
  • Rosemary37,38


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2. Ohye H, Sugawara M. Dual oxidase, hydrogen peroxide and thyroid diseases. Exp Biol Med Maywood NJ. 2010;235(4):424-433. doi:10.1258/ebm.2009.009241

3. Mortimer PM, Mc Intyre SA, Thomas DC. Beyond the Extra Respiration of Phagocytosis: NADPH Oxidase 2 in Adaptive Immunity and Inflammation. Front Immunol. 2021;12:733918. doi:10.3389/fimmu.2021.733918

4. Dröge W. Free radicals in the physiological control of cell function. Physiol Rev. 2002;82(1):47-95. doi:10.1152/physrev.00018.2001

5. Dolara P, Bigagli E, Collins A. Antioxidant vitamins and mineral supplementation, life span expansion and cancer incidence: a critical commentary. Eur J Nutr. 2012;51(7):769-781. doi:10.1007/s00394-012-0389-2

6. Forman HJ, Davies KJA, Ursini F. How do nutritional antioxidants really work: nucleophilic tone and para-hormesis versus free radical scavenging in vivo. Free Radic Biol Med. 2014;66:24-35. doi:10.1016/j.freeradbiomed.2013.05.045

7. Mason SA, Keske MA, Wadley GD. Effects of Vitamin C Supplementation on Glycemic Control and Cardiovascular Risk Factors in People With Type 2 Diabetes: A GRADE-Assessed Systematic Review and Meta-analysis of Randomized Controlled Trials. Diabetes Care. 2021;44(2):618-630. doi:10.2337/dc20-1893

8. González-Paramás AM, Brighenti V, Bertoni L, et al. Assessment of the In Vivo Antioxidant Activity of an Anthocyanin-Rich Bilberry Extract Using the Caenorhabditis elegans Model. Antioxid Basel Switz. 2020;9(6):E509. doi:10.3390/antiox9060509

9. Powers SK, Deminice R, Ozdemir M, Yoshihara T, Bomkamp MP, Hyatt H. Exercise-induced oxidative stress: Friend or foe? J Sport Health Sci. 2020;9(5):415-425. doi:10.1016/j.jshs.2020.04.001

10. Teskey G, Abrahem R, Cao R, et al. Glutathione as a Marker for Human Disease. Adv Clin Chem. 2018;87:141-159. doi:10.1016/bs.acc.2018.07.004

11. Minich DM, Brown BI. A Review of Dietary (Phyto)Nutrients for Glutathione Support. Nutrients. 2019;11(9):E2073. doi:10.3390/nu11092073

12. Barcelos GRM, Grotto D, de Marco KC, et al. Polymorphisms in glutathione-related genes modify mercury concentrations and antioxidant status in subjects environmentally exposed to methylmercury. Sci Total Environ. 2013;463-464:319-325. doi:10.1016/j.scitotenv.2013.06.029

13. Ates MB, Ortatatli M. The effects of Nigella sativa seeds and thymoquinone on aflatoxin phase-2 detoxification through glutathione and glutathione-S-transferase alpha-3, and the relationship between aflatoxin B1-DNA adducts in broilers. Toxicon Off J Int Soc Toxinology. 2021;193:86-92. doi:10.1016/j.toxicon.2021.01.020

14. Mekonnen TF, Panne U, Koch M. Glucosylation and Glutathione Conjugation of Chlorpyrifos and Fluopyram Metabolites Using Electrochemistry/Mass Spectrometry. Mol Basel Switz. 2019;24(5):E898. doi:10.3390/molecules24050898

15. Chen JG, Johnson J, Egner P, et al. Dose-dependent detoxication of the airborne pollutant benzene in a randomized trial of broccoli sprout beverage in Qidong, China. Am J Clin Nutr. 2019;110(3):675-684. doi:10.1093/ajcn/nqz122

16. Kumar P, Liu C, Suliburk J, et al. Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical Trial. J Gerontol A Biol Sci Med Sci. 2023;78(1):75-89. doi:10.1093/gerona/glac135

17. Pedret A, Valls RM, Fernández-Castillejo S, et al. Polyphenol-rich foods exhibit DNA antioxidative properties and protect the glutathione system in healthy subjects. Mol Nutr Food Res. 2012;56(7):1025-1033. doi:10.1002/mnfr.201100676

18. Spormann TM, Albert FW, Rath T, et al. Anthocyanin/polyphenolic-rich fruit juice reduces oxidative cell damage in an intervention study with patients on hemodialysis. Cancer Epidemiol Biomark Prev Publ Am Assoc Cancer Res Cosponsored Am Soc Prev Oncol. 2008;17(12):3372-3380. doi:10.1158/1055-9965.EPI-08-0364

19. Gouda M, Moustafa A, Hussein L, Hamza M. Three week dietary intervention using apricots, pomegranate juice or/and fermented sour sobya and impact on biomarkers of antioxidative activity, oxidative stress and erythrocytic glutathione transferase activity among adults. Nutr J. 2016;15(1):52. doi:10.1186/s12937-016-0173-x

20. Marnewick JL, Rautenbach F, Venter I, et al. Effects of rooibos (Aspalathus linearis) on oxidative stress and biochemical parameters in adults at risk for cardiovascular disease. J Ethnopharmacol. 2011;133(1):46-52. doi:10.1016/j.jep.2010.08.061

21. Marnewick JL, Joubert E, Swart P, Van Der Westhuizen F, Gelderblom WC. Modulation of hepatic drug metabolizing enzymes and oxidative status by rooibos (Aspalathus linearis) and Honeybush (Cyclopia intermedia), green and black (Camellia sinensis) teas in rats. J Agric Food Chem. 2003;51(27):8113-8119. doi:10.1021/jf0344643

22. Basu A, Betts NM, Mulugeta A, Tong C, Newman E, Lyons TJ. Green tea supplementation increases glutathione and plasma antioxidant capacity in adults with the metabolic syndrome. Nutr Res N Y N. 2013;33(3):180-187. doi:10.1016/j.nutres.2012.12.010

23. Hakim IA, Harris RB, Chow HHS, Dean M, Brown S, Ali IU. Effect of a 4-month tea intervention on oxidative DNA damage among heavy smokers: role of glutathione S-transferase genotypes. Cancer Epidemiol Biomark Prev Publ Am Assoc Cancer Res Cosponsored Am Soc Prev Oncol. 2004;13(2):242-249. doi:10.1158/1055-9965.epi-03-0193

24. Kumar M, Sharma VL, Sehgal A, Jain M. Protective effects of green and white tea against benzo(a)pyrene induced oxidative stress and DNA damage in murine model. Nutr Cancer. 2012;64(2):300-306. doi:10.1080/01635581.2012.648300

25. Zavorsky GS, Kubow S, Grey V, Riverin V, Lands LC. An open-label dose-response study of lymphocyte glutathione levels in healthy men and women receiving pressurized whey protein isolate supplements. Int J Food Sci Nutr. 2007;58(6):429-436. doi:10.1080/09637480701253581

26. Middleton N, Jelen P, Bell G. Whole blood and mononuclear cell glutathione response to dietary whey protein supplementation in sedentary and trained male human subjects. Int J Food Sci Nutr. 2004;55(2):131-141. doi:10.1080/096374080410001666504

27. Mills BJ, Lindeman RD, Lang CA. Magnesium deficiency inhibits biosynthesis of blood glutathione and tumor growth in the rat. Proc Soc Exp Biol Med Soc Exp Biol Med N Y N. 1986;181(3):326-332. doi:10.3181/00379727-181-42260

28. Bede O, Nagy D, Surányi A, Horváth I, Szlávik M, Gyurkovits K. Effects of magnesium supplementation on the glutathione redox system in atopic asthmatic children. Inflamm Res Off J Eur Histamine Res Soc Al. 2008;57(6):279-286. doi:10.1007/s00011-007-7077-3

29. Sun M, Gu Y, Glisan SL, Lambert JD. Dietary cocoa ameliorates non-alcoholic fatty liver disease and increases markers of antioxidant response and mitochondrial biogenesis in high fat-fed mice. J Nutr Biochem. 2021;92:108618. doi:10.1016/j.jnutbio.2021.108618

30. Żyżelewicz D, Oracz J, Bojczuk M, et al. Effects of Raw and Roasted Cocoa Bean Extracts Supplementation on Intestinal Enzyme Activity, Biochemical Parameters, and Antioxidant Status in Rats Fed a High-Fat Diet. Nutrients. 2020;12(4):E889. doi:10.3390/nu12040889

31. Fitó M, Cladellas M, de la Torre R, et al. Antioxidant effect of virgin olive oil in patients with stable coronary heart disease: a randomized, crossover, controlled, clinical trial. Atherosclerosis. 2005;181(1):149-158. doi:10.1016/j.atherosclerosis.2004.12.036

32. García-Rodríguez CE, Mesa MD, Olza J, et al. Does consumption of two portions of salmon per week enhance the antioxidant defense system in pregnant women? Antioxid Redox Signal. 2012;16(12):1401-1406. doi:10.1089/ars.2012.4508

33. Johnston CS, Meyer CG, Srilakshmi JC. Vitamin C elevates red blood cell glutathione in healthy adults. Am J Clin Nutr. 1993;58(1):103-105. doi:10.1093/ajcn/58.1.103

34. Lenton KJ, Sané AT, Therriault H, Cantin AM, Payette H, Wagner JR. Vitamin C augments lymphocyte glutathione in subjects with ascorbate deficiency. Am J Clin Nutr. 2003;77(1):189-195. doi:10.1093/ajcn/77.1.189

35. Navarro SL, Chang JL, Peterson S, et al. Modulation of human serum glutathione S-transferase-A1/2 concentration by cruciferous vegetables in a controlled feeding study is influenced by GSTM1 and GSTT1 genotypes. Cancer Epidemiol Biomark Prev Publ Am Assoc Cancer Res Cosponsored Am Soc Prev Oncol. 2009;18(11):2974-2978. doi:10.1158/1055-9965.EPI-09-0701

36. Steinkellner H, Rabot S, Freywald C, et al. Effects of cruciferous vegetables and their constituents on drug metabolizing enzymes involved in the bioactivation of DNA-reactive dietary carcinogens. Mutat Res. 2001;480-481:285-297. doi:10.1016/s0027-5107(01)00188-9

37. Debersac P, Vernevaut MF, Amiot MJ, Suschetet M, Siess MH. Effects of a water-soluble extract of rosemary and its purified component rosmarinic acid on xenobiotic-metabolizing enzymes in rat liver. Food Chem Toxicol Int J Publ Br Ind Biol Res Assoc. 2001;39(2):109-117. doi:10.1016/s0278-6915(00)00117-4

38. El-Demerdash FM, Abbady EA, Baghdadi HH. Oxidative stress modulation by Rosmarinus officinalis in creosote-induced hepatotoxicity. Environ Toxicol. 2016;31(1):85-92. doi:10.1002/tox.22024


  • Jonah Udall

    Jonah Udall is a Certified Nutrition Specialist, herbalist, and functional medicine healer based in Brooklyn, NY. He holds a Masters of Science in Human Nutrition and Functional Medicine from the University of Western States. Chronic health challenges taught him the importance of listening deeply, seeking the root causes of dysfunction, celebrating the individual, and finding collaborative paths to vibrant health with nature’s medicines. In addition to the healing arts, Jonah is a certified Deep Listening instructor and a lifelong musician and dancer.

  • Bojana Jankovic Weatherly, MD

    Dr. Bojana (Boy•ana) Jankovic Weatherly is an award winning physician, double board certified in internal and integrative medicine. After completing internal medicine residency, she did a fellowship in integrative medicine, trained in functional medicine, nutrition and mindfulness. Her approach is rooted in evidence-based medicine that is personalized to each individual she works with.


Nothing stated or posted in this article is intended or should be taken to be the practice of medical or counseling care. The information made available in this article, including, but not limited to, interviews, text, graphics, images, links to other articles, websites, and other material contained in this article, is strictly for informational and entertainment purposes only. The information in this article is NOT (and should not be used as) a substitute for professional psychiatry, psychology, medical, nursing, or professional healthcare advice or services, nor is it designed to suggest any specific diagnosis or treatment. Please always seek medical advice from your physician or a qualified health care provider regarding any medical questions, conditions or treatment, before making any changes to your health care regimen, medications or lifestyle habits. None of the information in this article is a representation or warranty that any particular drug or treatment is safe, appropriate or effective for you, or that any particular healthcare provider is appropriate for you. Never disregard professional medical advice or delay seeking help from a health care provider due to something you have read or seen in this article. Your reading/use of this article does not create in any way a physician-patient relationship, any sort of confidential, fiduciary or professional relationship, or any other special relationship that would give rise to any duties. This article does not recommend or endorse any specific tests, healthcare providers, procedures, or treatments, and if you rely on any of the information provided by this article, you do so solely at your own risk.

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About the Author

Jonah Udall

Jonah Udall is a Certified Nutrition Specialist, herbalist, and functional medicine healer based in Brooklyn, NY. He holds a Masters of Science in Human Nutrition and Functional Medicine from the University of Western States. Chronic health challenges taught him the importance of listening deeply, seeking the root causes of dysfunction, celebrating the individual, and finding collaborative paths to vibrant health with nature’s medicines. In addition to the healing arts, Jonah is a certified Deep Listening instructor and a lifelong musician and dancer.


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