Dr. Dwayne Jackson

The Vital Science Blog

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Free Radicals and Antioxidants

Free radicals are highly reactive atoms that, when left unchecked, promote oxidative stress—a process that causes damage and death to cells, DNA, and other molecules in the body. In fact, oxidative stress is a fundamental mechanism driving premature aging and disease. Environmental stressors like sun exposure and pollution promote free radical production, and, believe it or not, exercise is another (due to increased metabolism). Although exercise promotes free radical production, some level of training-induced oxidative stress is necessary to promote training adaptations, including upregulation of the body’s antioxidant defense system. As such, recent studies now question the use of antioxidants like vitamin C and E to aid exercise recovery and suggest that haphazard approaches to antioxidant supplementation may impede training adaptations.


What are antioxidants? 

Antioxidants are molecules (produced by the body and taken in the diet) which blunt oxidative stress. They can be enzymatic or non-enzymatic and can directly or indirectly blunt the effects of free radicals. In a perfect world, there should always be a balance between oxidative stress and antioxidant levels in the body; however, any imbalance in favor of oxidants (due to environmental stressors, inadequate diet, or heavy training) can lead to a state of elevated oxidative stress. In humans, unbalance between reactive oxygen species production and endogenous antioxidants is involved in the generation/progression of more than a hundred pathologic conditions! 


Interestingly, although endurance and weight training independently promote the formation of reactive oxygen species (ROS; a type of free radical) and oxidative stress, the body adapts by upregulating its enzymatic antioxidant defense during exercise recovery.  This adaptation improves the efficiency of the enzymatic antioxidant defense system and protects cells against oxidative damage during subsequent exercise bouts. It must be noted that low levels of ROS improve muscle force and adaptive responses to training, so you don’t want to completely eliminate them by super dosing antioxidants prior to training. On the other hand, high levels of ROS cause strength loss and contribute to muscular fatigue during prolonged and intense exercise.


So, in a nutshell, trained muscle requires an optimal amount of oxidative stress to maximize gains in exercise performance, but ROS over production can to lead to cellular dysfunction and DNA damage, ultimately resulting in decreased muscle performance and muscle damage. 


Current research suggests that antioxidant supplements are only beneficial to athletes under conditions where the body’s antioxidant levels are not keeping up with the demands of oxidative stress. If you are wondering what your status is, consider the following 3 questions: 


  1. Do you follow a diet that restricts fruit and vegetables (e.g., Ketogenic diet). Fruits and leafy green vegetables contain an abundance of antioxidant nutrients. If you limit these free radical scavenging powerhouses, then you may be subjected to damaging oxidative stress. 

  • Do you train or compete multiple times per day? Many athletes compete or train intensely multiple times in one day. Multiples significantly increase the body’s free radical load and may tax its antioxidant defenses. 

  • Are you above the age of 40 and train regularly and intensely? As we age, our ability to deal with heightened oxidative stress decreases. A study published in the Journal of Diabetes and Metabolic Disorders suggests that this is, at least partly, due to decreased levels of endogenous antioxidants directly related to aging. 

If you answered yes to any of the 3 questions above, then you are a likely candidate for antioxidant supplementation. Below we have highlighted 3 key supplements that help boost the body’s antioxidant capacity and, when combined with exercise, have been proven to promote fitness, and health.  You may wonder why vitamin C and E are not included in the list— This is simply because athletes who take a multivitamin tend not to be deficient in these two vitamins and super dosing vitamins C and E before training has been shown to (marginally) blunt gains. 



What is it? 

Withania somnifera, commonly known as Ashwagandha or Indian ginseng, is a perennial flowering shrub that is commonly used in Indian traditional (Ayurveda) medicine. In Sanskrit, Ashwagandha means “the smell of a horse”, as it is believed to produce vigor and strength in those who take it. In scientific terms, Ashwagandha is known as an adaptogen, which means it increases the body’s ability to handle stress and fatigue by maintaining hormonal balance.

What does the research say? 

In terms of strength training, recent research published in the Journal of the International Society of Sports Nutrition reported that those who took Aswagandha root extract (300 mg, twice daily), while completing an 8 week resistance training program, had greater increases in strength, muscularity, and fat loss compared to placebo. These results were (at least partially) due to a 15% increase in serum testosterone levels observed with Aswagandha treatment. 


As well, a recent study evaluated the efficacy of Ashwagandha root extract in enhancing cardiorespiratory endurance and improving quality of life (QOL) in 50 healthy male/female athletic adults. In this study, cardiorespiratory endurance was assessed by measuring the oxygen consumption at peak physical exertion (VO2 max) during a 20 m shuttle run test. As well, quality of life (QOL) was assessed throughout the 12-week experimental period using the World Health Organization self-reported QOL questionnaire. At the end of the 12-week study, those who received Ashwagandha benefitted with an approximately 6% increase in VO2max during the 20 m shuttle run test. In contrast, those who received the placebo saw no change in VO2max throughout the study. In terms of QOL, those who took Ashwagandha had significant improvements in all areas tested including benefits to physical and psychological health, and social relationships.

How do you use it? 

We recommend taking 300 mg Ashwagandha extract (standardized to 5% withanolides) upon waking and before bed.


Green Tea Extract

What is it?

Green tea extract (GTE) is derived from of the naive leaves of C. sinesis, the same species used for black tea. However, because green tea is non-fermented and non-oxidized it retains unique and beneficial components that are not available in black tea. GTE contains high concentrations of pharmacologically bioactive polyphenols including, epigallocatechin, epicatechin, epicatechin gallate, and epigallocatechin gallate. Although green tea has caffeine, GTE is caffeine-free and contains a standardized concentration of bioactive polyphenols, the most abundant being epigallocatechin gallate (EGCG).

What does the research say? 

Certainly, you have heard of all the fat burning, focus, and health promoting advantages of GTE— but did you know that it is also a unique antioxidant? We consider it unique because 2 recent studies (one published in the European Journal of Nutrition, and the other in Nutrition) illustrate that taking GTE before training boosts the body’s antioxidant defenses, without altering training adaptations. 

How do you use it? 

Take 500-1,000mg of green tea extract standardized for EGCG, 2 to 3 times per day. For best fat burning effects, always take one dose 30 minutes prior to doing cardio and take with 100-200mg caffeine.


Beet Root Extract

What is it?

Beet root extract (BRE) is the isolated nutrients taken from the root vegetable Beta vulgaris rubra, AKA red beetroot. You have likely heard of BRE and its high nitrate levels, which have been shown to boost nitric oxide in the body and promote increased blood flow to working muscles. What you may not know is that beetroot is rich in several other bioactive compounds that provide many other health and fitness benefits. Of note, BRE is a rich source of phytochemical antioxidant compounds, including ascorbic acid, carotenoids, phenolic acids and flavonoids.

What does the research say? 

You have likely heard the recent hype surrounding BRE’s positive effects on health, blood pressure, and exercise performance— indeed there is an abundance of research illustrating the benefits of taking BRE preworkout—from increasing muscular power to boosting aerobic efficiency. Most studies have focused on the benefits of BRE based on its ability to boost dietary nitrate levels and promote nitric oxide production. However, a recent study published in Applied Physiology, Nutrition, and Metabolism illustrated that the exercise performance benefits of beet root go beyond its nitrate boosting potential. In fact, when researchers gave subjects either beet root juice or sodium nitrate, they found that the beet root juice supplement increased exercise performance greater than the pure nitrate supplement. The authors concluded that the exercise performance benefits of BRE are likely due to the combination of increased dietary nitrate and the protective effects of BRE’s naturally occurring antioxidants on buffering oxidative stress and supporting nitric oxide production.

How do you use it? 

As always, we recommend taking 500-750 mg of high nitrate standardized beetroot extract, 30-60 minutes before training. 


Common Antioxidant Superfoods

Red Grapes/Raisins  Kale  Dark Coco/Dark Chocolate
Wild Blueberries Spinach  Cilantro
Red Delicious Apple Brussels Sprouts Pecans
Oranges  Broccoli Kidney Beans
Montmorency Cherries Alfalfa sprouts Cinnamon 
Strawberries Artichoke Wild Salmon
Blackberries Tomatoes  Red Wine
Goji Berries Sweet Potatoes Walnuts
Cranberries Carrots Flax Seeds 
Pomegranate Beets Lentils




Stanley IR Okoduwa, Ismaila A Umar, Sani Ibrahim, Fatima Bello, Nathan Habila. Age-dependent alteration of antioxidant defense system in hypertensive and type-2 diabetes patients

J Diabetes Metab Disord. 2015; 14: 32.


Wankhede S, Langade D, Joshi K, Sinha SR, Bhattacharyya S. Examining the effect of Withania somnifera supplementation on muscle strength and recovery: a randomized controlled trial. J Int Soc Sports Nutr. 2015 Nov 25;12:43. 


Choudhary B, Shetty A, Langade DG. Efficacy of Ashwagandha (Withania somnifera [L.] Dunal) in improving cardiorespiratory endurance in healthy athletic adults. Ayu. 2015 Jan-Mar;36(1):63-8. 


Kuo YC, Lin JC, Bernard JR, Liao YH. Green tea extract supplementation does not hamper endurance-training adaptation but improves antioxidant capacity in sedentary men. Appl Physiol Nutr Metab. 2015 Oct;40(10):990-6. 


Sugita M, Kapoor MP, Nishimura A, Okubo T. Influence of green tea catechins on oxidative stress metabolites at rest and during exercise in healthy humans. Nutrition. 2016 Mar;32(3):321-31. 


Jówko E, Długołęcka B, Makaruk B, Cieśliński I. The effect of green tea extract supplementation on exercise-induced oxidative stress parameters in male sprinters. Eur J Nutr. 2015 Aug;54(5):783-91. 


Clifford T, Howatson G, West DJ, Stevenson EJ. The potential benefits of red beetroot supplementation in health and disease. Nutrients. 2015 Apr 14;7(4):2801-22.


Flueck JL, Bogdanova A, Mettler S, Perret C. Is beetroot juice more effective than sodium nitrate? The effects of equimolar nitrate dosages of nitrate-rich beetroot juice and sodium nitrate on oxygen consumption during exercise. Appl Physiol Nutr Metab. 2016 Apr;41(4):421-9.


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