High Dose Antioxidant Supplementation
“Consuming megadoses of antioxidants in winter can decrease exercise-induced ros production. This is not only useless in terms of increasing strength, performance and enhancing, recovery but can cancel out much of your hard work in the gym.”
1- Antioxidants attenuate increases in insulin sensitivity
The lower your insulin levels are, the leaner you will tend to be. There are two ways to keep insulin levels consistently low. One is to limit carbohydrate intake. The other is to increase insulin sensitivity so that less insulin is needed to fulfill its primary function. This is where working out comes in; consistent, hard training plays a huge role in increasing insulin sensitivity. The effect this has on conditioning can’t be understated. Increased insulin sensitivity has a way of transcending the amount of calories you take in, or even macros; the more insulin sensitive you are the leaner, more anabolic you will be. Optimal insulin sensitivity also ensures that extra calories are used to build new muscle tissue, rather than stored as body fat.
It was only recently discovered that exercise-induced increases in insulin sensitivity are driven by increased ROS production, and totally suppressed by antioxidant supplements. In a study in 2009 by Ristow et al, the effects of supplementation with vitamin C (500mg twice/day) and vitamin
E (400IU/day) on changes in insulin sensitivity caused by exercise were investigated in both beginners and those with prior training experience. All subjects participated in a five day/ week training programme for four weeks, which consisted of both cardio and weight training. As expected, insulin sensitivity increased over the course of the training programme in both beginners and those with more training experience. This also correlated with a large increase in the expression of a number of signalling proteins that promote insulin sensitivity. Importantly, those who took antioxidant supplements during this four- week training period showed no increases in insulin sensitivity; the antioxidants completely eliminated this response. Keep in mind this happened at ‘normal’ supplement doses used every day, and the effect also occurred in both beginners and experienced subjects, ruling out any type of ‘beginner-effect’.
2- Antioxidant supplements limit mitochondrial biogenesis
As the cellular power-plants that provide ATP to fuel intense muscular contractions, and even life itself, mitochondria are pretty important. The more mitochondria we have, the greater our capacity to oxidise fuels for energy. As a result, endurance is largely a function of how many mitochondria we have, and how well they work. It has been known for some time that antioxidant supplements have subtle performance-suppressing effects on endurance exercise. One study noted that giving greyhounds 1g of vitamin C before racing significantly slowed racing times relative to dogs that did not receive antioxidants. Another study in the ’70s noted that vitamin E supplementation (400IU/day for six weeks) reduced endurance performance in swimmers.
How, exactly, antioxidants may limit endurance came to
light more recently, in a study by Gomez-Cabrera et al. The effects
of antioxidant supplementation on endurance performance were evaluated in 14 men, aged 27-36, during an eight-week endurance training programme. Five of these men received a 1000mg daily dose of vitamin C, while the rest received a placebo. The investigators found that vitamin C significantly suppressed endurance capacity, which was linked to a reduction in proteins that activate mitochondrial biogenesis. The ROS dependence of mitochondrial biogenesis induced by endurance training was later confirmed in a study by Kang et al, where antioxidants severely limited mitochondrial biogenesis in response to exercise.
The fact that antioxidants reduce mitochondrial biogenesis is not only a concern for endurance athletes, though. Two additional studies noted decreased performance with ubiquinone-10 supplementation (a fat-soluble antioxidant) in humans after a high-intensity training programme. In this case, both aerobic and anaerobic performance were affected. As with endurance training, resistance training also activates mitochondrial biogenesis. This is not a coincidence, as most proteins are synthesised in the proximity of mitochondria. The more mitochondria we have the better they work, and the better the cellular infrastructure for cranking out new proteins equates to better growth.
As such, the take-home message is this: Oxidative stress during exercise sends signals that increase mitochondrial number and efficiency to support the energy demands of exercise. Avoid antioxidant supplements
to maximise mitochondrial adaptations to training. This is important for both endurance and (indirectly) strength and size.
3- Antioxidants can stunt anabolism
In addition to limiting the indirect effects of mitochondria on muscle growth, a recent animal study suggests that antioxidant supplements may play a more active role in limiting muscle growth. In this study in rats, a ‘synergist ablation’ overload model was used, where the gastroc and soleus muscles on the right hindlimb were surgically removed, overloading and activating growth in the plantaris muscle. The opposite, left hindlimb of rats in this study did not receive the procedure, which served as an experimental control. Rats in this study were then treated with vitamin C at 500mg/kg orally once a day, or a placebo, for
14 days. Although both the placebo and vitamin C-treated rats experienced some new growth in the plantaris muscle, the vitamin C group experienced around 11% less muscle growth. This also correlated with reduced protein synthesis and increased protein breakdown.
Importantly, the results of this particular study need to be interpreted with a great degree of caution. Rats received a daily dose of 500mg/ kg of vitamin C, which is equivalent to around 50g of vitamin C in a 100kg
man. This is a huge amount of vitamin C, not to mention the
fact that vitamin C in doses that high could actually increase ROS production. The synergist ablation model used for muscle overload in this study is also very much a ‘sledgehammer’ approach that can’t easily be extrapolated to weight training in humans.
Considered in isolation, this study doesn’t hold much real-world relevance; the dose of vitamin C was too high and the model too out there, at least relative to weight training in humans. However, it is consistent with the larger picture, in that antioxidant supplements can throw a proverbial metabolic wrench in the cell signalling machinery that drives the adaptive response to exercise. Along those lines, it was also recently shown that ROS functions as important signalling molecules for muscle hypertrophy in vitro, where it was found that IGF-1-induced hypertrophy of myotubes in culture is suppressed by antioxidants.
Taken together, the current body of research teaches us an important lesson when it comes to ROS signalling and muscle growth; the acute increase in ROS induced by training is an intrinsic part of the exercise stimulus that turns on the switch for muscle growth and adaptation.