BY LANCE C. DALLECK
A myth can be defined as an untrue explanation for a natural phenomenon. Unfortunately, numerous myths remain pervasive and well-engrained throughout the fitness industry, in particular as it pertains to various performance and nutritional supplements. In this article, we closely examine nine common supplements and present scientific evidence for whether the use of each is based on myth or reality.
Scope of Practice and Quality of Evidence
Strictly speaking, it is beyond the scope of practice for health and exercise professionals to provide specific nutrition recommendations to clients. On the other hand, evaluating the scientific merit of performance and nutritional supplements, and providing a sound educational resource falls within the realm of your work with clients, helping them to make informed decisions. The myths and realities surrounding nine common performance and nutritional supplements are presented here. How did we reach these conclusions? The final consensus (myth or reality) was based on whether there is sound theoretical rationale and supporting evidence for the efficacy and safety of the performance and/or nutritional supplement.
Are Performance and Nutritional Supplements Safe?
When it comes to performance and nutritional supplements, safety is a critical issue that must be addressed. When no side effects have been reported, in the scientific literature this has been interpreted to mean that the performance and/or nutritional supplement in question is safe for the length of time and dosages evaluated.
In a comprehensive review recently published in the International Society of Sports Nutrition, the topic of exercise and sports nutrition safety was highlighted (Kerksick et al., 2018). Specifically, supplements found to have sound theoretical rationale with the majority of available research in relevant populations using appropriate dosing regimens demonstrating its safety were categorized as having Strong Evidence to Support Efficacy and Apparently Safe. In this article, performance and/or nutritional supplements were given a “reality” designation only if they could be placed into this same category.
It has been suggested that creatine monohydrate is the most effective supplement available to fitness enthusiasts for improving high-intensity exercise performance and increasing muscle mass (Kerksick et al., 2018). Indeed, there is a mountain of scientific literature demonstrating that creatine supplementation increases skeletal muscle mass during exercise training. Moreover, the long-term safety of creatine monohydrate has been well-established.
Creatine is an essential substrate for the phosphagen energy system and involved in adenosine triphosphate (ATP) regeneration during high-intensity exercise. As such, creatine supplementation has also been shown to result in an enhanced ability to match cellular ATP production and demand during high-intensity and repeated bouts of intense exercise.
It is worth noting that creatine use is allowed by the International Olympic Committee, National Collegiate Athletic Association (NCAA) and professional sports.
Creatine supplementation can increase creatine storage in skeletal muscle with a loading phase (20 to 25 grams/day for five to seven days) followed by a maintenance dose of 3 to 5 grams/day (Kerksick t al., 2018).
Final consensus: Reality
2. Chronic Use of Antioxidants
Conventional wisdom suggests that antioxidant supplementation may benefit exercise performance and enhance recovery by countering the increase in free radicals associated with exercise due to the long and well-established link between cell damage and free radicals. Now, more contemporary research is questioning the effectiveness of the antioxidant supplementation strategy altogether. In the past decade, in fact, a growing body of research suggests that superfluous (i.e., excessive) doses of antioxidant supplements consumed to retard free radical production during exercise training actually contributes to increased muscle fatigue and delayed recovery (Teixeira et al., 2009; Close et al., 2006). Moreover, it has also been reported that antioxidant supplementation with vitamin C hampers training-induced adaptations in endurance performance (Gomez-Cabrera et al., 2008).
Collectively, these findings strongly infer that antioxidant supplementation hampers favorable exercise training adaptations and interferes with the recovery process.
Final consensus: Myth
Caffeine is a natural stimulant found in coffee, tea and many nutritional supplements. There is robust scientific evidence demonstrating that caffeine ingestion serves as an effective ergogenic aid for both aerobic and anaerobic exercise performance. Caffeine ingested orally is quickly absorbed into the bloodstream and peaks within 30 to 60 minutes.
Caffeine mechanistically effects the central nervous system, primarily by antagonism of adenosine receptors, which results in enhanced mood, reduced perception of pain and increased attention. At the skeletal muscle level, caffeine ingestion promotes enhanced sodium/potassium pump activity, greater calcium release from the sarcoplasmic reticulum, and increased fat oxidation/glycogen sparing.
Overall, it has been recommended that a dosage of approximately 3 to 6 milligrams/kg of body weight ingested 30 to 60 minutes prior to exercise will increase work capacity and time to exhaustion and reduced perceived effort during endurance exercise (Naderi et al., 2016).
Final consensus: Reality
Carnitine is an ammonium compound produced endogenously by the liver and kidneys. It serves as a transporter of long-chain fatty acids into the mitochondria to be oxidized for energy production and thus plays a key role in the regulation of lipid metabolism. Accordingly, scientists and sport nutritionists alike have entertained the notion that supplementation could increase the bioavailability of carnitine and enhance overall capacity for lipid metabolism. This theoretical scenario could have both weight-loss and endurance-performance implications. In fact, Wall and colleagues (2011) demonstrated that 24 weeks of L-carnitine supplementation in men increased total muscle carnitine, enhanced lipid utilization (while sparing muscle glycogen) and elicited an 11% improvement in cycling work output.
Nevertheless, to date, the majority of research findings on carnitine supplementation reports it does not significantly alter total muscle carnitine content, enhance lipid metabolism, improve exercise performance and/or elicit weight loss in individuals who have overweight or obesity (Kerksick et al., 2018).
In summary, there is little to no evidence to support the efficacy of carnitine as an ergogenic supplement.
Final consensus: Myth
5. Post-exercise Carbohydrate Ingestion
This is a classic nutritional recommendation for recreational enthusiasts and athletes alike. After prolonged and exhaustive endurance-related exercise, the most important factor determining the timeframe to recovery is muscle glycogen replenishment (Ivy, 2004). It has been well established for quite some time that post-exercise carbohydrate (CHO) ingestion is critical to the synthesis of muscle glycogen.
More recently, both the precise timing of CHO ingestion and optimal CHO dosage have become better understood (Beelen et al., 2010). Post-exercise muscle glycogen replenishment occurs in two phases: a rapid rate that persists for 30 to 60 minutes after exercise cessation and a considerably reduced rate (60 to 90%) in the time period afterward. There is also evidence for a dose-response relationship between post-exercise dosage of CHO ingestion and the rate of muscle glycogen resynthesis. For example, it has been shown that consuming 1.2 grams per kilogram per hour (grams/kg/hour) of CHO increased muscle glycogen content 150% more than 0.8 grams/kg/hour of CHO (Beelen et al., 2010). However, ingestion of 1.6 grams/kg/hour of CHO provided no further increase in muscle glycogen content. Additionally, more frequent provision of this overall CHO dosage interspersed in smaller doses over a few hours is more effective at replenishing muscle glycogen compared to one or two large doses ingested less regularly.
In summary, to optimize muscle glycogen repletion after prolonged and exhaustive endurance-related exercise, it has been recommended to ingest 1.2 grams/kg/hour of CHO at 15- to 30-minute intervals immediately after exercise (Beelen et al., 2010).
Final consensus: Reality
Glutamine is an amino acid that is used in the biosynthesis of proteins. Common dietary sources of glutamine include beef, chicken, fish, dairy products, eggs, beans and vegetables such as carrots and spinach. It was originally suggested that glutamine supplementation may stimulate protein synthesis and thereby promote enhanced muscular performance. Indeed, research findings from Colker and colleagues (2000) assessed the effects of supplemental whey protein with or without added glutamine and branched-chain amino acids on body mass, body composition and exercise performance for a 10-week period. They observed that whey protein combined with glutamine and branched-chain amino acids, in addition to resistance exercise, elicited significant improvements in body composition and exercise performance. However, more recent research has found glutamine supplementation does not benefit muscular performance (Antonio et al., 2002; Candow et al., 2001).
In summary, there is insufficient scientific evidence to support glutamine supplementation for increases in lean body mass and/or muscular performance (Kerksick et al., 2018).
Final consensus: Myth
7. Sodium Bicarbonate
Recovery from cellular acidosis is paramount for restoring the capacity to regenerate ATP from both the phosphagen system and glycolysis. Muscle-buffering capacity can be augmented by nutritional strategies. Indeed, alkalizing agents have been studied extensively for their potential for enhancing performance by attenuating the extent to which metabolic acidosis contributes to fatigue during high-intensity exercise performance (Peart, Siegler and Vince, 2012).
One such alkalizing substance that has been found to improve recovery by increasing the muscle-buffering capacity is sodium bicarbonate. The mechanism by which sodium bicarbonate ingestion mediates an ergogenic effect is by promoting removal of protons from the skeletal muscle milieu. Given the fact that increased concentrations of proton molecules within the muscle cell are detrimental to skeletal muscle performance, it should be recognized that an increased rate of removal from the skeletal muscle environment will result in a more rapid recovery. This, in turn, will permit a better performance of subsequent high-intensity exercise bouts.
The main drawback to use of sodium bicarbonate is that some individuals experience gastrointestinal distress with its ingestion. Accordingly, it is a good idea to first purposefully experiment with the sodium bicarbonate loading protocols to maximize the alkalizing effects and minimize the risk of potential symptoms. The recommended dosage and timeframe for sodium bicarbonate ingestion is 0.2 to 0.4 grams/kg with 1 liter of fluids 60 to 120 minutes before exercising (Peart, Siegler and Vince, 2012). Sodium bicarbonate can either be ingested in capsule form or mixed in water.
Final consensus: Reality
Arginine is an amino acid that is used in the biosynthesis of proteins. In the body, arginine changes into the potent vasodilator nitric oxide (NO). Given that NO is known to promote vasodilation and enhance skeletal muscle blood flow, it has been suggested that arginine supplementation may increase exercise performance.
Indeed, some experimental research exists to support this line of reasoning. For example, Campbell and colleagues (2006) provided arginine (or a placebo) to 35 resistance-trained males in a double-blind study and concluded that upper-body strength and lower-body power output were significantly increased after supplementation. Despite these encouraging findings, however, most of the other published scientific studies regarding arginine supplementation have not reported a beneficial ergogenic result. Therefore, caution is warranted with regards to the use of arginine to enhance exercise performance.
Final consensus: Myth
The amino acid β-alanine is naturally occurring in foods such as fish and meat. β-alanine is also a precursor and rate-limiting molecule for synthesis of carnosine. Carnosine itself is found in skeletal muscle and has numerous important physiological functions, including the regulation of calcium, enzymes and pH. Therefore, β-alanine supplementation has been heavily studied given its potential mechanistic ergogenic benefits. The case for β-alanine supplementation appears to be quite clear. In a meta-analysis, Hobson and colleagues (2012) reported that β-alanine supplementation positively impacted individuals performing high-intensity exercises lasting between 60 and 240 seconds.
In terms of the most efficacious dosage, 3 to 6 grams per day of β-alanine for a duration of four to 10 weeks has been recommended (Naderi et al., 2016). Beyond that timeframe a maintenance dosage of 1.2 grams per day of β-alanine has been suggested (Naderi et al., 2016).
Final consensus: Reality
As a health and exercise professional, your aim should always be to provide your clients with evidence-based educational resources on the effectiveness of various performance and nutritional supplements. This will help make it possible for your clients to make informed decisions and fully understand how consuming these products will impact their health, performance and training.
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Campbell, B. et al. (2006). Pharmacokinetics, safety and effects on exercise performance of l-arginine alpha-ketoglutarate in trained adult men. Nutrition, 22, 872-881.
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Gomez-Cabrera, M.C. et al. (2008). Oral administration of vitamin C decreases muscle mitochondrial biogenesis and hampers training-induced adaptations in endurance performance. The American Journal of Clinical Nutrition, 87, 142-149.
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Peart, D.J., Siegler, J.C. and Vince, R.V. (2012). Practical recommendations for coaches and athletes: A meta-analysis of sodium bicarbonate use for athletic performance. Journal of Strength and Conditioning Research, 26, 1975-1983
Teixeira, V.H. et al. (2009). Antioxidants do not prevent post-exercise peroxidation and may delay muscle recovery. Medicine and Science in Sports and Exercise, 41, 1752-1760.
Wall, B.T. et al. (2011). Chronic oral ingestion of l-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. Journal of Physiology, 589, 963-973.
Lance C. Dalleck
Lance C. Dalleck, PhD, is an associate professor of Exercise and Sport Science at Western State Colorado University. His research interests include improving exercise performance and health outcomes through evidence-based practice, quantifying the energy expenditure of outdoor and non-traditional types of physical activity, and studying historical perspectives in health, fitness and exercise physiology. Dr. Dalleck is a member of the ACE Scientific Advisory Panel.