Athletic performance has many different aspects and some go beyond the physical. Generally, the focus of dietary supplements has been on increasing the duration/intensity of exercise, recovering faster, and building muscle/strength. Importantly, however, dietary supplements may also have a role in cognition and motor skills. The idea is that dietary supplements could affect the neurotransmitter system by regulating the chemicals that control nerve transmission and increasing blood flow to the brain (1).
Obviously athletes with better coordination, motor control, decision-making, reaction time, and overall brain function will have the advantage BUT can dietary supplements help? We found an article in Nutrition Reviews by Baker et al. (note the authors work for the Gatorade Sports Science Institute) on the role of dietary supplements and motor skills and cognition and share the highlights here (1).
**Before we get to the evidence, all athletes should check the purity and quality of their dietary supplements and that the dietary supplement is permitted in their sport.**
Branched-Chain Amino Acids (BCAA)
The BCAAs (leucine, isoleucine, and valine) are proposed to help combat central (brain and nervous system) fatigue during long bouts of exercise. The idea is that the BCAAs can decrease serotonin in the brain and serotonin is, of course, famous for its effects on mood, arousal and sleepiness. It is thought that higher levels of serotonin could make athletes feel tired more quickly and increase their ratings of perceived exertion – how hard they feel they are exercising (2,3). Conversely, if BCAA could lower levels, it would have the opposite effect and stimulate performance. At present, there are few scientific studies to support the theory and the results are generally mixed, so BCAA cannot be recommended at present (1). Stay tuned on this one though…
Caffeine has been found to increase passing accuracy in soccer players (4), sprint-dribble times and ball-handling in field hockey (5), passing accuracy in rugby players (6), serve velocity in tennis players (7), and repeated sprint ability (8); of course, there are studies that report no effects (1). Generally the dose used in the studies was between 5-6 mg per kg of body weight (the optimal dose is unclear) and the effects don’t tend to show up until later on in the event, when physical and mental fatigue is likely, suggesting it may not benefit shorter activities. Importantly, although caffeine can increase alertness and attention it can also increase anxiety, tenseness, and impair fine motor coordination; particularly in young athletes or those not habituated to caffeine (1).
Carbohydrates (sport drinks usually)
Sport drinks generally contain water, 6-8% carbohydrates (not as much as you may think – so you cannot substitute other sugar sweetened beverages), and electrolytes. Consuming carbohydrates during exercise has been found to improve sport-specific skills such as: shooting, passing, dribbling, agility, and whole-body motor skills, as well as reaction time in athletes but the results are not unanimous (1). The idea is that providing the brain with glucose can improve performance AND certainly low blood glucose levels can have an overall negative effect on performance.
The evidence is generally in support of carbohydrate consumption during endurance exercise, for a variety of performance reasons, just don’t overdo it and ensure you restrict sport drinks and supplements to activities that are longer than one hour of continuous exercise.
Cocoa flavanols are a set of phytochemicals found in unprocessed cocoa. We are into the realm of limited research from here on out… but two studies did find improved attention (9), visual function, and cognitive performance (10) with cocoa flavanols but these were not performed in athletes. Mechanisitically, cocoa flavanols are supposed to increase blood flow (nutrients and oxygen) to the brain (11, 12).
Gingko biloba is an herbal extract that has been proposed to increase blood flow to the brain, act as an antioxidant, and affect the neurotransmitter system (13). It was initially touted as a memory aid, however, the weight of the evidence suggests no effect on memory or attention (14) and it hasn’t been tested in athletes (1). We generally recommend staying away from this one as the benefits are unlikely and it’s not worth the expense or chance of contamination with a banned substance.
Ginseng can be tricky as there are several different forms, however, the most common is Panax ginseng (Korean ginseng). It has been suggested that ginseng (200 mg-600 mg) can enhance performance in people who are fatigued or stressed and there is some positive evidence but certainly not all studies are favourable (1). When it comes to sport, Baker et al (1) report Siberian ginseng improved shooting in biathletes, in a 1966 study performed by Dalinger, as compared to the control but we are awaiting further studies…
Guarana comes from plants found in the Amazon and contains caffeine among other phytochemicals. The two studies mentioned on guarana and cognitive performance found increased memory, subjective alertness, and speed (although not accuracy) – but again no studies in athletes, so we can’t comment on its role in performance (1).
Rhodiola rosea (golden root or arctic root) is a plant typically found in mountainous areas. Studies in athletes are few and far between, however, in the two that measured cognition, no effects were noted (1).
The Rest of the Bunch
Theobromine, tyrosine, L-theanine (found in tea especially green tea) were also not very promising. Sage (Salvia family) may have the ability to inhibit the neurotransmitter cholinesterase and thereby improve learning, memory, and attention. The evidence is more positive, as benefits have been noted in adults; however, studies in athletes are needed (1).
No Baloney’s advice? With the possible exceptions of caffeine and carbohydrate drinks in long duration events, there doesn’t seem to be much evidence to suggest that dietary supplements can improve motor skills or cognitive performance in athletes. The best course of action is probably to error on the side of safety (and frugality) and stay away, at least until there is more research.