By Christy Schuld, MS, RD
Nutrition plays a key role in optimizing athletic performance. And just as a pitcher in baseball will successfully respond to different training stimuli than a shooting guard on the basketball court, every athlete responds differently to the foods, nutrients, and supplements they consume. A growing field of research has explored these differences by examining the roles of genetics and nutritional status, known as nutrigenomics, and their effect on exercise performance. As this science advances, we can expect that sports dietitians and performance staff will begin to use an athlete’s genetic profile to customize recommendations that optimize the performance-enhancing effects of nutrition.
The most widely researched supplement within the field of nutrigenomics is caffeine. Caffeine is a broadly used stimulant that increases activity in the brain, with approximately 75% of competitive athletes using it as an ergogenic aid to enhance performance. It is commonly ingested through coffee, energy drinks, caffeinated tablets, gels or chews, and use is well-established in research. Studies indicate promising results in aerobic endurance, muscle strength and endurance, power, jumping performance, and exercise speed.
How Does Caffeine Work?
Caffeine metabolism primarily occurs in the liver where it is rapidly absorbed within an hour following ingestion. Its mechanism of action involves increased excitability in the brain by manipulation of a pre-existing lock and key mechanism. Adenosine (the key) is a naturally occurring chemical in the brain that binds to receptor sites (the lock) to slow down neural activity and increase feelings of tiredness. This process happens during exercise when the body has an increased demand for oxygen, but not enough available to regenerate energy. This, in part, leads to feelings of fatigue.
When caffeine is consumed, it blocks adenosine from binding to its receptors. This benefits athletic performance by reducing feelings of fatigue and perceived exertion thresholds, which can improve endurance. It also benefits muscular strength by improving motor recruitment throughout the body for stronger muscle contractions, potentially leading to performance improvements.
Genetic Variability – It’s Not One Size Fits All
While caffeine is widely used, not everyone responds to it the same way. The effects of caffeine vary based on an athlete’s rate of metabolism, which can be identified in their genetic profile. The gene hallmarked for this genetic variation is the CYP1A2 gene. This gene accounts for greater than 95% of caffeine metabolism, with metabolic speed encoded within the gene by a single nucleotide polymorphism (SNP) rs762551. It is the genotypic expression within this SNP that details whether an athlete has “fast” (AA genotype) or “slow” (AC or CC genotype) clearance of caffeine. Understanding this, and having the means to translate an athlete’s genetic profile into either a “fast” or “slow” metabolizer of caffeine, allows for appropriate supplement timing and dosage to maximize beneficial effects during training.
The usefulness of caffeine supplementation for exercise performance, paired with genetic profiles of athletes, have been researched extensively in different exercise and training modes. Several randomized controlled trials have examined this with significant variability in effects compared to placebo groups. While findings across studies suggest genetic factors do indeed relate to enhanced performance, specific recommendations are still somewhat unclear. There are still variables and under-explored phenomena that need to be considered to determine best practices, including the timing, amount, and mode of caffeine ingestion, and the athlete’s frequency of caffeine use.
Despite this gap in research, nutrigenomics and the power of profiling techniques supports the likelihood that the CYP1A2 gene plays a role in the performance value of caffeine. Therefore, sports dietitians and performance staff need to keep in mind the current evidence in this dynamic, developing field of nutrigenomics. Personalized caffeine intake strategies to maximize performance may not be of benefit in all athletes. Simply knowing this, and if able, considering supplemental strategies that are aligned with an athlete’s genetic makeup, can improve both knowledge and motivation, giving an athlete a competitive edge and the best possible effects in their performance.
This article was written by a Collegiate and Professional Sports Dietitian Association Registered Dietitian (RD). To learn more about sports nutrition and CPSDA, go to www.sportsrd.org
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