The Science Behind Athletes of the Future – Sport Genomics

by Nanci S. Guest, MSc, RD, CSCS, PhD (c) – Fall 2014

Human athletic performance is a highly complex phenotype. For example, two male power athletes of similar age, experience and body composition follow the same resistance training program under close supervision – at the end of 8 weeks one has gained 4 lbs of muscle and the other has gained none. And numerous studies, involving thousands of athletes, report significant increases in speed and endurance when ingesting caffeine before exercise, while others show no effect or slightly adverse outcomes (1-3). When we study diet and disease or supplements and performance or training methods and improved speed or power, why do the observed outcomes have such mixed results? Only over the last few years has this mystery started to unravel.

An extraordinary revolution in medical research was enabled by the completion of the human genome sequence in 2003. Although much of the research has focused on illness and disease, over 300 genes relevant to health and fitness have been identified since The Human Genome Project (HGP) decoded the 3 billion letter pairs that sequence our DNA. These range from genes affecting cardiovascular endurance, muscle power and strength, to genes related to heart rate, body composition, blood pressure, and metabolic factors such as lactic acid clearance or glucose and blood lipid utilization. Along with the identification of exercise-related genetic characteristics there is evidence that specific genetic profiles may be very responsive to a particular exercise modality and nonresponsive to another – so in a nutshell we can in fact aim to reach our genetic potential by training what we’re born with, while still considering the influence of environmental factors such as coaching and access to training facilities. In addition we can assess whether athletes may be more susceptible to tendon injuries such as Achilles tendinopathy (4) or increased complications after a concussion (5).

Strength and conditioning coaches have understood for years that there is a need to tailor workouts and training to each individual without knowing the genetics involved, but we are now able identify our unique genetic profile, and as the science emerges we can subsequently optimize individual training programs. For example over a decade ago, a polymorphism of the angiotensin I-converting enzyme (ACE) gene became the first genetic element shown to impact human physical performance (6). Although this gene has offered insight into an athlete’s likelihood to be more successful at endurance sports versus power sports, a panel that includes genetic variants involved in oxygen supply (NOS3, VEGF), muscle fiber type (oxidative; ACTN3), red blood cell production and function (EPOR; HBB) as well as mitochondrial numbers and activity (PGC1-a) and others, are all necessary to further determine potential endurance capabilities (7), and what areas need more attention in order to fulfill one’s genetic potential.

Not only is it an exciting time for exercise physiologists and strength and conditioning coaches, but nutritional physiologists and sport dietitians are keen to implement new assessment technologies and nutritional strategies originating from the new and intriguing field of nutrigenomics. Nutrigenomics is the study of how our genes affect the way we absorb, metabolize, and utilize nutrients and how the interaction between genes and diet can positively influence our health and performance. Genetic differences can affect how we respond to the foods we eat, and the interaction of our genes with the components in the food we eat can influence our nutritional status.

Why individuals experience different performance outcomes or struggle with body composition although they consume similar diets/calories or have similar pre-/ post-exercise nutrition strategies and comparable training protocols is an important question that’s been on the minds of sport science researchers and sport nutrition experts for years. While it’s long been suspected that genetics plays a critical role in determining how a person responds to foods and nutrients, only recently has research in the field of nutrigenomics demonstrated this. “Eat according to your genes” takes “personalized nutrition” to a whole new level. The excitement surrounding nutrigenomics stems from the notion that it’s the foundation for individually tailored diets and supplement regimes that will take into account one’s unique sports goals and genotype to allow more precision in optimizing sport performance. Individual genetic variations can affect how people respond to the foods, beverages and supplements they consume. It is now a well-known phenomenon in genetic nutrition research and practice that there is dramatic variability in inter-individual response to any type of supplement or dietary intervention. For example, some people do not absorb and process vitamin C from the diet as efficiently as others and are at a greater risk of vitamin C deficiency. Vitamin C is a well-known antioxidant that aids in the ability to reduce exercise-induced free radical damage which translates into better recovery from training and greater resistance to fatigue (8). However, too much Vitamin C can also be harmful to performance as it can interfere with the body’s natural adaptation to training [such as mitochondria production] (9) so the “more is better” approach may prove to be just as harmful as a deficiency.

It is becoming increasingly clear that our genes at least partially determine our specific and unique nutritional needs as well as our optimal training strategies when it comes to health and performance. However, sports genomics is still in the early phase and abundant replication studies are needed before these largely pioneering findings can be extended to mainstream practice in sport. And although DNA profiling cannot detect or determine superior athletes, it can predict potential abilities and weaknesses associated with sports performance. Future research including genome-wide association studies, whole-genome sequencing, epigenetic, transcriptomic and proteomic profiling will allow a better understanding of genetic make-up and molecular physiology of the broad-spectrum of athletic capabilities.

It’s an exciting time in sport genomics as we begin to create the necessary tools to develop personalized programs that will allow sport science professionals and practitioners to collaborate in a paradigm shift that will improve our ability to achieve optimal health, fitness and athletic performance. Once personalized training and nutrition is integrated into routine practice we can better predict efficacy of various training programs, diets and ergogenic aids, as well as determine risks for injuries and nutrient deficiencies that affect health and performance. When it comes to athletic performance, the emerging science of sport genomics will be the competitive edge of our future.

Nanci S. Guest MSc, RD, CSCS is a sport dietitian and strength and conditioning coach in Toronto, ON and Vancouver, BC, Canada. She is a PhD candidate currently researching the interactions among diet, supplements and genetics as they relate to athletic performance at the University of Toronto. She currently provides nutrigenomic genetic testing in her practice and plans to provide additional “genetically personalized” nutritional strategies to help athletes optimize body composition, training and competition performance based on her research in this area. Visit her at


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