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Nutrigenomics and Your Athletic Performance

Alexa Efraimson, Dietetic Student

Reviewed by Dana Eshelman, MS, RDN, CSSD


How understanding your genes can optimize your nutrition to feel your best! 


An athlete’s dietary and supplement strategies can influence their physical performance dramatically. An athlete’s personalized nutrition focuses on optimizing health, body composition, and exercise performance. Genetic differences are known to impact the absorption, metabolism, uptake, utilization, and excretion of nutrients and food bioactives, which ultimately affect various metabolic pathways. 


A gene-diet interaction may not be directly associated with quantifiable performance outcomes (ex. increased aerobic capacity, speed, strength) but rather with intermediate biomarkers or phenotypes, such as body composition and circulating Vitamin D levels, which are independent determinants of athletic performance, injury risk, and post-training recovery. 


A Quick Human Genetics Overview

Every person has 20,000-25,000 genes, each with a specific purpose. The purposes widely range, from metabolizing certain drugs and vitamins to determining what your eye color is to being correlated to certain diseases that you may be predisposed to (ex. if you have cancer that runs through your family, you have genes that may put you at a higher risk for developing cancer). For each gene, there are certain ‘variants’ or ‘alleles’, this is the genotype (the actual genetic makeup you have for each gene. An example would be AA or aa). These are different versions of the same gene. The version of each gene that YOU have is determined from meiosis and mitosis (from your mom’s egg getting fertilized by your dad’s sperm). The variant or version of a gene that you have will determine how ‘well’ that gene functions in your body. 


Here are a few practical applications of human genetics and your athletic performance: 


Caffeine

Found naturally in coffee, tea, and cocoa, caffeine is widely used in sports as a performance enhancer. In the field of nutrigenomics, caffeine is the most widely researched compound, investigating the modifying effects of genetic variation on athletic performance. Caffeine is primarily metabolized (over 95%) by the CYP1A2 gene and secondly metabolized by ADORA2A. In studies to date, there have been two groups of caffeine metabolizers based on this gene’s activity- ‘fast’ and ‘slow’ metabolizers. Those who are ‘slow’ metabolizers (AC or CC genotype) have an increased risk of heart disease, hypertension, and pre-diabetes with increased caffeine consumption, compared to those with the AA genotype (fast metabolizers). You may notice you are a ‘slow’ metabolizer if you feel sensitive to caffeine - jitters, nervousness, increased heart rate.


Caffeine + Athletic Performance

The second gene, ADORA2A, affects the role of caffeine in performance. This gene encodes for an adenosine receptor, which is responsible for making us feel tired. Caffeine competes with this receptor to stimulate wakefulness, concentration, and performance benefits. Variation in this gene (TT genotype) affects how much caffeine does or does not bind to those receptors, thus how much it improves performance.


Additionally, one of the largest caffeine and exercise study to date examined the effects of caffeine and CYP1A2 genotype in a 10K cycling time trial performance in competitive male athletes after ingesting caffeine at 0mg, 2mg, or 4mg per kg body mass. There was a 3% improvement in cycling time in the 2mg/kg body mass dose in all subjects! However, there was a significant caffeine-gene interaction in individuals with the AA genotype ('fast' metabolizers). Within that group, a 6.8% improvement in cycling time was observed at 4mg/kg. Those with the CC genotype ('slow' metabolizers), 4mg/kg caffeine IMPAIRED performance by 13%. What does this mean? Caffeine only improves athletic performance in those with the fast metabolizing (AA) gene. 








Vitamin A

Vitamin A plays a key role in vision and immunity in its biologically active forms (retinal and retinoic acid). Vitamin A has diverse immune system roles; Vitamin A deficiency has been associated with both immune dysfunction in the gut and systemic immune disorders. Provitamin A carotenoids (what we find in our foods) are converted to Vitamin A (retinal and retinoic acid) by the BCMO1 enzyme. Beta-carotene is the most abundant provitamin A carotenoid in the diet and the conversion to retinal or retinoic acid is necessary for Vitamin A to function in the body. Individuals with the GG genotype are inefficient at this conversion and may be at higher risk for Vitamin A deficiency. 


Vitamin A + Athletic Performance

High-performance athletes appear to have superior visual abilities based on their capacity to perform distinct visual skills, specifically for hand-eye coordination, dynamic acuity, and ocular judgment. In addition, deficiencies of certain micronutrients, such as Vitamin A, decrease immune defense. This can be exacerbated by low energy availability, poor food choices, jet lag, and physical and psychological stress. This is specifically relevant to athletes in high-volume, high-intensity training. Individuals with the GG genotype are considered ‘low responders’ to dietary beta-carotene. This means that it is especially important for them to consume enough dietary preformed Vitamin A (supplements) to ensure enough circulating levels of active Vitamin A. 


Anemia-Related Micronutrients: Iron

The importance of iron to athletes is established through its biological role in supporting the function of proteins and enzymes essential for maintaining physical and cognitive performance. Iron deficiency anemia is the most common type of anemia among athletes. Dietary intake, foot strike hemolysis, GI bleeding, exercise-induced inflammation, and non-steroidal anti-inflammatory drug (NSAID) use may influence iron metabolism in athletes. 


Low Iron Status + Athletic Performance

Three main genes (TMPRSS6, TFR2, and TF) can be used to assess genetic risk for low iron status, primarily due to their involvement in the regulation and expression of hepcidin, a peptide hormone that controls iron absorption. Variations in these genes determine the risk an individual has for lower ferritin and elevated transferrin when they possess a certain genotype. Although iron supplementation is common and frequently prescribed in athletes, many individuals are at risk of taking iron supplements in excess, which can not only be dangerous but also cause oxidative stress, the formation of free radicals, and reduced athletic performance. 


What does this mean?

Currently, few gene-diet interaction studies have directly measured performance outcomes. It has been established that serum levels and/or dietary intakes of several nutrients and food bioactives can impact overall health and body composition, both leading to effects on athletic performance. The strongest evidence to date appears to be caffeine on endurance performance. However, it should be noted that the effects of genetic variants do influence sports performance outcomes. Genetic testing for personalized nutrition is an evolving science and additional tool that will become more integrated into nutrition coaching for optimizing athletic performance. 


What does this mean for you? 

Just because there is research on a certain vitamin, mineral, or ergogenic aid that may be recommending its use (or disapproving the use), always, always, always listen to your body. You may have a genetic variant that does or does not metabolize these vitamins, minerals, or ergogenic aids in the way that the study or research has shown. If something that is deemed a ‘performance enhancer’ isn’t working for you, you don’t have to use it! Alternatively, if a ‘performance enhancer’ does or does not work for someone else, it may have a different effect for you! Listen to your body, you know it best.


If you are interested in having genetic testing done, this is something we offer at A Dash of Dana through Nutrigenomix. This is a one time salivary test and can help personalize your nutrition for day to day and performance!

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