As science draws ever closer to the reality of personalized nutrition for optimal performance, nutrigenomics — the study of the interplay between nutrition/bioactive food compounds and gene expression — offers an up-close view into human dynamics. In conjunction with the mapping of the human genome, we have the power to help clients not only remain healthy but understand the intricate relationship between nutrition, gene expression, and long-term health. Find out how nutrigenomics and nutrigenetics can help personal trainers guide their clients towards achieving their goals.

Understanding Nutrigenomics

The beauty of personalized nutrition lies in its potential to optimize health, body composition, and exercise performance. Nutrigenomics takes the process a step further than simply targeting dietary recommendations to an athlete’s goals; it also includes looking at one’s genetic footprint.

Nutrigenomics draws upon various technologies and genetic information to address issues related to nutrition and sports performance. Outside of a basic “clean eating” ideal, we must now consider the role that genetics plays in determining how an athlete responds to food/nutrients. Genetic variants affect the way nutrients react upon ingestion, specifically the alterations that might occur in the metabolic pathways critical to exercise output. The information gleaned from personal DNA/genetic testing can finely tune recommendations for individual protocols. Understanding why one’s body performs/reacts to certain nutrients can help trainers and sports dietitians propel an athlete’s success in a highly specific manner.

The Role of Nutrigenetics

Nutrigenetics addresses how genes determine the effects of nutrients upon the body. Hence, the manner in which an athlete’s body responds to the fuel ingested depends in part on his unique nutrigenetic profile. The profile categorizes nutrient absorption/utilization, food intolerances/allergies, and nutrient deficiencies.

We can consider nutrigenomics the polar opposite of nutrigenetics. While nutrigenetics provides information on one’s specific genome that might help influence what to eat for optimal athletic performance, nutrigenomics relates to how foods actually alter gene expression. Going one step further, scientists studying these fields strongly believe that diseases may arise as a function of dietary compounds (proteins, enzymes, and other chemicals) which, in turn, exert their power to affect gene expression.

Which Came First: Diet or Genetics?

The basis of nutritional genomics rests on the following principles ~

1) dietary chemicals harbor the ability to alter gene expression and/or structure

2) a specific meal plan can put one at risk for a number of diseases, especially if involving diet-regulated genes

3) genetic makeup may influence how diet affects/causes diseases

4) “individualized nutrition”, steeped in the knowledge of one’s genotype, may help to offset or even cure many common diseases

Training Clients Outside the Box

Personal trainers and bodybuilders have long clung to the tenet that in order to build lean muscle mass, or cut subcutaneous adipose tissue, one must carefully balance calories in/calories out as well as the appropriate ratio and timing of proteins, fats, carbohydrates, and micronutrients. Nutrigenomics points to the fact that, in addition to all of the above, our unique genetic makeup, too, plays a pivotal role in metabolic activity and the overall health of our bodies.

John Mathers, a Nutrition Scientist at the University of Newcastle in the UK, poses the question of how diet may interact with one’s genome, in an effort to extract the reasoning behind the expression of particular phenotypes. For example, many individuals in health-related endeavors adhere strictly to a clean and balanced meal plan. However, each of these individuals may possess a different set of genetic mutations, possibilities which can run well into the tens of millions, each leading to the expression of health or diseased states.

“We’ve started to better appreciate the fact that it’s not just the diet and it’s not just the genetic factors but it is an interaction of the two that permits a metabolic change that gets translated in a complex disease over time,” says Kenneth Kornman, Head of InterLeukin Genetics. 

Nutrition, Genome, and Disease Prevention

What does this say for the future of individualized precision nutrition based on one’s genome map? “Personalized nutrition advice may not be helpful to the general public if they don’t know their own genetics,” says Albert Koulman, an analytical chemist at the Medical Research Council in Cambridge, UK.

Now that scientists have come to view nutrition as an environmental factor that influences gene expression, nutrigenomics focuses upon how the pairing of food as fuel with an individual’s genetic anomalies can help foster a clearer understanding of the origins of many of today’s chronic health plagues: cancer, obesity, diabetes, cardiovascular disease, and aging in general.

A few examples may help elucidate this nascent yet compelling view. Delayed onset muscle soreness (DOMS), commonly experienced in the days following strenuous training, reflects exercise-induced muscle damage, which we know facilitates hypertrophy and strength. DOMS reflects oxidative stress, inflammation, and muscle protein degradation; the extent to which an athlete reacts to these side effects varies with age, training, and genetics. Specifically, subtle differences in variations of the ACTN3 gene influence susceptibility to muscle damage after tough workouts.

The ACTN3 (rs1815739) gene encodes the alpha-actin 3 protein, a primary player in the contraction of fast-twitch or power-type muscle fibers. Athletes who carry a genetic variant display a lower functioning ACTN3 protein, leaving them more vulnerable to muscle damage.

As such, these individuals may face a higher incidence of over-use injuries, especially without sufficient rest/recovery and adequate protein intake between training sessions. Armed with this genetic knowledge, a trainer might suggest more downtime between sessions, and a diet that emphasizes lean protein as well as foods that lessen inflammation (fresh produce, seeds/nuts/legumes).

DNA Testing and Individual Resistance

Although tremendous technological advances remain within our reach, many individuals shy away from delving too deeply into their personal information. Sometimes the fear associated with discovering the genetics for developing an incurable illness down the road paralyzes one’s effort to utilize genetic information to his advantage. Yet if a client does not see desired results having followed traditional bodybuilding nutritional advice, chances are good that he will give up. However, such personalized information offers an understanding of how and why one’s body responds to different diets and fitness plans, paving the way to increased motivation.

Applying Nutrigenomics

The more researchers learn about the intricacies of the genes/nutrient relationship, the more we can understand the benefits of including molecular science in the formula of turning out true performance-oriented athletes. For this process to have a high level of success, a truly personalized meal plan will take into all of the aforementioned factors. While much of the DNA testing no doubt lies outside the scope of most trainers’ practice, we can certainly educate clients about the possibilities open to them and allow them to take that next bold step.


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Cathleen Kronemer

Cathleen Kronemer is an NFPT CEC writer and a member of the NFPT Certification Council Board. Cathleen is an AFAA-Certified Group Exercise Instructor, NSCA-Certified Personal Trainer, ACE-Certified Health Coach, former competitive bodybuilder and freelance writer. She is employed at the Jewish Community Center in St. Louis, MO. Cathleen has been involved in the fitness industry for over three decades. Feel free to contact her at She welcomes your feedback and your comments!