Today, it is widely accepted that a well-structured diet is crucial for optimal athletic performance and overall physical fitness.

Increasingly, experts argue that we should move away from standardized dietary recommendations and tailor our diets to each person’s genetic predispositions.

This perspective is grounded in the rational understanding that every person is a unique individual, and none of us are the same—even identical twins differ. The human genome contains over 20,000 genes, which exhibit certain variations (referred to as genetic variability or gene polymorphisms). The products of these genes (proteins) can also be modified by post-translational modifications (known as epigenetics), further increasing the diversity among us.

We know that some people can eat as much as they want without gaining weight, while others can simply walk past the fridge and gain two kilograms. This effect has been demonstrated at the metabolic level—in a study involving 800 individuals, the metabolic response to nearly 50,000 meals was assessed, yielding clear conclusions about participants’ individual metabolic responses.

To complicate matters, our genes influence the metabolism of (not only) macronutrients, while our diet also affects our genes (these are the aforementioned post-translational modifications of proteins), and even the genes of gut bacteria and the overall composition of the gut microbiome, significantly altering functional metabolic relationships. For instance, obese individuals can derive up to 20% of their energy from so-called “indigestible” fiber through their gut bacteria, whereas this phenomenon does not occur in lean individuals.

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Nutrigenetics in disease

We now know that certain genes in each of us are crucial for the metabolism of macronutrients (proteins, carbohydrates, fats), as well as vitamins, antioxidants, trace elements, and other substances. This fact is eagerly exploited by commercial companies offering genetic services, which claim they can create personalized diets for everyone. But what does biomedical science say about this?

Medicine has been utilizing nutrigenetics for a long time, particularly in patients with certain conditions, such as celiac disease or gluten sensitivity, where the treatment of choice is naturally a gluten-free diet.

Similarly, this applies to lactose intolerance, some food allergies, and other diseases. For example, type 1 diabetes (diabetes mellitus) or insulin resistance associated with conditions like polycystic ovary syndrome (which causes amenorrhea and infertility). While it may seem that these diseases are unrelated to elite or performance sports, this is not true—over 50 elite athletes with type 1 diabetes are registered in the Czech Republic, and although this is not commonly tested, some elite athletes do indeed have insulin resistance and poorly tolerate fast sugars. Although athletes with the aforementioned conditions often manage without genetic diagnostics, these diseases are genetically conditioned, and thus, nutritional restrictions or measures are essentially a nutrigenetic approach.

There are dozens of genes that regulate our response to dietary interventions. These genes primarily influence the metabolism of essential nutrients, namely carbohydrates, fats, and proteins, and are intensively studied, especially concerning the rising prevalence of overweight and obesity and the associated lifestyle diseases.

What about sports?

In sports, the nutrigenetic and nutrigenomic approaches are perhaps surprisingly not applied in relation to the intake of essential nutrients (although we do know these genes, such as the FTO, CD36, or AMPK genes influencing fat metabolism, or GLUT-4 and PDH affecting carbohydrate metabolism), but rather to uncover potential health risks arising from the genetic makeup of specific athletes.

This primarily involves investigating gene variants involved in the metabolism of B vitamins (e.g., the MTHFR gene), calcium metabolism (e.g., the VDR gene, vitamin D receptor), iron absorption (e.g., the HFE gene), and those associated with latent inflammation risks (e.g., genes coding for TNF-alpha, IL-6, or CRP), which play a role in defense against increased oxidative stress that accompanies intense physical performance (including genes coding for antioxidant enzymes), or in the metabolism of certain substances used to enhance athletic performance (e.g., specific variants of the cytochrome P450 gene influencing the metabolism of caffeine used in sports as a psychostimulant).

Practical applications

However, it should be noted that there are currently no recommendations on how this issue should be addressed in sports, what spectrum (variants) of genes should be examined, and how reliable the outputs from these examinations would be.

This does not prevent many biotechnology and molecular biology companies from offering guaranteed personalized nutrition plans for every individual or athlete. Meanwhile, the vast majority of athletes (as well as the general population) who cling to these new technologies have not even begun to exhaust the possibilities offered by standard (sports) nutritional counseling, which can maximize athletic performance even without knowledge of each individual’s genetic predispositions.

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References:

1) Heck et al. Gene-nutrition interaction in human performance and exercise response. Nutrition 2004;20:598-602.
2) Zmora et al. Taking it Personally: Personalized Utilization of the Human Microbiome in Health and Disease. Cell Host Microbe 2016;19:12-20.
3) Kambouris et al. Genomics DNA profiling in elite professional soccer players: a pilot study. Transl Med UniSa 2014;9:18-22.
4) Kussmann et Stover. Nutrigenomics and proteomics in health and disease. Towards a systems-level understanding of gene-diet interactions. Wiley, Oxford 2017.

This article has been updated. It was first published on Bezky.net in February 2022.