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Sports and performance nutrition: what genes reveal and how to use it
Genes shape tendencies in sport. ACTN3 determines whether fast muscle fibers make the structural protein alpha-actinin-3; the R variant is more common among elite sprinters. CYP1A2 determines how quickly the body breaks down caffeine – and in studies it also influences how strongly caffeine boosts performance. For your counseling, this means: genes make strengths visible and help tailor nutrition, recovery and caffeine strategy to the individual.
A muscle protein that 18% of people lack
About 18% of healthy people of European descent do not make a particular muscle protein at all: alpha-actinin-3. And they live perfectly normal lives (North et al., Nature Genetics, 1999; Yang et al., American Journal of Human Genetics, 2003).
Alpha-actinin-3 sits in the fast muscle fibers – the ones that generate force in a flash during sprints, jumps and heavy lifts. Think of it as a cross-brace in the scaffolding of these turbo fibers. The blueprint is in the ACTN3 gene. A common variant, R577X, puts a stop signal in the middle of the instructions. People with two X copies make no alpha-actinin-3; a related protein, alpha-actinin-2, steps in.
It does leave a trace: elite sprinters carry the R variant considerably more often than control groups (Yang et al.). In the report, such results are deliberately described in simple terms as “functioning” or “impaired” genes – a simplification; the technically correct terms are genetic variants or polymorphisms.
Genes set the starting position, not the finish
ACTN3 shows impressively how genes shape our muscles. For your counseling, that is a treasure: anyone who knows their starting position can plan their route more wisely. Here is how to use the results:
- Self-understanding: “Why is endurance easier for me than sprints?” Genes provide part of the answer.
- Emphasis, not pigeonholes: Someone who leans toward endurance can still build strength – and vice versa.
- Realistic expectations: Progress is measured against one’s own history, not against others.
- A starting point for nutrition: Anyone who trains a lot and hard needs a diet that matches the load.
Performance comes from the interplay of many genes with training, technique, nutrition, sleep and motivation. Experts therefore recommend not using genetic tests to select talent among children and adolescents or to define their training (Webborn et al., British Journal of Sports Medicine, 2015). Their strength in counseling: they help adults understand their own profile and give conversations about nutrition and recovery a personal anchor.
The topics at a glance: what lies behind them
| Topic | What it is about | What it means in practice |
|---|---|---|
| Power or endurance | ACTN3 builds alpha-actinin-3 in the fast muscle fibers; the R variant is more common among elite sprinters. | discuss emphasis and expectations; match nutrition to power or endurance training loads |
| Caffeine and performance | CYP1A2 is the tool that breaks down caffeine; in studies, the genotype influences the performance effect. | test the caffeine strategy in training, tailor dose and timing to the individual |
| Recovery | genes associated with recovery after exercise | plan rest, sleep and post-workout nutrition deliberately |
| Injury risk | genes associated with injury risk | increase load gradually; have complaints checked by a physician |
Caffeine: same dose, different effect
Caffeine is one of the best-studied performance helpers in sport. According to the International Society of Sports Nutrition position stand, doses of 3–6 mg per kilogram of body mass improve performance in many studies, most consistently in endurance. Differences between people – including poor sleep or jitteriness after caffeine – may be linked to genetic differences in caffeine metabolism (Guest et al., Journal of the International Society of Sports Nutrition, 2021).
This is where CYP1A2 comes in – your body’s tool against caffeine. In a randomized, double-blind trial, 101 male competitive athletes rode a 10-km cycling time trial with 0, 2 or 4 mg of caffeine per kilogram (Guest et al., Medicine & Science in Sports & Exercise, 2018):
| CYP1A2 genotype | Time trial with caffeine (Guest et al.) | Meta-analysis (Barreto et al.) |
|---|---|---|
| AA – both copies functioning, fast breakdown | 4.8% faster with 2 mg/kg, 6.8% faster with 4 mg/kg | performance improved |
| AC – one copy impaired | no effect | performance slightly improved |
| CC – both copies impaired | 13.7% slower with 4 mg/kg | performance worsened |
A meta-analysis of 13 studies with 440 participants confirms this pattern: caffeine improved performance in AA and AC and worsened it in CC. Exciting for practice: in CC, performance was better the later exercise started after caffeine intake (Barreto et al., Medicine & Science in Sports & Exercise, 2024). A systematic review found the same direction: in the four studies in which the genotypes differed, AA responded more favorably than AC/CC in every case (Grgic et al., European Journal of Nutrition, 2021). Research keeps growing – the CC group in the studies has been small so far.
For your practice, this means:
- A CYP1A2 result is the ideal reason to plan the caffeine strategy deliberately and personally.
- Always test new strategies in training, never for the first time in competition.
- With impaired CYP1A2 genes, start with a low dose, test the gap between caffeine and exercise in training, and watch sleep and jitteriness.
- Avoid very high doses: the ISSN position stand links about 9 mg/kg with many side effects.
- With cardiovascular conditions, medications or pregnancy, the caffeine question belongs in a physician’s hands.
Recovery and injury risk: planning rest with purpose
Novogenia also analyzes genes related to recovery and injury risk – with the same rule as everywhere: each gene is supported by at least three independent studies. The logical conclusion: someone genetically prone to slower recovery has a particularly good reason to take recovery as seriously as training itself. The recommendations are logical conclusions, not scientifically proven.
In practice, this means: increase load gradually, build recovery firmly into the plan, get enough sleep, eat well after training. Ask specifically: How do you sleep? How do you feel the day after a hard session? What do you eat afterwards? Pain and injuries belong with a physician.
What this means for sports nutrition
Genes do not replace sports nutrition – they add accents. Energy, protein and carbohydrates depend first and foremost on training volume, intensity and goal. The genetic analysis helps you set the right priorities in the conversation: more attention to recovery, to the caffeine strategy, or to a diet that supports heavy strength sessions.
With micronutrients, it goes one step further: in Novogenia’s calculation of personalized supplements, competitive sport increases the requirement. Blood values take precedence, and every dose stays within fixed limits, at most up to the EFSA tolerable upper intake level. How that works in detail is explained in From genetic profile to personalized supplements.
An example: the runner with a power profile
A made-up, typical example: a client, 35, runs half marathons and wants to get faster. Her report shows functioning ACTN3 genes – a tendency toward power and speed – and impaired CYP1A2 genes.
- No contradiction: “Your genes lean toward power. That does not mean running is the wrong hobby. It may explain why short, fast sessions feel easier to you than long ones.”
- Nutrition to match the load: You discuss how she gets enough energy before long runs and eats well after hard sessions.
- Caffeine with a plan: Instead of a strong coffee before every run, she tests a low dose in training and skips caffeine before evening sessions so her sleep does not suffer.
- Review: training log and sleep notes until the follow-up appointment.
The pattern: genes provide talking points and fine-tuning. They do not write the training plan.
Checklist for counseling athletes
- Clarify the goal: performance, health, weight or the joy of exercise?
- Record training volume, intensity and competition calendar.
- Explain genetic results as tendencies – never as a verdict on talent or suitability.
- No testing of children and adolescents for talent selection or training control.
- Test the caffeine strategy in training and monitor sleep.
- Discuss the basics of recovery, regardless of the genetic profile.
- Check supplements against products already in use to avoid doubling up.
- Refer to a physician for pain, injuries, medical conditions or medications.
Dig deeper
The Performance page gives an overview of the analyses on training and sport. The science behind the individual traits is explained in the gene stories Power, endurance and the ACTN3 gene and Caffeine and the CYP1A2 gene.
Frequently asked questions
What is a sport genetic analysis good for?
What does it mean not to make alpha-actinin-3?
Should slow caffeine metabolizers avoid caffeine before exercise?
How much caffeine is usual in sport?
Do athletes need different nutrient amounts?
Related: Performance: the genetics of training and sport · Power, endurance and the ACTN3 gene · From genetic profile to personalized supplements
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Become a partner →Offer for nutrition professionalsNote: This guide is general information for professionals and does not replace medical or legal advice. The genetic traits determined in a genetic analysis are well documented (each gene included is backed by at least three independent studies); recommendations on nutrition, micronutrients and lifestyle derived from them are logical conclusions, not scientifically proven. Regulations can change; errors and changes excepted.