Genetics, Nutrition, and Performance

Genetics, Nutrition, and Performance: What Every Athlete Should Know

Sport Nutrition

We all know that genetics play an important role in health and performance. Genetics are also often used to explain differences we often see between people living in similar environments. They tend to be thought of as an uncontrollable factor, something we just need to live with. But, what if that wasn’t the case? What if we can learn more about our genes and how to work with them? What if we can use genetics to create personalized nutrition and training programs to help us truly perform our best? With nutrigenomic testing we can do just that!

Nutrigenomics (and nutrigenetics) are the fields of study that investigate the link between nutrition and our genetics. For many years in nutrition science we’ve created recommendations and guidelines based on “averages”. This means that while the guidelines can mostly apply at a large, population level, some people might be left out. For example: For some essential nutrients your needs may be higher than the “average”. Or, you may need a slightly different strategy than others to alter your body composition.

As a Dietitian, my goal has always been to provide personalized nutrition recommendations to my clients. Adding genetic information into my nutrition plans gets away from the trial and error of what will suit my clients best. In my practice I use a test called Nutrigenomix. They’ve recently launched a 70-gene test that provides some of the most exciting personalized information an athlete can get their hands on.

What can nutrigenomics tell us about gene-nutrient interactions?

Glad you asked! Today, I’ve selected my top genes for athletes who want to optimize their health and performance using nutrition and genetics. I’m sharing a detailed breakdown of why knowing your genetics is key for performance, and what strategies different athletes might use to work with their genes more effectively


When it comes to sport supplements, there are few more heavily studied (or used) than caffeine. But, depending on an athlete’s genes caffeine may not provide the “boost” we expect! Caffeine may also contribute to increased feelings of anxiety for some athletes. During competitions where anxiety and “jitters” can already be running high, caffeine may do more harm than good. Genetics can tell us who may benefit from caffeine and who may not!


The first gene identified in terms of it’s effects on athletic performance is the CYP1A2 gene. This gene determines how quickly caffeine is metabolized in the liver. People can be “fast metabolizers” (GG genotype) and “slow metabolizers” (GA or AA genotype). Fast metabolizers are more likely to see improvements in their athletic performance with caffeine use. Slow metabolizers on the other hand may see no effect. Some slow metabolizers may even experience performance impairment with caffeine. Since this is the last thing athletes want, knowing your genotype is key!


The ADORA2A gene also plays a role in caffeine and athletic performance. It’s the gene that can increase feelings of anxiety in some people when they take too much caffeine. It also impacts perception of pain, our motivation, and how we sleep. Those with the TT genotype of ADORA2A, are more likely to experience anxiety with caffeine use than those with the CC or CT variant. That being said you also are more likely to “feel” the effects of caffeine more than the others, so you may already naturally limit your caffeine.

The bottom line:

Caffeine can be a useful sport supplement for many athletes, but it may not be right for everyone! Knowing your genetics when it comes to caffeine can ensure you’re being smart about supplements!

For more about caffeine and athletic performance check out this article: Caffeine and Athletic Performance 101

Energy Balance (UCP1 rs1800592):

One question I often get asked as a Dietitian is “How many calories should I be eating per day?” New technology has made food tracking simple, with apps like cronometer or my fitness pal. Unfortunately knowing how many calories a person burns per day is not quite as simple. We have various methods of estimating, but none are 100% accurate. This can leave some folks frustrated when they aren’t seeing the results they expect. Knowing about our genetics however can get us a little closer!

The UCP1 gene has been indentified as playing a role in what a person’s resting energy expenditure actually is. We often refer to Resting energy expenditure as our “resting metabolic rate”. Research shows that those with the GG or GA variant of this gene can have a slightly lower metabolic rate than people with the AA variant. This difference works out to about 150 calories per day. This genetic difference in resting metabolic rate may explain the different results we see in people following the same nutrition plan!


The FTO gene is definitely one of the more well-studied gene when it comes to body composition. It’s been identified as a regulator in body weight and body composition in relation to nutrition and exercise patterns, and is a key factor when it comes to genetics and obesity.

Here are a few ways our dietary patterns can interact with the FTO gene and influence our body composition:


Ever wonder why some people seem to lose fat effortlessly on a higher protein diet? It’s not a fluke, it’s genetics! Studies have shown that people with the AA variant of the FTO genotype lose significantly more fat when following a calorie-reduced, higher protein diet than their TT or TA counterparts. Knowing this information can have a major impact on an athlete’s nutrition strategy!

Saturated vs Unsaturated Fat

The type of fat we eat can also interact with our FTO gene and lead to differences in body composition. People with the TA or AA variant are likely to have a lower waist circumference and body weight when eating a diet lower in saturated fat and higher in unsaturated fats. People with the TT variant are less likely to see a difference based on the type of fat they’re eating. However, as you’ll see next there’s actually a number of genes involved in various fat metabolism pathways!

Is it the type of fat, or the amount?

Well, it’s both! The total amount of fat in our diet certainly plays a role in our body composition. Interestingly, variations in response to the types of fat we eat are also influenced by our genetics! This can be a game-changer for an athlete’s nutrition plan depending on their body composition goals.

Total Fat

TCF7L2 is the gene responsible for producing a protein that impacts weight loss in response to the total amount of fat we consume. People with the TT variant of this gene tend to see more fat loss and a decrease in waist circumference when they eat a slightly lower fat diet. (15-25% of total calories). People with the TC or CC variant don’t see the same result. In fact, they actually have a tendency to lose muscle mass when they eat a very low-fat diet. This can have major implications when setting your macronutrient goals!

Saturated Fat

Another gene that interacts with saturated fat is called APOA2. This gene interacts with saturated fat from our diet and influences our weight. People with the CC variant of the APOA2 gene are more likely to have a higher weight when they eat a diet high in saturated fat. This is compared to people with the TT or TC variant who do not see the same response. Differences in genetics like this can help explain why some people lose far more weight than others while following higher fat diets!

Monounsaturated Fat

Monounsaturated fats are found in foods like olive oil, nuts/seeds, and avocado. The PPARy2 gene is involved in the formation of fat cells in our body. It appears to be influenced by how much monounsaturated fat a person consumes. People with the GG or GC variant experience more weight loss when they eat a diet with more monounsaturated fats. In one study, a diet containing 56% or more of total fats in the form of monounsaturated fats was used. People with the CC genotype do not need to prioritize monounsaturated fats in their diet for weight loss.

What can genetics tell us about micro-nutrients and our diet?

Many genes have been identified that interact with essential nutrients in our diet. Here are some vitamins and minerals that are key when it comes to athletic performance! Focusing on these as part of a well-rounded nutrition strategy will help athletes push their performance to the next level.


Personally, one of the reasons I was extremely excited for this next launch of Nutrigenomix tests is because of choline. Choline is a nutrient that most people actually haven’t heard of , but it you should definitely get to know it!

A deficiency of choline is associated with muscle damage and liver damage. In women, inadequate choline intake with certain genotypes can put them at 25X the risk of showing signs of choline deficiency. This is a big deal since choline is also a key nutrient for proper fetal development during pregnancy!

The MTHFD1 gene encodes an enzyme that is responsible for folate metabolism. This explains why these two nutrients are so tightly linked, particularly when it comes to pregnancy. People who have the GG variant of MTFD1 are less at risk of showing signs of choline deficiency. The GA and AA variants are more susceptible when their diet is lacking choline. Additionally, the PEMT gene also impacts choline needs, but variations based on this gene were surprisingly only found in women! Those with the GG variant had much lower odds of developing signs of deficiency vs their CG or CC counterparts.

Why does this matter?

Well, as I said before, choline is a key nutrient you probably haven’t even heard of! And, if you aren’t aware a nutrient even exists, how can you be sure you’re getting enough of it? Eggs are among the most common and best source of choline in our typical western diet. Beef liver is also a great source, but not many people are eating that these days! With a rise in plant-based eating many people are leaving eggs off their menus for various reasons. Even omnivores may not be getting close to reaching their daily choline requirement depending on their daily food choices.

Given that choline is known to be essential for fetal development during pregnancy, it may be a surprise to find out that very few brands of prenatals include it. So, if you’re a female athlete wanting to gain and preserve muscle, or even thinking about fertility keep choline on your radar!

Vitamin A

Vitamin A is a key nutrient for eye health and vision, as well as immune function. For athletes, vitamin A is critical for exercise recovery due to it’s anti-oxidant properties. We get vitamin A in our diet in two forms: Active vitamin A (retinol), and beta-carotene. In the body, beta-carotene needs to be converted to active vitamin A before it can be utilized. The BCMO1 gene plays a role in this conversion, and genetic variations here make some people ‘poor converters’. Those with the GG variant who are poor converters should include more pre-formed sources of vitamin A in their diet. They may also want to consume very good sources of beta carotene regularly.

Vitamin C

Vitamin c is best-known for it’s role in the body as an antioxidant. This makes it a key part of exercise recovery! Variations in a gene called GSTT1 plays a role in how much vitamin C we have circulating in our bodies. People with the ‘insertion’ variation have normal GSTT1 enzyme function. They can maintain their vitamin C levels with a lower dietary intake. Those with a “deletion” variant of the gene require more vitamin C from their diet in order to achieve the same circulating levels. This means that people with the deletion variant getting in your fruits and vegetables is even more critical!

Should athletes just take a vitamin C supplement?

Interestingly, for athletes vitamin C can also cause an issue if we consume it in excess. This is typically seen with people who take large doses of vitamin C supplements. Large amounts of this vitamin can actually impair exercise recovery. This is especially true if supplements are taken right around the time we train. So, focus on a food-first approach with vitamin C!

Calcium and Vitamin D

Vitamin D is created in the body through the exposure of our skin to UV rays. The CYP2R1 gene is responsible for encoding the enzyme which converts vitamin D into it’s active form. People with the GG or GA variant of the CYP2R1 gene are less capable of converting vitamin D into it’s active form. This puts them at higher risk of vitamin D deficiency. AA genotypes on the other hand are better converters, but they may still be at risk! A different gene regulates how vitamin D actually gets into our bodies cells, which we’ll talk about next!

Both calcium and vitamin D are impacted by the GC gene. This is a gene that encodes the protein that transports vitamin D into our bodies’ cells. People with the GG variant of the GC gene are at higher risk of a vitamin D deficiency when they aren’t getting enough of the sunshine vitamin (which many of us Canadians aren’t!) People who possess the TT or TG variant are less at risk, even with a lower vitamin D consumption.

Calcium is also impacted by the GC gene, which leads to some folks having a higher risk of bone fractures when their calcium intake is lowered. For athletes this means knowing your genes can help ensure you’re avoiding serious injuries likes stress fractures!


Iron is a key nutrient in that is responsible for transporting oxygen around the body. It also plays a role in our immune system function, both of which are key for optimal athletic performance. When it comes to iron and genetics though, the story is a little complicated! There are a number of genes that regulate iron in the body. From it’s absorption in the gut (TMPRs56), to moving iron into our body’s cells (TFR2), to transporting iron around the body (TF).

People with the AA variant of the TMPRs56 and TFR2 gene are at greater risk of iron deficiency. This is because they absorb less iron in the gut, and are less able to get iron into the cells where it’s needed to function. Athletes with a higher risk of low iron status (based on an algorithm taking into account all of these genetic variations) should take special care to have their iron levels tested regularly, and always pair iron-rich foods with vitamin C for enhanced absorption. Choosing foods that provide heme-iron (such as meat or chicken) can also increase absorption over non-heme iron (from plant sources)

For vegan athletes who do not consume heme-iron sources, monitoring iron levels and supplementing as needed can help avoid serious performance and health complications that can arise when iron levels are too low.

Vitamin B12

Vitamin B12 is a nutrient that plays a role in normal brain and nervous system function. Without adequate vitamin B12 levels in the body we can experience weakness, fatigue, and a decrease in aerobic performance potential. The FUT2 gene is involved in vitamin B12 absorption and transport in the body. People with the GG or GA variant are most at risk when compared with those with the AA variant. They can experience poor B12 absorption which increases their chances of having low vitamin B12 levels in the body. These folks should focus on getting more vitamin B12 in their diet from more bioavailable sources, and supplement if needed. Vitamin B12 supplements should also be taken on an empty stomach for best absorption!

Performance Potential

Nutrigenomics can tell us a lot about our personalized nutrition needs based on our genes. But can it also predict our athletic performance potential? To some extent, nutrigenomics research has identified several genes involved in athletic performance and how one may respond to training. While it can’t predict who will be the next Olympic gold medalist, it can provide a little guidance about how we can train better!


Five genes have identified and are used by Nutrigenomix to determine someone’s endurance performance potential. They are ADRB3, NFIA-AS2, NFR2, GSTP1, and PGC1a. Some of these genes predict things like who will have a higher V02 max. Others predict one’s response to endurance training. Things like running economy, V02 max, anaerobic threshold, and body temperature regulation. Athletes may have a ‘response’ variant in one area, but not in another. Athletes with response variants across all of these genes would be considered to have an “ultra” advantage when it comes to endurance sports.

How can this information help athletes train smarter?

Well, it can help an athlete guide and prioritize their training. For example I have the response variant for the NFIA-AS2 gene, which is associated with a higher V02 max. I don’t however, have the response gene for improvements in my anerobic threshold (PGC1a). This means if I want to run a faster half-marathon I should put more emphasis on training my anaerobic threshold since this will not come as easily to me. A sprinter on the other hand, who has the opposite gene variants as myself, may need to train their V02 max much more heavily. They may not concern themselves with much anaerobic threshold training. It doesn’t mean either of us can’t still improve and excel at our sport, it just means we may need to work a little harder than athletes who are more naturally ‘gifted’!

Strength and Power

When it comes to muscle strength and power, our genes can also predict which athletes might excel. The ACTN3 gene encodes a protein called alpha-actin 3, which is found in fast-twitch muscle fibres. People with the TC variant of this gene have an enhanced training response when it comes to power and strength activities. People with the CC variant have been shown to have an even better response, and are considered “ultra” responders.

One of the reasons why athletes with the CC variant excel above either of the T-containing ones, is because people with the TT or TC variant have been shown to have an increase in muscle damage with training. This means these athletes need a solid recovery strategy, including adequate nutrition and rest between training sessions. They may not be able to train as frequently as their CC counterparts. But, with an efficient, effective training program and a solid recovery strategy these athletes can excel too!

When it comes to training, nutrition, and genetics, as you can see it’s all about personalization!


When it comes to athletic performance, sleep is as important as our training program and nutrition plan. Sleep is a time when our body heals, recovers, and recharges. When we lack sleep our brain cannot function properly, which means we can see an impairment in reaction time, accuracy, and decision-making skills. This is a big deal for athletes who rely on things like hand-eye coordination and split-second decision making to succeed. Adult athletes need 7-9 hours of sleep per night, while youth and adolescent athletes need a whopping 10 hours.

The CLOCK gene has been associated with predicting people who are likely to sleep for a shorter duration. This can put them at risk of these impairments. People with the TC or CC variant of the CLOCK gene are more likely to be “shorter sleepers” than people with the TT variant.

Athletes who are “short sleepers” should make an effort to incorporate good sleep hygiene practices into their schedule. This includes avoiding caffeine later in the day, turning off screens and work at least 1 hour before bed, and sleeping in a cool, quiet, dark room. This can help increase sleep duration and quality, and help maximize athletic performance.

The latest edition of the Nutrigenomix test looks at 70 different genes and provides personalized nutrition recommendations to optimize overall health, performance, or fertility. Here I’ve shared my top genes related to athletic performance and how athletes can work with their genes to become the best athletes they can be. To learn more about a Nutrigenomix test and to find your best diet and training program, click here!

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