I have never believed in one size fits all for anything nutrition related, particularly with sports nutrition, and other sports performance experts are finally starting to look at things differently. The American College of Sports Medicine, the Academy of Nutrition and Dietetics and the Dietitians of Canada recently released a statement that “Nutrition plans need to be personalized to the individual athlete… and take into account specificity and uniqueness of responses to various strategies.” This is music to my ears!
Let’s look at caffeine first. There have been many studies that show that caffeine can enhance athletic performance, increase time to exhaustion, enhance cognitive function and reduce the perception of pain… too many studies for me to link here. That said, we are now learning that genetics and daily usage of caffeine impacts if, and how much, performance enhancement actually occurs for each of us.
Caffeine is metabolized by the CYP1A2 enzyme, which is encoded by the CYP1A2 gene. Depending on your genetic makeup, you may be a slow or fast metabolizer. The AA genotype is a fast metabolizer because their genotype encodes more the of the CYP1A2 enzyme. Those are the people that can have an espresso after dinner and lie next to you snoring a few hours later. The AC genotype is a slow metabolizer and the CC genotype is the ultra slow metabolizer. The AC or CC people are those that can have limited amounts of caffeine comfortably and if they have too much may feel anxiety or experience disturbed sleep. The AC or CC genotypes also have more health risks associated with high levels of caffeine, such as myocardial infarction, high blood pressure and impaired glucose regulation.
Regarding athletic performance the research is showing that fast metabolizers (AA) see more performance enhancement from caffeine intake. In the various studies, the AC genotypes found either no enhancement from caffeine or a slight improvement. The differentiation is linked to athletic training and daily diet. The trained subjects had performance enhancements, while the untrained subjects did not. This is likely because exercise and the intake of broccoli increases the expression of CYP1A2.
Another gene that can potentially modify how caffeine affects performance is the ADORA2A gene. This gene encodes the adenosine receptor. In the brain the adenosine receptor regulates glutamine and dopamine release, which affects sleep and pain perception. When adenosine binds to the receptor, nerve cell activity slows leading to drowsiness and blood vessels dilate allowing in more oxygen. Caffeine blocks the adenosine receptor, which causes more feelings of alertness and constricts blood vessels. Because of the effects on the adenosine receptors, caffeine can attenuate the negative effects from lack of sleep but the ability to do so depends on a person’s specific genetic coding. Those with the TT genotype have more favorable performance benefits than those with CT or CC genotype but those with TT genotype may also experience more anxiety from caffeine usage. Those with a C genotype typically experience more sleep disturbances from caffeine use. In this case if you have the TT genotype using caffeine can provide some benefits. If you are the CC genotype you may not get any benefit and could potential disrupt sleep, but that may depend on daily caffeine habits. In the study, the participants with CT or CC genotype did not consume any or very little caffeine on a daily basis, likely because of the negative effects on sleep. It’s unknown if there would be performance benefits for these genotypes if they were regularly consuming caffeine.
So what does this mean for you? Should you consume caffeine during your next athletic event? If you are an AA genotype for the CYP1A2 gene and a well trained athlete with a healthy diet, definitely. If you are an AC genotype, probably, but make sure you have been training consistently and eat more broccoli to help increase the likelihood of performance enhancement. The AC genotypes may also want to allow more time for the caffeine to take effect so consuming earlier is better. It’s also beneficial to reduce caffeine consumption in the week leading up to the event so that you get a bigger impact from caffeine on race day. If you are a CC genotype, you may want to skip the caffeine, particularly if it causes more anxiety, hypertension or heart issues on race day. That said I am a CC genotype and consume only small amounts of caffeine daily, eat a lot of cruciferous vegetables and feel I do get a boost from caffeine. I time it appropriately and use versions that are quickly absorbed. If you are a CC or CT genotype for the ADORA2A gene, consume it early in the day so that is does not disrupt sleep significantly. If you are a TT genotype for the ADORA2A gene, use caffeine but only if you are pre-disposed to anxiety.
If you don’t have any genetic data, look at how you typically feel with caffeine use. Do you get a boost in productivity? Do you have sleep disturbances if you drink it too late in the day? Does a little go a long way for you? Does it cause anxiety? The answers to those questions can help you determine where your genotype may fall. As always, it’s good to experiment as our genes do not define us. Our nutrition and lifestyle habits determine how our genes express, so you have the power!