On Your Mark Nutrition


What I Did to Personalize My Caffeine Intake for Sport Performance and Heart Health

Photo by ArtTim/iStock / Getty Images
Photo by ArtTim/iStock / Getty Images

Will caffeine actually improve your sport performance or fitness class? Do you need to rethink the venti Starbucks coffee in the morning and mid-afternoon espresso to protect your future heart health?

The (annoying) answer: it depends.

Remember those headlines claiming that drinking beetroot juice improves exercise performance? Once again, it depends.

Why does it depend? Because this is the era of personalized nutrition. Not everyone responds to generalized guidelines. A one-size-fits-all approach isn’t cutting it anymore in nutrition, especially in the sport performance field.

For caffeine, the current guidelines suggest consuming 3-9 mg/kg of body weight approximately one hour before exercise. Yet, people experience either an improvement, no effect or a decrease in their performance.

Responses to caffeine are individualized, especially since many different factors influence its effect in the body. There’s enough research to say that much of the answer as to why you can drink coffee before bed and sleep fine (compared to someone else who can’t drink coffee after 3 p.m.) lies in YOUR genes.

In this blog, I discuss some of the caffeine gene research and how testing for the gene helped me refine my caffeine amount, form of intake and timing to enhance my speed and power on the bike and confirm my daily over-consumption of coffee habit.


What is Caffeine?

Caffeine, a natural compound in plant foods, is a central nervous system (CNS) stimulant typically used for improving well-being and work capacity. Needless to say, it’s a popular, legal psychoactive drug that is the main ingredient in coffee and energy drinks. In fact, of all the ingredients found in energy drinks, the main ergogenic value is actually the carbohydrate and caffeine.

Within 15 minutes of consumption, caffeine can get into your bloodstream (especially depending on what form the caffeine is consumed). Caffeine levels peak after approximately one hour. About half of it is broken down within 3-4 hours (also referred to as “half-life”).

The liver is the main site of caffeine breakdown by an enzyme called cytochrome P4501A2 (CYP1A2). (Side Note to Detox Enthusiasts: the liver is one of our “detoxifying” organs!)

Adenosine is a neurotransmitter involved in regulating the sleep/wake cycle. When you’re awake, adenosine builds up in the brain and causes drowsiness and signals your body to rest. Caffeine acts upon our CNS by binding to adenosine receptors and preventing adenosine from attaching. Therefore, caffeine increases energy because the brain can neither detect adenosine nor slow down your nervous system.

The performance benefits of caffeine are applicable to both endurance and high-intensity exercise. Caffeine:

  • Increases neurotransmitter release and muscle contraction;

  • Promotes adrenaline release;

  • Lowers perception of fatigue, effort and pain during exercise; and

  • Spares carbohydrate use and promotes fat use.

Here is a list of the caffeine content of some popular drinks:

  • Coffee, brewed (8 fl oz): 163 mg

  • Coffee, brewed, decaf (8 fl oz): 6 mg

  • Espresso (1.5 fl oz): 77 mg

  • K-Cup Coffee (8 fl oz): 120 mg

  • McDonald’s Coffee (16 fl oz): 145 mg

  • Tea (8 fl oz): up to 80 mg

  • Coke (12 fl oz): 34 mg

  • Dunkin’ Donuts (14 fl oz): 210 mg

  • Redbull (8.5 fl oz): 80 mg

  • Starbucks Tall (12 fl oz): 248 mg

  • Starbucks Grande (16 fl oz): 330 mg

  • Starbucks Venti (24 fl oz): 495 mg


Caffeine Does Not Improve Everyone’s Performance

A study used 13 cyclists to investigate the performance effects of a 15-minute all-out effort on the bike using caffeine doses of 1, 2 and 3 mg/kg of bodyweight. Compared to a placebo, caffeine improved the average performance by 3.9% for the 2 mg/kg group and 2.9% for the 3 mg/kg group. The 1 mg/kg group saw no improvements.

Does this mean that 2 mg/kg is better than 3 mg/kg? Not necessarily.

The study based their conclusion using the average of the group’s response. So what they found was a performance improvement on average. But, the true answer lies in examination of the data for each subject. Some cyclists experienced a decrease in performance at certain caffeine dosages and some experienced an increase in performance.

Other studies have also shown variation among individuals – either showing a negative, neutral or positive effect for caffeine supplementation.

This situation in which some people respond and others don’t is also typical studies investigating other popular ergogenic aids, such as beetroot juice. This is why it’s important for studies to show data on individual subjects so we can see this.

Inconsistent study results and differences in response can suggest genetic variation, which is a big research gap. If studies tested the genetic component (if applicable), then this could help tease out inconsistent results and help us better apply the results in the real-world (i.e., give more personalized nutritional recommendations).


The Caffeine Gene

The gene CYP1A2 encodes an enzyme that is the head honcho for up to 95% of all caffeine metabolism, or breakdown. The normal form of the gene is the 1A allele, but there is another common form called the 1C allele. Both produce the enzyme, but the 1C variant produces less of it. Those with one or two copies of 1C generate less of the enzyme. Consequently, they metabolize caffeine at a slower rate and caffeine stays at high levels in the body for a longer period of time.

  • CYP1A2 1A/1A: there are two copies of the “fast” variant, which makes you a fast metabolizer. These individuals can metabolize caffeine 4x more quickly than someone who has 1 or 2 copies of the slow variant. There’s a spike in alertness and then a dip in energy

  • CYP1A2 1A/1C: intermediate metabolizer

  • CYP1A2 1C/1C: slow metabolizer

Coffee has a stronger effect on those who are an intermediate or a slow metabolizer. This is not necessarily a desired effect because it may ultimately increase blood pressure due to being in our body longer.

Studies have investigated how being a fast or slow metabolizer effects performance. One study tested 35 trained male cyclists. The cyclists consumed either 6 mg/kg of body weight of caffeine or a placebo and then completed two 40-km time trials on the bike. They found that those who were fast metabolizers had a 4.9% improvement compared to slow metabolizers who only had a 1.8% improvement.


Heart Health: Do You Need to Rethink Your Starbucks Venti?

Knowing your caffeine gene isn’t just about performance. At the end of the day, athletes are human first. Meaning – we need to prioritize our health, especially for the long-term, over performance. That being said, caffeine has evidence for effects on heart health.

Those headlines claiming coffee is bad for your heart are not the true story because it depends on the person. There is some evidence of the effects of caffeine on your heart – specifically, heart attack (i.e., myocardial infarction, MI) – as it relates to a slow or fast metabolizer:

  • If you are a slow metabolizer AND drink a lot of coffee then caffeine may increase your risk for heart problems, such as MI.

  • If you are a fast metabolizer AND drink a lot of coffee, then this may reduce your risk for MI. In this situation, coffee has a protective effect on your heart.

So when you hear/read that drinking too much coffee is bad for the heart we have to look at who in that population is driving the risk. If the population are those who are mostly “slow metabolizers” then that conclusion is a bit distorted because “fast metabolizers” have a protective effect.

For hypertension, the evidence suggests:

  • If you're a slow metabolizer AND a heavy/moderate coffee drinker, then you may have an increased risk for hypertension. Therefore, it is suggested that the person eliminate or drastically reduce their caffeine intake, especially from coffee.

  • If you’re a fast metabolizer AND drink a lot of coffee, then you may have a reduced risk for hypertension. Therefore, it is suggested that the person can safely consume caffeine, especially from coffee.

Obviously, there are other genetic and environmental factors in play in the risk for heart disease and hypertension as both have a multifactorial etiology.

One cup of coffee per day is not going to affect our health. But 2-3 cups of coffee per day may lead to problems over time in those who are slow metabolizers.

Note: the above is NOT medical advice. It is simply discussed for educational purposes.


Why I Tested for the Caffeine Gene

When I make recommendations, the first and foremost, is to do NO harm. If something (i.e., a supplement) will have a neutral or potentially positive effect based on promising research – I say go with it. (As long as it is feasible, practical and cost-effective.)

As we see, caffeine could potentially cause a performance decrement in some people. Or – even worse – the habitual recommendation of a high caffeine intake in the nutritional plans used for exercise or competition may have consequences in the long-term.

Caffeine is one of my top ergogenic aids that I recommend to athletes and use strategically for myself. I’ve known for years that caffeine definitely improves my performance compared to not having caffeine. Therefore, I select a coffee brand based on their caffeine amount. (This is why Cuban coffee and Death Wish Coffee – 485 mg caffeine per 8 fl oz – are two of my go-to’s depending on context.)

But, I’ll be honest, I’ve struggled to figure out how to strategically use it given that I compete in different types of races (from short-time trials up to 100-mile road races).

  • How much caffeine I should have (given the wide range)?

  • What should my protocol be (e.g., consume only beforehand, space it out every hour or consume only near the end)? Creatine and beetroot juice are examples of supplements needing nutrient timing to maximize effectiveness for performance. So caffeine also needs refined recommendations.

This past October, I did physiological testing to figure out how many calories and carbohydrate grams I need per hour based on my heart rate and power that I’m working at on the bike. This means, no more following guidelines! I can now “fuel” based on my physiological needs!

This testing was one of my biggest steps toward further personalizing my nutrition. Long story, short, the information was very eye-opening to me and made me determined to personalize my nutrition even more in every aspect that was practical.

Given the solid caffeine gene research and that caffeine is a staple in my daily life and competition nutrition, I decided to test for the caffeine gene. (Side Note: I’m very excited for the promising nutrigenomics field, and I intend to do a full genomic test next year to further personalize my nutrition, but for now, I highly valued knowing my caffeine gene.)

The process was very simple:

  • Order the test from a reputable company that I knew would protect my private information and destroy my sample once they tested it.

  • Take a swab of the inside of my cheeks.

  • Mail the sample back to the company.

I found out in less than one week of the company receiving my sample. I was so excited that I felt like a kid on Christmas Eve. When I got the email that my results were available, I also was very nervous. I had a feeling that I was a rapid metabolizer though….

Below are my results, which were explained to me from the company:


Testing for the caffeine gene was a worthwhile investment for multiple reasons:

  • Personalized Nutrition: genetic information is not going to change. Therefore, as further research is released, I can use my information to further tailor my intake. For example, if research shows that fast metabolizers are less likely to experience habituation from caffeine then I could focus less on tapering my use leading up to competition (which is still out for debate if we should follow a caffeine taper or not).

  • Sport Performance: it gives me further insight on how I can maximize my caffeine use to enhance my performance. Of course, we don’t have research suggesting that those who are fast metabolizers need to have a certain amount of mg/kg of body weight. But there’s enough information to tell me: 1) which side of the guideline spectrum should I follow; 2) nutrient (caffeine) timing; 3) what form (e.g., liquid, capsule, etc.) I should consume caffeine as this will lead to quicker or slower absorption; and 4) how I could use caffeine to spare my carbohydrate use during training, which could improve my metabolic efficiency and my endurance capacity. Let’s just say, I’m now not going to take 200 mg of caffeine an hour before a short-time trial…

  • Heart Health: I love coffee. If my future risk for heart health had called for it, this information would’ve motivated me to make a behavior change.

How does this compare to when I tested for the gene for speed, alpha-actinin-3 (ACTN3)? The caffeine gene gave me actionable results that I could easily apply. The gene for speed was simply cool information about myself. Read my blog, If You Have the Gene for Speed, Can You Succeed as an Endurance Athlete?

Note: there are also non-genetic factors that impact caffeine effects, such as sex, medications, habitual caffeine intake, training status and the person’s own expectations. But this discussion is out of the scope of this blog.


Practical Advice

The devil is in the details regarding the effects of caffeine on performance and heart health.

And there are still a lot of interesting questions regarding how to apply what we know about the caffeine gene (e.g., how does habitual intake or sex play a role?).

Consider the following questions:

  • Will caffeine improve my performance?

  • If you’re using caffeine for a performance benefit, then:

    • What range of the spectrum (2-9 mg/kg) should you follow?

    • What form should you take caffeine in during a race?

    • What should your protocol be related to nutrient timing (e.g., consume all of it 1 hr before a race or space the dosage out)?

  • If you’re using caffeine for alertness, alleviate fatigue, etc., then:

    • How could this impact your heart health over time?

    • How many milligrams of caffeine per day should you healthfully consume?

This blog is not intended to downplay caffeine as an ergogenic aid. It’s intended to educate about the nuances of its effectiveness and to suggest testing for the caffeine gene as a tool to help you tease out the answers to the above questions that will further personalize your caffeine intake.

This is an example of taking research data and a person’s biology to help guide real-world application.

Forget the trial and error of personalizing your caffeine intake.

For more information on how you to take control of your ability to maximize your caffeine intake that personally aligns with you for sports nutrition practices and/or alertness at work, reach out to me via the Contact page.


Further Information