Is caffeine good for running? - She Runs Eats Performs

Episode 69

Published on:

16th Sep 2021

Is caffeine good for running?

Is caffeine good for running?

Caffeine may support a runner as an ergogenic aid. An ergogenic aid being a performance enhancer, something which may support you in achieving a physical or mental edge whilst training or competing. Ergogenic aids can be foods, supplements, training techniques or equipment. Caffeine is well researched in sports science as far back as the 1920’s and is known to;

·      Enhance various aspects of exercise performance in runners such as muscular endurance and sprinting

·      Appears to improve physical performance in trained and untrained individuals

·      Has an ergogenic effect on cognitive function i.e. attention, vigilance and may induce a decreased perception of effort/fatigue (rate of perceived exertion RPE), so your training may feel easier and you may be able to maintain pace longer

 We are going to look at:

1.    How does caffeine support running performance as an ergogenic aid

2.    Are there any downsides to consuming caffeine (as a runner and for general health)

3.    Sources of caffeine you may consider as a runner

Show Notes


How much caffeine should someone consume to experience the ergogenic benefits?

Quoting from a review published in January 2021 - International Society of Sports Nutrition ISSN position stand: caffeine and exercise performance

Research indicates Caffeine has consistently been shown to improve exercise performance when consumed in doses of 3–6 mg/ kg body mass.

We’ve never really considered how much caffeine is in a cup of coffee, but to give you an idea an espresso (75mg/shot), black tea (30-80mg/8oz), green tea (35-60mg/8oz), and some energy gels and sports/soft drinks include caffeine – varying from 25g – 100g per sachet

So for example if you are 70kg you’d be looking at consuming between 210g and 420g to potentially get these benefits – so the equivalent of 3- 6 espressos – that seems an awful lot of caffeine to us!!

Minimal effective doses of caffeine currently remain unclear, but they may be as low as 2 mg/kg body mass. That means the smallest dose that will produce the desired outcome.


How much caffeine would be too much and how should you time caffeine consumption for optimal results?

Very high doses of caffeine (e.g. 9 mg/kg) are associated with a high incidence of side-effects and do not seem to be required to elicit an ergogenic effect. So their message is you don’t need to over consume for results.

Caffeine is rapidly absorbed from the gastrointestinal tract and it appears in the blood within minutes, with peak caffeine plasma concentrations ranging from 30 to 120 mins. Typically, the most common timing of caffeine supplementation is 60 min PRE-EXERCISE. The effects of caffeine last for three to five hours, so you don't have to try to drink it or consume a supplement immediately before your run.

Caffeine’s effects will last for several hours, depending on how quickly or slowly it is metabolised by the body. Caffeine has a half-life of approximately four - five hours. That means amount of time it takes for caffeine to be reduced to half the original amount. So if you've consumed 10 milligrams (mg) of caffeine, after 5 hours, you'll still have 5 mg of caffeine in your body.

This timescale may be reduced or extended in certain groups of individuals such as pregnant women, those who smoke and people with impaired liver function.


 Are there any benefits to consuming caffeine during exercise or training?

Some runners prefer to delay their caffeine intake until they're running so they can get a mid-race boost, in which case they’ll probably consume a gel or chew containing caffeine. This was backed up by a recent review in 2018 by Shen, concluded that timing caffeine intake closer to a time of greater fatigue, i.e., later in the race, may be most beneficial

Also, it seems that optimal timing of caffeine ingestion depends on the source of caffeine. For example, caffeine chewing gums may require a shorter waiting time from consumption to the start of the exercise session than a caffeine capsule.


How does the body processes it caffeine to give us these performance enhancements?

The action of caffeine on the central nervous system (CNS) is widely accepted as the primary way caffeine alters performance.

Caffeine is believed to exert its effects on the CNS via the antagonism of adenosine receptors, leading to increases in neurotransmitter release, motor unit firing rates, and pain suppression.

There are 2 sub types of adenosine receptors (subtypes, A1 and A2A,) which are highly concentrated in the brain, and are thought to be the main targets of caffeine.

Caffeine has a similar molecular structure to adenosine. Caffeine binds to adenosine receptors after ingestion and therefore increases the concentration of neurotransmitters including serotonin, dopamine, acetylcholine, norepinephrine and glutamate.

This results in positive effects on mood, vigilance, focus, and alertness in most, but not all, individuals.


Caffeine is thought to enhance muscular endurance – what is the theory around this?

Caffeine appears to have an ergogenic affect on muscle It’s believed that caffeine may influence muscle contraction through calcium ion (Ca2+) mobilisation. Fatigue caused by the gradual reduction of calcium ion release may have a reduced effect after consumption of caffeine.

There are many studies across many different types of sport which supports caffeine as an effective ergogenic aid for enhancing velocity and power in resistance exercise.

The ISSN paper we have been discussing today summarises by saying;

“caffeine has been consistently shown to be effective as an ergogenic aid when taken in moderate doses (3–6 mg/kg), during endurance-type exercise and sport. Dozens of endurance studies are highlighted through this review is various sections, showing consistent yet wide-ranging magnitudes of benefit for endurance performance under caffeine conditions”


Are there any downsides to consuming caffeine (as a runner and for general health)?

 How we consume, metabolise and respond to caffeine is personalised and related to our genetics.

The liver metabolises and detoxifies caffeine by the CYP1A2 enzyme.

CYP1A2 is the key liver enzyme (special proteins that breakdown and use other substances) responsible for metabolising caffeine.

Variations in the CYP1A2 gene have a big impact on how caffeine affects our bodies.

Based on your CYP1A2 genetics you may be a fast or slow caffeine metaboliser.

If you are a Slow Metaboliser - you process caffeine at a slower rate, caffeine has the potential to build up in the bloodstream and caffeine may have longer-lasting stimulant effects and may do more harm than good.

Negative side effects of caffeine consumption may result in insomnia, anxiety and upset stomach.

There is also evidence linking slow metabolisers with an increased risk of having a nonfatal heart attack and/or high blood pressure with higher amounts of coffee intake. 

Slow metabolisers may need to limit or avoid caffeine based on their body’s individual response to minimise risk of serious health issues.

If you are a Fast Metaboliser, you process caffeine at a more rapid rate and, hence, caffeine might not have as great or as lasting of an effect.

For fast metabolisers (independent of other risk factors), coffee may be safely consumed to help provide beneficial antioxidants and bioactive properties and will not increase the risk of heart attack and hypertension.

Ss well as your genetics, your body’s ability to metabolise caffeine also depends on your lifestyle. For example, your diet, stress levels, sleep, or activity level, can impact how you respond to caffeine. How much coffee you drink, the time of day, whether you smoke, or whether you take hormonal birth control may also play a role. In other words, it may be your lifestyle and nutrition choices which are affecting how you metabolise caffeine not just your genetics.

Researchers now factor in this information into their studies. For example, a 2012 study looked into “the influence of a CYP1A2 polymorphism on the ergogenic effects of caffeine” and observed a caffeine-gene interaction, indicating improved time trial cycling performance following caffeine consumption only in those with the AA genotype – that’s the fast metaboliser type.

If you are interested in finding out more, please email us as and we’ll point you towards test panels we recommend.


Caffeine consumption has the potential to interfere with sleep – what is the reason for that?

Adenosine acts as a signal between brain cells to bring on sleepiness. Caffeine blocks adenosine's signals, making you feel more alert. This is also why caffeine can make it hard to fall asleep and interfere with deep sleep.

From a sporting point of view this may help athletes under conditions of jetlag, and irregular or early training or competition schedules. Genetic variations in ADORA2A may contribute responses of caffeine consumption on sleep. If you had this variant it would be another reason to limit your caffeine intake


Female Factors related to caffeine consumption

·      Excessive caffeine intake can also be detrimental to bone health as it can prevent the absorption of vitamins and minerals in our system.

·      Oestrogen based oral contraception can decrease how quickly the body breaks down caffeine. Women may experience jitteriness, headaches, fast heartbeat.

·      When pregnant, the current UK and international guidance that women should avoid high caffeine intake (>200mg a day). High consumption may be linked to low birth weight, miscarriage and still birth – suggest anyone concerned speak to medical practitioner and read this document

·      In general medications may increase or decrease the metabolism of caffeine – it’s always advisable to read medication leaflets to check their advice.


What do WADA say about caffeine consumption?

 Caffeine was added to the list of banned substances by the IOC in 1984 and the World Anti-Doping Agency (WADA) in 2000.

A doping offence was defined as having urinary caffeine concentrations exceeding a cut-off value. The cut-off value was chosen to exclude typical amounts ingested as part of common social coffee drinking patterns and it ranged between 12-15 μg/ml urine.

However in IOC and WADA removed the classification of caffeine as a “controlled” substance in 2004, leading to a renewed interest in the use of caffeine by athletes.

Caffeine is still monitored by WADA, and athletes are encouraged to maintain a urine caffeine concentration (below the limit of 12 μg/ml urine) which corresponds to 10 mg/kg body mass orally ingested over several hours, and which is more than triple the intake reported to enhance performance.


Are there any negative effects of caffeine consumption?

 Caffeine is a stimulant and can be a stimulate a stress response and also a spike in blood sugar which both may be detrimental to health and body composition. Many runners also notice gut issues such as urgency to go, diarrhoea, nausea and vomiting related to caffeine too.

Reviews of the literature show that caffeine is, on average, ergogenic for a wide range of sport-specific tasks, its use might not be appropriate for every athlete.

Caffeine consumption needs to be balanced with the side-effects experienced and individuals should experiment to how much caffeine to consume and assess if there are benefits to their performance and overall health.


Sources of caffeine you may consider as a runner

The obvious one if COFFEE and as long as you don’t experience any negative side effects it would be fine to drink a cup of coffee in advance of your run. We’d suggest that you do this in the morning only or you may experience problems with relaxation and sleep later in the day. Even if you are a fast metaboliser you’ll still experience the half-life effect. It’s usually advisable not to have a coffee after 12 noon.

Supplement forms of caffeine include gels/chews/bars/shots and energy drinks which have caffeine in them. Our advice is to do your research and read the labels carefully. The amount of caffeine varies considerably – 100mg up to 300mg – so be careful. Often the products are for a variety of sports so check you’re choosing one designed for a runner.


We review some brands and highlight INFORMED SPORT ACCREDITED products. Informed Sport is a global testing and certification programme for sports and nutritional supplements. Supplement products are tested by LGC’s world-class anti-doping laboratory for contamination against a broad range of banned substances in sport, using ISO 17025 accredited methods. When you see the Informed Sport quality mark on a product, you can be assured that it has passed the most stringent sports supplement testing.


Combining carbohydrate with caffeine.

Gels combining carbohydrate and caffeine may be a convenient way of supplementing with caffeine during a training session if you are a runner who uses gels.

The ISSN review, comments that to date it appears caffeine alone, or in conjunction with carbohydrate is a superior choice for improving performance, when compared to carbohydrate supplementation alone.

Most studies focus on consumption pre or during exercise, but there’s been some interest in investigating benefits on glucose metabolism using CHO and caffeine for example;

Pedersen et al. [413] report faster glycogen repletion rates in athletes who co-ingested caffeine (8 mg/kg body mass) and carbohydrate (4 g/kg body mass), compared to carbohydrate alone (4g/kg body mass).

Another study indicated that caffeine may potentiate glycogen resynthesis when high dosages of caffeine (~ 8 mg/kg body mass) are consumed during the recovery phase of exercise; though, when adequate carbohydrate is provided post- exercise, caffeine may not provide any glycogen- resynthesising benefit.

The review also highlights athletes are advised to consider the potential negative impact of caffeine consumption close to rest/sleep periods so using this concept for recovery should only be considered earlier in the day.


The placebo effect is a consideration, that’s where study participants are given a non- caffeine substance and they report beneficial effects. A number of studies have provided evidence for placebo effects associated with caffeine ingestion or other “beneficial” interventions during exercise. 


Are there are benefits to running performance by habitually consuming caffeine?

There does not appear to be a consistent difference in the performance effects of acute caffeine ingestion between habitual and non-habitual caffeine users but this is open to interpretation. One area that has been researched is if there are any benefits to abstinence of caffeine for a period before supplementing prior to exercising. For example, abstaining from caffeine for 1-4 days before supplementing prior to exercise.

Results are varied, one study concluded that improved performance under caffeine conditions at 6 mg/kg is not related to prior caffeine habituation in recreational athletes.

Our personal view is that we should minimise caffeine for general good health however there may be performance benefits from using caffeine strategically in training and competition.


Key Takeaways 

1.    Caffeine has an ergogenic effect on cognitive function i.e. attention, vigilance and may induce a decreased perception of effort/fatigue (rate of perceived exertion RPE), so your training may feel easier and you may be able to maintain pace longer

2.    Research indicates caffeine has consistently been shown to improve exercise performance when consumed in doses of 3–6 mg/ kg body mass.

3.    Very high doses of caffeine (e.g. 9 mg/kg) are associated with a high incidence of side-effects and do not seem to be required to elicit an ergogenic effect. You don’t need to overconsume for results.

4.    If you are considering supplementing with caffeine, start with a low amount to begin with and only increase when you can tolerate without negative side effects.

5.    Caffeine’s effects will last for several hours, depending on how quickly or slowly it is metabolised by the body. Caffeine has a half-life of approximately four - five hours. Our advice is to consume caffeine before lunchtime so there is a minimum effect on sleep quality later in the day.

6.    You may be a fast or slow metaboliser of caffeine – you may wish to consider a genetic test to establish your status.

7.    Your lifestyle and nutrition choices may affect how you metabolise caffeine not just your genetics.

8.    Health Factors to consider

a.   Caffeine consumption may be detrimental to bone mineral density

b.   Pregnant women are advised to minimise caffeine consumption

c.    Oral Contraception and other medications may affect metabolism of caffeine

9.    Caffeine is still monitored by WADA, and athletes are encouraged to maintain a urine caffeine concentration (below the limit of 12 μg/ml urine) which corresponds to 10 mg/kg body mass orally ingested over several hours.

10. There are a range of caffeine sources which may be appropriate for pre and during running i.e. gels/chews/bars/shots and energy drinks, our advice is to read labels carefully and choose products and caffeine doses appropriate for you.

11. You don’t need to be a habitual caffeine consumer to gain performance benefits from supplementing strategically, however if you are not caffeine sensitive you many enjoy a daily coffee without it negatively affecting your...

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About the Podcast

She Runs Eats Performs
for mid-life female runners of all abilities
Are you confused about the science around nutrition for runners? Listen in to learn about the WHY, HOW, WHAT, and WHEN of eating to fuel your running performance.

We are here to help you translate sports nutritional science, into easy to apply tips and plans, helping you enjoy peak running performance. We focus on the FEMALE FACTORS every mid-life woman needs to know to be a healthy runner.

About your host

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Aileen Smith

Nutritionists, Educators, Podcasters, Runners and Friends

We have a love of running and a passion for nutrition, delicious food and healthy living. She Runs Eats Performs for female runners of all abilities who are looking for simple ways to improve their running performance and their health with nutrition and lifestyle.
We enjoy sharing our nutritional expertise, reviewing the latest sports science and most of all helping you to take easy action so you can enjoy your running life to the full.
We are here to help you achieve great health and good shape whilst staying injury-free with easy-to-understand sports nutritional concepts and easy-to-implement tips and plans.

Aileen and Karen are BANT and CNHC Registered Nutritional Therapists.