Effect of caffeine on sleep and recovery

Caffeine is a well-recognised performance-enhancing substance, but the effect of caffeine on athlete sleep and recovery is less known.

Coffee and caffeine

Caffeine is the most prominent component of coffee and the reason why most people who drink coffee do so.

Caffeine is not only present in coffee but coffee is likely the most popular caffeine-containing item among other foods (e.g. tea, chocolate) and supplements (e.g. pre-workout, gums, tablets).

As a reminder, the actual amount of caffeine in a cup of coffee varies depending on many factors (learn more in Coffee and health. However, most standard coffee drinks will contain somewhere between 65 and 120mg of caffeine.

Caffeine metabolism

As seen previously, the relationship between caffeine and performance has been recognised for a while. Caffeine is a well-known and supported ergogenic aid for many athletic modalities, including combat sports.

There is a genetic component to caffeine metabolism and therefore people differ in the rate at which they break down caffeine (1, 2). The half-life of caffeine (the time it takes for half of the ingested caffeine to leave your body) is generally regarded as 4-6 hours but in reality it can be anywhere between 1.5 to 10 hours (1).

As it’s the case with other nutrients and food components, caffeine metabolism is also dependent on the gut microbiome (3).

The factors that alter caffeine metabolism include:

• Pregnancy: ↓
• Hormonal contraceptives: ↓
• Heavy caffeine use: ↑
• Smoking: ↑
• Genetic variation: ↑ or ↓ (1)

On the topic of genes, there are a number of genes that have been identified as influencers of caffeine metabolism. Variations in these genes can, for example, determine how well you can perform in a sleep-deprived state, how much time it takes you to fall asleep, how long you spend in the non-rapid eye movement (non-REM) sleep stage, how anxious you get after consuming caffeine, etc. (1)

Of course, most athletes don’t kneed a genetic test to know if caffeine intake affects their sleep or anxiety levels. Conversely, a genetic test or data from a wearable can help convince an athlete to tidy up their caffeine intake to avoid detrimental side effects. Habitual caffeine intake can induce tolerance, so heavy drinkers of caffeine might not experience side effects (positive or negative) to the same degree as non-regular drinkers (4). On the flip side, athletes who have developed tolerance to caffeine may not benefit from improved performance from caffeine intake.

Athletes and sleep

Sleep is essential for physiological and psychological/cognitive recovery from training.

The physiological functions that can be negatively impacted by chronic sleep deprivation include:

• Glucose metabolism (important for fuelling and glycogen restoration) (1, 3)
• Neuroendocrine function (important for digestion, air and blood flood to the lungs, blood pressure, heart rate, blood glucose regulation, bone and muscle growth) (1, 3, 5)
• Appetite and food intake (important for adequate energy and macronutrient supply) (1, 3)
• Protein synthesis (important for muscle growth and tissue repair) (1, 3)

The cognitive functions that can be negatively impacted by chronic sleep deprivation include:

• Attention
• Learning
• Memory (1)

Caffeine and sleep

Caffeine may negatively impacts several aspects of sleep quality such as:

• Sleep latency (time to fall asleep)
• Wake time after sleep onset (how long it takes you to wake up after falling asleep)
• Sleep efficiency
• Sleep duration (1, 2, 4)

Sleep has a huge effect on physical and mental recovery, consequently impacting the following day’s training or competition.

There is evidence that the optimal time to stop consuming caffeine is:

• 13.2 h prior to bedtime for a standard serve of pre-workout supplement
• 8.8 h prior to bedtime for a cup of coffee
• no cut-off time for a cup of black tea (4)

This is not necessarily bad news, though. This means caffeine can be used as a tool by athletes who need to acutely increase alertness and/or physical performance while sleep deprived (1, 2, 3), for example due to jetlag, intense training, study/work commitments, parenting, etc.

Coffee and recovery

There is conflicting evidence that caffeine can affect glycogen muscle recovery (2, 3). Two components in coffee, cafestol and caffeic acid may improve muscle glycogen recovery (2). Coffee has also been reported to have antioxidant properties (3), so the net effect of coffee ingestion on recovery may be beneficial.

In theory, athletes could benefit from both enhanced performance and enhanced post-exercise muscle glycogen recovery from drinking coffee prior to training or competition.

Interestingly, some studies have demonstrated that the performance enhancing effects of caffeine are lowered or non existing when consumed later in the day (2).

As seen in the article Will coffee dehydrate you?, the net effect of coffee intake is positive fluid balance.

Effect on caffeine on sleep and recovery

Below are a few recommendations for athletes who consume coffee or other sources of caffeine:

• Coffee has a variable amount of caffeine. This makes it difficult to determine how much coffee to have for performance purposes or how much coffee is likely to negatively affect sleep.
• Coffee is more than caffeine. Coffee also counts toward fluid intake and, when taken with milk, also calcium, protein and carbohydrate. Other coffee components can have beneficial effects in health and recovery from exercise.
• Know your body. Everyone has a different rate of caffeine metabolism and response to coffee and other sources of caffeine.
• Prioritise sleep. Figure out your cut-off for caffeine intake (start with the suggested cut-offs of 13.2 h prior to bedtime for a standard serve of pre-workout supplement and 8.8 h prior to bedtime for a cup of coffee) and adjust based on your response. If you consume caffeine on a regular basis, you might not experience the same detrimental effects.
• Decaffeinated coffee is a good alternative if you are sensitive to caffeine but enjoy the taste of coffee. There is also evidence that decaf coffee has similar health benefits to caffeinated coffee.
• You don’t need genetic testing or wearables to determine the effect caffeine has on your sleep. Pay attention to your alertness and performance the following day, recovery measures (e.g. muscle soreness), etc.
• Use coffee or other sources of caffeine as a tool to improve alertness and performance when it matters most, such as when jetlagged or sleep deprived

References

1. Guest NS, VanDusseldorp TA, Nelson MT, Grgic J, Schoenfeld BJ, Jenkins NDM, et al. International society of sports nutrition position stand: caffeine and exercise performance. Vol. 18, Journal of the International Society of Sports Nutrition. BioMed Central Ltd; 2021.
2. Pickering C, Grgic J. Caffeine and Exercise: What Next? Sport Med [Internet]. 2019;49(7):1007–30. Available from: https://doi.org/10.1007/s40279-019-01101-0
3. Lowery LM, Anderson DE, Scanlon KF, Stack A, Escalante G, Campbell SC, et al. International society of sports nutrition position stand: coffee and sports performance. J Int Soc Sports Nutr [Internet]. 2023 Dec 31;20(1):2237952. Available from: https://doi.org/10.1080/15502783.2023.2237952
4. Gardiner C, Weakley J, Burke LM, Roach GD, Sargent C, Maniar N, et al. The effect of caffeine on subsequent sleep: A systematic review and meta-analysis. Sleep Med Rev. 2023 Jun;69:101764.
5. Canadian Cancer Society. The neuroendocrine system [Internet]. Available from: https://cancer.ca/en/cancer-information/cancer-types/neuroendocrine-tumours/what-are-neuroendocrine-tumours/the-neuroendocrine-system

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