Amount of Evidence: Very High Potential Benefits: High Safety: Reasonable
TABLE OF CONTENTS
What is caffeine?
Caffeine is the most popular stimulant in the world. As a supplement, it is usually extracted from coffee beans and used primarily to increase energy, productivity, and athletic performance. In this article, we will look at the main benefits and drawbacks of caffeine, as well as how to use it the right way.
Potential benefits
It is important to note that all of the potential benefits mentioned below are dose-dependent. In general, the higher the dose you take, the more pronounced the effects will be. However, they do reach a plateau at a certain point. We will discuss the best dosing protocol later in this article.
Also, there are many additional benefits associated with tea, coffee, and other sources of caffeine. The benefits mentioned below in this article are specifically related to caffeine itself.
Major benefits
Reduced fatigue and sleepiness – Caffeine has a similar molecular structure to adenosine and because of that, it can enter and fill adenosine receptors. When adenosine molecules enter the receptors, they send a signal to the body that it is time to fall asleep, making you relaxed and sleepy. When caffeine fills the receptors instead of adenosine, adenosine molecules cannot enter the receptor for as long as the caffeine remains in the system, which delays the sleep-inducing effect of adenosine.
Increased power output – This benefit is significant and applies to all forms of high-intensity exercise, including sprints and strength training.
Increased aerobic capacity – Caffeine significantly increases the ability to do aerobic exercise (cardio). This effect has been studied primarily in runners but applies to all forms of endurance training. This benefit is likely due to the stimulant effect of caffeine.
Up-regulation of dopamine – Caffeine significantly increases the upregulation of some dopamine receptors. Because of this, it makes you able to experience more dopamine-related effects without significantly increasing dopamine levels in your system. Caffeine also increases dopamine levels to some extent but the increase is small.
Lowered risk of heart disease – A meta-analysis found that coffee drinkers have a significantly lower risk of heart disease than those who don’t drink coffee (the difference is typically 4-11%). It is important to note that this benefit likely doesn’t apply to caffeine itself but it almost certainly does for other beverages that contain this stimulant, such as tea and yerba maté.
Minor benefits
Increased testosterone levels – This effect was noted in trained individuals who took 250 mg prior to a training session. A 12% increase in testosterone was noted in these individuals. Although 12% sounds like a lot, this is a relatively small increase compared to many other supplements that have been shown to increase testosterone. This benefit is also dependent on physical activity and does not apply to individuals who do not exercise.
Increased adrenaline and noradrenaline – Depending on how you look at it, this can either be viewed as a benefit or as a negative. The increase in those two neurotransmitters can be very useful if you want to increase alertness and exercise performance.
Increased blood pressure – This can also be viewed as both a benefit and a side effect, depending on your health conditions. If you are a healthy person, there is no need to worry about an increase in blood pressure unless you are taking extremely high doses (1000+ mg). Caffeine supplements increase blood pressure more than if you ingest the same amount from tea or coffee.
Chelation of heavy metals – While the effect is not profound, caffeine (as well as a few other compounds in tea and coffee) can bind heavy metals and help detoxify them.
Fat loss – It is important to note that caffeine itself is not as effective for burning fat as green tea or coffee, because of the other compounds in these beverages. Nevertheless, caffeine supplements have still been associated with improved fat oxidation and this compound can certainly lead to an improvement in body fat percentage.
Increased endurance – Rating of perceived exertion (RPE) decreases in most people when they take caffeine before an exercise session. Caffeine has also been shown to increase training volume (the total work done during an exercise session) in both endurance and strength training.
Improved reaction time – While this benefit is small and the evidence is rather limited, caffeine has been shown to improve reaction time in certain situations.
Increased blood flow – Caffeine causes a slight increase in blood flow.
Increased subjective well-being – Numerous studies have shown that caffeine significantly improves mood and well-being in the short term. The long-term effects on well-being have not yet been established and depend greatly on the individual. It appears that caffeine can both increase and decrease long-term well-being, depending on how one responds to it, what time of day one takes it, etc.
Increased thermogenesis – Caffeine increases the body’s ability to generate heat from brown fat.
Unproven benefits
The effect of caffeine on these parameters has either not been sufficiently researched or the science shows little to no efficacy in these areas.
Memory – The evidence is highly mixed. From the studies we have so far, there seems to be an increase in spatial memory but a decrease in working memory. The negative effect on working memory may be due to overstimulation.
Metabolic rate – Caffeine may and may not affect your metabolic rate. As of now, the evidence is mixed. However, there is a good amount of evidence that caffeine can aid fat loss in people who exercise. Because of this, it seems to be the case that caffeine can increase metabolic rate indirectly by increasing power output during exercise.
Appetite – The effect is not significant.
Cholesterol – There is no significant change in LDL or HDL cholesterol levels.
Triglycerides – No influence on fasting or postprandial triglycerides was ever noted.
VO2 max – Caffeine does not improve VO2 max in the short term, but it may increase your VO2 max in the long term by increasing power output and making you more effective at aerobic and anaerobic exercise.
Possible side effects
These side effects are dose-dependent and the risk for them increases (most often linearly but sometimes exponentially) as the dose is increased. Some of the side effects are relevant only at very high doses.
Anxiety – This effect varies greatly from person to person. Your genes and your psychological state play a huge role in whether or not caffeine is likely to make you anxious.
Shaking – This is one of the effects that seem to increase exponentially as you increase the dose. The shaking could in one way be viewed as a positive effect as it might be a form of somatic releasing. However, we do not know yet whether or not the shaking induced by caffeine can lead to improved psychological well-being in the long run. It may simply be an unpleasant sign of overstimulation.
Worsened sleep quality – Caffeine can make it harder to fall asleep and shorten the time you spend in deep sleep. This effect can occur even if you take caffeine earlier in the day, as the half-life is about 5 hours and can be as long as 9.5 hours in people who metabolize caffeine slowly.
Disruption of circadian rhythms – This can happen for two reasons: either because of the effect the stimulant has on your sleep or because of disrupting the natural morning cortisol rise when you take the substance in the first 90 minutes after you wake up. We will look into this effect more deeply later in the article.
Dependence – When you consume caffeine on a regular basis, more adenosine receptors are formed, making you dependent on caffeine. You will then need more and more caffeine to get the same effect.
Yellow teeth – This effect does not seem to be directly caused by caffeine itself, but any beverage that contains this compound (such as tea, coffee, and energy drinks) can turn your teeth yellow if consumed regularly.
Caffeine withdrawal – When you stop consuming caffeine, the adenosine receptors will start getting broken down, which leads to the symptoms of withdrawal, such as headaches, fatigue, and getting angry and annoyed easily.
Adrenal fatigue – Caffeine can cause adrenal fatigue and adrenal burnout if you regularly consume it to the point where you do not allow the body to rest enough and repair the adrenals. Adrenal fatigue can lead to a variety of health problems. This is perhaps the main reason to cycle caffeine and stop using it for a week or so every once in a while.
Decreased absorption of certain minerals – Specifically, caffeine worsens the absorption of iron and zinc, which may and may not be a concern to you. Since a somewhat high percentage of people are deficient in those two minerals, you may want to avoid caffeine close to your meals to minimize this effect, especially if you are experiencing signs of deficiency in these two minerals. On the other hand, this effect can also be viewed as a benefit since many people have too much iron in their bloodstream, which can lead to iron toxicity and faster aging.
Increased blood pressure – While the rise in blood pressure is not as high as is sometimes thought, people with already high blood pressure should be aware of this side effect and probably limit their caffeine intake.
Increased cortisol – This effect has primarily been noted when caffeine was taken at high doses (200+ mg). However, smaller doses can also cause an increase in cortisol.
Increased heart rate – An increase has been noted especially in people who are sensitive to caffeine and have not yet developed tolerance. However, the effect is not significant in most people.
Worsened insulin sensitivity – Fortunately, this effect only occurs acutely when caffeine is combined with a meal rich in carbohydrates. Insulin sensitivity then quickly returns to normal and is not affected in the long term.
Diarrhea – This effect is relatively common and can happen even at low doses.
Toxicity – Caffeine can be toxic at doses of 20-40 mg/kg. Even lower doses could potentially lead to toxicity if you are sensitive to the substance. While fatalities caused by caffeine are rare, it is strongly discouraged to ever take such high doses.
Who should not take caffeine?
You should probably avoid taking caffeine if you:
have a zinc or iron deficiency (caffeine can reduce the bioavailability of these minerals)
suffer from high blood pressure
do not experience low energy throughout the day
have difficulty falling asleep and staying asleep
are pregnant
suffer from certain heart problems
are a slow caffeine metabolizer
feel anxious or jittery after consuming caffeine
Who will benefit the most?
You should definitely consider taking caffeine if you:
are a serious athlete trying to maximize exercise performance
need to increase cognition and alertness on certain occasions
Sources of caffeine
Caffeine supplements – Even though many of the benefits above also apply to caffeine supplements, it is not the preferred way to take the compound because you would miss out on all of the other benefits of guarana, tea, coffee, or other sources. Caffeine supplements are rarely worth it unless you are a serious athlete or hate the taste of caffeinated beverages. Even in those cases, guarana supplements or tea and coffee extracts would be much better.
Guarana– Guarana (Paullinia cupana) is a plant traditionally used in and around the Amazon rainforest. The seeds of Paullinia contain more caffeine than coffee or any other plant in the world (3.6-5.8% of their dry weight is caffeine).
Coffee – The caffeine content of coffee varies greatly from coffee to coffee. Generally, a regular cup contains between 40 and 180 mg, with the average being around 135 mg. So if you drink relatively normal coffee, you can probably count one cup as 135 mg. Decaffeinated coffee contains about 2 mg per cup.
Green tea – An average cup contains around 20 mg of caffeine and 50-100 mg of EGCG.
Decaf green tea – Decaffeinated green tea contains on average 1-2 mg of caffeine and 60 mg of EGCG per cup.
Matcha green tea – Matcha is significantly higher in both caffeine and catechins than other forms of green tea. Or, more precisely, you get to consume more of these since you ingest the powder.
Pu-Erh – Pu-Erh is comparable to black tea as far as its caffeine and catechin content.
Black tea – Black tea contains about 2 times as much caffeine as green tea, so on average 40 mg.
Oolong tea – Oolong tea’s caffeine and catechin content is somewhere between green and black tea. An average cup contains 30 mg of caffeine and 40 mg of EGCG.
White tea – White tea has around the same level of catechins as green tea and contains an average of only 10 mg of caffeine per cup. This is potentially a very good thing because it allows you to drink a lot of white tea and reap more benefits connected to EGCG and other catechins in it.
Yellow tea – This type is extremely similar to white tea.
Cacao – Cocoa powder has around 0.21% caffeine by weight. Therefore, one gram contains an average of 2.1 mg.
Yerba maté – Yerba maté has a much higher caffeine content than regular tea. Typically, an average cup of yerba maté contains about 80 mg of caffeine.
Soda and energy drinks – This is undoubtedly the worst way to consume caffeine, mainly because of the sugar and/or artificial sweetener content in these drinks. There are brands on the market that sell relatively harmless energy drinks sweetened with stevia, xylitol, or erythritol. While these are definitely a better choice than regular energy drinks, they are still not better than coffee, tea, or other natural sources. As for caffeine content, energy drinks almost always contain around 30 mg per 100 ml, and Coke contains around 10 mg per 100 ml.
How much caffeine you should ingest depends on many factors, such as your weight, how sensitive you are to caffeine, and how fast you metabolize the compound.
You should also take into consideration your personal goals and what you want to get from the stimulant. For example, if you wish to maximize exercise performance, that will require a different approach to dosing than if you simply want to increase alertness and reduce fatigue.
Most scientific studies on caffeine use doses of 4-6 mg/kg. However, this dose seems to be a little too high unless you are a serious athlete and want to maximize power output during exercise.
If you are an average individual with an average tolerance, a dose of 100-200 mg a day appears to be ideal for most people. This dose will still allow you to be more energetic and productive but it will not impact your sleep negatively if you take it (or drink it) early in the day.
If you have been taking higher doses of caffeine on a regular basis, you may be able to consume more than 200 mg without the negative impact on your sleep.
The best way to determine whether or not you can handle higher doses is by listening to your body. Specifically, how easy or hard it is for you to fall asleep is a good indicator of whether or not you should cut back on caffeine.
If you experience more anxiety after taking the stimulant, that is a sign you may want to cut back on it and lower your dose. So caffeine dosing depends heavily on an individual and varies greatly from person to person. To know the optimal dose you should take, you will need to experiment a bit.
It is important to note that you do develop tolerance to caffeine over time and the higher the dose you are taking, the sooner the tolerance will develop and the more intense it will be. Fortunately, you can get rid of the tolerance by going through a caffeine cycle at least once in a while.
Probably the best caffeine cycling protocol to reset your tolerance for the compound is going cold turkey for a week every 3 months. While the week without the stimulant will probably be unpleasant (most people experience headaches, low energy, and get agitated very easily), the pain is worth going through if you wish to maximize the benefits of caffeine.
If you have been consuming caffeine every day or nearly every day for many years, you will probably need more time than a week to get back to baseline and become fully sensitive to the stimulant. In the most extreme cases, this takes up to 3 months. However, 1-2 weeks should lead to most of the restorative effects.
Also, if you wish to get through the withdrawal phase faster, one very effective way to do it is sleep banking, where you try to sleep as much as possible (even if it’s 12-16 hours a day) to allow your body to get back to baseline faster.
Doses of 20-40 mg/kg can be toxic and are not recommended to anybody. Even 10 mg/kg is too much and this amount would almost certainly cause more harm than good for the vast majority of people.
Best time to take caffeine
The best time to ingest caffeine is around 90 minutes after you wake up.
This is because in the early morning, there is a natural increase in cortisol responsible for waking you up and getting you ready for the day. By drinking coffee, tea, or ingesting caffeine from other sources right after you wake up, you would interrupt this natural increase in cortisol and your body would not be producing as much of it in the following days. This would lead to increased production of cortisol at the wrong times of the day, such as in the evening. After the morning cortisol increase that typically lasts for 90 minutes, you want to take caffeine as soon as possible so that most of it leaves your system before it’s time to go to bed.
The half-life of caffeine is on average around 5 hours but this depends heavily on your genes. Some people metabolize the stimulant very fast but some are so-called slow caffeine metabolizers. The half-life can therefore last anywhere from 1.5 to 9.5 hours. If you have your genetic results available, CYP1A2 is the main gene that regulates caffeine metabolism and how fast your body gets rid of the compound.
As a general rule of thumb, drinking coffee or strong tea after 2 pm is not a good idea unless you know you are a fast metabolizer. But obviously, this advice is very simplified and doesn’t take into consideration all the variables.
Again, the best way to determine whether or not caffeine is damaging your sleep is to listen to your body and specifically look at how easily you fall asleep and how refreshed you wake up.
While taking caffeine early in the day but not in the first 90 minutes after waking up is the most important timing rule to keep in mind, there are a few more things to consider.
One of them is exercise. If you wish to use the stimulant to increase exercise performance, take it at least 45 minutes before your exercise session. If you exercise in the evening, forget about this recommendation.
The other thing to consider is spreading the dose of caffeine and not consuming all of it at the same time. This will make the energy-increasing effects more stable throughout the day and it will also lower some of the potential side effects.
The last thing to consider is caffeine’s effect on iron absorption. It is shown that the compound can decrease the bioavailability of iron which could be both an issue and a benefit, depending on how much iron you have in your bloodstream. If you experience symptoms of anemia, do not ingest caffeine close to your meals.
Interactions with other supplements
L-Theanine This compound naturally occurs in tea and can reduce the negative effects of caffeine, including anxiety, jitteriness, and even the potential negative impact on sleep to some extent. If you take caffeine or drink coffee, it is highly recommended to combine these with 100-200 mg of l-theanine. Besides theanine’s ability to lower the side effects of the stimulant, the combination is also very effective at improving focus and attention.
Taurine The combination is often used in energy drinks. When used together, the effects of each of the supplements get slightly enhanced.
EGCG EGCG has been shown to reduce the blood pressure increase from caffeine. It also reduces its effects on adrenaline and noradrenaline. Overall, EGCG leads to a smoother peak of the stimulation effect.
Danshen This Chinese herb increases the half-life of caffeine by 12-16%.
Creatine There is a concern that high doses of caffeine (300+ mg) co-ingested with creatine lead to the inhibition of some beneficial effects of creatine (such as the atherosclerotic effect). However, the scientific evidence for this is still limited and the impact of caffeine likely isn’t significant.
MDMA Caffeine increases the potential neurotoxicity of MDMA (although, unless you take high doses of MDMA on a regular basis, the substance doesn’t appear to be very neurotoxic).
Methamphetamine Just like with MDMA, caffeine can increase the neurotoxicity of methamphetamine and other popular amphetamines.
Alcohol As a stimulant, caffeine can negate the depressant effect of alcohol, making the drinker feel as if he is not impaired. This makes the drinker likely to drink more.
Propranolol Propranolol has been shown to reduce caffeine’s thermogenic effects, making it less effective for fat loss. On the other hand, propranolol can reduce sperm motility which is countered by caffeine.
Where to buy caffeine
Amazon seems to be the best option for ordering caffeine supplements in most countries. They offer some very affordable products that are backed by many positive reviews. Also, you can choose from a wide range of brands there without having to spend time searching through other markets on the internet.
One thing you should pay attention to is that some brands display the dosage per serving and not per pill or capsule. Therefore, you may accidentally buy something that is less potent than you intended. Do not fall for this marketing trick.
FAQ
It is important to note that you do develop tolerance to caffeine over time and the higher the dose you are taking, the sooner the tolerance will develop and the more intense it will be. Fortunately, you can get rid of the tolerance by going through a caffeine cycle at least once in a while.
Probably the best caffeine cycling protocol to reset your tolerance for the compound is going cold turkey for a week every 3 months. While the week without the stimulant will probably be unpleasant (most people experience headaches, low energy, and get agitated very easily), the pain is worth going through if you wish to maximize the benefits of caffeine.
If you have been consuming caffeine every day or nearly every day for many years, you will probably need more time than a week to get back to baseline and become fully sensitive to the stimulant. In the most extreme cases, this takes up to 3 months. However, 1-2 weeks should lead to most of the restorative effects.
Also, if you wish to get through the withdrawal phase faster, one very effective way to do it is “sleep banking”. Basically, what that means is you try to sleep as much as possible (even if it’s 12-16 hours a day) to allow your body to get back to baseline faster.
Keep the supplement in a cold, dark, and dry place and it should remain just as potent for a few months or even years.
The first effects will become notable around 15 minutes after ingestion. You can expect the peak effect to occur around 45 minutes after you ingest caffeine and last for up to a few hours.
The half-life of the stimulant can be anywhere from 1.5 hours to 9.5 hours, depending mainly on your genes. The average half-life is 5-6 hours. Therefore, it takes a few days for the compound to fully leave your system but the effects will be less and less potent.
Doses of 20-40 mg/kg have been shown to be toxic and are not recommended to anybody.
Even 10 mg/kg is too much and this amount would almost certainly cause more harm than good for the vast majority of people.
To stay on the safe side, you want to stay below 150 mg/day. This amount is found in a strong cup of coffee, 7-8 cups of green tea, or 3-4 cups of black tea.
Here is a brief explanation of why the withdrawal happens:
Caffeine has a similar molecular structure to that of adenosine and is, therefore, able to enter and fill adenosine receptors. When adenosine molecules enter the receptors, they send a signal to your body that it is time to sleep, which makes you relaxed and sleepy. When caffeine fills the receptors instead, adenosine molecules cannot enter the receptors until caffeine leaves them, which postpones the sleep-inducing effect of adenosine. Because of this, your body starts creating more and more adenosine receptors that adenosine can fit into, making you more reliant on caffeine. When you stop consuming caffeine, the adenosine receptors will start getting broken down, which leads to the symptoms of withdrawal, such as headaches, fatigue, and getting angry and annoyed easily.
Fortunately, it takes only around a week to get rid of the excess adenosine receptors.
It takes about a week to get through the withdrawal and become fully sensitive to the stimulant again. The first days of the withdrawal phase are usually the worst but once you get through them, the symptoms of withdrawal will gradually get less and less intense.
Both of these have the potential to be beneficial for long-term health. Which of these beverages is better for you depends on many variables.
One important factor to take into consideration is that coffee has considerably more caffeine per cup than tea. Compared to green tea, one cup of coffee is usually 2-7 times higher in caffeine.
As for the health benefits, one cup of average coffee can be just as beneficial as one cup of average tea. However, this means that tea is significantly more beneficial than coffee per mg of caffeine.
So if you look at benefits per cup, the difference is not too big and will depend on the quality and type of coffee or tea you are drinking. If you look at benefits per caffeine, tea is almost always going to be a clear winner.
Also, beware that this answer is extremely simplified. Coffee has a considerably different chemical structure than tea and leads to different health effects. This answer applies to general health but not to all areas of health. In some areas, tea is significantly more effective and in other areas, the opposite is the case.
No, it doesn’t. In fact, it can actually increase some of the benefits of fasting, such as fat loss and ketone production.
References
Most of the information provided in this guide is based on scientific research that can be found and verified in the PubMed medical library. We excluded from consideration studies that are either confounded or have a high conflict of interest.
Anecdotal evidence (from reports on Reddit, YouTube, and other sources) is also taken into account unless it contradicts scientific research.
