How You Can Die From a Caffeine Overdose

Last month Davis Allen Cripe, a healthy teenager from South Carolina, died after downing a McDonald’s latte, a large Mountain Dew soda, and a highly caffeinated energy drink.

According to a South Carolina coroner, the mixture of beverages led to a “caffeine-induced cardiac event causing a probable arrhythmia.”

The coroner was careful to say that “this was not a caffeine overdose.”

But the incident has still raised questions about the safety of caffeine, especially when ingested in large amounts over a short period of time.

Read more: Effects of caffeine on the body “

Caffeine overdose is rare

Caffeine overdose is quite rare.

It usually involves high doses of caffeine taken in powder or tablet form, not beverages.

The reason is simple.

“It’s very hard to get that much caffeine when you’re drinking beverages because of the time it takes to drink them,” Jennifer Temple, PhD, associate professor of exercise and nutrition sciences in the University at Buffalo School of Public Health and Health Professions, told Healthline.

The lethal dose of caffeine for most people, says Temple, is about 10 grams, although this varies from person to person.

A cup of coffee has around 100 to 200 milligrams of caffeine. An energy drink contains anywhere from 50 to 300 mg of caffeine. A can of soda typically has less than 70 mg.

So even with the most highly caffeinated energy drink, you would still have to drink around 30 of them in rapid succession to reach the 10 g range.

Chances are, if you tried to drink that much, your body would stop you before you reached toxic levels.

“Most of the time, if people have acute symptoms of caffeine toxicity, it starts with nausea and vomiting,” said Temple. “So usually that’s sort of protective because you just get sick and you throw up the caffeine before it becomes too toxic.”

With caffeine powder or tablets, though, you can ingest a large amount at the same time. A teaspoon of the powder has 3,200 mg of caffeine.

Read more: Facts about caffeine overdose “

Benefits and risks of caffeine

Around 90 percent of adults in the world consume caffeine daily — in the form of coffee, tea, soda, energy drinks, and other beverages. Even chocolate contains small amounts of caffeine.

Caffeine has many effects on the body, not all of them harmful.

“The research that we’ve done in our lab, and the research that has been done in many other labs around the world, shows that in moderate doses, caffeine is probably not harmful,” said Temple.

Some studies show that caffeine can increase alertness, mental energy, and concentration, especially in people who are tired.

And, of course, there’s the big one.

“The primary effect of caffeine, and the reason why people consume it, is that it counteracts fatigue,” said Temple.

Of course, the downside of using caffeine to stay awake is not being able to sleep.

At moderate doses — a couple of cans of soda or cups of coffee — caffeine increases a person’s blood pressure and decreases the heart rate.

Some people, though, can drink several cups of coffee a day and hardly feel the effects. Others have trouble sleeping after eating too much chocolate before bedtime.

Genetics may play a role in determining why some people are more sensitive to caffeine. Underlying health problems — like those that involve the heart — or medications can also lead to a stronger reaction to caffeine.

And people who consume caffeine less frequently may be able to tolerate it less.

Temple’s research also found that caffeine can affect boys and girls differently after puberty.

Read more: Is there such a thing as safe energy drinks? “

Can caffeine kill?

At toxic levels — especially when taken in a short time — caffeine can start to cause a number of unpleasant side effects: headache, nausea, vomiting, jitteriness, and irritability.

More severe effects of caffeine toxicity include abdominal pain, seizures, increased blood acid levels, irregular or fast heartbeat, and reduced blood flow to the heart — all of which increase your risk of dying.

Death by caffeine, though, is rare.

One study earlier this year identified 51 caffeine-related deaths.

Another review from this year, published in Food and Chemical Toxicology, found that 14 of 26 caffeine overdose reports resulted in death.

“Many of those were associated with exposures on the order or 10 g of caffeine or more, which is quite a bit of caffeine,” study author Daniele Wikoff, PhD, a health sciences practice leader at ToxStrategies Inc., told Healthline.

One person who died ingested 51 g of caffeine.

“In many of these instances,” said Wikoff, “it was consumption of a large amount in a very small amount of time, often from a source like a caffeine pill or the powdered form of caffeine, rather than energy drinks or coffee.”

Even when people didn’t die, they still experienced many of the severe symptoms of caffeine overdose.

“Pounding a bunch of energy drinks in a short period of time,” said Temple, “even if it doesn’t result in death, can certainly result in heart problems or in something that’s going to require an emergency room visit.”

And again, some people seem to be more affected by caffeine than others, even at higher doses. That makes it difficult to predict who will have a bad reaction.

“The evidence does show that there were some individuals who are sensitive,” said Wikoff, “whether it’s somebody that has a condition that makes them more susceptible, something that interacts differently with the caffeine receptors, or perhaps they metabolize it differently.”

In one case, a person suffered cardiac arrest and died after ingesting only 240 mg of caffeine.

Researchers write that this case is unusual and may be related to preexisting conditions.

But as with the death of Cripe, chugging caffeinated beverages can sometimes have unexpected consequences — even when drinking less than 500 mg of caffeine, as Reuters reported that Cripe did.

“We’re not saying that it was the total amount of caffeine in the system,” Gary Watts, the coroner of Richland County, South Carolina, told Reuters. “It was just the way that it was ingested over that short period of time, and the chugging of the energy drink at the end was what the issue was with the cardiac arrhythmia.”

Energy drinks can also contain other stimulants like guarana, L-carnitine, and taurine that complicate how the body reacts.

So how much caffeine is safe?

The review by Wikoff and her colleagues found that less than 400 mg per day for healthy adults — or less than 2.5 mg per kilogram of body weight per day for healthy teens — is “acceptable.”

The American Academy of Pediatrics recommends that adolescents aged 12 to 18 years should not ingest more than 100 mg of caffeine per day. Younger kids should avoid it altogether.

Recent deaths or toxic reactions to caffeine offer another lesson for parents, teens, and others.

“Just because these products are legal doesn’t mean that overuse of them can’t be harmful,” said Temple.

Read more: Effects of energy drinks on your heart “

Caffeine Overdose Symptoms: Signs, Cases, Prevention

Caffeine overdose is becoming increasingly more common as higher caffeinated products flood the marketplace and as people’s dependence on caffeine increases.

Top 15 Caffeine Overdose Symptoms

Here are the usual caffeine overdose symptoms in order from the first ones to be experienced to the more severe, later stage symptoms resulting from even larger doses of caffeine.

  1. Jitters, Restlessness, and Nervousness
  2. Scattered thoughts
  3. Excessive talking
  4. Inability to focus on anything
  5. Irritability
  6. Elevated blood pressure
  7. Increased heartbeat
  8. Nausea
  9. Anxiety
  10. Heart palpitations (cardiac arrhythmia)
  11. Insomnia
  12. Sweating
  13. Dizziness
  14. Vomiting
  15. Cardiac arrest

There can be many common symptoms that indicate too much caffeine consumption, but these are the most prevalent.

The beginning symptoms should be recognized and further caffeine intake should be stopped to avoid the more serious and even life-threatening symptoms found at the end of the list.

Ingesting massive doses of caffeine all at once is particularly dangerous as it doesn’t give your body time to react since early overdose symptoms serve as a warning system.

Caffeine’s major effects are experienced for at least 4 hours.

  • This is longer for those sensitive to caffeine.
  • This is longer with extremely large doses.
  • This is based on the half-life of caffeine which is 4-6 hours.

However, it can be hard to pinpoint an amount of caffeine that will cause caffeine overdose symptoms since people can have different tolerance levels to caffeine.

Are You Addicted to Caffeine?

If you want to reduce your caffeine intake (or quit entirely), here’s how:
1.Download our book Awake(it’s free).
2. Do the Overcoming Caffeine Withdrawal course at Udemy.
3. Use the Wean Caffeine supplement (something we helped get to market). It helps you avoid the painful withdrawal symptoms that often come when quitting caffeine abruptly.

Prevention: Maximum Daily Intake

You can prevent caffeine overdose by adhering to the recommended safe dosage guidelines.

Generally, a single dose between 250-500 mg (check caffeine amounts here) could produce some of the above mild to moderate symptoms, especially in those with no tolerance or high caffeine sensitivity.

Those with caffeine allergy or sensitivity could have severe symptoms even after a much smaller dose.

to find out how much of a popular drink would it take for you to overdose.

DSM-5 Criteria

Caffeine Intoxication is now included in the DSM-5 physician manual. (This is the official manual doctors and psychiatrists use to diagnose a person’s condition.)

The official diagnosis can be made when any 5 of the following symptoms are present: restlessness, nervousness, excitement, insomnia, flushed face, diuresis (you keep passing urine), gastrointestinal disturbance (upset tummy, diarrhea), muscle twitching, rambling flow of thought and speech, tachycardia or cardiac arrhythmia, periods of inexhaustibility, or psychomotor agitation.

The DSM-5 now also lists Caffeine Withdrawal as a mental disorder. Sufferers can experience withdrawal symptoms when ceasing caffeine intake.

So far, caffeine addiction as a disorder has been rejected from being placed in the manual.

Doctors and nurses in emergency rooms are now being trained to recognize the overdose of caffeine since it is becoming more common among their patients.

Reducing the Impact of Caffeine

There is some research indicating products that contain rutaecarpine can actually reduce the impact of caffeine’s side effects. They do this by assisting with caffeine metabolism*. Learn more here.

Caffeine Overdose Documented Cases

Caffeine overdose does happen and has been documented. Here are some of the more recent cases of an overdose resulting in death or hospitalization;

  • 19-year-old James Stone dies after taking 25 to 30 No-Doz pills in 2007. (at least 2.5 grams of caffeine)
  • A 56-year-old Brittish man drank 25 Red Bulls in an evening and awoke the next morning with a brain hemorrhage. src.
  • 17-year-old Jasmine Willis, a Durham, UK waitress overdosed by drinking 7 double espressos in 2007. She was taken to the hospital but recovered soon after. (that’s roughly 1.078 grams)
  • In the late 1990s an Australian woman, with a heart condition died after consuming a guarana based shot from her local health food store. This product is no longer on the market. (10g/liter, ok that’s just nuts!)
  • 2010 a 23-year-old British man from Mansfield, England died after taking to 2 spoonfuls of pure caffeine powder washed down by an energy drink at a party. His death was ruled accidental.
  • 2011 Fourteen-year-old Anais Fournier, died after she consumed two 24 ounce Monsters (480mg of caffeine) in a 24 hour period. The cause of death was a heart arrhythmia due to caffeine toxicity. There seem to be some conflicting stories as to how much she really consumed and this seems true since 480mg in a 24 hour period isn’t a toxic amount. Update October 2012: Her parents are suing Monster Energy for wrongful death although the girl did have a known pre-existing heart condition.
  • 2012 The FDA is investigating Monster Energy since the energy drink has been linked to five deaths over the past year.
  • 2013: According to the Substance Abuse and Mental Health Services Administration, energy drink-related ER visits have doubled in the last 4 years, however, 42% of these visits involved caffeine in combination with other drugs such as alcohol or other narcotics. src.
  • 2013 a New Zealand woman died from cardiac arrhythmia associated with her 10 liters/day Coca-Cola habit. She also smoked 30 cigarettes a day and barely ate. Caffeine was a contributing factor, but the 900-1000mg daily dose wasn’t the only factor. src.
  • 2013 A mother is suing Monster Energy for the death of her 19-year-old son, Alex Morris, after he died of cardiac arrest. She claims that he drank two 16 ounce Monsters the day before his death and at least two a day for the 3 years preceding his death. A California Coroner’s office reported that he died from cardiomyopathy and cardiac arrhythmia.
  • October 2013: John Jackson from the UK dies after eating a whole tin of HERO Energy Mints. Each tin contains 12 mints, so he consumed 984mg of caffeine. He also had cirrhosis of the liver, which prevented him from processing the caffeine properly allowing it to build up in his bloodstream to lethal levels. (src.)
  • March 2014: A 14-year-old boy from Norway was hospitalized with kidney failure after drinking 4 liters of a caffeine-laced energy drink while gaming for 16 hours straight. This would be around 1,280mg of caffeine if he was consuming a “Red Bull” similar energy drink. (src.)
  • September 2014: A Tennessee man was taken to the hospital after consuming 20 caffeine pills to “test the limits of his body” according to what the man told the paramedics. He ingested 4000 mg of caffeine at once. src.

Some Additional Caffeine Overdose Facts

Luckily for us, we have mechanisms built into the human body that let us know we’ve had enough of something.

This is true with caffeine overdose. Well before we are at a toxic level we experience side effects that prevent us from consuming more, i.e. nausea and vomiting.

This means that before the 149 or so cans of Red Bull that it would take to kill an average adult male, vomiting would most certainly happen.

For most people, that would happen after about can number 5!

However, it’s important to note that caffeine is a drug and should be respected and not abused. Since some people have an extremely low tolerance or high sensitivity to caffeine, they could – in theory – overdose quite easily.

How to Know If You’ve Overdosed?

Most people feel the “jitters” first – a sensation of tremors or shaking.

This is your signal to stop consuming caffeine for the day.

You should also be aware of the caffeine levels in what you are drinking. Please consult the caffeine database since some of the caffeine amounts might surprise you.

If you find that you’re often tired after consuming caffeine, this is a sign that you need to change your long-term caffeine habits and consider a detox.

The bottom line is to be aware of what you are consuming.

How common is caffeine overconsumption?

With the plethora of caffeinated products in the marketplace, one could assume that overdosing on caffeine is quite common.

However, if we look at the statistics gathered from The American Association of Poison Control Centers we find that, while caffeine overdose does exist, it isn’t as common as people may think.

In fact, overdosing on Tylenol is a lot more common than overdosing on caffeine.

Written by Ted Kallmyer, last updated on November 14, 2019

Too Much Coffee: Protecting Yourself & Your Kids From Caffeine Overdose

While the risk of a caffeine overdose is low, too much coffee can disrupt the sleep teens and children need for good health.

Caffeine Overdose Kills South Carolina Teen. That was the headline a few months ago, in May 2017, after a 16-year-old boy downed a latte, an energy drink and a large Mountain Dew and died. Parents, along with coffee addicts around the world, panicked, wondering if they had to now add caffeine to the list of dangers to worry about.

But Christopher Holstege, MD, of the Blue Ridge Poison Center, warns against paranoia. “You would have to drink a lot of coffee to overdose on caffeine. The highest reported caffeine blood level following a survivor of a caffeine overdose was equivalent to 1,000 cups of coffee, for instance.”

Taking too many caffeine pills – about 48 cups of coffee’s worth – killed a man in 2006. But episodes like these — a caffeine overdose causing seizures or a heart arrhythmia that kills — are rare.

Too Much Coffee?

“Caffeine isn’t bad; in fact, evidence shows maybe some benefit from it,” Holstege says, easing the minds of coffee-drinkers everywhere. “Everything is about dose. Drink in moderation.”

What exactly is moderation, when it comes to coffee? That’s where things get murky.

“It’s really hard to know with caffeine and adults, and there’s lots of different literature out there,” Holstege says. According to the European Food Safety Authority, for instance, an adult’s daily consumption of caffeine shouldn’t exceed 400 milligrams, which adds up to about two cups of coffee, a lot of soda, five Red Bulls and two caffeine pills. The Food and Drug Administration here in the U.S., however, has said that five cups of coffee (per day) are safe. The indications have changed over time, adding to the confusion.

Whatever the recommendations, really, the dose of caffeine a person can handle varies. As Holstege explains, “Caffeine is a chemical, and we have different make-ups regarding how our bodies react to different chemicals.”

And this is why Holstege warns us to take the scary headlines with a grain of salt.

“Pre-existing health conditions or genetics play a role,” he says. Connective tissue disease, for instance, increase the risk for an aorta to rupture due to too much caffeine. “There’s been a number of deaths at fairly low doses. But even if someone drinks a large amount of coffee and dies — it doesn’t mean they died from the beverage. We don’t really know. We often don’t hear the final autopsy reports,” just the anxiety-causing headlines.

Caffeine and Children

The indications don’t clear up when it comes to children.

While the American Academy of Pediatrics discourages any caffeine and stimulant use by children, the FDA does not have any regulations regarding children and caffeine.

Studies suggest that energy drinks can be harmful when consumed without caution, especially by young children. And it’s not just coffee and energy drinks parents need to watch for and regulate. You can buy almost anything in a caffeinated form these days: from water and syrup to gum and jelly beans.

Parents should definitely take heed.

“Caffeine is a stimulant, and you can get addicted to it. And children’s brains are still developing. Most prefer children under 12 to avoid it altogether,” Holstege says. And, he adds, teens especially need to limit caffeine intake because of how much sleep they need.

The Biggest Risk: Putting Off Sleep

More than the risk of dying from too much coffee, Holstege expresses his concerns about teens taking so much coffee they don’t get the sleep they need.

“You look around at students these days, like here at UVA, and you see a fair amount of coffee being bought,” he says. “Students will drink a large coffee just before bed as they cram for an exam and expect to go to sleep, but that’s not going to happen. Sleep will be impossible.”

Caffeine has to get metabolized and out of your system, and Holstege says that can take four to six hours, although that varies between individuals.

And if you find yourself unable to go to sleep because you’ve had too much caffeine?

“The only thing you can do is wait it out if you have too much,” Holstege says. “Your body has to metabolize it and can only do that so much.”

He notes that both teens and adults can get in an over-caffeinated state and “take depressants or sleeping pills because they can’t sleep at night – it becomes a vicious cycle.” If your teen is using pills to stay awake and study, you may need to intervene.

Caffeine Overdose: What to Do?

If you’re worried your child has overdosed on caffeine, in whatever form, call the Blue Ridge Poison Center.

Avoid the Caffeine Cycle

Avoid the cycle by planning, Holstege says.

• Don’t cram in middle of night
• Don’t take stimulants like caffeine in the evening before going to bed
• Never take drugs that are not prescribed to you, such as Ritalin or Adderall
• Read labels – don’t forget that many sodas have caffeine
• Caffeine can augment medicine, so be careful to read prescription labels/talk to your doctor

“If you need to stay awake in a dull meeting, sometimes just the motion of drinking any kind of liquid can help,” he suggests. “Drinking plenty of water each day is a good substitute.”

Aug. 15, 2006 — That cup of coffee you’re craving might not be such a good idea.

Research in the September issue of Epidemiology suggests coffee can trigger a heart attack within an hour in some people.

Java junkies can take some comfort from the finding that the risk was highest among light coffee drinkers (those who consumed up to one cup a day).

For those people, the risk of heart attack increased fourfold when they indulged.

Couch potatoes and those with other risk factors for heart disease were also at greater risk of having a heart attack after drinking a cup of coffee, the study showed.

As a result of these findings, “people at high risk for a heart attack who are occasional or regular coffee drinkers might consider quitting coffee altogether,” says researcher Ana Baylin, a research associate at Brown University School of Medicine in Providence, RI, in a news release.

Baylin, who works in the department of nutrition at Brown, adds that for these individuals, a cup of coffee could be “the straw that broke the camel’s back.”

Baylin and colleagues suggest caffeine causes short-term increases in blood pressure and sympathetic nervous activity that could trigger a heart attack.

On the other hand, previous studies have shown coffee drinkers may be at decreased risk for Parkinson’s disease, diabetes, and certain types of cancers.

Is coffee bad for the heart or not?

The participants also self-reported how much coffee they typically drank on a day-to-day basis. Following these reports, the investigators then categorized the participants into three groups, according to their coffee consumption habits:

  • people who drank one or fewer cups of coffee a day
  • those who drank between one and three cups of coffee per day
  • those who drank more than three cups of coffee per day

In their final analysis, Prof. Petersen and team excluded individuals who drank more than 25 cups of coffee per day, as well as those who had cardiovascular disease at baseline.

When comparing measurements of arterial stiffness between the three groups, the researchers found no differences between moderate and heavy coffee drinkers (those who drank between one and three or more than three cups of coffee per day, respectively) and those who had one cup off coffee or less per day.

These results, the investigators say, suggest that even drinking significant amounts of coffee is unlikely to have an ill effect on arterial health, so it may not negatively influence heart health and vascular function.

“Despite the huge popularity of coffee worldwide, different reports could put people off from enjoying it. Whilst we can’t prove a causal link in this study, our research indicates coffee isn’t as bad for the arteries as previous studies would suggest,” explains study coauthor Kenneth Fung.

These findings remained in place after the investigators adjusted for possible factors contributing to arterial stiffness, including age, biological sex, ethnicity, smoking status, alcohol consumption, height, weight, eating habits, hypertension (high blood pressure), high cholesterol, and diabetes.

What should and what shouldn’t we believe?

The researchers also noted that moderate and heavy coffee drinkers were more likely to be male, habitual smokers, and frequent drinkers of alcohol.

“Although our study included individuals who drink up to 25 cups a day, the average intake amongst the highest coffee consumption group was five cups a day. We would like to study these people more closely in our future work so that we can help to advise safe limits,” Fung also specifies.

Prof. Metin Avkiran, who is Associate Medical Director at the British Heart Foundation, and who was not involved in the current research, explains that such studies about the relationship between coffee consumption habits and heart health can help individuals make better-informed decisions.

“Understanding the impact that coffee has on our heart and circulatory system is something that researchers and the media have had brewing for some time. There are several conflicting studies saying different things about coffee, and it can be difficult to filter what we should believe and what we shouldn’t.”

Prof. Metin Avkiran

“This research will hopefully put some of the media reports in perspective, as it rules out one of the potential detrimental effects of coffee on our arteries,” Prof. Avkiran says.

Coffee Consumption and Coronary Heart Disease in Men and Women

The relation between coffee consumption and cardiovascular disease has been studied extensively. Although many previous cohort studies found no significant association between coffee and coronary heart disease (CHD),1–4 more recent results have been inconsistent. Although case-control studies found a positive association between coffee consumption and risk of CHD,5,6 prospective cohort studies reported a lower risk among individuals with higher coffee consumption.7,8 In addition, other studies suggested that both high and low coffee intake were associated with an increase in the risk of CHD compared with moderate coffee consumption.9,10

Clinical Perspective p 2053

In view of these discrepancies and recent findings that coffee consumption may protect against diabetes mellitus,11–15 we extended our previous analysis4,16 and assessed the association between coffee consumption and risk of CHD in 2 ongoing large cohort studies of men and women. We also examined whether the association between coffee consumption and CHD was modified by the presence of type 2 diabetes mellitus, smoking, alcohol consumption, or obesity. The long duration of follow-up (14 years for men and 20 years for women) and the use of repeated measurements allowed us to assess both the short- and long-term effects of coffee.


Study Population

The Health Professionals Follow-up Study (HPFS) was established in 1986 and the Nurses’ Health Study (NHS) in 1976. Information on the cohorts has been updated every 2 years. Further details have been published elsewhere.17 In the present study, after excluding participants with cardiovascular disease or cancer at baseline, we obtained 44 005 men and 84 488 women who were followed up until 2000. The Harvard School of Public Health and Brigham and Women’s Hospital Human Subjects Committee Review Board approved the study protocol.

Assessment of Coffee Consumption

Dietary questionnaires were sent to the HPFS participants in 1986, 1990, 1994, and 1998 and to the NHS participants in 1980, 1984, 1986, 1990, 1994, and 1998. On each questionnaire, participants were asked how often on average during the previous year they had consumed coffee and tea. The participants could choose from 9 responses. The method of coffee preparation was assessed only in 1990 in both studies. Decaffeinated coffee and different types of caffeinated soft drinks were first assessed in 1986 in the HPFS and in 1984 in the NHS. In addition, we also inquired in the NHS questionnaire of 1980 whether the participant’s consumption for each beverage had greatly increased or decreased over the past 10 years. Using the US Department of Agriculture food composition sources, supplemented with other sources, we estimated that the caffeine content was 137 mg per cup of coffee, 47 mg per cup of tea, 46 mg per can or bottle of cola beverage, and 7 mg per serving of chocolate candy. We assessed the total intake of caffeine by summing the caffeine content for a specific amount of each food during the previous year (1 cup for coffee or tea, one 12-ounce bottle or can for carbonated beverages, and 1 ounce for chocolate) multiplied by a weight proportional to the frequency of its use. In our validation study, we obtained high correlations between consumption of coffee and other caffeinated beverages estimated from the food frequency questionnaire and consumption estimated from repeated 1-week diet records (coffee, r=0.78; tea, r=0.93; and caffeinated sodas, r=0.85).18

Assessment of Nonfatal Myocardial Infarction and Fatal CHD

The primary end point for this analysis was CHD, which included symptomatic nonfatal myocardial infarction (MI) or fatal CHD that occurred after the return of the 1986 questionnaire in men and the 1980 questionnaire in women but before June 1, 2000. We requested permission to review medical records from subjects who reported having a nonfatal MI on a follow-up questionnaire. Physicians unaware of the self-reported risk factor status systematically reviewed the records. MI was classified as confirmed if the criteria of the World Health Organization were met, specifically, symptoms and either ECG changes or elevated cardiac enzyme levels.19 We included confirmed and probable cases for the analyses. Deaths were identified from state vital statistics records and the National Death Index or reported by the families and the postal system. Fatal CHD was considered to have occurred if fatal MI was confirmed by hospital records or an autopsy or if CHD was listed as the cause of death on the death certificate, if it was listed as an underlying and the most plausible cause of death, and if evidence of previous CHD was available.

Assessment of Medical History, Anthropometric Data, and Lifestyle Factors

On the baseline questionnaires, we requested information about age, weight, and height; smoking status; parental history of MI; use of hormone therapy in women; and personal history of MI and other diseases. This information, with the exception of height and parental history of MI, has been updated on the biennial follow-up questionnaires. Body mass index (BMI) was calculated as weight in kilograms divided by the square of height in meters. Physical activity was assessed biennially. In the HPFS, participants were queried about the average time spent per week during the preceding year in specific activities (eg, walking outdoors, jogging, and bicycling).20 The time spent in each activity in hours per week was multiplied by its typical energy expenditure, expressed in metabolic equivalent tasks (METs) and then summed over all activities to yield a METs/h score. In the NHS, physical activity was reported in hours per week of moderate (eg, brisk walking) and vigorous (eg, strenuous sports and jogging) exercise.21 Standard portion sizes for alcoholic drinks were specified as a can/bottle or glass for beer, 4-oz glass for wine, and 1 drink or shot for liquor. Detailed information on the validity and reproducibility of the questionnaire has been reported elsewhere.18,22–25

Statistical Analyses

Participants were classified according to levels of coffee consumption. Person-years of exposure were calculated from the date of return of the baseline questionnaire to the date of nonfatal MI, fatal CHD, or June 1, 2000, whichever came first. For individuals who developed a nonfatal MI and later died of fatal CHD during the follow-up, we only included follow-up time to the nonfatal event in the overall analysis to avoid double counting. Participants who had a nonfatal MI and later died of CHD within the same 2-year period were counted only for the fatal event.

Sex-specific Cox regression models were used to investigate the association between coffee consumption and incidence of CHD events. Hazard ratios were used to estimate relative risks (RRs). To reduce within-subject variation and best represent long-term diet, we used the cumulative average of dietary intakes from all available dietary questionnaires up to the start of each 2-year follow-up interval26; for example, the average of the 1986 and 1990 intake was used for the follow-up between 1990 and 1994, and the average of the 1986, 1990, and 1994 intake was used for the follow-up between 1994 and 1998. In alternative analyses, we also used simple updating (the most recent information on coffee consumption before the event) to study short-term effects of coffee on CHD.

Physical activity, alcohol intake, BMI, smoking status, and use of hormone therapy, aspirin, multivitamin supplements, and vitamin E supplements were also updated during follow-up with the most recent data for each 2-year interval. Models were first adjusted for age and smoking status. Furthermore, we adjusted for BMI, physical activity, alcohol intake, use of hormone therapy for women, parental history of MI, aspirin use, multivitamin use, vitamin E supplement use, and history of hypertension, hypercholesterolemia, and diabetes mellitus at baseline. To test for linear trends across categories, we modeled coffee consumption as a continuous variable in the models with the median value of each level of coffee consumption. Stratified analyses were conducted according to smoking status, alcohol consumption, history of diabetes mellitus, and BMI. We studied the association between caffeine intake, decaffeinated coffee and tea consumption, and CHD. We also examined separately the effect of filtered and non–paper-filtered (espresso/percolator) coffee on CHD.

As a complementary study, we examined the association of caffeinated and decaffeinated coffee and plasma levels of total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol. We conducted these analyses in men and women who were selected as control subjects in 2 previous nested case-control studies of MI.27 Blood samples were collected in 1990 in women and 1994 in men; therefore, we used dietary information from the 1990 food frequency questionnaire for women and from the 1994 food frequency questionnaire for men. We calculated multivariable-adjusted means of plasma cholesterol levels across categories of consumption. All analyses were performed with SAS software, version 8.2 (SAS Institute Inc, Cary, NC).

The authors had full access to the data and take responsibility for its integrity. All authors have read and agree to the manuscript as written.


During 14 years of follow-up in the HPFS, we documented 2173 cases of CHD, including 1449 nonfatal MIs and 724 fatal CHD events. During 20 years of follow-up in the NHS, we documented 2254 cases of CHD (1561 nonfatal MIs and 693 fatal CHD events). Characteristics of the population are presented by levels of coffee consumption in Table 1. Frequent coffee consumption was strongly associated with smoking: 30% of the men and more than half of the women who drank ≥6 cups/d also smoked cigarettes. In addition, individuals who drank more coffee were more likely to drink alcohol and to use aspirin and less likely to drink tea, to exercise, and to use multivitamin and vitamin E supplements.

In age-adjusted analyses, we found no significant association between long-term coffee consumption and risk of CHD for men but a positive association for women (Table 2). However, when we further adjusted for smoking status, the positive association in women disappeared, which suggests that the age-adjusted results were strongly confounded by smoking. After multivariable adjustment, the RRs were somewhat attenuated. Additional adjustment for total energy intake, glycemic load, cereal fiber, folate, and polyunsaturated, saturated, trans, and n-3 fatty acids did not appreciably alter the results. Interestingly, the consumption of ≥6 cups/d of coffee was associated with a slightly lower risk of fatal CHD in both men (RR 0.60, 95% confidence interval 0.26 to 1.36) and women (RR 0.61 95% CI 0.37 to 1.02); the pooled RRs across categories of coffee consumption were 1.0, 1.06 (95% CI 0.90 to 1.26), 1.04 (95% CI 0.89 to 1.21), 0.93 (95% CI 0.79 to 1.09), 1.01 (95% CI 0.81 to 1.28), and 0.61 (95% CI 0.39 to 0.93).

The null association between coffee and CHD was independent of smoking status (Table 3; Figure; P for interaction=0.51 in men and P=0.96 in women) and alcohol consumption (P for interaction=0.32 in men and P=0.90 in women). The association was also similar for participants with and without type 2 diabetes mellitus and for obese (BMI ≥30 kg/m2) and nonobese participants (Table 3).

RRs (with 95% CIs) of CHD from 1986 to 2000 in men and from 1980 to 2000 in women, by levels of coffee consumption and smoking status (never and past combined). Reference category was nonsmokers who drank <1 cup of coffee per month. Data were adjusted for variables in Table 2, except for smoking.

Alternative analyses with the most recent coffee consumption data showed no association between shorter-term intake (2- to 4-year interval) and CHD (multivariable RRs for men were 1.0, 0.88, 0.91, 0.93, 0.96, and 0.80 ; the corresponding RRs for women were 1.0, 0.96, 1.09, 0.98, 0.96, and 0.98 ). When we stopped updating coffee consumption after the person developed angina, hypertension, hypercholesterolemia, cancer, or type 2 diabetes mellitus, it did not change the results. We also tried excluding participants who reported a change in their coffee consumption during the 10 years before baseline and excluding the first 4 years of follow-up to avoid latent disease; these exclusions did not appreciably affect the association between coffee consumption and risk of CHD. Finally, we excluded from the analyses participants who reported hypertension, hypercholesterolemia, or diabetes mellitus at baseline, as well as those who developed these diseases during the follow-up, again obtaining similar results. The multivariable adjusted means of total, LDL, and HDL cholesterol across categories of caffeinated and decaffeinated coffee are presented in Table 5. No significant associations were observed between coffee consumption and blood lipids.


In this large prospective study, we did not find a detrimental effect of coffee consumption on risk of CHD in either men or women. No association was observed for total caffeine intake, decaffeinated coffee, or tea. These results provide strong evidence against the hypothesis that coffee consumption increases the risk of CHD.

Coffee is one of the most widely consumed beverages in the United States and worldwide.28 The health effects of coffee consumption have been studied and debated extensively. In an earlier meta-analysis,2 cohort studies did not support an association between coffee intake and risk of CHD (pooled RR=1.05, 95% CI 0.99 to 1.12 for drinking 5 or more cups/d versus none), whereas case-control studies tended to suggest a positive association (RR=1.63, 95% CI 1.50 to 1.78). Several biases could explain the difference. For instance, recall bias in case-control studies may explain a positive association if individuals who developed CHD were more likely to overreport coffee intake than healthy controls.

Results from recent epidemiological studies are mixed. Woodward and Tunstall-Pedoe7 followed a Scottish population for 8 years. Their results suggested that higher coffee consumption was associated with lower risk of cardiovascular disease among men but not among women. Kleemola et al8 assessed coffee consumption in a Finnish population 3 times during 10 years of follow-up and found a lower risk of nonfatal MI in men with high coffee consumption (>7 cups/d); however, they also observed a slightly increased CHD mortality in the same group. Additionally, in a case-control study, Hammar et al6 reported that daily consumption of 7 to 9 dL of filtered coffee was associated with an increased risk of CHD in men compared with a daily consumption of 3 dL or less; however, this association was not observed for women. Two other studies suggested a J-shaped relationship between coffee consumption and risk of CHD.9,10 The present analyses, which used repeated measures of coffee consumption over 14 to 20 years of follow-up, found no evidence of either short-term (2 to 4 years) or long-term effects. Likewise, we found no association with decaffeinated coffee or total caffeine intake. Repeated measurement of diet was a unique advantage in the present study because our analysis using a cumulative average of intake was able to best represent long-time diet and reduce within-subject variations.

Coffee is a major source of caffeine. Caffeine is an adenosine-receptor antagonist,29 and all tissues with adenosine receptors may be affected by caffeine exposure. Caffeine stimulates fat oxidation in muscle30 and increases basal energy expenditure.31 Also, caffeine stimulates free fatty acid release from peripheral tissues32 and decreases insulin sensitivity in skeletal muscle.33 In addition, caffeine might impair insulin action by stimulating the release of epinephrine, which is a potent inhibitor of insulin activity.34 Finally, caffeine increases blood pressure35 and homocysteine levels36 in short-term studies. However, the above effects of caffeine could be transient, because partial tolerance might develop after several days of use.37 Thus, some of these mechanisms cannot be extrapolated to long-term use,15 whereas others mechanisms could counterbalance the effects of caffeine. For instance, substances in coffee such as potassium, niacin, and magnesium have previously been shown to be beneficial for glucose and insulin metabolism.38 In addition, antioxidants in coffee such as chlorogenic acid and other phenolic compounds might improve insulin sensitivity.39 These mechanisms may explain the recent findings that habitual coffee intake is associated with a lower risk of developing type 2 diabetes mellitus.11–15 In the present study, coffee consumption had no adverse or beneficial effect on CHD in participants with or without diabetes mellitus. In both men and women, there was some suggestion that heavy consumption (6 cups or more per day) was associated with a lower risk of fatal CHD (Table 2); however, the number of fatal CHD cases was relatively small, and the results should be interpreted with caution.

Coffee consumption was strongly correlated with smoking; thus, it is not surprising that coffee intake was positively associated with CHD in age-adjusted analyses in the NHS cohort, in which smoking was more prevalent. However, this association disappeared after adjustment for smoking and in analyses stratified by smoking status. A recent study suggested a synergistic detrimental effect of acute smoking and caffeine (200 mg) on aortic stiffness.40 However, we did not find an interaction between smoking and coffee consumption in relation to CHD risk. Although smoking was strongly correlated with coffee consumption, the detrimental effects of smoking on CHD were the same among coffee drinkers and nondrinkers.

Finally, most participants in the present study consumed filtered coffee. Neither filtered caffeinated coffee nor filtered decaffeinated coffee was substantially associated with plasma levels of total, LDL, and HDL cholesterol. Among those who reported consuming non–paper-filtered coffee, we did not find an increased risk of CHD. Boiled coffee increases serum cholesterol,41,42 and some evidence suggests that high consumption of this beverage is related to CHD risk.6,43 The lack of association between non–paper-filtered coffee in the HPFS and the NHS I cohorts is likely to be due in part to (1) the inclusion of espresso in this category, which has lower concentrations of the cholesterol-increasing components kahweol and cafestol,44 and (2) the modest consumption even in the highest categories (≥2 cup/d), compared with intervention studies such as Bak and Grobbee’s work,45 which examined the effect of the consumption of 4 to 6 cups of boiled coffee per day. The results of the present study do not exclude a relation between high nonfiltered coffee consumption and CHD risk.

In conclusion, in these 2 large cohorts, after a follow-up of 14 years for men and 20 years for women, we found no evidence of an adverse association between coffee intake and the risk of developing CHD. Likewise, we found no association for consumption of total caffeine, decaffeinated coffee, or tea. These data do not provide any evidence that coffee consumption increases the risk of CHD.

This study was supported by National Institutes of Health research grants CA87969, DK55523, DK58845, and HL34594. Dr Lopez-Garcia’s research is supported by a fellowship from the Secretaria de Estado de Educacion y Universidades (Ministerio de Educacion y Cultura de España) and Fondo Social Europeo. Dr Hu’s research is supported in part by an American Heart Association Established Investigator Award.




Reprint requests to Dr Frank B. Hu, Departments of Nutrition and Epidemiology, Harvard School of Public Health, 665 Huntington Ave, Boston, MA 02115. E-mail

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Here’s Exactly How Much Caffeine You Need to Drink to Overdose

Thanks in large part to television shows and movies, most people don’t think there’s anything wrong with drinking several cups of coffee a day. You watch a show like Gilmore Girls, in which a recurring motif is the frantic search for coffee, or see doctors carrying cups in between shifts in Grey’s Anatomy, or watch Carrie hold a Starbucks cup while strolling through New York in Sex and the City, and you think drinking copious amounts of coffee is glamorous and cool.

The truth is that coffee is a widely used and unregulated psychoactive drug. Like cocaine, caffeine is a central nervous system stimulant that helps you stay awake and, in some cases, even gives you a temporary high. Like cocaine, caffeine is highly addictive, and going off it after habitual usage prompts some nasty withdrawal symptoms. Like any other drug, caffeine can also be abuse and lead to an overdose. (Yes, those can actually be lethal.)

According to the FDA, it’s safe for an adult to drink 400 milligrams of caffeine per day, or 4 cups. The reason that’s misleading, however, is that people forget that, here in the U.S., we don’t drink out of standard-size cups, which are 8 ounces. We drink out of mugs that contain 12 ounces or more. How much you can safely consume varies depending on your weight, but the basic guideline is that over 500 mg can lead to caffeine intoxication. That means that even just one Venti Caramel Macchiato (which is 20 oz, aka 567 milligrams), could give you supraventricular tachycardia, the medical term for an accelerated heart rate, and having another one of those could even hours later could even kill you. A study in 1997 found that drinking more than 687 mg a day increased the risk of heart attack by 44%.

If you think death-by-caffeine sounds a bit dramatic—or even ridiculous—please know that it’s happened before. Just last year, a 16-year-old named Davis Allen Cripe, of Chapin, South Carolina, died from a caffeine overdose, having had a large Mountain Dew, a latte from McDonalds, and an energy drink within the span of two hours. The tragedy spurred people to spread awareness over the dangers of drinking too much caffeine, and prompted people to check just how much caffeine a product had before consuming it.

The scary thing is that you’re already probably consuming more caffeine that you realize. In 2013, the FDA announced that they were investigating new products after it was found that some companies were adding caffeine to jelly beans, waffles, syrup, marshmallows, sunflower seeds, and even water, to get help people get addicted to their product. The worst part of this is that a lot of these products are marketed to teens and kids, who are the most likely to die of a caffeine overdose. The announcement came just after Wrigley’s began promoting a new pack of 8-piece gum that contained as much caffeine as four cups of coffee.

A heart attack isn’t even the only potentially fatal disease you can get from coffee. California is currently debating whether or not to place warning signs on coffee, because it contains acrylamide–a chemical that is known to increase the risk of cancer and birth defects.

So if you’re thinking of quitting coffee, but worried it’ll inhibit your ability to stay awake, check out 25 Non-Coffee Ways to Boost Your Energy Levels.

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A 21-year-old died after drinking a protein shake with a caffeine supplement so powerful it knocked him unconscious

  • A young man in Australia died after drinking a protein shake with a caffeine supplement. At least two other caffeine overdose deaths have been traced to supplements.
  • Many people enjoy a cup of coffee to start their days, but too much caffeine can cause anxiety, heart palpitations, and even death.
  • Concentrated caffeine, which is cheap and easy to buy online, can contain as much caffeine as 32 cups of coffee per teaspoon, making it easy to use a deadly amount.

  • Avoid high doses of caffeine by sticking to natural sources like tea or coffee that dilute the drug. If you must use a supplement, know how much you’re consuming in each cup, can, or scoop.
  • Visit INSIDER’s homepage for more.

Most Americans can’t imagine getting through the day without the boost from (at least) one morning cup of joe, and plenty of evidence suggests drinking it can be good for your brain and body and may even lead to a longer life.

But too much caffeine can be deadly.

Lachlan Foote, a 21-year-old from Sydney, Australia, died 18 months ago after drinking a highly-caffeinated protein shake. He reportedly mixed the shake himself after coming home from a few drinks with his friends, and his last Facebook message mentioned an odd bitter taste in his shake.

“I think my protein powder has gone off … Anyway … night lads. Cya in the morning,” he wrote, according to News Corp Australia. In the morning, though, his parents found him dead on the bathroom floor.

Now, the coroner has determined that his death was a caffeine overdose, and Foote’s family is speaking out about the dangers of powdered caffeine supplements similar to those Foote had added to his shake, the Blue Mountain Gazette reported.

Read more: We bought a bag of caffeine equivalent to 15,625 cans of Coca-Cola for $30

“I want the truth to be out there … for Lachlan’s sake and so that it won’t happen again,” his dad told the Gazette. “Maybe his death will benefit someone else.”

Caffeine can be lethal because it stresses the cardiovascular system

Caffeine is the world’s most popular psychoactive drug, added to everything from soda to soap.

It’s found naturally in coffee, tea, and chocolate, and acts as a central nervous system stimulant to make you feel a rush of energy, elevated mood, and increased focus.

But not all of its effects are positive: Even in normal doses, like your morning latte, it increases your heart rate, breathing, and blood pressure, according to registered dietitian Leslie Bonci.

And, at higher doses, it can be dangerous. The Mayo Clinic recommends 400 mg of caffeine per day as a safe amount for most adults (kids and teens should avoid it). Any more than that, Bonci said, could make you feel anxious or jittery. It could even make you feel like your heart is racing or you can’t catch your breath, she added, sending some people to the ER.

The amount in a lethal dose varies based on body weight, but could be as little as 1,500 milligrams, Bonci said. That’s because in extreme cases, caffeine causes vomiting, cramps, and a fast, irregular heart beat, combined with low blood pressure that can lead to unconsciousness and eventually death.

Caffeine supplements are highly concentrated, making it dangerously easy to consume a lethal dose

Highly concentrated, readily-accessible online supplements are making it easy to cross the line between a quick boost and a lethal overdose. At least two deaths in the U.S. have been attributed to caffeine overdose.

The amount found in supplements is “just ridiculously high,” Bonci said. “You would never see that amount in a cup of Starbucks; it’s impossible.”

While most people would have to drink more than 20 cups of coffee at once to reach a fatal level of caffeine intoxication, caffeine in supplement form, whether tablets, powder or, liquid “energy shots,” are especially dangerous because they can hit your system all at once.

“The amount is so concentrated, and you don’t have anything to dilute it,” Bonci said. “There’s nothing to slow down the absorption, and the brain is going to feel that caffeine a lot faster.”

The U.S. Food and Drug Administration is cracking down on sales, but it’s still cheap and easy to buy caffeine supplements online.

Last year, the FDA issued warning letters to two American companies selling illegally high doses of concentrated caffeine. One of these contained 3,200 milligrams per teaspoon, as much as 20 to 30 cups of coffee or 80 cans of soda.

“Despite being informed of the dangers of highly concentrated and pure caffeine, we’re still finding companies that are disregarding consumer safety by illegally selling products with potentially dangerous and lethal amounts of caffeine,” said FDA Commissioner Dr. Scott Gottlieb in a June 2018 press release.

Serving sizes of caffeine supplements are deceptive

The proper “serving size” of pure caffeine powder is 1/16 of a teaspoon, according to one product website. Most people don’t have a measuring spoon that small, and would need a precise digital scale to measure a safe dose, the FDA warned.

In other cases, users may not even have access to dose information. For Foote, there was no record of him purchasing the supplement himself, so he likely obtained it from a friend and may have been unaware of how concentrated it was, his father Nigel Foote, told the Blue Mountain Gazette.

“It’s just insane that something so dangerous is so readily available. Please warn your friends, talk to your children, and perhaps check your kitchen cupboards. Pure caffeine powder looks just like any other white powder, but a heaped teaspoon of it will kill you,” he said.

Despite the FDA crackdown, a search for “caffeine” on the website of one of the FDA-cited companies led to a page for “special customers only,” with an unspecified product available in orders of up to 5.5 pounds. The smallest size, 3.5 ounces, is advertised for $16.99. It contains 340 servings — roughly as much as 480 cups of coffee or 10 times a lethal dose.

The risk of caffeine can be be multiplied by other drugs, such as alcohol, that have a negative effect on your heart, lungs, and brain. Exercise also elevates your heart rate and breathing and can compound the side effects of caffeine, added Bonci, who specializes in sports nutrition.

Here’s how much caffeine you can safely consume in a week

Surprising ways that caffeine affects your body and brain

Here’s why caffeine is so addictive — and why it’s so hard to give it up

A sudden jolt from cortisol prompts your blood pressure to rise, heart to beat faster and energy level to soar, which no doubt enabled some early humans to escape a hungry lion in pursuit. Few of us today have to worry about becoming prey to a wild beast. Still, many live in a near-constant state of biochemical stress with the body’s alarm system turned on high all day long.

A constant outpouring of too much cortisol can result in a number of health problems, including anxiety, depression, problems with memory and concentration, trouble sleeping, weight gain and — yes, dear brother — heart disease.

Although the cortisol responses to caffeine are reduced in people who consume it every day, they are not eliminated, a controlled trial by a multidisciplinary research team demonstrated. In a report published in 2005 in Psychosomatic Medicine, the team, led by William R. Lovallo, an expert on stress at the University of Oklahoma Health Sciences Center, concluded that “chronic elevations of cortisol secretion may have implications for long-term health.”

Among the possible harmful effects the team listed are impaired responses by the immune system and central nervous system, memory deficits and changes in the workings of the brain’s frontal lobe and limbic system involved in critical factors like problem solving, judgment, motivation, attention, memory, learning, emotions and empathy.

For those at risk of heart disease, perhaps the most serious adverse effect of excessive caffeine consumption is its ability to raise blood pressure. As Dr. Lovallo’s team reported, “daily caffeine intake does not abolish the blood pressure response to caffeine” even in healthy young men and women.

Other studies have shown that in people with hypertension or at risk of developing it, cortisol responses to caffeine are exaggerated. In an earlier study, Dr. Lovallo and colleagues found that “borderline hypertensives and those with a positive family history have more rapid and prolonged cortisol responses to caffeine than do low-risk persons.”

My brother has long been treated for hypertension and is now very conscientious about staying on a low-sodium diet. But maybe it would be even more helpful if he also reduced the amount of caffeine he regularly consumes, replacing some of that caffeinated coffee with decaf, a suggestion he categorically rejected when I offered it.

Coffee consumption and coronary heart disease risk

The majority of studies on coffee and coronary heart disease (CHD) found no association between coffee consumption and coronary heart disease. However, there is considerable variation between the studies, for both statistically significant inverse and positive associations. Some studies observed statistically significant inverse associations, particularly for women10,11. A U-shaped association has also been reported12.

Meta-analyses have suggested there is either no association between CHD and coffee intake; or a potential protective effect:

  • A 2009 meta-analysis of 21 prospective cohort studies on coffee consumption and coronary heart disease showed variation between the results of the individual cohort studies, with two studies reporting a positive correlation, and two a negative correlation both for the group who drank 4-6 cups of coffee per day and for those who drank more than cups per day10. However, the overall evaluation did not show a statistically significant association between coffee drinking and long-term risk of coronary heart disease. In addition, habitual moderate coffee consumption was associated with a lower risk in women.
  • A meta-analysis published in 2013 suggested a small protective effect (5% risk reduction) of coffee consumption on CHD2.
  • A 2014 meta-analysis of 36 studies with 1,279,804 participants and 36,352 CVD cases concluded that coffee consumption was associated with small reduction in CHD risk. The authors suggested an 11% risk reduction at lower coffee intakes (1.5 cups per day) and a 7% risk reduction at higher coffee intakes (5 cups per day)5.

A number of studies have considered coffee and coronary heart disease, also suggesting overall that there is no association with CHD, and indeed in some cases a protective benefit was observed at moderate coffee intakes:

  • A Japanese study followed 37,742 participants over 10 years, with 426 deaths from cardiovascular disease and 2,454 deaths from all causes. The study observed statistically significant inverse associations between coffee consumption and both mortality from all causes as well as mortality from coronary heart disease in women. In men, no association with coronary heart disease was seen11.
  • A Dutch study followed 37,514 participants over 13 years with 1,387 cases of coronary heart disease. For coffee consumption, a U-shaped association with slightly reduced risk for coronary heart disease was observed, with the lowest risk in the group seen at 2-3 cups per day12.
  • A Swedish study assessed 37,315 male participants over 9 years with 784 cases of heart failure. In this study, coffee consumption was not associated with incidence of heart failure, including those consuming more than five cups per day14.
  • A further Swedish study, using case-control instead of the prospective cohort design and smaller in size (375 cases of first myocardial infarction), observed a statistically significant positive association but only for filtered coffee in men. In women, no association reached statistical significance15.

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Coffee and Your Heart: Stimulant or Stressor?

These are just the latest in a string of positive research findings. For example, an analysis published in 2013 in Circulation compiled the results of 36 studies on coffee that included more than one million patients. Researchers concluded that people who drank coffee in moderation were significantly less likely to develop cardiovascular disease than those who didn’t drink coffee. Again, the review showed that three to five cups offered the greatest level of protection. Additionally, an analysis published in 2012 in Circulation: Heart Failure of five clinical studies, including more than 140,000 patients, found that those who drank four cups of coffee daily were least likely to develop heart failure.

What Is It About Coffee That Affects Your Heart?

Coffee’s heart-health perks may be related to naturally-occurring compounds in coffee beans other than caffeine. Coffee contains hundreds of unique phytochemicals that may help reduce inflammation, which is good news for your heart, says Jellis, because, “There’s thought to be an inflammatory component underlying some causes of heart failure, atherosclerosis, and other conditions, so the anti-inflammatory properties of coffee compounds may be contributing to the perceived long-term benefits in terms of cardiovascular disease.”

But if you’re anxiety-prone, even drinking coffee in moderation may not be healthy for you. “If individual patients feel they’re having cardiovascular symptoms that are worsened with coffee — most commonly palpitations or feelings of being anxious — the common-sense advice is to go decaf,” says N. A. Mark Estes, MD, director of the New England Cardiac Arrhythmia Center at Tufts Medical Center in Boston.

Caffeine and Your Blood Pressure

Studies investigating the effect of coffee on blood pressure have yielded varied results. In general, caffeinated coffee causes a short-term spike in blood pressure in people who don’t drink it regularly. This is because caffeine stimulates the heart and blood vessels, according to the Mayo Clinic. In a 12-year study of more than 1,000 people ages 18 to 45 who had high blood pressure, those who drank four or more cups of coffee per day were four times more likely to have a heart attack or stroke. In contrast, long-term studies have shown that most people develop a tolerance to caffeine over time. Reviews of numerous studies show coffee drinkers were no more likely to develop hypertension than abstainers, and those who already had high blood pressure were no more likely to develop cardiovascular disease.

Some people are more sensitive to caffeine-induced stress than others, and evidence suggests genetic differences are at play. In a study of more than 2,000 heart attack cases published in The Journal of the American Medical Association, people who were slower to metabolize caffeine — because of their genes — were found to be more likely to have heart attacks.

RELATED: 9 Healthy Reasons to Indulge Your Coffee Cravings

“I do think there may be a small subgroup of people with hypertension in whom caffeine should be restricted,” says Dr. Estes, emphasizing the need for individualized recommendations.

You can use a standard home blood pressure monitor to gauge your personal caffeine tolerance and how it affects your blood pressure; test and record your numbers before and a few hours after morning coffee. After a couple weeks of cutting back on coffee, do the test again and then review the results with your healthcare provider.

If you do choose to give up caffeinated coffee to help lower your blood pressure, experts recommend curtailing intake gradually to avoid unpleasant caffeine withdrawal symptoms, such as headaches, fatigue, and mood changes.

Caffeine and Your Heart Rhythm

In a large review of studies published in 2013 in Heart that included more than 115,000 people, researchers found that drinking coffee didn’t raise the risk of irregular heartbeat, including the most common type, atrial fibrillation.

Still, many physicians advise patients with heart arrhythmias to limit their intake of caffeinated beverages or to avoid them altogether. But Estes suggests an individualized approach. You may be able to enjoy a few cups of coffee daily if it doesn’t appear to worsen your arrhythmia symptoms, he says.

If you want to do everything possible to keep your heart arrhythmia from negatively affecting your quality of life, Estes recommends switching to decaf coffee. But take this step in addition to making other lifestyle changes: getting regular exercise, following a healthy diet, drinking alcohol only in moderation (if at all), and losing weight if you’re overweight or obese.

Avoid caffeinated energy drinks if you have an abnormal heart rhythm or a history of cardiovascular disease. Unlike coffee, energy drinks combine high doses of caffeine with herbal extracts and potentially dangerous ingredients. “There are clearly many patients in whom arrhythmias worsen related to taking these drinks,” Estes cautions.

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