Caffeine is the most widely used stimulant and psychoactive substance in the world, and coffee is where most people consume caffeine. Most adults can safely consume up to 400 mg of caffeine per day (or up to five 8-ounce cups of caffeinated coffee per day), according to a new scientific statement from the American Heart Association. For some people, moderate coffee consumption may also be associated with a lower risk of cardiovascular disease.
The situation changes as the dose increases. Energy drinks that contain concentrated sources of caffeine, especially energy shots, can increase your risk of cardiovascular problems. The study results were published in the American Heart Association’s flagship peer-reviewed journal. circulation In a scientific statement called “Caffeine and Cardiovascular Disease.”
“Caffeine ingested in coffee is an important part of daily life for millions of people, and a review of the latest research shows that for most adults, caffeine intake of 400 mg/day, equivalent to up to five cups of caffeinated coffee per day without added sugar or fillers, is safe and does not increase cardiovascular risk,” said Gregory M. Marcus, MD, MAS, FAHA, Chair of the Scientific Statement Volunteer Writing Group. Professor of Medicine at the University of California, San Francisco, and Associate Director for Cardiology Research at the University of California, San Francisco School of Health. “However, the high doses of caffeine found in energy drinks, including energy shots, can have negative effects on the heart and should be avoided.”
Why caffeine research is complicated
It’s difficult to understand exactly how caffeine affects the cardiovascular system. Although coffee is the main source of caffeine in most studies, coffee contains many other substances that can affect your health. Experimental studies suggest that some bioactive compounds in coffee have antioxidant and anti-inflammatory properties, which may contribute to coffee’s benefits.
It’s also difficult to distinguish the effects of caffeine from those of ingredients commonly added to coffee, such as milk, cream, flavored syrups, and sugar. Most caffeine studies are also observational, so while they can identify associations, they cannot establish cause and effect.
Coffee isn’t the only source of caffeine. Tea, chocolate, soda, energy drinks, and over-the-counter and prescription medications can all add to a person’s daily intake. Researchers say further research is needed to clarify the caffeine content and cardiovascular effects of these other products.
The new statement reviews recent evidence about the possible links between caffeinated coffee and high blood pressure, cholesterol, type 2 diabetes, coronary heart disease, stroke, heart failure, atrial fibrillation, other arrhythmias, and other cardiovascular diseases.
How much caffeine is considered safe?
Based on the latest research included in the review, up to 400 mg of caffeine per day is considered safe for most adults. This amount is equivalent to no more than 3 to 5 (8 ounce) cups of regular caffeinated black coffee (without sugar, sweeteners, flavors, or additives) per day. Regularly brewed non-specialty caffeinated coffee typically contains 9.4 to 20.6 mg of caffeine per fluid ounce.
Drinking caffeinated coffee without added sugar, flavoring, or cream was associated with a lower risk of type 2 diabetes, heart disease, stroke, heart failure, and some irregular heart rhythms.
Randomized trials, considered the most rigorous and reliable research designs, have linked caffeine in coffee to a lower risk of atrial fibrillation. However, the same study also associated a higher risk of premature ventricular beats.
Adding sugar, flavored syrups, milk and/or cream can reduce the potential health benefits of coffee. Researchers say more research is needed to determine exactly how these additives affect health outcomes.
Consuming large amounts of caffeine may pose a greater risk. Levels commonly found in energy drinks, including energy shots, were associated with high blood pressure and arrhythmias. Energy drink shots can contain 40 to 69 mg of caffeine per fluid ounce, which is three to four times more caffeine than regular caffeinated coffee.
How does caffeine work in the body?
Once in the body, the caffeine in coffee is processed by the liver and typically reaches its maximum concentration within about an hour. The rate at which this happens depends on your genetics, metabolism, age, and previous caffeine use.
People who regularly consume large amounts of caffeinated coffee may develop a tolerance over time. Some people experience strong effects with much smaller doses. In the short term, caffeine can temporarily increase blood pressure, heart rate, blood sugar levels, and alertness. In some people, it may cause palpitations and sleep disturbances.
caffeine and blood pressure
Coffee can have different effects on blood pressure depending on how much you drink. Among people with optimal blood pressure, consuming 1 to 3 cups a day was found to increase the risk of developing high blood pressure. Surprisingly, the researchers found that drinking three or more cups a day lowers the risk.
Consuming high doses of caffeine (such as in energy drinks or energy shots) can significantly increase blood pressure. This effect may be particularly concerning for people who already have high blood pressure.
Possible effects on type 2 diabetes
Research shows that caffeinated coffee can temporarily reduce insulin sensitivity. At the same time, regularly drinking caffeinated black coffee (without additives, flavors, or sweeteners) was associated with a lower risk of developing type 2 diabetes.
Scientists don’t yet know whether caffeine plays a role in the association. Other compounds in coffee may be responsible for some or all of the effects. Additional research is needed to distinguish between the effects of caffeinated coffee and the various compounds found in coffee.
Coffee preparation may affect cholesterol
A randomized clinical trial found that cafestol (a substance found in both caffeinated and decaf coffee) is associated with increased levels of low-density lipoprotein (also known as “bad” cholesterol).
Cafestol is present in unfiltered coffee (such as espresso, French press, Turkish coffee, and brewed coffee), but not in coffee made with paper filters or instant coffee. Researchers need to determine which products contain the highest levels of cafestol and how cafestol affects cholesterol.
coffee, caffeine, heart rhythm
A recent analysis based on participant-reported health information found that consuming 1 to 3 cups of caffeinated coffee per day was not associated with an increased risk of atrial fibrillation or heart rhythm abnormalities.
However, the same amount may be associated with more premature ventricular contractions (or PVCs). These are the early beats that begin in the lower chambers of the heart.
Very high doses of caffeine (such as in caffeinated energy drinks or energy shots) are associated with abnormal heart rhythms, even in people who are usually considered to be at low risk for cardiovascular disease, including healthy adults under 30.
heart disease, heart failure, stroke
Drinking two to four cups of caffeinated coffee a day was found to reduce the risk of heart disease, heart failure, and stroke.
However, at higher levels the relationship may change. Consuming four or more cups of caffeinated coffee a day may increase your risk of heart failure.
Not all caffeine sources are the same
Researchers stress that all caffeine products should not be treated as interchangeable. Further research is needed to compare different types of caffeinated coffee with tea, soda, energy drinks, energy shots, and edibles.
Tea has received less research attention than coffee. Still, like caffeinated coffee, tea consumption is associated with a lower risk of atrial fibrillation, heart failure, and stroke.
Energy drinks, bars, gels, and caffeine-based supplements may contain additional ingredients that help your body absorb caffeine faster. These additives can accelerate the action of caffeine, increase blood pressure and increase the risk of cardiovascular problems.
More rigorous research is needed
The writing group called for more randomized controlled trials investigating caffeine in coffee and other caffeine-containing products. Scientists need to understand more clearly why people react differently and how each caffeine source affects cardiovascular health.
The researchers also highlighted the limited evidence available regarding caffeinated energy drinks and other increasingly popular caffeinated products. Caffeine was not included in the Association to Improve Cardiovascular Health’s 2026 Dietary Guidance because there is not yet enough rigorous evidence to establish a formal recommended intake.
“While research suggests that caffeine intake may be associated with certain cardiovascular effects for some people, it is important to remember that there is no ‘one-size-fits-all’ strategy for safe caffeine intake.” “Reactions to caffeine vary widely from person to person, and even doses that are reasonable for one person can cause undesirable effects such as heart palpitations, anxiety, and sleep,” Marcus said.
Main findings
- Current evidence indicates that caffeine intake of up to 400 mg per day (equivalent to five 8-ounce cups of caffeinated coffee per day) is generally safe for most adults. For some people, this level of intake may also be associated with a lower risk of heart failure, heart disease, and stroke.
- Increased intake of caffeine, including the amount found in energy drinks and energy shots, can increase the likelihood of high blood pressure and irregular heart rhythms and arrhythmias.
- Researchers say more evidence is needed to understand how caffeine affects the body, how different sources of caffeine affect heart health, and why the effects vary so widely from person to person.
Co-authors are Vice Chair Frank B. Hu, MD, MPH, Ph.D., FAHA; Dr. Rob M. Van Dam. Dr. Marilyn C. Cornelis. Thomas A. Durand, MD. JungHee Kang, PhD, MPH, RN. Dr. Susannah C. Larson. Robert L. Page II, Pharm.D., M.D., FAHA. and Dr. Niyati Parekh, FAHA. Author disclosure information is provided in the manuscript.
