Caffeine is one of the most common beverages on the planet. Most people consume it first thing in the morning, in a warm cup, which feels more like a ritual. Surprisingly, it’s difficult to pinpoint exactly how this daily habit affects the heart. Coffee contains much more than just caffeine, from antioxidants to natural oils, making it truly challenging to isolate the effects of individual components. In a new scientific statement from the American Heart Association (AHA), the most compelling available data was compiled, and a figure acceptable to most coffee lovers was established. The study results were published in the journal Circulation. “Caffeine consumption is an integral part of daily life for millions of people, and based on our review of recent research, for most adults, consuming up to 400 mg of caffeine per day, equivalent to up to 5 cups of caffeinated coffee per day without added sugar or fillers, is safe and does not increase the risk of cardiovascular disease,” said Gregory Marcus. “However, high doses of caffeine, such as those found in energy drinks, including energy shots, can have harmful effects on the heart and should be avoided.” People have been using caffeine for a very long time, with records dating back to 2737 BC. Over 60 plants, from cocoa beans to tea leaves, produce this substance naturally. Caffeine reaches nearly every part of the body within an hour of the first sip. In healthy adults, the liver eliminates about half the dose in roughly four to five hours. Genes set the pace, so two people drinking the same cup may experience completely different sensations. Some develop a tolerance over time, while others feel stimulated from a single serving. Short-term doses of caffeine can increase blood pressure, heart rate, and alertness. In some people, this same effect can lead to heart palpitations or poor sleep. The relationship between caffeine and blood pressure takes a curious form. In people with normal blood pressure, consuming one to three cups of coffee per day was associated with a higher likelihood of developing hypertension. More intense regular coffee consumption, more than three cups, indicated an opposite trend. Over time, an established coffee-drinking habit seemed to lower blood pressure rather than raise it. A single strong dose acts differently. One dose of 250 mg sharply increased blood pressure in men already suffering from hypertension. Timing and habit matter just as much as quantity. A body accustomed to caffeine reacts calmly, while one that rarely uses it reacts more strongly. Regular consumption of black coffee continues to be beneficial. In a review of 28 long-term studies, the risk of developing type 2 diabetes decreased by 20–30% among people who drank an average of several cups per day. Stroke follows a similar pattern. An analysis of 20 studies showed that the lowest risk was observed with consuming three to four cups of coffee per day, representing a reduction of nearly 21%. Additionally, coffee consumption is linked to a decrease in rhythm disturbances in the upper chambers of the heart, known as atrial fibrillation. In one randomized study, it was found that people prone to this condition had 39% fewer episodes when they continued to drink caffeinated coffee. Heart failure and artery blockages show a similar pattern. The risk is lowest at about four cups of coffee per day, then rises again when daily intake significantly exceeds that mark. However, not all news is good. The same coffee that seems to calm the upper heart chambers can trigger extra contractions in the lower chambers, called premature ventricular contractions. Cholesterol adds another nuance. A compound called cafestol, found in unfiltered coffee, such as that made in a French press or boiled coffee, raises levels of harmful cholesterol, though a paper filter removes most of it. What goes into the cup also matters. Sugar, flavored syrups, and cream can negate many of the health benefits of plain coffee. Much of this evidence comes from years of observing large groups of people, rather than controlled experiments. This leaves open the possibility that regular coffee drinkers were simply healthier to begin with. Energy drinks and energy shots are a separate category. One shot contains three to four times more caffeine than a regular cup of coffee, all in a tiny volume. At such levels, the consequences become severe. Blood pressure can spike rapidly, sometimes to dangerous values. Even young, healthy people without cardiovascular disease have experienced rhythm disturbances after consuming these products. Doctors have documented such cases in people barely out of their teenage years. Adding ingredients like taurine can accelerate the absorption of caffeine into the blood and intensify its effects. It is this combination that most concerns the group of authors. Caffeine was not included in the American Heart Association’s 2026 dietary guidelines, as the available data was insufficient to make firm recommendations. “Although research suggests that caffeine consumption may be associated with certain cardiovascular benefits in some people, it’s important to remember that there is no one-size-fits-all strategy for safe caffeine intake,” said Marcus. “People’s reactions to caffeine can vary greatly depending on various factors such as age, medication use, underlying health conditions, genetic predisposition, and the body’s metabolic rate.” “What is a reasonable dose for one person may cause unwanted effects in another, such as heart palpitations, anxiety, or sleep disturbances. Therefore, it’s important to pay attention to your body’s response to caffeine and consult with a doctor about what is right for you,” the study authors emphasized.
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