When you wake up in the morning, you may be desperate for that cup of joe (or three) to kick off your day. But a new study says overdoing in on caffeine could have implications for your heart.
Zydus Medical College and Hospital in Dahod, India, released their findings, saying regularly drinking more than 400 mg of caffeine daily could increase the likelihood that otherwise healthy individuals will develop the disease. Per the Mayo Clinic, 400 mg is the equivalent of around four cups of brewed coffee, two energy drinks, or ten cans of soda.
The small study looked at 92 healthy people between 18 and 45 years old, 19.6% of whom were considered chronic caffeine users. Researchers discovered that those consuming over 400 mg of caffeine each day had elevated blood pressure and heart rates. This effect was even more pronounced in those consuming 600 mg daily—the equivalent of six to seven cups of brewed coffee.
The study’s authors say caffeine’s impact on the autonomic nervous system (which helps to control things like blood pressure and heart rate) could put undue stress on the heart and other body parts.
Hypertension, also known as high blood pressure, increases the risk of health issues, including heart failure, heart attacks, strokes, chronic kidney disease, and aneurysms — and is often called the “silent killer.”
What do experts say?
Caffeine is a stimulant. Associate professor of pharmacology and toxicology at Michigan State University, Dr. Jamie Alan, said consuming caffeine “will increase heart rate, open up the lungs and increase wakefulness.” That is why many reach for a coffee first thing in the morning.
According to the Mayo Clinic, caffeine might also raise blood pressure — although it may be temporarily. Contrary to the study’s findings, this effect is seen more commonly in individuals who don’t regularly consume caffeine and, therefore, haven’t developed a tolerance for the stimulant. While it remains unclear why some people experience this, some researchers believe it might be related to caffeine causing the adrenal glands to release more adrenaline (increasing blood pressure) or a hormone that blocks caffeine and causes arteries to widen. Despite this, people with high blood pressure aren’t typically advised to cut caffeine out completely.
Professor of medicine at the University of California, San Francisco, and cardiologist Dr. Gregory Marcus says these findings remind us that substances commonly consumed, like caffeine, could affect our blood vessels and heart. However, he notes that it’s possible the effects attributed to caffeine could have been caused by other factors, like fitness levels or age.
“It is important to remember that while blood pressure and heart rate are important determinants of health, the best way to determine health effects is to examine actual cardiovascular outcomes, such as rates of stroke, heart attack, and heart rhythm disturbances,” says Marcus.
Other studies have suggested that coffee could be beneficial for the heart. For example, one study from 2023 discovered that regular coffee consumption is associated with a decreased risk of hypertension, atrial fibrillation, and heart failure. Research from 2021 additionally found that caffeinated coffee may reduce the risk of heart failure.
What is too much caffeine?
Family medicine specialist Dr. Brynna Connor said the Food and Drug Administration recommends no more than 400 mg of caffeine daily. “Anything beyond that is considered too much, and people may start to experience symptoms such as headaches, irritability, and jitters,” says Connor.
However, she adds, the severity of these symptoms is dependent on each individual’s sensitivity to caffeine and how rapidly it is metabolized. “While the average half-life of caffeine is between three and seven hours, people with a slower metabolism or liver problems may experience the effects of caffeine longer and more acutely, as the stimulant would take longer to pass and subsequently stay in their bloodstream longer.”
Connor warns that caffeine in quantities of 1,200 mg, particularly if consumed in a short amount of time, can be “toxic and lead to severe side effects such as seizures.” That’s the equivalent of 12 to 15 cups of coffee—or around three of Panera’s Charged Lemonades, which are now discontinued.
Marcus states that it’s difficult to say what amount of caffeine is universally applicable because tolerance of caffeine varies significantly among individuals due to genetic variants that cause us to break down caffeine at different speeds and the amount of caffeine we consume regularly.
Individuals who regularly consume caffeine become more tolerant of its effects because our bodies ramp up the systems that rid the body of caffeine, explains Marcus. He says someone who doesn’t drink much caffeine may feel sick after drinking only one espresso. Still, an individual who drinks caffeinated beverages regularly might experience minimal effects even after numerous cups of coffee.
“Ultimately, individuals should listen to their body and learn to recognize the amount of caffeine for them that results in uncomfortable sensations, such as feeling tremulous or shaky, nervous or experiencing a racing heart,” says Marcus.
