NEW YORK, Aug. 17 (UPI) — Growing interest in the harmful effects of caffeine on blood pressure and heart rate sparked Nency Kagathara’s curiosity to investigate the damage it can cause to cardiovascular health.
The Indian medical student then found in a study she led that daily consumption of more than 400 milligrams of caffeine on most days of the week can increase the risk of cardiovascular disease in otherwise healthy people.
“There is a gradual increase in the burden of non-communicable diseases such as hypertension,” or high blood pressure, Kagathara, a second-year student at Zydus Medical College and Hospital in Dahod, Gujarat, India, told UPI via email.
Explaining her research, Kagathara said: “Some of the risk factors for high blood pressure are known, such as older age, genetic predisposition, obesity and a high-sodium diet. Caffeine consumption, on the other hand, is not yet recognized.”
She will present the study’s results on Saturday at the American College of Cardiology’s Asia 2024 conference in Delhi, India.
“Chronic consumption of caffeine and caffeinated beverages sensitizes the autonomic nervous system to the effects of caffeine, resulting in sustained increases in heart rate and blood pressure over time,” Kagathara and her colleagues wrote in the abstract of their presentation.
“This prolonged modulation can contribute to cardiovascular problems such as high blood pressure and an increased risk of cardiovascular events.”
High blood pressure is associated with an increased risk of coronary heart disease, heart failure, chronic kidney disease and dementia.
The researchers defined chronic caffeine consumption as the consumption of caffeinated beverages five days per week for more than a year. Their study focused on tea, coffee and carbonated drinks such as Coca-Cola, Pepsi, Red Bull, Sting and Monster.
“This study complements previously published studies that have found similar results,” said Dr. Eugene Yang, co-chair of the conference.
However, “nothing is yet known about the long-term effects of high caffeine consumption and cardiovascular events,” said Yang, professor of clinical medicine in the department of cardiology at the University of Washington School of Medicine in Seattle.
For this study, the researchers randomly recruited 100 healthy individuals aged 18 to 45 years. They measured the participants’ blood pressure and pulse and collected data on sociodemographic characteristics and daily caffeine intake.
Participants then completed a three-minute step test, followed by blood pressure and heart rate measurements one minute and five minutes after the test.
A total of 92 participants completed the study; the majority were male (62%), older than 30 years (60%), and lived in urban areas (79.3%).
19.6% of participants consumed more than 400 mg of caffeine daily – equivalent to four to five cups of coffee.
Women, people in commercial or managerial positions, and those living in urban areas showed significant associations with higher daily caffeine intake.
A 230-ml cup of coffee contains between 95 and 200 mg of caffeine, a 340-ml can of cola contains 35 to 45 mg, a 230-ml energy drink contains 70 to 150 mg and a 230-ml cup of tea contains 14 to 60 mg, Kagathara estimated.
The U.S. Food and Drug Administration recommends that healthy adults consume no more than 400 mg of caffeine per day.
In the study, daily consumption of more than 600 mg of caffeine was strongly correlated with increased heart rate (100 beats per minute) and increased blood pressure (over 140/90 mmHg) after five minutes of rest following a three-minute step test.
This test is designed to measure aerobic fitness by measuring how quickly the heart rate recovers after exercise. “The more aerobically fit you are, the faster your heart rate will return to normal after exercise,” Kagathara said.
Frequent consumption of more than 600 mg of caffeine per day can have long-term effects, such as increased anxiety, insomnia, bone weakness and fractures, and hyperacidity, she noted, adding that sweating and heart palpitations may also occur.
In addition, Kagatharashe pointed out that people in older age groups may suffer from cardiovascular diseases, which could affect their heart rate and blood pressure during a step test.
“If a person has a cardiovascular disease — such as high blood pressure that requires medication or a previous heart attack or stroke — or is sensitive to caffeine, it’s wise to consume only small amounts or avoid it altogether,” said Dr. Usman Baber, chief of the cardiovascular disease division at OU Health in Oklahoma City. He was not involved in the study.
“Overall, this study shows that caffeine consumption above a certain threshold actually increases heart rate and blood pressure, which is not surprising since caffeine is a stimulant,” Baber said.
However, he pointed out that the number of participants was too small to draw any firm conclusions.
In addition to the amount of caffeine, other factors may have influenced the study’s results, such as whether participants who consumed more caffeine were less physically fit, says Dr. Gregory Marcus, chair-elect of the American Heart Association’s Committee on Drugs, Alcohol and Tobacco.
“The amount of caffeine affects different people differently,” he said. “Each of us has a set of genes that determine how quickly or slowly we metabolize caffeine,” said Marcus, who is also a cardiologist and professor of medicine at the University of California-San Francisco.
He added: “While some people may experience a worsening of high blood pressure, others may even experience a reduction in blood pressure due to its diuretic effect.”
Dr. Jacqueline Hollywood, a cardiologist at Hackensack University Medical Center in Hackensack, New Jersey, said the stimulating effects of caffeine are often felt within a few minutes but can last for many hours.
“While moderate caffeine consumption is generally safe for healthy adults, excessive intake can have negative effects on heart rate and blood pressure,” Hollywood said.
To reduce potential risks, she recommends that people with existing cardiovascular disease regularly monitor their heart rate and blood pressure, especially after consuming caffeine.
“Individuals who have concerns about caffeine consumption or its effects on heart health should seek personal advice from a healthcare professional,” Hollywood said.
