In persons with severe high blood pressure (160/100 mm Hg or above), but not in those with high blood pressure, two or more cups of coffee per day may increase the risk of mortality from cardiovascular disease. The study’s results were published in the open-access, peer-reviewed Journal of the American Heart Association, a publication of the American Heart Association. Nevertheless, the study found that consuming one cup of either coffee or green tea per day did not increase the risk of dying from cardiovascular disease at any blood pressure measurement, despite the fact that both drinks contain caffeine.
According to the FDA, a cup of green or black tea has between 30 and 50 milligrammes while a cup of coffee has more like 80 to 100. One cup of coffee per day may lessen the chance of mortality for heart attack survivors, according to prior study, and it may also help healthy people avoid heart attacks or strokes. Additionally, various studies have suggested that drinking coffee regularly may lower the risk of contracting chronic diseases like Type 2 diabetes and some cancers, may aid in appetite control, may lessen the risk of depression, or may increase alertness, though it is unclear whether these effects are due to the caffeine in coffee or something else.
On the negative side, drinking too much coffee can increase blood pressure, cause anxiety, heart palpitations, and make it harder to fall asleep.
“Our study aimed to determine whether the known protective effect of coffee also applies to individuals with different degrees of hypertension; and also examined the effects of green tea in the same population,” explained the study’s senior author Hiroyasu Iso, M.D., PhD, M.P.H., director of the Institute for Global Health Policy Research, Bureau of International Health Cooperation, National Center for Global Health and Medicine in Tokyo, Japan, and professor emeritus at Osaka University. “To the best of our knowledge, this is the first study to find an association between drinking 2 or more cups of coffee daily and cardiovascular disease mortality among people with severe hypertension.”
When the amount of blood pushing against the blood vessel walls is continually too high, high blood pressure, also known as hypertension, results, making the heart work harder to pump blood. Mercury millimetres are used to measure it (mm Hg). According to the American College of Cardiology and American Heart Association’s most recent blood pressure recommendations, hypertension is defined as a level of 130/80 mm Hg or greater.
The study’s blood pressure requirements varied somewhat from the ACC/AHA recommendations. The ideal and normal blood pressure range is less than 130/85 mm Hg; high normal is between 130 and 139/85 and 89 mm Hg; grade 1 hypertension is between 140 and 159/90 and 99 mm Hg; grade 2 is between 160 and 179/100 and 109 mm Hg; and grade 3 is over 180/110 mm Hg. In this study, blood pressure readings in grades 2 and 3 were regarded as severe hypertension.
More than 12,000 women and over 6,570 men, aged 40 to 79 at the commencement of the study, participated in it. They were chosen from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk, a sizable prospective study of individuals residing in 45 Japanese municipalities that was conducted between 1988 and 1990. Through health exams and self-administered questionnaires examining lifestyle, food, and medical history, participants gave data.
Through 2009, almost 19 years of follow-up, 842 cardiovascular-related fatalities were recorded. Data analysis for all participants revealed the following:
1. People whose blood pressure was 160/100 mm Hg or greater were twice as likely to die from cardiovascular disease when they drank two or more cups of coffee per day compared to those who did not.
2. Regardless of blood pressure category, consuming one cup of coffee per day was not linked to a higher risk of dying from cardiovascular disease.
3. Regardless of blood pressure category, green tea drinking was not linked to an increased risk of cardiovascular disease death.
“These findings may support the assertion that people with severe high blood pressure should avoid drinking excessive coffee,” said Iso. “Because people with severe hypertension are more susceptible to the effects of caffeine, caffeine’s harmful effects may outweigh its protective effects and may increase the risk of death.”
Regardless of blood pressure group, the study revealed that those who drank coffee more frequently were more likely to be younger, current drinkers and smokers, consume less vegetables, had higher overall cholesterol levels, and have lower systolic blood pressure (top number).
The presence of polyphenols, which are micronutrients with advantageous antioxidant and anti-inflammatory effects found in plants, may help to explain the advantages of green tea. Although both green tea and coffee contain caffeine, the researchers emphasised that polyphenols may play a role in why only coffee intake was linked to a higher risk of mortality in those with severe high blood pressure.
The study has several limitations, including the self-reporting of coffee and tea consumption, the use of a single point of measurement for blood pressure that did not account for changes over time, and the observational design that precluded the creation of a cause-and-effect relationship between coffee consumption and the risk of cardiovascular disease in individuals with extremely high blood pressure.