Drinking two or more cups of coffee a day linked to cardiovascular disease mortality among people with severe hypertension

Drinking two or more cups of coffee a day may double the risk of death from cardiovascular disease among people with severe high blood pressure (160/100 mm Hg or higher) but not people with high blood pressure not considered severe, according to research published today in the Journal of the American Heart Association, an open access, peer-reviewed journal of the American Heart Association.

In contrast, the study found that one cup of coffee and daily green tea consumption did not increase the risk of death related to cardiovascular disease at any blood pressure measurement, though both drinks contain caffeine. According to the FDA, an 8-ounce cup of green or black tea has 30-50 milligrams of caffeine, and an 8-ounce cup of coffee has closer to 80 to 100 milligrams.

Previous research found that drinking one cup of coffee a day may help heart attack survivors by lowering their risk of death after a heart attack and may prevent heart attacks or strokes in healthy individuals. In addition, separate studies have suggested drinking coffee regularly may reduce the risk of developing chronic illnesses, such as Type 2 diabetes and some cancers; may help to control appetite; may help to lower the risk of depression or boost alertness, though it is not clear if this effect is from the caffeine or something else in coffee. On the harmful side, too much coffee may raise blood pressure and lead to anxiety, heart palpitations and difficulty sleeping.

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. 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."

Hiroyasu Iso, M.D., Ph.D., M.P.H., study's senior author, 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

High blood pressure, also known as hypertension, occurs when the force of blood pushing against the walls of blood vessels is consistently too high, making the heart work harder to pump blood. It is measured in millimeters of mercury (mm Hg). The current blood pressure guidelines from the American Heart Association and the American College of Cardiology classifies hypertension as a blood pressure reading of 130/80 mm Hg or higher.

The blood pressure criteria for this study are slightly different from the ACC/AHA guidelines. Researchers classified blood pressure into five categories: optimal and normal (less than 130/85 mm Hg); high normal (130-139/85-89 mm Hg); grade 1 hypertension (140-159/90-99 mm Hg); grade 2 (160-179/100-109 mm Hg); and grade 3 (higher than 180/110 mm Hg). Blood pressure measures in grades 2 and 3 were considered severe hypertension in this study.

Study participants included more than 6,570 men and more than 12,000 women, ages 40 to 79 years at the start of the research. They were selected from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk – a large, prospective study established between 1988 and 1990 of adults living in 45 Japanese communities. Participants provided data through health examinations and self-administered questionnaires assessing lifestyle, diet and medical history.

During nearly 19 years of follow-up (through 2009), 842 cardiovascular-related deaths were documented. The analysis of data for all participants found:

  • Drinking two or more cups of coffee a day was associated with twice the risk of cardiovascular disease death in people whose blood pressure was 160/100 mm Hg or higher compared to those who did not drink any coffee.
  • Drinking one cup of coffee a day was not associated with increased risk of death from cardiovascular disease across any blood pressure categories.
  • Green tea consumption was not associated with an increased risk of cardiovascular disease mortality across any blood pressure categories.

"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."

The study found that people with more frequent coffee consumption were more likely to be younger, current smokers, current drinkers, eat fewer vegetables, and have higher total cholesterol levels and lower systolic blood pressure (top number) regardless of the blood pressure category.

The benefits of green tea may be explained by the presence of polyphenols, which are micronutrients with healthy antioxidant and anti-inflammatory properties found in plants. The researchers noted that polyphenols may be part of the reason only coffee consumption was associated with an increased risk of death in people with severe high blood pressure despite both green tea and coffee containing caffeine.

The research has several limitations: coffee and tea consumption were self-reported; blood pressure was measured at a single point, which did not account for changes over time; and the observational nature of the study could not draw a direct cause-and-effect connection between coffee consumption and cardiovascular disease risk among people with severe high blood pressure.

Further study is needed, researchers said, to learn more about the effects of coffee and green tea consumption in people with high blood pressure and to confirm the effects of coffee and green tea consumption in other countries.


  1. frank kushner frank kushner United States says:

    Another study showed more than one coffee delays dementia with caffene free about 1/2 the benefit. So if normal pressures men 3 and women 2 MAY be optimum. But also be sure Vitamin D-3 isn't low especially if out of sun a lot in winter.

  2. Dwayne Simpson Dwayne Simpson United States says:

    Well I can see this I love my coffee and I love my green tea but I must have at least two cups of coffee a day in the afternoon I drink me some green tea and five cups of water so and I have sleep apnea who can help me and what do that mean

  3. rick gattermeir rick gattermeir United States says:

    I for one must be a mutant. I have been drinking at least 3 pots of coffee daily for about 25 years now. My heart is healthy

  4. Ted Bartlett Video Channel Ted Bartlett Video Channel Philippines says:

    All these comments help to give stress and anxiety which is far more harmful than the supposed effect of drinking coffee

  5. Tom Canty Tom Canty United States says:

    Worst study and title ever. 1. This is stating that “caffeine” is the culprit not coffee. 2. These were self reported stats, which doesn’t account for other factors like “what were they eating with their coffee?” Donuts? This is far from a scientific study/report.

  6. Tom Canty Tom Canty United States says:

    Let me translate the second to last paragraph “this report is worthless and has no basis in science”.

  7. peter dohan peter dohan United States says:

    The title on the smart phone did not include that the increased morbidity was restricted to patients with severe hypertension. From other comments, other missed this key fact. Perhaps your title should begin with: ,"In those with severe hypertension, coffee..." There seems to be a new study weekly on the positive health effects of coffee in the general population. Your style of title left out the most important aspect--the negative findings were restricted to an at-risk subgroup -- hypertensive patients. Happy New Year, Peter H Dohan, MD

  8. Robert Barbosa Robert Barbosa Brazil says:

    The one and only problem with COFFEE consumption is the fact of Quality of the coffee beans, If they are high standards,  you will never ever have any problem whatsoever about your consumption of good quality Coffee.  Just check on for the best brands and origin we have available.  Keep on drinking your Coffee & GET RID OF ALL JUNK FOOD . Rbt. B.

  9. Reba Summers Reba Summers United States says:

    Awhile back they tell us coffee is good for us and good for our heart & blood pressure. NOW they're saying it's NOT, which is it because this back & forth bit is getting OLD! Do these scientists, and doctors know anything anymore? Cause my blood pressure has always been so high since I was little. 200/210, reason why I had my enuyism 6 yrs ago. It took 9 doctors & a month in Vanderbilt hospital to get my pressure down. Still goes up & down. And I'm not over weight I'm actually 145 5'9. So, doctors don't know everything. Just take things in moderation I always say and drink decaf. 😉

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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