There have been loads of research done about the benefits of drinking coffee, but you may want to limit yourself to one cup of coffee a day if you have severely high blood pressure, according to a new study.
The study, published in the peer-reviewed Journal of the American Heart Association on Wednesday, found people with hypertension who drink two or more cups of coffee a day could double the risk of dying from a heart attack, stroke or other cardiovascular diseases.
However, drinking just one cup of coffee a day – or green tea – didn’t have the same affect.
Study observed 18,000 people over 20-year period
Researchers came to their conclusion by observing over 18,000 people – 12,035 women and 6,574 men – at the Japan Collaborative Cohort Study for Evaluation of Cancer Risk. The participants ages ranged from 40 to 79 years old when they enrolled in the program in between 1988 and 1990, with their health followed through 2009. Participants also self reported their coffee and tea consumptions during the near 20-year observation.
Since the American Heart Association and American College of Cardiology defines high blood pressure a reading of at least 130 mmHg/80 mmHg, researchers used five categories to classify various blood pressure levels. They were:
- Optimal and normal: less than 130/85
- High normal: 130-139/85-89
- Grade 1 hypertension: 140-159/90-99
- Grade 2 hypertension: 160-179/100-109 (people with blood pressure 160/100 or higher were considered to have severe hypertension0).
- Grade 3 hypertension: 180/110 or higher
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Study: People with normal blood pressure saw no significant effects from coffee
During the observations, 842 people died of a cardiovascular disease. The final observations found:
- People with grades 2 and 3 hypertension had an increased risk of dying of a cardiovascular disease when drinking at least two cups of coffee a day compared to those who didn’t drink coffee.
- People who drank at least two cups and had normal blood pressure, high normal blood pressure or grade 1 hypertension saw no significant effects.
“To the best of our knowledge, this is the first study to find a positive association between heavy coffee consumption and (cardiovascular disease) mortality among people with severe hypertension,” the study says.
Researchers noted those with grade 2 and 3 hypertension didn’t have an increased risk of death when drinking only one cup of coffee or green tea. Although both drinks contain caffeine, researchers believe polyphenols – micronutrients in green tea that have antioxidant anti anti-inflammatory properties – could be a factor.
The authors of the study said more research is needed to confirm the effects coffee has on those with high blood pressure, but for now, they suggest affected people limit their daily intake.
“These findings may support the assertion that people with severe high blood pressure should avoid drinking excessive coffee,” senior study author Dr. Hiroyasu Iso said in a news release.
Follow Jordan Mendoza on Twitter: @jordan_mendoza5.
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