According to new research, drinking more than one cup of coffee per day may double the risk of death from cardiovascular disease in people with severe high blood pressure. The American Heart Association published the findings of the study in their Journal, which is an open-access, peer-reviewed journal of the American Heart Association.
However, the study indicated that drinking one cup of coffee or one cup of green tea every day did not raise the risk of dying from cardiovascular disease at any blood pressure measurement despite the fact that both beverages contain caffeine. The U.S. Food and Drug Administration estimates that a cup of green or black tea contains 30 to 50 milligrams of caffeine, whereas a cup of coffee contains more like 80 to 100 mg.
Earlier researches found that drinking one cup of coffee a day may help heart attack survivors by lowering their risk of the death after a heart attack and may prevent heart attacks or strokes in healthy individuals. Other studies have suggested drinking coffee regularly may reduce the risk of developing chronic illnesses, such as Type 2 diabetes and some cancers, and so many illnesses, but it is not clear if this effect is from the caffeine or something else in coffee. On the other hand, too much coffee may raise blood pressure and heart palpitations, lead to anxiety and difficulty in sleeping.
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).
The Blood pressure measures in grades 2 and 3 were considered severe hypertension in this study.