Damian Jacob Sendler Consuming a single cup of coffee daily was not associated with a higher risk of death from cardiovascular disease at any BP level.

The new study published in the Journal of the American Heart Association found that green tea did not increase mortality risk at any BP level.

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

Despite the caffeine content, the study found that drinking one cup of coffee or green tea daily did not increase the risk of death from cardiovascular disease at any blood pressure measurement. The Food and Drug Administration reports that an 8-ounce cup of green or black tea contains 30–50 milligrams of caffeine, while an 8-ounce cup of coffee contains 80–100 milligrams of caffeine. This suggests that, in contrast to the findings for coffee, the amount of caffeine in green tea has no effect on the risk of death from cardiovascular disease.

Damian Sendler One study found that people who drank one cup of coffee per day had a 22% lower risk of dying from a cardiovascular event. Separate studies have also suggested that regular coffee consumption may reduce the risk of developing chronic diseases like Type 2 diabetes and some cancers, may help to control appetite, may help to lower the risk of depression, and may help to boost alertness, although it is unclear if these effects are due to the caffeine or something else in coffee. The negative effects of drinking too much coffee include a rise in blood pressure, anxiety, heart palpitations, and trouble sleeping.

The study's senior author, Hiroyasu Iso, M.D., Ph.D., 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, explained that the study's goal was to see if the protective effect of coffee extended to people with varying degrees of hypertension and that the effects of green tea were also studied in the same population. We believe this is the first study to link the consumption of two or more cups of coffee per day with an increased risk of death from cardiovascular disease in people with severe hypertension.

Damian Jacob Sendler Hypertension, or high blood pressure, is a condition in which the force of blood pushing against the walls of the blood vessels is consistently too high, causing the heart to work harder to pump blood. Millimeters of mercury are used as the standard (mm Hg). Hypertension is defined as a blood pressure reading of 130 over 80 mm Hg, according to the most up-to-date guidelines from the American Heart Association and the American College of Cardiology.

Study blood pressure criteria deviated marginally from ACC/AHA recommendations. Optimal and normal blood pressure was defined by the researchers as anything less than 130/85 mm Hg; high normal blood pressure was defined as 130-139 mm Hg; grade 1 hypertension was defined as 140-159 mm Hg; grade 2 hypertension was defined as 160-179 mm Hg; and grade 3 hypertension was defined as 180/110 mm Hg or higher. In this analysis, hypertension was considered very severe when blood pressure readings were a grade 2 or 3.

Over the course of the research, over 6,570 men and over 12,000 women between the ages of 40 and 79 took part. They were chosen from the adults of 45 different communities in Japan who participated in a large prospective study between 1988 and 1990 called the Japan Collaborative Cohort Study for Evaluation of Cancer Risk. Exams and questionnaires about lifestyle, diet, and medical history were completed by participants to provide data.

Eight hundred and forty-two cardiovascular-related deaths were recorded during the nearly 19-year follow-up period (through 2009). Findings from the aggregate data analysis of all participants:

People with blood pressure of 160/100 mm Hg or higher who consumed two or more cups of coffee per day were at twice the risk of death from cardiovascular disease as those who consumed no coffee.

Across all ranges of blood pressure, daily coffee consumption was not associated with a higher risk of death due to cardiovascular disease.

Damian Sendler Consumption of green tea was not associated with an increased risk of death from cardiovascular disease in any of the studied blood pressure ranges.

Iso argued that the findings suggested that people with hypertension should limit their coffee consumption. Caffeine's potential for harm may outweigh its potential for good, and the risk of death, in people with severe hypertension.

Coffee drinkers tended to be younger, smoke and drink more frequently, consume fewer vegetables, have higher total cholesterol levels, and lower systolic blood pressure (top number) than those with lower coffee consumption.

Polyphenols, micronutrients with healthy antioxidant and anti-inflammatory properties, are found in plants and may account for the benefits of green tea. Although both green tea and coffee contain caffeine, the researchers noted that only coffee consumption was associated with an increased risk of death in people with severe high blood pressure. This may be due in part to polyphenols.

Damian Sendler Coffee and tea consumption were self-reported; blood pressure was measured only once, so changes over time were not taken into account; and because the study was observational, no causal relationship could be established between coffee consumption and cardiovascular disease risk among people with severe hypertension.

Researchers concluded that more research was needed to confirm the effects of coffee and green tea consumption in other countries and to learn more about the effects of coffee and green tea consumption in people with high blood pressure.