Most of the literature shows that coffee is good for you, but it makes sense for patients with high BP to reduce their intake, an expert says.
Drinking several cups of coffee a day may increase the risk of CVD mortality in people with severe hypertension, according to an analysis of a Japanese population.
The increased risk was seen only in those whose blood pressure classified them as grade 2-3 hypertension (160 to > 180 mm Hg systolic or 100 to > 110 mm Hg diastolic, according to European guidelines for 2018) and who self-reported drinking two or more cups of coffee every day.
The researchers, led by Masayuki Teramoto, MD (Osaka University Graduate School of Medicine, Japan), note that for most people in the general population, adverse effects of caffeine such as transient elevation of blood pressure are likely offset by demonstrated protective effects such as lowering serum cholesterol levels and improving endothelial function. However, “the harmful effects of caffeine may outweigh its protective effects and increase the risk of mortality in people with severe hypertension.”
Commenting for TCTMD, Christopher Gardner, PhD (Stanford University School of Medicine, CA), said the literature over the past 20 years has been overwhelmingly positive in demonstrating the health benefits and lack of harm of coffee consumption. That being said, he acknowledged that the new data is sobering.
“I see no reason not to take this seriously enough,” said Gardner, who serves as chair of the American Heart Association’s nutrition committee. Still, the data doesn’t suggest that people with severe hypertension should give up java altogether or lose their morning ritual: they should simply cut back to just one cup a day or consider incorporating tea or decaf. This small change is “not really a request” for someone with a serious health condition like severe hypertension, he said.
That being said, Gardner also pointed out some flaws in the study that need to be addressed. Specifically, the increased risk of CVD mortality associated with two or more cups of coffee per day and grade 2-3 hypertension only applied to 19 of the 18,000 people in the study, a finding that would have been hidden if the researchers had not gone in such conditions. great difficulty in classifying people according to their level of coffee consumption and their degree of hypertension. It also revealed wide confidence intervals, which puts the actual increased risk in heavy RT coffee drinkers potentially as low as 7%.
In light of these issues hampering the interpretation of the study, Gardner said it might be relevant for others like the Nurses’ Health Study or the European Cancer and Nutrition Prospective Survey ( EPIC), for example, to replicate the Japanese analysis in larger, more diverse populations to see if the association holds.
No impact of coffee or tea at lower BP levels
For the study, published online last week in the Journal of the American Heart Association, Teramoto and colleagues looked at data from 18,609 men and women aged 40 to 79 who participated in the Japan Collaborative Cohort Study for Cancer Risk Assessment. These individuals completed a lifestyle, diet, and medical history questionnaire and underwent health examinations beginning in 1988-1990.
Participants were grouped into four BP categories: optimal and normal (< 130 mm Hg systolic/< 85 mm Hg diastolic), high-normal (130-139 mm Hg systolic or 85-89 mm Hg diastolic), grade 1 ( 140-159 mm Hg mm Hg systolic or 90-99 mm Hg diastolic), grade 2 (160-179 mm Hg systolic or 100-109 mm Hg diastolic) and grade 3 (≥ 180 mm Hg systolic or ≥ 110 mm Hg diastolic) . The 2nd and 3rd graders were combined into one cohort due to the small number of students.
Over nearly 19 years of follow-up, 842 deaths have occurred. In people with grade 2-3 hypertension, mortality was not increased with less than one cup of coffee per day compared with no coffee (HR 0.98; 95% CI 0. 67-1.43) or with one cup per day (HR 0.74; 95% CI 0.37-1.46), but was increased with two or more cups per day (HR 2.05; 95% CI 95% 1.17-3.59). Looking across the spectrum of optimal and normal BP, high normal BP, and grade 1 hypertension, no difference was observed in CVD mortality by level of coffee consumption.
Green tea, even at five to six cups per day, showed no impact on mortality at any BP category.
For Gardner, another factor that needs to be brought to light to understand any potential link between coffee consumption and mortality is how much caffeine people drink and what they consider “coffee.” He noted that while ancient coffee studies looked at people who drank mostly black coffee, today’s coffee drinkers may have more sugar and calories in their cup than real coffee.
“Different populations [can] mean different types of coffee. . . and that goes for [assuming] coffee is also beneficial, which I’m a bit wary of people saying,” Gardner added.