Just when we thought we had a definitive take on the the risks versus benefits of coffee, along comes a new study that contradicts the prevailing wisdom. So… Where does medical science currently stand?
Jolly young coffee drinkers: Hope none of them suffers from uncontrolled hypertension…
I’m getting jittery just thinking about recent contradicting studies concerning the risks versus benefits of coffee. But I’m – momentarily at least – not sure if I should grab a comforting cup of hot Java to settle my nerves. The latest study says folks who have significantly higher blood pressure than ‘normal’ face twice the risk of death from heart disease as folks with normal BP.
Nearly 20 years of survey stats
A longitudinal survey including more than 6,570 men and more than 12,000 women, aged 40 to 79 years at the start of the research. They were selected from 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.
“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,” explained study senior author Dr. Hiroyasu Iso, professor emeritus at Osaka University”
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.
What they found
According to an abstract of the study findings: “During nearly 19 years of follow-up (through 2009), 842 cardiovascular-related deaths were documented [among participants]. 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 concluded. “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.”
However, the study could 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.
The takeaway
“To the best of our knowledge, this is the first study to find [a LINK] between drinking 2 or more cups of coffee daily and cardiovascular disease mortality among people with severe hypertension,” Iso reported. As usual, he recommends further study.
Curiously, a parallel study of people who drank varying amounts of coffee and those who drank green tea alongside coffee or without any coffee showed that green tea had no effect one way or the other, neither amplifying or mitigating the effects of the coffee. That led to Dr. Iso to conclude that specific flavonols and other compounds found exclusively in coffee might be behind the negative effects.
My take
I was kind of disappointed to hear about the holes in the study already mentioned above. I was particularly surprised to see that Iso failed to comment on any similarities or differences in the reaction to coffee of folks with high BP who had it under control with drugs. I’m going to assume that information was not available over the span of the study.
But the degree of difference in risk of cardio-related death in high-BP folks compared to normal folks was severe enough to compel me to comment – and share the story with you. My conclusion – at least until more information comes in – is to recommend you draw your own conclusions…
A while ago, I made a commitment to drink more Green Tea. I have not succeeded in living up to that promise to the degree I intended to. But I can say, I’ve felt no negative repercussions from the tea – by itself or close to consumption of coffee. I’ll continue working on the commitment to drink more green tea.
~ Maggie J.