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A study published in Journal of the American Heart Association looks at coffee and green tea consumption, and cardiovascular disease mortality among people with and without hypertension.
Prof Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:
“This study suggests a marginally statistically significant relationship between high coffee intake and cardiovascular death (CVD) in participants with severe high blood pressure. However, the number of deaths in this category was small and overall in the whole group there was no association between coffee intake and CVD death. Consequently, the finding could be a play of chance resulting from data dredging.
“The study was a long term follow up of Japanese participants and only one estimate of coffee intake was made at baseline whereas the follow up was for 19 years. A more reliable estimate of coffee intake would have been to estimate intakes at 5 year intervals during follow up, as has been done in the more robust prospective studies in the US where coffee is more widely consumed. These find no adverse associations with cardiovascular death or risk of heart failure. A U.K. Biobank study which included more participants (468,629 vs 18,600 in this Japanese study) found participants who drank 3 cups of coffee a day had a 17 % lower risk of CVD. This new study, therefore, does not provide evidence of sufficient quality to make specific advice about the coffee intake to individuals with severe high blood pressure.”
Dr Simon Steenson, Nutrition Scientist, British Nutrition Foundation, said:
“Coffee is one of the most widely consumed beverages globally, although the observational research on the potential health effects of coffee consumption has been largely inconsistent. This new study from Japan analysed self-reported data on coffee and tea consumption from 18,609 participants (6,574 men and 12,035 women), aged between 40 and 79 years at recruitment. The researchers found that there was a 2-fold higher risk of death from cardiovascular disease after almost 19 years of follow up among those who had more severe (grade 2 or 3) hypertension, but not among those people who fell into other blood pressure categories.
“This new study adds to our current knowledge of the relationship between coffee and tea consumption and heart health by investigating how health effects may differ according to whether a person has hypertension (high blood pressure) or not. Although the researchers suggest that their results may caution against drinking a high amount of coffee for those with high blood pressure, there are a number of things to bear in mind when considering this new research. Firstly, the adults who took part lived in Japan, and so the results might not be applicable to other populations in countries such as the UK, due to differences in other aspects of diet and lifestyle. Also, the results contradict other studies that have suggested drinking coffee may have a protective effect on heart health. For example, a study published earlier this year using data from just under 450,000 UK adults reached the opposite conclusion – suggesting that 2-3 cups of instant, ground or decaffeinated coffee each day was associated with a significantly lower risk of cardiovascular disease (including death from cardiovascular disease). There are a number of potential reasons for this inconsistency, including differences in the people who were studied, how coffee intake was assessed, and the statistical methods used to analyse the data.
“A limitation of this new study from Japan is that coffee consumption was only asked about within the baseline questionnaire when participants enrolled in the study, and so this may have changed over time. Moreover, blood pressure was only measured at the start of the study and so may have changed when participants were followed up. Also, while the number of daily cups of green tea was divided into categories from ‘none’ to ‘7 or more’ cups per day, there were fewer categories for coffee consumption (from ‘none’ to ‘two or more’ cups per day). As a result, the relationship between green tea drinking and cardiovascular death may have been assessed in more detail than for coffee. However, as with all dietary questionnaires, the information is self-reported and so relies on people accurately judging and reporting their level of consumption and, when the questionnaire is not repeated over time, it is hard to know whether dietary habits change.
“These new findings do suggest that more research into the health effects of coffee consumption among people with high blood pressure is justified. However, it is important to remember that there are many other lifestyle factors that can help determine our risk of high blood pressure and heart disease. Aiming for a healthy body weight, finding ways to stay more physically active, and cutting down on the amount of salt in our diets, are all changes we can make to help reduce blood pressure, one of the major risk factors for heart disease.”
‘Coffee and Green Tea Consumption and Cardiovascular Disease Mortality Among People With and Without Hypertension’ by Masayuki Teramoto et al. was published in Journal of the American Heart Association at 10.00am UK time on Wednesday 21 December 2022.
DOI: 10.1161/JAHA.122.026477
Declared interests
Prof Tom Sanders: “No conflicts of interest.”
Dr Simon Steenson: “Funding to support the British Nutrition Foundation’s charitable aims and objectives comes from a range of sources including membership, donations and project grants from food producers and manufacturers, retailers and food service companies, contracts with government departments; conferences, publications and training; overseas projects; funding from grant providing bodies, trusts and other charities. Further information about the British Nutrition Foundation’s activities and funding can be found at http://www.nutrition.org.uk/aboutbnf/.”