Drinking two or more cups of coffee per day may significantly raise the risk of heart disease-related death in some patients, a study suggests.
Japanese researchers found people whose blood pressure was above 160/100 mmHg – considered extremely high – were twice as likely to die from a cardiac issue compared to people with lower levels.
Interestingly, the raised risk did not apply to people with high blood pressure not considered severe.
Whether or not coffee is good for health has long been debated by scientists. Previous studies have found that multiple cups of coffee each day could reduce all-cause mortality, while others have linked the brew to cancer.
Researchers found that people with a blood pressure of more than 180/100mmHg were twice as likely to die of heart disease if they drank two cups of coffee each day (file photo)
Caffeine, the most notable ingredient in coffee, is known to increase a person’s blood pressure and heart rate for a temporary period of time.
It is still unclear whether consistent coffee drinking can cause long-term increases in blood pressure, cholesterol or other harmful effects to the heart.
There are also outside factors at play with coffee drinking that can cloud these types of studies, like how much sugar or milk a person puts in their drink.
The research team cites previous studies, where a person who had survived a heart attack could prevent future complications with a cup each day.
They also note previous research linking the morning brew to a reduced risk of chronic illnesses like type 2 diabetes and cancers.
‘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,’ Dr Hiroyasu Iso, a researcher from the center, said in a statement.
‘To the best of our knowledge, this is the first study to find an association between drinking two or more cups of coffee daily and cardiovascular disease mortality among people with severe hypertension.’
Researchers, who published their findings Wednesday in the Journal of the American Heart Association, gauged how drinking coffee and green tea each day could impact heart health.
The study included nearly 20,000 participants, with over 12,000 women and more than 6,570 men living in Japan from 1990 to 2009.
Data was gathered from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk, an annual study that determines risk of cancer-based on lifestyle choices.
As part of the yearly survey, participants would report their dietary habits, like how much coffee they drank each day.
They would also report health conditions they had been diagnosed with, including hypertension.
Researchers split the sample population into five groups. The first group was the optimal group, with a healthy blood pressure of 130/85mmHg.
The second was a group with higher, but still healthy, blood pressure at 130/85mmHG.
Anyone with a blood pressure higher than 140/90mmHG was considered to have hypertension.
Sufferers with a blood pressure below 160/100mmHG were placed in category 1, and those higher than category 1 but below 180/110mmHG were in category 2.
Any participant with a blood pressure more than 180/110mmHG was placed into category 2.
Coffee consumption had no link to heart disease mortality in each group other than category 3. Green tea had no link to cardiovascular death in any of the groups.
For the group with the highest blood pressure, researchers found that drinking two cups of coffee each day raised risk of heart disease death over the study period two-fold.
Interestingly, there was no notable increased risk for people who drank only one cup.
‘These findings may support the assertion that people with severe high blood pressure should avoid drinking excessive coffee,’ Dr Iso went on to say.
‘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.’
People who drank more coffee were also more likely to be younger, smokers, drinkers, have higher cholesterol, lower blood pressure and worse diets.
The Centers for Disease Control and Prevention (CDC) reports that 45 percent of US adults have uncontrolled hypertension – at least 140/90mmhg or higher – which would put then in at least category 1 in this study.
There is no data on how many Americans have blood pressure higher than 180/110mmHg.
High blood pressure can damage arteries and blood vessels throughout the body. Over time, this can lead to less oxygen-rich blood making its way to the heart.
This can lead to severe complications like heart disease, stroke, a heart attack or heart failure.
