- One study found that people with symptoms of cardiovascular health problems, such as angina and heart palpitations, tend to drink less coffee, avoid coffee entirely, or drink decaffeinated coffee.
- Scientists have used a genetic technique to show that these symptoms determine how much coffee people drink, rather than the other way around.
- Research casts doubt on the observational evidence that drinking moderate amounts of coffee can benefit cardiovascular health.
Coffee’s incomparable taste and smell – not to mention its ability to wake people up in the morning – has made it one of the most popular drinks in the world.
Better yet, observational studies indicate that coffee may protect against cardiovascular disease, diabetes, Parkinson’s disease, and some cancers.
However, a new study suggests that some of coffee’s supposed cardiovascular health benefits may have been overstated. The research was limited to white British participants.
Due to the caffeine in coffee, excessive consumption can cause unpleasant symptoms such as tachycardia (rapid resting heartbeat) and palpitations.
Drinking coffee can also cause a moderate and temporary increase in blood pressure.
It may therefore be surprising that regular coffee drinkers have normal or reduced blood pressure compared to people who do not drink coffee.
One explanation may be that coffee drinkers develop a physiological tolerance to the effects of caffeine.
But a new study suggests that people at high genetic risk for cardiovascular disease subconsciously reduce their intake to avoid unpleasant cardiovascular symptoms.
Research found that people with high blood pressure, angina, or arrhythmia drank less caffeinated coffee and were more likely to drink decaffeinated coffee.
Importantly, there was strong evidence that their genetic vulnerability to cardiovascular disease led to a reduction in their coffee consumption.
This rules out the alternative explanation that consuming less coffee made them more vulnerable to cardiovascular disease.
Researchers at the University of South Australia in Adelaide conducted the study, which appears in
“If your body tells you not to drink that extra cup of coffee, there’s probably a reason for it,” she adds. “Listen to your body – it’s more in tune with your health than you might think.”
In observational studies, this effect could give the false impression that coffee prevents high blood pressure and protects the heart.
In fact, people vulnerable to high blood pressure may simply avoid drinking coffee because, for them, caffeine is more likely to cause unpleasant symptoms.
Scientists drew on information from 390,435 white British participants aged 39 to 73 who are part of a medical and genetic database called UK Biobank.
During recruitment, participants declared their regular coffee consumption. The researchers also measured their blood pressure and heart rate and noted any cardiovascular symptoms.
Participants with high blood pressure, angina, or arrhythmia consumed less caffeinated coffee than those without these symptoms.
To determine if regular coffee consumption caused the symptoms or if the symptoms caused a reduction in coffee consumption, the researchers used a statistical technique called
This technique exploits the random inheritance of genetic variants that increase a person’s risk of a particular outcome later in life – in this case, the association between blood pressure and heart rate with habitual coffee consumption. .
Because factors, such as lifestyle or diet, cannot alter a person’s genetic sequence, any associations researchers find must be due to genetic variants rather than other factors.
When they analyzed the data, it showed that having a particular genetic variant determined how much coffee a person drank.
“This means that someone who drinks a lot of coffee is probably more genetically tolerant of caffeine than someone who drinks very little,” says Professor Hyppönen.
“Conversely, a drinker without coffee, or a person who drinks decaffeinated coffee, is more susceptible to the side effects of caffeine and more sensitive to hypertension,” she adds.
“This is not something that we looked at in our study, but any unpleasant sensations experienced by an individual in response to coffee consumption is likely to reduce their desire to drink coffee,” Professor Hyppönen said.
MNT asked Dr Edo Paz, a doctor with digital primary care platform K Health, about the effects of drinking too much coffee.
He has answered:
« [D]drinking too much coffee can lead to headaches, anxiety, tremors, and difficulty sleeping. With regard to the heart, in particular, excessive coffee consumption can lead to palpitations and trigger cardiac events, such as abnormal heart rhythms, in sensitive people.
The results of the new research suggest that observational studies that have found an association between coffee consumption and better health may fall prey to “reverse causation.”
In other words, heart health issues have led people to drink less coffee, rather than the other way around.
Professor Hyppönen said Mendelian randomization studies cast doubt on other apparent protective effects.
For example, epidemiological studies have led people to conclude that moderate alcohol consumption protects against cardiovascular disease, and that being overweight reduces mortality compared to moderate weight.
“According to [Mendelian randomization] studies, there does not seem to be any benefit to be had [excess weight] against [slim or moderate] weight, with the possible exception of smokers, ”she said.
Smoking reduces appetite and therefore weight, but it also has links with a wide range of negative health effects.
“Also for alcohol, [the] the evidence suggests linear increases in blood pressure and stroke risk, with no benefit for light alcohol consumption, ”she added.
While more studies are needed with a more diverse population, this study suggests using a thoughtful and personalized approach when promoting high coffee consumption.