An examination of coffee consumption habits of almost 400,000 people suggests that those habits are largely driven by a person’s cardiovascular health.
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Data from a large population database showed that people with essential hypertension, angina, or cardiac arrhythmias drank less coffee than people who had none of these conditions. When they did drink coffee, it tended to be decaffeinated.
The investigators, led by Elina Hyppönen, PhD, director of the Australian Centre for Precision Health at the University of South Australia, Adelaide, say that this predilection for avoiding coffee, which is known to produce jitteriness and heart palpitations, is based on genetics.
“If your body is telling you not to drink that extra cup of coffee, there’s likely a reason why,” Dr. Hyppönen said in an interview.
The study was published online in the American Journal of Clinical Nutrition.
“People drink coffee as a pick-me-up when they’re feeling tired, or because it tastes good, or simply because it’s part of their daily routine, but what we don’t recognize is that people subconsciously self-regulate safe levels of caffeine based on how high their blood pressure is, and this is likely a result of a protective genetic mechanism, [meaning] that someone who drinks a lot of coffee is likely more genetically tolerant of caffeine, as compared to someone who drinks very little,” Dr. Hyppönen said.
“In addition, we’ve known from past research that when people feel unwell, they tend to drink less coffee. This type of phenomenon, where disease drives behavior, is called reverse causality,” Dr. Hyppönen said.
For this analysis, she and her team used information on 390,435 individuals of European ancestry from the UK Biobank, a large epidemiologic database. Habitual coffee consumption was self-reported, and systolic and diastolic blood pressure and heart rate were measured at baseline. Cardiovascular symptoms at baseline were gleaned from hospital diagnoses, primary care records, and/or self report, the authors note.
To look at the relationship of systolic BP, diastolic BP, and heart rate with coffee consumption, they used a strategy called Mendelian randomization, which allows genetic information such as variants reflecting higher blood pressures and heart rate to be used to provide evidence for a causal association.
Results showed that participants with essential hypertension, angina, or arrhythmia were “all more likely to drink less caffeinated coffee and to be nonhabitual or decaffeinated coffee drinkers compared with those who did not report related symptoms,” the authors write.
Those with higher systolic and diastolic BP based on their genetics tended to drink less caffeinated coffee at baseline, “with consistent genetic evidence to support a causal explanation across all methods,” they noted.
They also found that those people who have a higher resting heart rate due to their genes were more likely to choose decaffeinated coffee.
“These results have two major implications,” Dr. Hyppönen said. “Firstly, they show that our bodies can regulate behavior in ways that we may not realize, and that if something does not feel good to us, there is a likely to be a reason why.”
“Second, our results show that our health status in part regulates the amount of coffee we drink. This is important, because when disease drives behavior, it can lead to misleading health associations in observational studies, and indeed, create a false impression for health benefits if the group of people who do not drink coffee also includes more people who are unwell,” she said.
For now, doctors can tell their patients that this study provides an explanation as to why research on the health effects of habitual coffee consumption has been conflicting, Dr. Hyppönen said.
“Our study also highlights the uncertainty that underlies the claimed health benefits of coffee, but at the same time, it gives a positive message about the ability of our body to regulate our level of coffee consumption in a way that helps us avoid adverse effects.”
“The most common symptoms of excessive coffee consumption are palpitations and rapid heartbeat, also known as tachycardia,” Nieca Goldberg, MD, medical director of the NYU Women’s Heart Program at NYU Langone Health, said in an interview.
“This study was designed to see if cardiac symptoms affect coffee consumption, and it showed that people with hypertension, angina, history of arrhythmias, and poor health tend to be decaffeinated coffee drinkers or no coffee drinkers,” Dr. Goldberg said.
“People naturally alter their coffee intake base on their blood pressure and symptoms of palpitations and/or rapid heart rate,” she said.
The results also suggest that, “we cannot infer health benefit or harm based on the available coffee studies,” Dr. Goldberg added.
The study was funded by the National Health and Medical Research Council, Australia. Dr. Hyppönen and Dr. Goldberg have disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.