Drinking two to three cups a day was associated with greatest heart benefits
American College of Cardiology
These trends held
true for both people with and without cardiovascular disease. Researchers said
the analyses -- the largest to look at coffee's potential role in heart disease
and death -- provide reassurance that coffee isn't tied to new or worsening
heart disease and may actually be heart protective.
"Because coffee can quicken heart rate, some people worry that drinking it could trigger or worsen certain heart issues. This is where general medical advice to stop drinking coffee may come from. But our data suggest that daily coffee intake shouldn't be discouraged, but rather included as a part of a healthy diet for people with and without heart disease," said Peter M. Kistler, MD, professor and head of arrhythmia research at the Alfred Hospital and Baker Heart Institute in Melbourne, Australia, and the study's senior author.
"We found coffee drinking had either a neutral effect -- meaning that it
did no harm -- or was associated with benefits to heart health."
Kistler and his team used data from the UK BioBank, a large-scale prospective database with health information from over half a million people who were followed for at least 10 years. Researchers looked at varying levels of coffee consumption ranging from up to a cup to more than six cups a day and the relationship with heart rhythm problems (arrhythmias); cardiovascular disease, including coronary artery disease, heart failure and stroke; and total and heart-related deaths among people both with and without cardiovascular disease.
Patients were
grouped by how much coffee they reported drinking each day: 0, <1, 1, 2-3,
4-5, >5 cups/day. Coffee drinking was assessed from questionnaires completed
upon entry into the registry. Overall, they either found no effect or, in many
cases, significant reductions in cardiovascular risk after controlling for
exercise, alcohol, smoking, diabetes and high blood pressure that could also
play a role in heart health and longevity.
For the first study, researchers examined data from 382,535 individuals without known heart disease to see whether coffee drinking played a role in the development of heart disease or stroke during the 10 years of follow up. Participants' average age was 57 years and half were women. In general, having two to three cups of coffee a day was associated with the greatest benefit, translating to a 10%-15% lower risk of developing coronary heart disease, heart failure, a heart rhythm problem, or dying for any reason.
The risk of stroke or
heart-related death was lowest among people who drank one cup of coffee a day.
Researchers did observe a U-shaped relationship with coffee intake and new
heart rhythm problems. The maximum benefit was seen among people drinking two
to three cups of coffee a day with less benefit seen among those drinking more
or less.
The second study included 34,279 individuals who had some form of cardiovascular disease at baseline. Coffee intake at two to three cups a day was associated with lower odds of dying compared with having no coffee. Importantly, consuming any amount of coffee was not associated with a higher risk of heart rhythm problems, including atrial fibrillation (AFib) or atrial flutter, which Kistler said is often what clinicians are concerned about.
Of the 24,111 people
included in the analysis who had an arrhythmia at baseline, drinking coffee was
associated with a lower risk of death. For example, people with AFib who drank
one cup of coffee a day were nearly 20% less likely to die than non-coffee
drinkers.
"Clinicians
generally have some apprehension about people with known cardiovascular disease
or arrhythmias continuing to drink coffee, so they often err on the side of
caution and advise them to stop drinking it altogether due to fears that it may
trigger dangerous heart rhythms," Kistler said. "But our study shows
that regular coffee intake is safe and could be part of a healthy diet for
people with heart disease."
Although
two to three cups of coffee a day seemed to be the most favorable overall,
Kistler said that people shouldn't increase their coffee intake, particularly
if it makes them feel anxious or uncomfortable.
"There
is a whole range of mechanisms through which coffee may reduce mortality and
have these favorable effects on cardiovascular disease," he said.
"Coffee drinkers should feel reassured that they can continue to enjoy
coffee even if they have heart disease. Coffee is the most common cognitive
enhancer -- it wakes you up, makes you mentally sharper and it's a very
important component of many people's daily lives."
So
how might coffee beans benefit the heart? People often equate coffee with
caffeine, but coffee beans actually have over 100 biologically active
compounds. These substances can help reduce oxidative stress and inflammation,
improve insulin sensitivity, boost metabolism, inhibit the gut's absorption of
fat and block receptors known to be involved with abnormal heart rhythms,
Kistler said.
In a third study, researchers looked at whether there were any differences in the relationship between coffee and cardiovascular disease depending on whether someone drank instant or ground coffee or caffeinated or decaf. They found, once again, two to three cups a day to be associated with the lowest risk of arrhythmias, blockages in the heart's arteries, stroke or heart failure regardless of whether they had ground or instant coffee.
Lower rates of death
were seen across all coffee types. Decaf coffee did not have favorable effects
against incident arrhythmia but did reduce cardiovascular disease, with the
exception of heart failure. Kistler said the findings suggest caffeinated
coffee is preferable across the board, and there are no cardiovascular benefits
to choosing decaf over caffeinated coffees.
There
are several important limitations to these studies. Researchers were unable to
control for dietary factors that may play a role in cardiovascular disease, nor
were they able to adjust for any creamers, milk or sugar consumed. Participants
were predominantly white, so additional studies are needed to determine whether
these findings extend to other populations. Finally, coffee intake was based on
self-report via a questionnaire fielded at study entry. This should be
considered when interpreting the study findings, though Kistler noted that
research suggests people's dietary habits don't change much in adulthood or
over time. Kistler said the results should be validated in randomized trials.
The
study, "Effects of Habitual Coffee Consumption on Incident Cardiovascular
Disease, Arrhythmia, and Mortality: Findings from UK BioBank," will be
presented on Sunday, April 3.
The
second related study, "Regular Coffee Intake is Associated with Improved
Mortality in Prevalent Cardiovascular Disease," will be presented
virtually on Saturday, April 2.
The
third related study, "Ground, Instant, or Decaffeinated Coffee? Impact of
Different Coffee Subtypes on Incident Arrhythmia, Cardiovascular Disease and
Mortality," will be presented on Sunday, April 3.
