Drinking two to three daily cups of – ground, instant, or decaffeinated – is associated with significant reductions in new cardiovascular disease (CVD) and mortality risk, compared with avoiding coffee, a new analysis of the prospective UK Biobank suggests.
Ground and instant coffee, but not decaffeinated coffee, also was associated with reduced risk of new-onset arrhythmia, including atrial fibrillation.
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“Our study is the first to look at differences in coffee subtypes to tease out important differences which may explain some of the mechanisms through which coffee works,” Peter M. Kistler, MD, of the Alfred Hospital and Baker Heart and Diabetes Institute, Melbourne, Australia, told this news organization.
“Daily coffee intake should not be discouraged by physicians but rather considered part of a healthy diet,” Dr. Kistler said.
“This study supports that coffee is safe and even potentially beneficial, which is consistent with most of the prior evidence,” Carl “Chip” Lavie, MD, who wasn’t involved in the study, told this news organization.
“We do not prescribe coffee to patients, but for the majority who like coffee, they can be encouraged it is fine to take a few cups daily,” said Dr. Lavie, with the Ochsner Heart and Vascular Institute in New Orleans.
The study was published online in the European Journal of Preventive Cardiology.
Clear cardiovascular benefits
A total of 449,563 UK Biobank participants (median age 58 years; 55% women), who were free of arrhythmias or other CVD at baseline, reported in questionnaires their level of daily coffee intake and preferred type of coffee.
During more than 12.5 years of follow-up, 27,809 participants (6.2%) died.
Drinking one to five cups per day of ground or instant coffee (but not decaffeinated coffee) was associated with a significant reduction in incident arrhythmia. The lowest risk was with four to five cups per day for ground coffee (hazard ratio [HR] 0.83; 95% confidence interval [CI], 0.76-0.91; P < .0001) and two to three cups per day for instant coffee (HR, 0.88; 95% CI, 0.85-0.92; P < .0001).
Habitual coffee drinking of up to five cups perday was also associated with significant reductions in the risk of incident CVD, when compared with nondrinkers.
Significant reductions in the risk of incident coronary heart disease (CHD) were associated with habitual coffee intake of up to five cups per day, with the lowest risk for CHD observed in those who consumed two to three cups per day (HR 0.89; 95% CI, 0.86-0.91; P < .0001).
Coffee consumption at all levels was linked to significant reduction in the risk of congestive cardiac failure (CCF) and ischemic stroke. The lowest risks were observed in those who consumed two to three cups per day, with HR, 0.83 (95% CI, 0.79-0.87; P < .0001) for CCF and HR, 0.84 (95% CI, 0.78-0.90; P < .0001) for ischemic stroke.
Death from any cause was significantly reduced for all coffee subtypes, with the greatest risk reduction seen with two to three cups per day for decaffeinated (HR, 0.86; 95% CI, 0.81-0.91; P < .0001); ground (HR, 0.73; 95% CI, 0.69-0.78; P < .0001); and instant coffee (HR, 0.89; 95% CI, 0.86-0.93; P < .0001).
“Coffee consumption is associated with cardiovascular benefits and should not empirically be discontinued in those with underlying heart rhythm disorders or cardiovascular disease,” Dr. Kistler told this news organization.
Dr. Peter M. Kistler
Plausible mechanisms
There are a number of proposed mechanisms to explain the benefits of coffee on CVD.
“Caffeine has antiarrhythmic properties through adenosine A1 and A2A receptor inhibition, hence the difference in effects of decaf vs. full-strength coffee on heart rhythm disorders,” Dr. Kistler explained.
Coffee has vasodilatory effects and coffee also contains antioxidant polyphenols, which reduce oxidative stress and modulate metabolism.
“The explanation for improved survival with habitual coffee consumption remains unclear,” Dr. Kistler said.
“Putative mechanisms include improved endothelial function, circulating antioxidants, improved insulin sensitivity, and reduced inflammation. Another potential mechanism includes the beneficial effects of coffee on metabolic syndrome,” he said.
“Caffeine has a role in weight loss through inhibition of gut fatty acid absorption and increase in basal metabolic rate. Furthermore, coffee has been associated with a significantly lower incidence of type 2 diabetes mellitus,” Dr. Kistler added.
Direction of relationship unclear
Charlotte Mills, PhD, University of Reading, England, said this study “adds to the body of evidence from observational trials associating moderate coffee consumption with cardioprotection, which looks promising.”
However, with the observational design, it’s unclear “which direction the relationship goes – for example, does coffee make you healthy or do inherently healthier people consume coffee? Randomized controlled trials are needed to fully understand the relationship between coffee and health before recommendations can be made,” Dr. Mills told the UK nonprofit Science Media Centre.
Annette Creedon, PhD, nutrition scientist with the British Nutrition Foundation, said it’s possible that respondents over- or underestimated the amount of coffee that they were consuming at the start of the study when they self-reported their intake.
“It is therefore difficult to determine whether the outcomes can be directly associated with the behaviors in coffee consumption reported at the start of the study,” she told the Science Media Centre.
The study had no funding. Dr. Kistler has received funding from Abbott Medical for consultancy and speaking engagements and fellowship support from Biosense Webster. Dr. Lavie has no relevant disclosures. Dr. Mills has worked in collaboration with Nestle on research relating to coffee and health funded by UKRI. Dr. Creedon has reported no relevant financial relationships.
A version of this article first appeared on Medscape.com.