Coffee and health: Three studies present fresh insights

At first glance, it's just black liquid in a cup. Yet coffee has become one of the most prolific subjects of study in modern medical literature. For more than 20 years, cohorts, meta-analyses and even umbrella reviews have been piling up in an attempt to settle a seemingly simple question: Does this beverage, one of the most widely consumed in the world, protect health or endanger it? A review published in 2017 in the British Medical Journal already listed 201 meta-analyses covering 67 health outcomes, from cancer to cardiovascular mortality, with an overall favourable signal for moderate consumption.Cardiometabolic effects, liver, kidneys, brain, microbiota, aging—Other reviews have since been added to this body of work. Coffee seems to be, in turn, an antioxidant shield, a metabolic modulator, a stimulant for the nervous system, and a sleep disruptor. Among this abundance of articles, three recent studies shed new light on cellular aging, liver health and heart rhythm.Coffee, mental health and cellular agingTelomeres, the DNA sequences that protect the ends of chromosomes, shorten with age and oxidative stress. In people living with severe mental disorders, this cellular aging often appears to be accelerated. A Norwegian team wanted to find out whether coffee, which is rich in antioxidant compounds, could reverse this trend. Their cross-sectional study, conducted among 436 patients with schizophrenia or affective disorders, compared telomere length according to daily consumption.The results, published in BMJ Mental Health, reveal an “inverted J” relationship, with maximum benefit at three or four cups per day. The authors point out that coffee consumption within the recommended limits “is associated with longer telomeres, comparable to a biological age five years younger.” Compared to non-drinkers, this moderate consumption is associated with the most significant differences, even after adjusting for age, smoking and medication.Key findings:significant relationship between coffee consumption and telomere length (F=3.29; p=0.02)notable difference between non-drinkers and consumers of three to four cups/day (p=0.04)estimated benefit equivalent to five years of biological agingAccording to the researchers, these data suggest that, “Moderate coffee consumption may help counteract certain cellular mechanisms associated with premature aging in people with severe mental disorders.” The study remains observational, based on self-reported consumption and without specifying the types of coffee. But it opens up an exciting avenue of research: that of a simple, widespread daily habit capable of modulating a key biological marker in a particularly vulnerable population.Coffee and liver healthLiver diseases often progress silently, driven by inflammation, fibrosis and metabolic steatosis. In this landscape, coffee appears to be an unexpected ally. A review published in Biochemical Pharmacology brings together epidemiological and mechanistic data showing that it could slow down several major pathological trajectories. “Evidence is mounting in favour of coffee's protective effect on inflammation and fibrosis,” the authors noted. Meta-analyses agree: Regular drinkers have less advanced fibrosis, less cirrhosis and a reduced risk of hepatocellular carcinoma.This clinical signal is supported by solid biological arguments. Coffee reduces stellate cell activation, limits the expression of pro-inflammatory cytokines, and stimulates antioxidant pathways. It also modulates steatosis and improves insulin sensitivity. Large cohorts also show a decrease in ALT (alanine aminotransferase), AST (aspartate aminotransferase), and GGT (gamma-glutamyl transferase) in regular consumers, including those with viral hepatitis or alcohol-related liver disease.Key findings:non-alcoholic fatty liver disease: reduced risk of fibrosis (RR 0.70; 95% CI 0.60–0.82) for ≥ 3 cups per day compared with two cups per daychronic liver disease: reduced incidence (HR 0.79; 95% CI 0.72–0.86) in regular consumers (two to three cups per day) compared to non-drinkersliver-related mortality: HR 0.51 (95% CI 0.39–0.67) for two to three cups per day compared to non-drinkersFor the authors, these data justify “renewed attention to daily habits that may influence the progression of liver disease.” However, their review remains descriptive and dependent on observational studies. But it highlights an essential point: For many at-risk patients, a few cups of coffee a day could help change the natural course of the disease.Atrial fibrillation and risk of recurrenceThere is a persistent belief that coffee promotes arrhythmias. However, no randomized study had evaluated its effect on the recurrence of atrial fibrillation after cardioversion. The DECAF trial, published in the Journal of American Medicine, fills this gap. Two-hundred patients, all regular coffee drinkers, were assigned either to strict caffeine abstinence or to daily consumption of one caffeinated coffee for six months. The objective was to determine whether maintaining moderate consumption could reduce recurrence of atrial fibrillation (AF) or atrial flutter.The results were surprising. The authors note that daily consumption is “associated with a significantly lower risk of recurrence of atrial fibrillation.” They add that “drinking coffee does not cause arrhythmia in regular drinkers and may even offer a slight protective effect.” Adverse effects were similar in both groups.Key findings:AF/flutter recurrence: 47% in the coffee group, 64% in the abstinence grouprisk reduction: HR 0.61 (95% CI 0.42–0.89; p=0.01)hospitalizations related to AF or flutter: 10 in the coffee group, 15 in the abstinence groupThe study provides useful information for clinical practice. In regular drinkers, coffee does not appear to increase the risk of recurrence. However, the study remains open, limited to coffee drinkers, and cannot be extrapolated to non-drinkers. But it offers a reassuring message: In patients who consume coffee moderately and regularly, it does not appear to be an aggravating factor in AF.

Coffee and health: Three studies present fresh insights

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