Published last week in the European Heart Journal, the research suggests that morning coffee drinkers may have a lower risk of cardiovascular disease and overall mortality than those who drink coffee later in the day or not at all.
“This is the first study testing coffee drinking timing patterns and health outcomes,” Professor Lu Qi, who led the study at Tulane University, said in a statement. “Our findings indicate that it’s not just whether you drink coffee or how much you drink but the time of day when you drink coffee that’s important. We don’t typically give advice about timing in our dietary guidance, but perhaps we should be thinking about this in the future.”
The study, which also gathered researchers affiliated with the Harvard T.H. Chan School and George Washington University, was supported by grants from the National Heart, Lung, and Blood Institute and the National Institute of Diabetes and Digestive and Kidney Diseases.
Considering circadian rhythms
While Dr. Qi acknowledged that the research does not explain what might be responsible for the associations between morning coffee and reduction in death risk, he said that internal circadian rhythms might be at play.
Consuming coffee later in the day may disrupt these rhythms responsible for the sleep-wake cycle, the study suggested, referencing a previous clinical trial showing that heavy coffee consumption in the afternoon or evening was associated with a 30% decrease in peak melatonin production at night compared to controls.
“Melatonin is a neuroendocrine hormone with a key role in the circadian rhythm, and some evidence suggests that low levels of melatonin are associated with higher oxidative stress levels, blood pressure levels and CVD risk,” the researchers wrote, noting that this explanation applies only to caffeinated coffee consumers.
For decaf drinkers, they submitted that the anti-inflammatory and antioxidant effects of bioactive compounds in coffee (like chlorogenic acids, trigonelline, diterpenes and melanoidins) might be responsible for health benefits and more so when consumed in the morning, when pro-inflammatory cytokines and inflammatory markers in the blood are typically highest.
In an accompanying editorial, Professor Thomas F. Lüscher from Royal Brompton and Harefield Hospitals in London, explained that there is usually a marked increase in sympathetic activity (also known as the “fight-or-flight” response) triggered by the onset of morning activities, an effect that fades away during the day and reaches its lowest level during sleep.
“In this context, it is of interest that coffee seems to suppress melatonin, an important sleep-inducing mediator in the brain,” he noted. “Overall, we must accept the now substantial evidence that coffee drinking, particularly in the morning hours, is likely to be healthy. Thus, drink your coffee, but do so in the morning!”
Study details
The observational study conducted by Professor Qi and colleagues evaluated dietary data from 40,725 adults from the National Health and Nutrition Examination Survey 1999-2018 and a subgroup of 1,463 adults from the Women’s and Men’s Lifestyle Validation Study.
Patterns of coffee drinking (36% morning type, 16% all-day type and 48% non-coffee drinkers) were then linked to death records over a period of approximately 10 years that included 4,295 all-cause deaths, 1,268 cardiovascular disease deaths and 934 cancer deaths.
“After adjustment for caffeinated and decaffeinated coffee intake amounts, sleep hours and other confounders, the morning-type pattern, rather than the all-day-type pattern, was significantly associated with lower risks of all-cause and cardiovascular disease-specific mortality as compared with non-coffee drinking,” the study reported.
Contrasted with non-coffee drinkers, morning coffee drinkers were 16% less likely to die from any cause and 31% less likely to die from cardiovascular disease, however no reduction in risk was observed between non-coffee drinkers and all-day coffee drinkers.
What’s more, the research revealed that while morning coffee drinking decreased risks in moderate (two to three cups) or heavy (more than three cups) doses, those who drank one cup or less in the morning or drank more coffee in the afternoon did not decrease their mortality risk to the same extent.
“Coffee drinking timing significantly modified the association between coffee intake amounts and all-cause mortality; higher coffee intake amounts were significantly associated with a lower risk of all-cause mortality in participants with morning-type pattern but not in those with all-day-type pattern,” the researchers wrote.
For future study, they called for clinical investigation in other populations to validate the findings and evaluate the potential impact of modifying the time of day people drink their coffee.
Source: European Heart Journal
doi: https://doi.org/10.1093/eurheartj/ehae871
“Coffee drinking timing and mortality in US adults”
Authors: Lu Qi, et al.
