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It is rare that the PEN Team comes across a nutrition topic that has never been studied before, but that is exactly what happened a few weeks ago. A recent, large study published in the European Heart Journal reported the effect of coffee on heart health (1). The authors examined whether the timing of coffee intake (just in the morning or throughout the day) influenced people’s risk of dying over a 10-year period.

After sifting through food diaries from 40,725 people who took part in the US National Health and Nutrition Examination Survey (NHANES) between 1999 and 2018 (and validating their findings against a smaller, more rigorous sample), the authors came to a surprising conclusion: people who drank coffee only in the morning (before 12 noon, 36% of the group) had a 16% lower risk of dying from any cause and a 31% lower risk of dying from heart disease compared to people who didn't drink coffee at all (48% of the group). The size of this effect was smaller (but still present) in people who drank one cup or less every day. Otherwise, the amount of coffee a person drank (as long as it wasn’t zero) didn’t influence their risk of dying. Interestingly, people who drank coffee all day (16% of the group) did not differ significantly from people who didn't drink coffee at all. 

This risk reduction wasn’t due to other factors that happened to be present in morning coffee drinkers more or less often than the other groups, such as chronic conditions (e.g., diabetes, hypertension or dyslipidemia) or lifestyle factors (e.g. smoking or physical activity). The researchers felt that the possible benefits of drinking coffee in the morning may be due to a lack of disruption in circadian rhythm, supporting better sleep patterns and possibly the anti-inflammatory effects of coffee that may be strongest in the morning when levels of inflammation can peak. 

While this observational study did have a long study period (10 years), it also had some limitations. Coffee intake was self-reported, which introduces bias. The authors only accounted for each participant’s coffee intake (caffeinated and decaffeinated) and did not consider what might have been added to the coffee, such as cream or sugar (or any foods that may have been eaten along with the coffee, such as pastries or donuts). Finally, it should be noted that the authors only looked at coffee intake – they did not look at other forms of caffeine, such as cola, chocolate or energy drinks.

Because this study was the first of its kind, we will have to wait and see whether the findings are repeated in other studies. If they do, dietitians may need to pay more attention to the timing of their clients’ coffee intake, particularly those with heart disease. For now, this is just an interesting study that can inspire other researchers to investigate the same thing. As the effects of coffee consumption on cardiovascular disease mortality are uncertain and may be different for each individual (2), dietitians should continue to follow country-specific recommendations for caffeine intake available in the International Caffeine Guideline Collection.

See Additional Content:
Q: Do the oils in coffee (cafestol and kahweol) raise blood lipids or increase cardiovascular risk?
Q: What is the effect of caffeine and dietary sources of caffeine on blood pressure?
Q: What effect does caffeine consumption have on long-term complications in individuals with type 1 and type 2 diabetes?