Timing Your Coffee Consumption Might Matter More Than You Think

The health benefits of coffee have long been debated. There is at least some consensus on the amount of caffeine you should have in a day: less than 400 mg. This works out to about four cups of coffee maximum, and that's 8-ounce cups of coffee, not those venti treats. But some recent research has illuminated a correlation between long-term health outcomes and another component we don't typically consider: the time of day that coffee is consumed. There appears to be an association between drinking that cup of joe in the morning and staving off death.

Researchers from Harvard and Tulane University looked into large-scale survey data related to coffee drinking habits and compared those with mortality records. They noted two distinct patterns of coffee consumption among those surveyed. One group restricted coffee drinking to the morning, between 4 a.m. and 11:59 a.m. The other group would drink coffee throughout the day, into the afternoon and evening.

The authors of this study then looked at causes and rates of death around 10 years later. Interestingly, they found that the survey participants who drank coffee in the morning were less likely to die of any cause compared to non-coffee drinkers by 16%. However, the starkest contrast was that morning drinkers were 31% less likely to die of cardiovascular disease in particular. No such association was found for those who drank coffee throughout the day, indicating that the full benefits of coffee consumption could be based on timing.

It might be surprising that something as small as whether coffee drinking occurs in the morning or not could have such a strong association with long-term health outcomes. However, our bodies operate on an internal timeline known as a circadian rhythm. As a diurnal species, these patterns help us to stay awake during the daytime and sleep at night. Typically, that entails increased secretion of cortisol and adrenaline during the day and melatonin at night.

External factors, such as light at night and drug use, can throw off these internal cues and prevent you from getting the right amount of sleep. Studies have shown that high caffeine intake in the afternoon and evening can reduce melatonin release, which promotes rest at night. This could lead to disrupted sleep and grogginess during the day. Importantly, melatonin also facilitates a reduction in nocturnal blood pressure. Previous research has suggested a link between melatonin dysregulation and cardiovascular issues, such as hypertension.

Circadian rhythms also play a role in immune system function. For instance, certain proteins that promote inflammation are secreted at the highest rate during the morning. Importantly, some studies have indicated that the benefits of coffee are rooted in its anti-inflammatory properties. High inflammation is related to many health issues, including cardiovascular and neurodegenerative diseases. Therefore, restricting coffee intake to the morning could potentially help by reducing inflammation at its worst point in the day.

Although these are fascinating findings, and this is the only study to investigate the association of coffee timing and mortality, these implications require further evaluation. Of note, the conclusions are based on large, self-reported survey data. This type of data collection has severe limitations, including self-bias and relying upon the memory of the participant. While that does not mean the supplied data are necessarily false, it is something to keep in mind.

Second, these data are strictly correlational, not causal. In other words, the authors were able to establish an association even when controlling for variables like age, income, and physical activity, but that does not definitively mean that a morning cup of coffee will lead to a long life. As an example, those who drink coffee later in the day might do so because they are shift workers. We know that individuals within these professions have disparate health outcomes, likely due to pervasive circadian disruptions, which could contribute to the greater mortality rate reflected in the paper. In fact, this is a specific limitation that the authors acknowledged.

Thirdly, their time-of-day parameters were large, and their group sizes were highly variable. Morning coffee drinkers made up 36% of participants, while all-day drinkers made up merely 14%. The vast difference in these groups makes statistical analysis trickier. Overall, the findings highlighted in this study are a useful jumping-off point to investigate the effects of caffeine-intake timing further.