Coffee is one of the most commonly-consumed beverages in the world. It's also good for you. Moderate coffee consumption can reduce the risk of type 2 diabetes and cardiovascular diseases. Little has been known, however, about whether the timing of coffee consumption affects these health benefits in the same way that eating earlier improves metabolism.

What kind of coffee drinker are you? Do you have a big mug in the morning, or an espresso or cappuccino and that's it, or do you refill your cup now and again throughout the day? Researchers from Tulane University and Harvard University recently examined the health profiles of two types of coffee drinkers: morning coffee drinkers, who mostly drank coffee before noon, and all-day coffee drinkers, who drank coffee in the morning, afternoon and evening.

Because of its circadian pattern, the anti-inflammatory effects of coffee may be greater in the morning than similar amounts of coffee consumed throughout the day.

“Given the effects of caffeine on the body,” Lu Qi, lead author on the study, told TheDoctor, “we wanted to see if the time of day you drink coffee has any effect on heart health.”

The researchers analyzed complete dietary information from almost 41,000 people who took the National Health and Nutrition Examination Survey from 1999 to 2018 and seven-day dietary recalls from a subgroup of almost 1,500 participants in the Women's and Men's Lifestyle Validation Study.

About 36 percent of participants were morning coffee drinkers and 16 percent were all-day coffee drinkers. The remaining 48 percent were non-coffee drinkers.

They found that, at the population level, drinking coffee only in the mornings, rather than drinking it all day, may significantly reduce mortality risk.

Morning coffee drinkers were 16 percent less likely to die of any cause and 31 percent less likely to die of cardiovascular disease compared with non-coffee drinkers. All-day coffee drinkers, however, had no reduction in all-cause or cardiovascular mortality risk.

The amount of coffee consumed did not matter, although moderate (two to three cups) coffee drinkers and heavy (three or more cups) drinkers had a greater reduction in all-cause mortality risk than light (one to two cups) morning coffee drinkers. All-day coffee drinkers had an insignificant reduction in all-cause mortality risk, regardless of how much coffee they drank.

The findings suggest that limiting coffee consumption to the morning has more health benefits than drinking it throughout the day, Qi explained. Two mechanisms may be at work: Drinking coffee in the afternoon and evening may disrupt circadian rhythm, the body's natural clock, by interfering with the production of melatonin. This neuroendocrine hormone is connected to the sleep/wake cycle and is affected by exposure to light. This explanation applies only to caffeinated coffee drinkers, however.

Morning coffee drinkers were 16 percent less likely to die of any cause and 31 percent less likely to die of cardiovascular disease. All-day coffee drinkers had no reduction in all-cause mortality risk.

Nutrients in coffee are also likely to be behind the health boost we get from a cup of coffee early in the day, Qi, a Distinguished Professor at the Tulane School of Public Health and Tropical Medicine, added.

These benefits come mostly from the way the bioactive compounds coffee contains reduce inflammation. Polyphenols, for example, compounds found in both caffeinated and decaffeinated coffee, have antioxidative and anticancer properties that inhibit the growth and spread of cancer cells and are linked to the timing of the body's clock.

Cytokines, small proteins that control the activity of cells in the blood and help them mount an inflammatory response when the body needs to fight an infection, are also found in caffeinated and decaffeinated coffee. Some of these pro-inflammatory cytokines have an internal circadian pattern. Levels of these cytokines peak in the morning, then gradually decline until they are at their lowest levels in the late afternoon. Because of this circadian pattern, the anti-inflammatory effects of coffee may be greater in the morning than similar amounts of coffee consumed throughout the day.

The study is published in the European Heart Journal.