A strong coffee after a poor night’s sleep is the kick-start many people need in the morning but new research suggests that it might be best to have a bite to eat first.
A study has found that drinking coffee first thing can have a negative effect on blood sugar control — a risk factor for diabetes and heart disease.
“We know that nearly half of us will wake in the morning and, before doing anything else, drink coffee — intuitively the more tired we feel, the stronger the coffee,” said Professor James Betts, professor and co-director of the Centre for Nutrition, Exercise and Metabolism at the University of Bath in the U.K., in a press statement.
“Up until now we have had limited knowledge about what this is doing to our bodies, in particular for our metabolic and blood sugar control.”
For their study, researchers at the University of Bath got 29 healthy men and women to take part in three different overnight experiments, with at least a week between them.
In one, the participants had a normal night’s sleep, roughly from 11 p.m. to 7 a.m., and were asked to consume a sugary drink on waking in the morning.
They then experienced a disrupted night’s sleep, where the researchers woke them every hour for five minutes by sending them text messages to which they had to respond — and upon waking were given the same sugary drink.
On another night, participants experienced the same sleep disruption but this time were first given a strong black coffee 30 minutes before consuming the sugary drink.
The glucose drink mirrored same amount of calories as a typical breakfast.
They found that one night of disrupted sleep did not worsen the participants blood glucose and insulin responses when compared to the normal night’s sleep — although previous research has suggested that losing many hours of sleep or many nights of poor sleep can have a negative effect.
However, strong black coffee consumed before breakfast substantially increased the blood glucose response by around 50% — suggesting that relying on coffee after a bad night to stop feeling sleepy could limit your body’s ability to tolerate the sugar in your breakfast.
“Most breakfasts are rich in carbohydrate (often sugar), so it is fair to suggest that the same effect would persist for other typical breakfast foods,” he said.
“Of course, if you did consume a breakfast that was lower in carbohydrate, especially sugar, then that would certainly reduce (or even remove) the blood glucose spike we see after eating.”
One reassuring takeaway from the study was that one night of disrupted sleep doesn’t have much affect on your metabolic control, he said.
He said it may be advisable for people not to consume a strong coffee within the hour before a carb-rich breakfast. While the team used black coffee for the experiment, he said that the same effect would likely be seen with a latte or flat white.
“Milk would have complicated the comparisons by providing additional nutrients,” he said. “I suspect the effect of caffeine per se would be the same had milk been included because the physiological effects of caffeine are quite potent,” he said via email.
Whether coffee is good for you or not has been one of medicine’s big debates. A massive review of the scientific literature on coffee published in the British Medical Journal in 2017 found that drinking three to four cups of black coffee a day provides the most health benefits overall.