Drinking coffee before breakfast impairs metabolism, study suggests

Morning brew found to impair blood sugar response by 50 per cent when consumed on empty stomach

It is the world’s most popular drink, acting as a vital elixir for the bleary and baggy-eyed. But could the way we consume our morning caffeine fix be causing us unnecessary harm? 

Drinking coffee as soon as you wake up from a poor night’s sleep significantly impairs metabolism and blood sugar control, a new study suggests.

By holding off on the bean-derived brew until after breakfast, UK researchers found that our bodies’ ability to break down our food healthily is drastically improved.

Examining the effects of broken sleep and morning coffee across a range of different metabolic markers, scientists at the University of Bath found that, while one night of poor sleep had a limited impact on metabolism, drinking coffee could have a negative effect on blood glucose control.

Given the importance of keeping our blood sugar levels within a safe range to reduce the risk of conditions such as diabetes and heart disease, the researchers believe these results could have “far-reaching” health implications.

In their study, published in the British Journal of Nutrition, 29 healthy men and women underwent three different overnight experiments in a random order.

In the first two scenarios, participants were given a sugary drink upon waking - first from a normal night’s sleep, and then again after a poor night’s sleep during which they were woken up for five minutes every hour.

In the third, their sleep was similarly disrupted, but they were given a strong black coffee 30 minutes before consuming the sugary drink.

Blood samples from participants were taken following the glucose drink, which mirrored the calories of a typical breakfast, in each experiment.

Results showed that one night of disrupted sleep did not worsen the participants' blood glucose responses at breakfast when compared to a normal night of sleep.

However, strong black coffee consumed before breakfast - a pattern likely adopted by many consumers of the two million cups sunk per day - increased the blood glucose response to the drink by around 50 per cent.

“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, co-director of the Centre for Nutrition, Exercise and Metabolism at the University of Bath.

“This study is important and has far-reaching health implications, as 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.

“Put simply, our blood sugar control is impaired when the first thing our bodies come into contact with is coffee especially after a night of disrupted sleep.

“We might improve this by eating first and then drinking coffee later if we feel we still need it. Knowing this can have important health benefits for us all.”

It will be “reassuring to many" that one night of disrupted sleep alone does not appear to worsen our metabolic response in comparison with a normal night’s sleep, said lead researcher, Harry Smith, a PhD student at Bath’s Department for Health. 

“There is a lot more we need to learn about the effects of sleep on our metabolism, such as how much sleep disruption is necessary to impair our metabolism and what some of the longer-term implications of this are, as well as how exercise, for instance, could help to counter some of this,” Mr Smith said.

Additional reporting by PA