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Coffee before breakfast has a negative impact on metabolism

A new study from the University of Bath suggests that drinking coffee first thing in the morning on an empty stomach can interfere with the body’s metabolism. The experts have found that coffee can limit your ability to tolerate the sugar in your breakfast.

A team of researchers in the University’s Centre for Nutrition, Exercise & Metabolism investigated the effects of disrupted sleep and morning coffee across a range of different metabolic markers. The results suggest that while one night of poor sleep has limited impact on our metabolism, a strong coffee the next morning may interfere with the body’s control over blood glucose.

Keeping our blood sugar levels within a safe range is important for reducing the risk of chronic conditions such as diabetes and heart disease. According to the experts, the findings could have “far-reaching” health implications, especially considering the global popularity of coffee.

Coffee is currently the most popular drink in the world, with around two billion cups consumed every day. 

“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. “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 feel the need it. Knowing this can have important health benefits for us all.”

The study was focused on 29 healthy men and women who were assigned three different overnight tasks in a random order. 

Under one condition, participants were instructed to get a normal night’s sleep and were asked to consume a sugary drink upon waking in the morning. On a separate occasion, the volunteers had their sleep disrupted every hour for a few minutes at a time, followed by the same sugary drink.

Under the third condition, participants experienced the same sleep disruption followed by a strong black coffee 30 minutes before consuming a sugary drink.

For each trial, blood samples were collected from each volunteer following the glucose drink- which had about the same amount of calories as a typical breakfast. 


The study revealed that one night of disrupted sleep did not worsen the participants’ blood glucose responses at breakfast when compared to a normal night’s sleep. However, strong black coffee consumed before breakfast substantially increased the blood glucose response to breakfast by around 50 percent.

While a growing collection of research has linked coffee to substantial health benefits, there are also previous studies which demonstrated that caffeine has the potential to cause insulin resistance. 

“These results show that one night of disrupted sleep alone did not worsen participants’ blood glucose/insulin response to the sugary drink compared to a normal night of sleep which will be reassuring to many of us,” said study lead author Harry Smith.

“However, starting a day after a poor night’s sleep with a strong coffee did have a negative effect on glucose metabolism by around 50%.

“As such, individuals should try to balance the potential stimulating benefits of caffeinated coffee in the morning with the potential for higher blood glucose levels and it may be better to consume coffee following breakfast rather than before.”

“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.”

The study is published in the British Journal of Nutrition.

By Chrissy Sexton, Staff Writer

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