Updated 14 October 2020

Coffee before, or after breakfast? Scientists say after, and here's why

Your morning coffee fix, especially after a bad night’s sleep, could have a bad effect on your metabolism.

  • If you need to rev up your metabolism, it's best to keep your morning coffee for after breakfast.
  • This is according to a new study, which suggests that strong coffee before breakfast may increase your diabetes risk.
  • For the study, the research team conducted overnight experiments involving 29 healthy individuals

Ah, coffee! Many people can't start their day without it. But if your love for it runs deep, it's best that you know that drinking it the wrong way may have unfortunate consequences for your health.

According to a new study, drinking strong, black coffee first thing in the morning can have a negative effect on blood sugar control – a risk factor for diabetes and heart disease.

The researchers, from the Centre for Nutrition, Exercise and Metabolism at the University of Bath (UK), say their findings could have "far-reaching" health implications, especially considering that coffee's one of the world's most popular drinks.

"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," Professor James Betts, co-director of the Centre for Nutrition, Exercise and Metabolism at the University of Bath, said in a news release.

"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."

The study, which is the first to explore the combined effects of sleep fragmentation and coffee on glucose control upon waking, was published in the British Journal of Nutrition

The study

For their study, the researchers recruited 29 healthy men and women to take part in three different overnight experiments, in a random order.

  • In one experiment, the participants had a normal night's sleep (roughly from 23:00 to 07:00) and were asked to consume a sugary drink on waking in the morning. 
  • In another experiment, participants experienced a disrupted night's sleep, where the researchers woke them every hour for five minutes. Upon waking, they consumed the same sugary drink.
  • On another night, participants experienced the same sleep disruption, but this time they were first given a strong black coffee, 30 minutes before consuming the sugary drink.

The glucose drink they consumed mirrored the same amount of calories as a typical breakfast. In each of these tests, blood samples from participants were taken following the consumption of the drink.

What the researchers found

Their results indicated that one night of disrupted sleep did not worsen participants' blood glucose and insulin responses when compared to a normal night's sleep.

Previous research, however, suggested that losing many hours of sleep or many nights of poor sleep could have a negative effect. So it is, perhaps, reassuring to know that a single night of fragmented sleep does not have the same effect, the researchers wrote.

However, they found that strong black coffee consumed before breakfast substantially increased participants' blood glucose by about 50%, suggesting that while relying on coffee after a bad night of sleep may help you to stay awake, it can end up limiting your body's ability to tolerate the sugar in your breakfast.

"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," Betts explained, adding that this could be improved by eating first and drinking coffee later – if we feel we still need it.

"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 also 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."

His advice: Don't consume a strong cup of coffee within an hour before a carb-rich breakfast. 

Does this apply to strong black coffee only?

Although the researchers used black coffee for their experiment, Betts told CNN that the same effect would likely be seen with a latte or flat white.

"Milk would have complicated the comparisons by providing additional nutrients.

"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 in an email.

READ | Why early bedtime may be best for people with type 2 diabetes

READ | What's wrong with microwaved tea? Science weighs in

READ | Should you drink coffee on an empty stomach?

Image: Madison Inouye/Pexels


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Diabetes expert

Dr. May currently works as a fulltime endocrinologist and has been in private practice since 2004. He has a variety of interests, predominantly obesity and diabetes, but also sees patients with osteoporosis, thyroid disorders, men's health disorders, pituitary and adrenal disorders, polycystic ovaries, and disorders of growth. He is a leading member of several obesity and diabetes societies and runs a trial centre for new drugs.

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