A strong coffee consumed first thing after a poor night's sleep can impair blood sugar control, according to research from the University of Bath. The study found that drinking caffeinated coffee before breakfast negatively affected glucose metabolism by around 50%.
The work, funded by the University of Bath, suggests that having coffee after breakfast rather than before may offer better metabolic control. A separate survey cited by the university found that approximately 40% of people in the UK drink caffeinated coffee upon waking.
Impact on Breakfast Sugar Tolerance
The university warned that consuming a strong black coffee to wake up after a bad night's sleep could impair the body's ability to tolerate the sugar in breakfast. "This study therefore reveals that the common remedy of drinking coffee after a bad night's sleep may solve the problem of feeling sleepy but could create another by limiting your body's ability to tolerate the sugar in your breakfast," the University stated.
Professor James Betts, co-director of the Centre for Nutrition, Exercise and Metabolism at the University of Bath, who oversaw the work, said: "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.
"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 need it."
Sleep Disruption Alone Not the Main Factor
Lead researcher Harry Smith, from the Department for Health at Bath, noted that one night of disrupted sleep alone did not worsen participants' blood glucose or insulin response to a sugary drink compared to a normal night of sleep. However, starting the day after a poor night's sleep with a strong coffee did have a negative effect on glucose metabolism by around 50%.
Smith added: "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."
The full study, titled 'Glucose control upon waking is unaffected by hourly sleep fragmentation during the night, but is impaired by morning caffeinated coffee', is published in the British Journal of Nutrition.
