This article was updated on September 6, 2021.
Although we’re conditioned to believe a cup of coffee goes best at the top of our to-do list, new research suggests that may not be the case.
A study published in the British Journal of Nutrition found that ingesting the compounds found in a cup of coffee yields negative effects on our glucose response especially if we haven’t eaten beforehand.
Insulin and glucagon are hormones secreted by islet cells located in our pancreas. Both are produced in reaction to blood sugar levels and contribute meaningfully to glucose metabolism.
In addition to providing the physiological means for important brain functions, glucose metabolism regulates neuronal and non-neuronal cellular maintenance and the production of neurotransmitters epicentral to mood.
Why drinking coffee before eating can be bad for you
When one consumes coffee before eating, these processes are dramatically disrupted, according to researchers at the University of Bath.
Moreover, drinking any liquid after food consumption facilitates digestion and the prevention of constipation. These parameters are further influenced by sleep quality.
All of this to say if you haven’t got a good night’s rest, save your coffee until after breakfast.
“Morning coffee is a common remedy following disrupted sleep, yet each factor can independently impair glucose tolerance and insulin sensitivity in healthy adults. Remarkably, the combined effects of sleep fragmentation and coffee on glucose control upon waking per se have never been investigated,” the authors wrote in the new paper.
“In a randomized crossover design, twenty-nine adults (mean age: 21 (sd 1) years, BMI: 24·4 underwent three oral glucose tolerance tests (OGTT). One following a habitual night of sleep (Control; in bed, lights-off trying to sleep approximately 23.00–07.00 hours), the others following a night of sleep fragmentation (as a Control but waking hourly for 5 min), with and without morning coffee approximately 1 h after waking.”
Blood samples were subsequently drawn from each participant in order for the researchers to establish baseline insulin and glucose responses. Upon waking, the researchers gave the study pool the same sugary drink except for one instance wherein the participants were given a strong black coffee.
Although no impairment to the subjects’ glucose/insulin response was observed following a single night of disrupted sleep alone, those who consumed coffee after a disrupted night of sleep but before breakfast evidenced impaired metabolic ability as well as a limited ability to effectively tolerate sugar throughout the day.
In fact, these functions were hindered by roughly 50%. More broadly, disruptions to slow-wave sleep phases appeared to be the most metabolically and neurophysiologically destructive.
“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,” Dr. James Betts, who is a corresponding author on the new study explained. “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.”
For healthy adults, coffee can offer a plethora of benefits if consumed in moderation (3 to 4 cups a day) and if prepared correctly. Independently published literature even suggests that the beverage can aid digestion and contribute to glucose metabolism if consumed after sufficient energy intake.
“Starting a day after a poor night’s sleep with a strong coffee did have a negative effect on glucose metabolism by around 50 percent. 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 authors conclude.
“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. Knowing this can have important health benefits for us all.”