Previous research had used higher doses of caffeine (around 2-4 cups) to arrive at the same effect, but researchers from the University of Surrey and Campden BRI in the UK found low caffeine levels worsened glucose response in a small study with 10 overweight men.
They varied caffeine consumption at either placebo, 2 g (equivalent to one cup of coffee), 4 g (2 cups) or 8 g (4 cups) blended into instant decaffeinated coffee (DC) in the double-blind cross-over study.
“Our study adds to the body of evidence from previous acute studies demonstrating a temporary worsening in glucose response following coffee ingestion,” the researchers wrote.
“We have shown, for the first time, that a single serving of instant caffeinated coffee, as typically consumed in the UK, is sufficient to disrupt the 2-h postprandial glucose response.”
“Furthermore, Part B of our study demonstrates that the amount of caffeine found in one serving of coffee can attenuate any possible beneficial effects of escalating doses of the other coffee components.”
But they noted the systems of the ‘healthy’ overweight men returned to normal in about an hour, and therefore called for more research, especially among those with insulin sensitivity issues.
“What is not known is whether this statistically significant increase in blood glucose is physiologically relevant and the implications for individuals with abnormal glucose tolerance. Although we observed a high percentage difference in peak values, it was quickly resolved in insulin-sensitive individuals with all treatments, including control, displaying similar responses from 60 min onwards.”
They added: "Longer-term interventions investigating these chronic effects are now needed if we are to confirm the beneficial effects of coffee suggested by the epidemiology."
28 August 2015 (DOI: http://dx.doi.org/10.1017/S0007114515002640)
‘A single serving of caffeinated coffee impairs postprandial glucose metabolism in overweight men’
Authors: Tracey M. Robertson, Michael N. Clifford, Simon Penson, Gemma Chope, M. Denise Robertson