Young people who consume caffeinated energy drinks can experience a spike in their blood insulin levels. This could make them more prone to a condition which increases their susceptibility to type 2 diabetes later in life, according to early results from a small Canadian study.
However, one UK expert says linking caffeinated energy drinks to diabetes is premature.
Canadian researchers who tested the effects of these popular drinks on adolescents say caffeine inhibits the body’s ability to deal with a high load of sugar. They say this could lead to ‘ insulin resistance’ in which the body has to produce increasing amounts of insulin to clear blood sugar circulating in tissues.
Young people are more vulnerable to these effects because they are smaller than adults and therefore likely to consume relatively larger quantities of caffeine per drink, they say.
Heidi Virtanen from the University of Calgary, who led the study, explains in a statement: “Results show that consumption of a caffeine-containing energy drink results in a 20 to 30% increase in insulin and glucose levels in response to a glucose load.
“Since caffeine persists in the system for 4 to 6 hours after consumption, continuous insulin resistance associated with regular caffeine-containing energy drink consumption in adolescents could contribute to increased metabolic risk in susceptible individuals later in life through persistent interference with their regular glucose metabolism.”
The study was overseen by Jane Shearer from the University of Calgary who says: “Elevated glucose and insulin responses may contribute to increased metabolic risk, including type 2 diabetes and cardiovascular disease in susceptible individuals later in life.”
The researchers note that despite warning labels on caffeinated energy drinks that say they are not suitable for children, their marketing often makes them appealing to children, adolescents and young adults. They estimate that in Canada, around 30% of adolescents regularly drink them, while 50% of athletes in full-time education report using them.
The study involved 10 males and 10 females aged 13 to 19 with an average age of 17. After fasting for 24 hours, abstaining from caffeine and taking no exercise, the adolescents were randomly assigned to have either a caffeinated energy drink or one without caffeine. Both energy drinks were sugar-free in order to determine the effects of the caffeine in the drink.
Blood samples were taken periodically during a 2 hour period and a standard oral glucose test was administered 40 minutes after drinking.
The results displayed a 25% increase in blood glucose levels over a 2 hour period for those who had been given the caffeinated drink compared to those having the decaffeinated version.
Elevations in glucose with the caffeine containing energy drink were accompanied by a 26% increase in insulin levels. The researchers say that, since the half-life of caffeine is in the range of 4 to 6 hours, these results suggest that consumption of a caffeine-containing energy drink in adolescents could affect glucose regulation for hours after it is drunk.
The results, presented at the World Diabetes Congress in Vancouver, should be treated with caution as they have not yet been published in a peer-reviewed journal.
The researchers are planning a follow-up trial in which energy drinks will be given to adolescents containing both caffeine and glucose. Participants will then be followed for 3 days.
Commenting on the findings in a statement, Tom Sanders, professor emeritus of nutrition and dietetics at King’s College London, says: “The measurement made in this study does not really predict diabetes. Caffeine stimulates the release of non-esterified fatty acids which may transiently influence insulin sensitivity.
“It is a jump too far to suggest caffeine containing beverages increase the risk of [type 2 diabetes] based on acute measurement in such a small sample… especially as there can be marked variation in women with the menstrual cycle.”
He adds: “This is also a pilot study, so further studies will be needed to corroborate the findings.”
‘Energy drink consumption impairs oral glucose tolerance in adolescents: a randomized, double-blind, crossover pilot study’, H Virtanen et al, poster presentation, World Diabetes Congress.
Science Media Centre.