A study of adolescents consuming caffeinated energy drinks has shown that such drinks can cause blood insulin levels to spike and may lead to subsequent problems bringing blood sugar levels down to normal. The study is being presented at this week’s World Diabetes Congress in Vancouver — organized by the International Diabetes Federation (IDF) — and was performed by graduate student Heidi Virtanen in the laboratory of Jane Shearer, PhD, of the University of Calgary, Canada.
Virtanen says: “Results show that consumption of a caffeine-containing energy drink results in a 20-30% increase in insulin and glucose levels in response to a glucose load. Since caffeine persists in the system for four-six 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.”
Increased Energy Drink Consumption Harmful To Children
There has been an exponential growth of the caffeine-containing energy drink market over the past 10 years. Despite a warning label stating these drinks are not recommended for ‘children’, caffeine containing energy drinks are aggressively marketed to, and increasingly consumed by, children, adolescents and young adults. Current data indicates that around 30% of adolescents regularly consume these drinks, while 50% of college-aged athletes report use. While energy drinks contain a myriad of ingredients, the primary ingredient of concern in adolescents is caffeine. Children and adolescents are smaller compared to adults, therefore they are much more likely to ingest higher amounts of caffeine per kg of body mass, especially if it is presented in an appealing format and sweetened with sugar (with similar if not more appeal to some other sugar-sweetened beverages).
In adults, co-administration of a carbohydrate load in the presence of caffeine has been shown to cause insulin resistance meaning that the body has to release much more insulin to clear blood sugars from the circulation into our tissues. Overall, caffeine in energy drinks results in a 20-30% decline in our body’s ability to deal with a high sugar load. However, relatively little is known about the metabolic impacts of these beverages in teenagers who represent an understudied and potentially vulnerable population. Thus the authors carried out a study to investigate the metabolic impacts of both caffeinated and decaffeinated energy drink consumption on insulin sensitivity and whole-body glucose disposal.
Adolescent participants (mean age 17 years — range 13-19 years, 10 males and 10 females) arrived at the laboratory in a fasted state having abstained from caffeine and vigorous exercise for 24 hours, so that the effects of the drinks on insulin and blood sugar could be accurately assessed. Each subject underwent two double-blind randomized trials where they consumed either a common caffeinated energy drink (5 mg caffeine/kg) or an equivalent volume of a decaffeinated energy drink (containing only vitamins and minerals). The brand of drink used was 5-Hour Energy Original and 5-Hour Energy Decaf. Consumption of the drink was followed 40 minutes later by a standard two-hour oral glucose tolerance test (OGTT, 75g). Both energy drinks were sugar-free, so the effects of the caffeine contained in the drink could be determined. Blood samples were collected at -40 (baseline), 0 (initiation of OGTT), 30, 45, 60, 90, and 120 minutes.
Results showed a 25% increase in blood glucose levels over the two-hour measurement period following consumption of the caffeine containing energy drink compared to the control, decaffeinated version. Elevations in glucose with the caffeine containing energy drink were accompanied by a significant increase in insulin levels by 26%. Since the half-life of caffeine is in the range of four-six hours, these results suggest that consumption of a caffeine-containing energy drink in adolescents could affect glucose regulation for hours after ingestion.
In the next trial, Shearer’s team will be administering energy drinks to adolescents that contain both caffeine and glucose. Subjects will be asked to drink two servings of ‘large format’ energy drinks a day or a control drink each day for three days. Their blood glucose levels will be continuously monitored over this period. “In this trial,” she says, “we anticipate that caffeine-containing energy drinks will also impair blood glucose regulation in everyday situations where subjects freely choose their food. Activity levels, sleep disturbances and mood will also be assessed.”