The common denominator shared by caffeine and glucose is diabetes. Problems in glucose metabolism give rise to diabetes, and the media has given attention to studies performed on caffeinated coffee drinkers that show a protective effect from caffeine. To understand the relationship, it's helpful to know a little about the biochemistry of glucose and its relationship to caffeine.
Glucose
According to the National Institutes of Health, the body breaks food down into glucose and transports it to the bloodstream, where it's known as blood glucose or blood sugar. Naturally, after a meal, blood glucose levels rise, and in response, the pancreas secretes a hormone called insulin to signal blood cells to take up blood sugar for storage in liver, muscle and fat cells. When something goes wrong with this pathway, blood sugar levels remain high, giving rise to a condition called pre-diabetes as the intermediate step to full-blown diabetes.
Caffeine
The association of caffeine to glucose levels has been a subject of scientific scrutiny for decades. According to a study published in the "Journal of Caffeine Research" in April 2011, more than 600 studies were published since 1968 on the subject of coffee drinking and blood glucose levels in relation to diabetes risk. Although some of the studies discussed the benefits of the coffee bean and its antioxidant compounds, the majority deal specifically with caffeine. Nonetheless, researchers reported no healthful benefits found from consuming other types of caffeinated beverages.
Positive Benefits
A meta-analysis is a review by qualified researchers of studies published on a given topic. The reviewers summarize findings and present an authoritative analysis. One such analysis was performed by researchers reporting in the July 2005 issue of the "Journal of the American Medical Association." They reviewed studies involving 193,473 participants and 8,394 cases of type 2 diabetes in relation to caffeine intake and blood glucose levels. They found that higher caffeinated coffee consumption was consistently associated with a lower prevalence of high blood glucose levels. The effect was particularly pronounced after subjects ate a meal.
Post-load Effects
Doctors are primarily interested in your fasting glucose level, which is simply a measure of how much glucose is circulating in the blood eight hours after eating. They expect sugar levels to be high after a meal because insulin hasn't had a chance to do its job yet. Levels after a meal are known as post-load. Researchers reporting in the December 2004 issue of "Diabetologia" found results similar to those discussed in the "Journal of the American Medical Association" meta-analysis. This study involved 2,394 participants who were followed for six years. The researchers found that caffeine reduced post-load levels, but not fasting glucose levels.
References
- NIH: Insulin Resistance and Pre-diabetes
- "Journal of Caffeine Research"; Caffeine, Glucose Metabolism, and Type 2 Diabetes; James Lane; April 2011
- "Journal of the American Medical Association"; Coffee Consumption and Risk of Type 2 Diabetes: A Systematic Review; Rob van Dam and Frank Hu; July 2005
- "Diabetologia"; Coffee Consumption and Incidence of Impaired Fasting Glucose, Impaired Glucose Tolerance, and Type 2 Diabetes: The Hoorn Study; Rob van Dam et al.; December 2004
