Caffeine ingestion elevates plasma insulin response in humans during an oral glucose tolerance test.


Graham TE, Sathasivam P, Rowland M, Marko N, Greer F, Battram D. from the Canadian Journal of Physiol Pharmacol - 2001 Jul;79(7):559-65

We tested the hypothesis that caffeine ingestion results in an exaggerated response in blood glucose and (or) insulin during an oral glucose tolerance test (OGTT). Young, fit adult males (n = 18) underwent 2 OGTT. The subjects ingested caffeine (5 mg/kg) or placebo (double blind) and 1 h later ingested 75 g of dextrose. There were no differences between the fasted levels of serum insulin, C peptide, blood glucose, or lactate and there were no differences within or between trials in these measures prior to the OGTT. Following the OGTT, all of these parameters increased (P < or = 0.05) for the duration of the OGTT. Caffeine ingestion resulted in an increase (P < or = 0.05) in serum fatty acids, glycerol, and plasma epinephrine prior to the OGTT. During the OGTT, these parameters decreased to match those of the placebo trial. In the caffeine trial the serum insulin and C peptide concentrations were significantly greater (P < or = 0.001) than for placebo for the last 90 min of the OGTT and the area under the curve (AUC) for both measures were 60 and 37% greater (P < or = 0.001), respectively. This prolonged, increased elevation in insulin did not result in a lower blood glucose level; in fact, the AUC for blood glucose was 24% greater (P = 0.20) in the caffeine treatment group. The data support our hypothesis that caffeine ingestion results in a greater increase in insulin concentration during an OGTT. This, together with a trend towards a greater rather than a more modest response in blood glucose, suggests that caffeine ingestion may have resulted in insulin resistance.

Human Biology and Nutritional Sciences, University of Guelph, ON, Canada. terrygra~uoguelph.ca

SO: never drink coffee before you go for a glucose tolerance test - the lab will make you rebook.

I'm still not sold on this idea that it's all the fault of caffeine - caffeine may stimulate insulin but if there are no / minimal carbs present (in the case of a LCer) all it's going to do is slow down fat burning for a while - if that.

Nat

Effects of caffeine on glucose tolerance: a placebo-controlled study. from European Journal of Clinical Nutrition 1998 Nov;52(11):846-9

Pizziol A, Tikhonoff V, Paleari CD, Russo E, Mazza A, Ginocchio G, Onesto C, Pavan L, Casiglia E, Pessina AC.


OBJECTIVE: The investigation was performed to study the effects of 200 mg oral caffeine on glucose tolerance. DESIGN: Single-blind Latin square with active treatment (caffeine) and placebo. SETTING: The University of Padova, Department of Internal Medicine. SUBJECTS: 30 nonsmoking healthy subjects aged 26-32 years who abstained not only from coffee but also from tea, chocolate and cola for 4 weeks and who had given their informed consent. INTERVENTIONS: A 75 g oral glucose tolerance test (OGTT) was performed after giving caffeine or placebo (highly decaffeinated coffee). RESULTS: The glycaemic curve was normal in all subjects and was similar in the two groups until the second hour; in subjects taking caffeine a shift towards the right was detected at the 2nd, 3rd and 4th hours in comparison to those taking the placebo. Blood insulin levels were comparable after caffeine and after placebo along the entire OGTT. CONCLUSIONS: The data suggest that caffeine intake induces a rise in blood glucose levels that is insulin independent.

Department of Clinical and Experimental Medicine, University of Padova, Italy.

http://mega.ist.utl.pt/~rmlbgs/nutri.html
According to this website, caffeine encourages lipolysis and...

"Caffeine increases the level of circulating
fatty acids. This has been shown to increase
the oxidation of these fuels, enhancing fat
burning. Caffeine has been used for years by
runners and endurance people to enhance fatty
acid metabolism. But apparently the effect is more
pronounced in people who are not habitual users
of caffeine. For the above reasons, it is a myth
that taking 'too much' caffeine will cause an insulin
burst and lead to weight gain."

This seems to contradict what is stated above... and as coffee is really the only vice left to me, I'd love to know what the real story is!

Well, I do know from MUCH testing and observation that coffee caffeine makes my blood sugar go UP UP UP!! (I'm diabetic and I test *everything* I eat--many times if necessary to determine exactly what kind of affect on my BG it has) I do occasionally drink sodas with caffeine and I drink tea, but I haven't found that they have any affect at all. Which I find interesting. Decaf coffee has virtually no affect at all.

I have been trying to find out a definite position either way on this subject... a small amount of physiological info claims that caffeine causes insulin and bloodsugar to go haywire.. but the majority of the info( mostly sports medicine) I have read says that caffeine mobilises fattty acids into the bloodstream, causing the fat to be used as a preferential source of energy, sparing glycogen... meaning.. as far as I can understand... that in the absence of carbs, caffeine will burn fat when you exercise.. anyone have any scientiftic evidence refuting this?