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Wednesday, November 17, 2010

Caffeine and Insulin Sensitivity

Caffeine and Insulin Sensitivity  (full text PDF free till end of the month)

A number of reports have observed that acute caffeine ingestion decreases glucose tolerance and insulin sensitivity, and have raised the question whether its increased consumption throughout the world in the form of coffee and cola beverages might be of public health concern in the development of type 2 diabetes. Although some epidemiologic studies have found strong associations between coffee intake and detrimental lifestyle factors that favor obesity and diabetes, it is interesting that in spite of this, they have demonstrated that increased coffee consumption is associated with a decreased risk of developing type 2 diabetes.  When lifestyle confounders are taken into account, individuals consuming 6 cups coffee per day have at least 50% less risk of developing type 2 diabetes than those consuming 2 cups per day. Although it is perhaps premature to recommend increased coffee or caffeine intake to prevent the development of type 2 diabetes, there is little or no evidence to warrant the recommendation that it should not be a part of a normal healthy diet.
This is an interesting summary article.  In the section entitled Caffeine and Carbohydrate Metabolism, a case for acute caffeine consumption impairing glucose tolerance by inducing insulin resistance (decreases glucose uptake) is laid out which goes counter to the results of the coffee study highlighted above.   Perhaps it's something else in the coffee?  
More modest inverse associations were also observed for decaffeinated coffee consumption, caffeine intake from noncoffee sources, and total caffeine intake, as well as the incidence of type 2 diabetes, suggesting that caffeine and other components of coffee contribute to this inverse relationship.
Seems in part the case.  The authors discuss the conflicting short term "laboratory measured" effects and those seen in epidemiologic studies.

... it is very obvious that the results and conclusions of the acute and epidemiologic studies do not agree, and this illustrates the problem of extrapolating shortterm observations to a chronic disease (with an etiology that is influenced by a variety of interacting genetic and lifestyle factors.)
This seems even more surprising given the rather strong correlation between coffee intake and other lifestyle factors that are deleterious such as drinking, poor diet, etc.  Below I've summarized in bullet point fashion how the authors believe increased coffee intake decreases the risk of developing T2:

  • Caffeine stimulates resting metabolic rate.  It could be as simple as fewer coffee drinkers getting overweight?
  • Caffeine increases epinepherine
  • Caffeine + epinepherine act together to promote lypolysis leading to an increase in plasma free fatty acid levels. (<- at first glance this might seem to not be a good thing)
  • C+E have a thermogenic effect.  (thus the FFA's are likely readily oxidized with the boosted metabolism)
  • The combined effects increase lipid turnover (less ROS hanging around??) "which may in the long-term have beneficial effects on body weight, body composition, and substrate use that could help to prevent the development of glucose intolerance, insulin resistance, and diabetes."
They go on:
However, such arguments are very speculative, and it may well be that the observed acute effects of coffee or caffeine on glucose tolerance and insulin sensitivity are suppressed by habituation to its repeated consumption.  Indeed, repeated caffeine consumption over 5 days induces complete tolerance to its effects on blood pressure, heart rate, and, in particular, blood glucose concentrations.52 

They also consider the other components of coffee:

  • Coffee contains many bioactive compounds, most of which have as yet unknown metabolic effects.
  • Coffee contains a quinide that improves insulin-mediated glucose uptake in rats
  • Phenolic compounds in coffee influence GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide I) levels.  (These two peptides are called incretins and are associated with beta cell proliferation and decreased apoptosis (death) 

"Consequently, the combined physiologic effects of coffee’s many components may well be very different from that of one of the components studied alone."

Posted by CarbSane after her third very large mug of coffee 8*)


dietconcepts said...

Excellent writeup, and this confirms everything I've read and concluded about coffee for years. Plus, coffee is delicious. :)

CarbSane said...

When coffee has hampered my weight loss it has always been because I put too much extra stuff in it (aka cream). I'm one of those people who cannot abide black coffee (low fat nightmares?), but also cannot do the whole heavy whipping cream some HF LCers do.

Matt Stone said...

Coffee makes me feel wicked crappy, so I don't usually drink it. Just on occasion. I'm still not certain that it has some protective effect for type 2 diabetes because epidemiological studies suck so hard.

dietconcepts said...

I never take anything in it - black coffee or (preferably) espresso is my thing. It's not that I don't like cream, but I get more pleasure out of something like hot cocoa with cream than putting that stuff in my coffee. It may also be conditioning - I prefer to avoid cream and sugar in my coffe precisely because I know it has an adverse effect on my health.

Matt - personally, I don't need convincing. Search for the terms coffee and diabetes in and look at the research data.
Of course, if it makes you feel crappy then don't drink it. :)

Melchior Meijer said...

Coffee is a big conundrum to me. I'm a believer in HPA-axis dysfunction as a strong causal factor in the pathogenesis of metabolic syndrome, diabetes and CHD. Cushing's disease is a fenomenal model for this. Anything that skrews up cortisol rhythms or is associated with this (Cushing's, depression, cocaine use, use of anabolic steroids, long term medication with cortico steroids, social dislocation, discrimination, spinal cord injury, etc) leads to the same cluster of symptoms:

- chronic hyperinsuliamia
- impaired glucose tolerance
- Increased clotting tendency
- Visceral fat accumulation
- Hypertension
- Reduced production of endothelial progenitor cells
- And I forget a bunch

One could argue that chronically elevated cortisol levels are the culprit.

Then alongs comes coffee. Coffee consumption sends cortisol into the sky. The effet is quite prolongued. Yet coffee is consistently associated with reduced diabetes and even CHD risk.

What element in coffee (or the habit of drinking coffee) could possibly override the cortisol spike?

I have one meager suggestion. Coffee contains chlorogenic acid, which has anti diabetic properties, but is also one of the few compounds able to bind and remove excess iron. Excess iron - subclinical hemochromatosis - is clearly an underestimated causal factor in many diseases. But would the effect be that huge? I think it must be something else.

CarbSane said...

I would add that for me coffee is an appetite suppressant. Of course this is n=1 anecdotal, but if I find myself getting mid-afternoon munchies, a mug of joe takes care of that and often I won't be hungry come dinner time. I'm not usually hungry in the morning, so rarely eat breakfast, and there's just not that many calories in the cream to account for the fact that I'm often not hungry until mid-afternoon on days I chug an extra mug.

Nigel Kinbrum said...

Having watched some lectures by Dr Robert Sapolsky, it would appear that cortisol spikes are good but chronic hypercortisolaemia is bad.

CarbSane said...

I have one meager suggestion. Coffee contains chlorogenic acid, which has anti diabetic properties, but is also one of the few compounds able to bind and remove excess iron. Excess iron - subclinical hemochromatosis - is clearly an underestimated causal factor in many diseases. But would the effect be that huge? I think it must be something else.

Interesting .... didn't know this. I admit to being well behind the curve on iron. I see a lot of making sure there's no iron in one's chosen multi (I don't take a multi) but not sure why.

Yeah, as Nige says, we have to distinguish between spikes of certain hormones and chronic elevated levels. Same certainly goes for insulin and probably a whole host of hormones we never really think about.

Melchior Meijer said...


Sapolsky is an incredible scientist (although he seems to fear saturated fat and cholesterol ;-) ).

The rhythm might be what counts, indeed. CHD patients often have a relatively low morning cortisol (but high avarage readings). They lack flexibility. Cortisol pattern reflects HPA-axis function. However, the problems occuring on cortison therapy suggest that spikes also harm directly. That said, you probably cannot administer cortisol without influencing HPA-axis function.

Melchior Meijer said...


If you get a chance, please read Anthony Colpo’s ‘The Great Cholesterol Con’ (the other TGCC by Malcolm Kendrick is great as well). Colpo covers the iron issue quite extensively. If I wasn’t such a terrible coward regarding white coats, I would definitely donate blood. It adds 5 years to a males life, I believe (but that’s observational, of course, blood givers could just be nicer, less neurotic people ;-) ).

CarbSane said...

Thanks for that reference. I've heard good things about Colpo's work on this. Without reading, I'm glad I never fell for the women need iron stuff. Sometimes being supplement lazy is a beneficial? LOL!

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