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Diabetes Developments - A blog on latest developments in diabetes by David Mendosa

Does Caffeine Cause Blood Sugar Changes?

May 17th, 2011 · 7 Comments

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The first thing I did after reading the new study that caffeine can increase our blood glucose level was to switch to drinking green tea. The second thing I did was to switch again — this time to decaffeinated green tea.

I overreacted. Several years ago I had switched from coffee to Darjeeling tea, which has about half the caffeine per cup. While green tea has even less, I don’t like it much and only drink it rarely. I disliked the decaffeinated green tea so much that I threw out the package after taking the first sip.

Now, I’m almost entirely back to Darjeeling tea. People call it a black tea, although it is light-colored and is technically more oolong than black and is therefore lower in caffeine than true black teas.

While I control my blood glucose level, I’m not a purist. I have to enjoy everything that I eat or drink. While my diet includes no starch, sugar (no sucrose or high-fructose corn syrup), salt, or alcohol, except occassionally when I eat out, I don’t miss any part of this standard American, or SAD, diet. My recent A1C result was 5.3 percent.

Caffeine may well raise my blood glucose level. But after carefully reading the new study, I doubt it.

The new study is a review in the April 7 issue of the Journal of Caffeine Research by James D. Lane, associate research professor in the department of psychiatry and behavioral sciences at Duke University Medical Center. Dr. Lane sent me the full-text of the study, which is now free online.

Dr. Lane reviewed 17 studies that showed that caffeine increased insulin resistance or impaired glucose tolerance of people who don’t have diabetes. Using accepted study design — double-blind and placebo-controlled — and moderate doses of caffeine equivalent to two or three cups of brewed coffee, these studies consistently showed a transient increase in insulin resistance.

Yet many other studies of people who don’t have diabetes show apparently contradictory results. Consistently, these studies have found that when people without diabetes drink a lot of coffee they are much less likely to get diabetes.

So, who knows whether coffee is good or bad for them. But for us who have diabetes, other studies found that caffeine exaggerates the rise in glucose when people with diabetes ate carbohydrates. Dr. Lane thinks that the effect is clinically significant. He compares the effect — an increase of 18 to 26 percent in blood glucose — to a similar, albeit somewhat less, decrease in blood glucose when we take a sulfonylurea, Starlix, or Precose.

“Caffeine in coffee, tea, or soft drinks,” Dr. Lane says, “causes a transient insulin resistance that can produce exaggerated glucose and insulin responses when carbohydrate is consumed.” This seems to me to be the key.
It’s really the same old story. “Diabetes,” as Dr. Lane points out, results “from defects in carbohydrate metabolism.” Carbs, more than caffeine, is the story.

Since I follow a very low-carb paleo diet, eliminating caffeine entirely might well increase my insulin sensitivity. A bit. I will try to drink fewer cups of tea, but no way will I switch to decaffeinated tea.

But coffee drinkers, particularly those who still consume starch and sugar, may well want to test for themselves. My friend Gretchen Becker, who also writes here at HealthCentral, has done just that.

Gretchen’s testing shows that for her “caffeine does seem to have an effect.” But while her blood glucose level rose by 15 points, that was because of the carbs she ate. The caffeine just delayed the peaks and didn’t seem to increase them.

She recommends this procedure:

Get up and have caffeine or no caffeine. Wait an hour. Eat breakfast. Measure every hour until lunch. Then measure for a few hours after lunch, as the effect is supposed to persist.

Now, what effect does caffeine have on your blood glucose levels?

This is a mirror of one of my articles that was originally published on Health Central.

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Posted in: Diabetes Diet

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7 responses so far ↓

  • 1 Ron // Jun 25, 2012 at 9:35 am

    I am not diabetic but became worried about being prediabetic after I had switched to a low carb diet. My readings prior to this had been normal, at least the last time I had checked which was probably a year ago. So, I decided I had better check to see where I am at after being about 7 weeks into this new diet. fbg 104. I thought this can’t be. So I did the research and found info this was normal for some low carbers. I have been doing a lot of exercise to drop weight along with this new diet. I completed an almost two hour workout (still had not eaten anything since the night before) checked by bg it was 136 (within 5 minutes of workout). 1 hr it was back down to 104. My number during the day post meal 1 and 2 hours were good and always back down to the 104. I did an A1c test it was 5.1 However, this still troubled me because the 5.1 must have been higher than what it would have otherwise been because if the 104 was my new base that would be up from before beginning the diet. In the last couple of years I began drinking coffee throughout the day. A few days back I only had one cup and then switched to decafinated green tea and drank that through the day. I check bg and it was 95 then again 85. Next morning fbg 85, I drank no caffeine just decaf tea. It stayed in this lower range. Did that for a couple of days. Then thought I would try regular green tea. That morninf it went from and 89 fbg to 104 after drinking it and still had not eat. Dropped the caffeine and it went back down. I don’t get it >s< but I thought I would share my story with you.

  • 2 Maia // Jan 3, 2013 at 1:37 pm

    Ron,

    Do you have an update of how your caffeine-free test went?

  • 3 David Mendosa // Jan 3, 2013 at 1:47 pm

    Dear Maia,

    That’s the lastest info I’ve seen.

    Namaste,

    David

  • 4 Jennifer // Jan 5, 2013 at 1:36 pm

    After 2 cups of decaf coffee in the morning my blood sugar increases by 70+ points. I only use coffee mate as a creamer and no sugar. I don’t understand because just about everything I read says that coffee doesn’t raise your blood sugar.

  • 5 David Mendosa // Jan 5, 2013 at 1:52 pm

    Dear Jennifer,

    I suggest that you might drink your coffee without Coffeemate and use heavy cream instead. Coffeemate comes in dozens of different flavors and formulations, and some, if not all of them, have several grams of carbohydrate. Heavy cream and coffee itself doesn’t.

    Namaste,

    David

  • 6 Prabodh Kumar // Sep 15, 2013 at 9:12 am

    Whether coffee is suitable to diabetes ?

  • 7 David Mendosa // Sep 15, 2013 at 8:45 pm

    Dear Prabodh,

    Yes, coffee is perfectly fine for us (although personally I prefer black tea). But do drink your coffee black. The sugar and milk or half and half have too many carbs. Full cream, however, doesn´t have carbs.

    Namaste,

    David

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