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Researchers at Duke University have been taking aim at caffeine for some years now, and they think that people with type 2 diabetes should avoid coffee. According to the results of two small but significant studies, Dr. James Lane believes that caffeine affects the way that diabetics metabolize carbohydrates and leads to increased blood sugar levels.
Back in 2004, Dr. James Lane and fellow researchers tested the effects of caffeine in 14 people with type 2 diabetes. They tested the fasting blood sugar levels of each person, then gave them two caffeine pills and tested blood sugar levels an hour later. Each person then drank a high-carb meal replacement drink with a third caffeine pill, and blood sugar levels were tested one hour and two hours after their ‘meal’. Each person was tested on two different days. On one of those days, half the group got real caffeine and the other half took a placebo. On the second day, those who got a placebo on day one got the real deal, and those who got caffeine the first study day took a placebo. Neither researchers nor subjects knew which was which.
Even though fasting blood sugar levels weren’t affected by the caffeine, the blood sugar levels of those who took the caffeine pills showed significantly higher levels of blood sugar after meals than those who did not. The researchers concluded that caffeine has some effect on the interaction between glucose and insulin, though the study could not determine exactly what the mechanism was. They did advise, based on the results of the study, that people with diabetes might do better to avoid coffee or drink decaf.
In January 2008, the same group of researchers released the results of a second study. In this study, which included ten participants with type 2 diabetes, researchers implanted a small glucose monitoring device under the skin to measure blood sugar levels throughout the course of the day. That allowed researchers to track the effects of the caffeine on blood sugar levels over the course of 72 hours while participants carried on with their lives.
The patients were each given a caffeine pill on one day and a placebo on another day. Researchers found that on the days that they took caffeine pills, their blood sugar levels averaged 8% higher over the entire course of the day than on the days that they took a placebo. The effect was especially marked after meals. Blood sugar levels after breakfast were an average of 9% higher, 15% higher after lunch and 26% higher after dinner.
Researchers not sure why caffeine raises blood sugar levels
Lane says that there are two possible reasons for the increases in blood sugar levels on the days that patients received caffeine pills. Caffeine may interfere with the process that moves glucose from the blood into muscle and other cells in the body, breaking into the chain of metabolism in some way. Caffeine may also trigger adrenaline, which boosts blood sugar levels. Other researchers have speculated that caffeine makes the body less sensitive to insulin levels in the blood. Lane plans further research to determine whether cutting caffeine from the diet will help diabetics better control blood sugar levels.
“My advice would be, if patients are having trouble controlling their blood glucose and they are coffee drinkers, particularly heavy coffee drinkers, they might want to give it a try to see if it makes a difference to them,” he said. He believes that it may make a big difference to some, while others will see little difference at all.
A care advisor at Diabetes UK said that the research is “interesting”, but the sample is very small, so it proves very little. She said, “More research is needed before we ask people with diabetes to stop drinking coffee. The best way to control glucose levels is through healthy eating and exercise.”
Other critics of the study’s recommendation pointed out that the researchers used caffeine pills, not brewed coffee which may contain other components that negate the effect of caffeine. Other studies have shown that drinking coffee reduces the risk of developing diabetes.
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Harji says
Yes. it is same to me. coffee increase my blood sugar also. Fasting 110. after a cup of coffee goes to 150 to 160. I had a doubt so check for 5 days in a raw same effect. may be everyone’s genetic code difference but sure, coffee increase my blood sugar.
But what can I do? I usually works 14 to 16 hour shift as dialysis Nurse.
William McCarey says
Caffeine and/or coffee definitely raises my blood sugar levels.
William McCarey says
Yep, same effect that I experience with decaf coffee. I have now switched to Sencha tea. Does not elevate the blood sugars.
William McCarey says
Yep, decaf coffee still jacks up my blood sugar level by 30 points in the morning. I am not sure if this effect is the same in the afternoon.
Adria says
Caffeine impairs insulin action, but doesn’t necessarily affect blood sugar.
William McCarey says
Caffeine and/or coffee definitely raises my blood sugar levels.
Olive says
I noticed significant increase in my blood sugar level and High LDL following my frequent I take of coffee. I am not diabetic but my sugar level shoot up to 148.9mg/dl for reasons I know not within just 1 year of frequent intake of decafinated coffee. I find this your research useful because I ve wondered what might have caused the problem.
Marla says
This morning when I woke up my blood sugar was 109. I had restricted coffee from my diet since I thought it was the creamer that I just had to have in my coffee and absolutely hate it black. I was looking for a substitute for the creamer and read that heavy cream was 0 carbs. Upon trying this in my coffee I checked my BL just one hour later and it is 200 and rising! I take janumet and 2mg glimiperide twice a day and trying to keep my sugar in check before my next labs to decide if I’m going to have to take insulin which I am trying so hard to avoid. After this mornings results I will give up coffee period and hope this rise in BS does not appear in my labs. Since I have a couple of months before labs, does anybody know how far back this blood work will go? I really don’t want to be put on insulin over this mistake.
Chris says
I find this to be true as well. I’ve been on a juice fast for 60 days, which required cutting out coffee and my numbers returned to normal in just a few short days. But, my numbers jumped way up 250- 260 once I introduced coffee (black) back into my diet. So, now I’m avoiding it again and my numbers have returned to normal levels. Coffee does affect my blood sugar numbers.
den says
while sugar level high is not good , maybe coffee artificially boost sugar level to high is not all bad as it suppresses hunger and less calories are comsumed bring overall 24 hours sugar levels down !
DONALD ABRAMSKY says
Yes I found that after I have a cup of black coffee my blood sugar will rise 10 to 20 percent.
I have checked this multi times.
kerrie says
In my experience, after being a diabetic for 26years, is porridge is deadly. you only need to smallest amount of porridge to push blood levels up. It’s all carbs. You need to look at putting more Protein in your breakfast. I personally find porridge elevates bsl’s considerably.
walter clemens says
This a.m. I had porridge, blueberries with a teaspoon of honey for breakfast. Got a coffee, double cream and double sweetner, and blood sugar went from 12.6 to 21.2 (Canadian scale-metric???) within an hour. Is it the coffee, sweetner, or combination or the breakfast and coffee? HELP??
Danny says
I woke up this morning with a 130. Two and a half hours later after consuming nothing except 3 cups of coffee I had a 181.
William McCarey says
Yep, same effect that I experience with decaf coffee. I have now switched to Sencha tea. Does not elevate the blood sugars.
james says
I can say with out a doubt that caffee raise my sugar levels. two strong cups black will raise my level by 200 points. I have been experimenting for months now and with taking no pills nor eating and only being at home on the pc my levels always go up. though ice tea does not.
Dana says
I have PCOSy combined with insulin resistance. I have tried to cut a caffeine and it helped me a lot to stabilize my blood sugar levels. Every time when I sleep in the afternoon, when I wake up I have to eat something sweet. When I cut caffeine I did not have that problem.
Lynette Hornung says
I am pre-diabetic and take 500 mg of Metformin per day. my sugar level usually is around 130. I recently started on 12.5mg of Hydroclorot to help with swelling of feet. I take it around 8am each day. I drink up to 4 cups of coffee by noon. (nothing new). would this cause blood sugar to pick around noon to 300+ level?
chris duke says
it seems to jump my bloodsugar up i went to bed with a 150 and after coffee this morning with a tiny bit of skim milk its 176
Desta Kassa says
I would like to get piece of informations on this issue. please, would you mind to help me?
Taiseer Hamid says
I am type 2 diabetes , from my experience , drinking coffee has significant impact on blood sugar , it increases the blood sugar in my case by at least 30%. i am testing my blood sugar on daily basis more than twice a day , and i found this result …i am pretty sure …!!!
colin says
hi, i have tried decaff coffee instead of regular but still find it increases my blood sugar. would welcome your comments, many thanks colin
William McCarey says
Yep, decaf coffee still jacks up my blood sugar level by 30 points in the morning. I am not sure if this effect is the same in the afternoon.