A small study conducted at Duke University has suggested that caffeine may hurt blood glucose control in people with Type 2 diabetes. The study’s authors have suggested that people with diabetes may want to avoid caffeinated beverages based on these findings; however, not all medical experts agree that total avoidance is necessary.
The study, which was published in the February issue of the journal Diabetes Care, looked at 10 people with Type 2 diabetes, average age 63. These people were all regular coffee drinkers before the study started and treated their diabetes with diet, exercise, and oral medicines, but not insulin.
The researchers gave the study participants identical packets of pills to take with breakfast and lunch for two days. One day’s pills contained the amount of caffeine present in four cups of coffee, while the other day’s pills were placebos (inactive pills). The participants did not know which pills they were taking on which days and did not consume any other caffeine during the study.
The researchers used continuous glucose monitors to track the participants’ glucose levels during the study. They found that the participants’ average daily glucose levels were about 8% higher on the days that they took the caffeine pills than on the days when they took the placebos. Their post-meal glucose levels were also significantly higher on the days when they consumed caffeine.
These results were consistent with the findings of two previous small studies of caffeine’s effect on people with Type 2 diabetes. The new study was also small, but it was well-designed in that it was double-blind (the participants did not know if they were getting the caffeine pill or the placebo) and featured a crossover (all participants received the caffeine pill and the placebo at different times). However, its results are puzzling in light of some large observational studies, which have found that people who drink coffee appear to have a reduced risk of developing Type 2 diabetes. However, this effect may be due to the presence of compounds in coffee other than caffeine, such as antioxidants.
Some possible explanations for why caffeine may raise blood glucose levels are that it may interfere with the process that transports glucose from the blood into the body’s cells and that it may trigger the release of hormones that raise blood glucose levels.
The Duke researchers indicated that more studies are needed to fully understand caffeine’s effect on blood glucose. However, James Lane, Ph.D., the medical psychologist who led the Duke study, stated of people with Type 2 diabetes that “They may find that it’s easier for them to keep their glucose down if they avoid caffeine.” Writing on the subject in the January/February 2008 issue of Diabetes Self-Management magazine, though, Lynn Grieger, R.D., C.D.E, C.P.T., suggests that “Until more studies are conducted, it is probably best to limit coffee intake to moderate levels.” She also points out that a “cup” of coffee from a café or fast-food restaurant often contains more than 8 fluid ounces, so people looking to limit their caffeine intake should pay attention to portion sizes.
What have your experiences been with caffeine? Do you think it affects your blood glucose control? Bloggers Eric Lagergren and Andy Stuckey—both of whom have Type 1 diabetes, which wasn’t looked at in this study—have blogged about their suspicions that caffeine may have raised their blood glucose levels. (Check out Eric’s entry “In Praise of the Diabetes Contact List” and Andy’s entry “You’re Always On My Mind: Questions and Thoughts About Diabetes” for more.)
I totally missed this cause and effect until the old light bulb went off in my head. Yep, my levels do go higher on days I have caffeine. It happened today as a matter of fact. I dismissed it out of hand as a possible meter/meter strip fluctuation. Not much, but enough as to make me wonder. I only have caffeine on days I drive a lot. Diet Mountain Dew for me. I need to do a couple weeks of no caffeine and see if my levels are lower without it. Very cool stuff.
Posted by Philbur | Feb 01, 2008 at 5:22 pmI was amazed how much my BS when up and for how long it stayed up when I drank a big cup of real coffee. Also you can forget about any sleep the following night which is a problem for most type II diabetics. My advice stick to decaf or omit entirely.
Posted by CalgaryDiabetic | Feb 06, 2008 at 4:34 pmWhat about caffeinated tea? I drink about 16-20 ounces a day. Also, which caffeinated teas cause lower blood sugar boosts?
Posted by kmcewen | Feb 06, 2008 at 6:52 pmWent over to mixing 1/2 reg coffee and decaf in the am and decaf for later in the day…numbers in late afternoon are running about 120 instead of 160 4 out of 5 days!
Posted by hararm13 | Feb 06, 2008 at 7:34 pmI agree with Philbur totally. I am a type II patient for several years now and a coffee drinker. After reading a similar report from another diabetes letter I decided to cut out my coffee for a couple of days. What do you think happened? My glucose remained mostly stable for the whole two days. I also was drinking decaffinated green tea. Does anyone want my left over coffee?
Posted by tldell | Feb 06, 2008 at 7:40 pmI have found that drinking a cup of coffee in the morning after I take my blood count does not seem to change my blood sugar count significantly…..bob
Posted by Robert Baker | Feb 07, 2008 at 10:31 amI’m one of the few it seems who has noticed lower blood sugars when I drink a cup of coffee. I never drink more than one a day, however, and no sugar (not even the “fake stuff”). I also drink herbal teas a lot, and plain water throughout each day. (The coffee does, however prevent sleep for a very long time —which it never did before diabetes “hit”.)
Posted by Pati | Feb 08, 2008 at 12:55 pmThanks for the tip,going to try not having any caffeine for a few days.My sugar has been running high….Nancy G
Posted by Nancy G. | Feb 09, 2008 at 11:48 ami drink coffee every morning- no change
Posted by mimi r | Feb 13, 2008 at 5:39 pmI really have a lot of doubt about any study which only has 10 subjects. At most it might suggest further, more rigorous study.
Posted by skip | Feb 17, 2008 at 10:39 pmNever noticed any increase in BG after a coffee and I’m drinking a strong expresso.
Posted by MIKI | Apr 30, 2008 at 9:10 amThis morning I tested my fasting blood sugar and it was 102. After having a cup of caffeinated tea (no sugar), it went up to 129. Recently, after having a cup of coffee with breakfast, my blood sugar went up to 177! I’m definitely switching to decaf.
Posted by Susan | Jun 04, 2008 at 6:51 amSince certain natural substances added to the diet have been shown to lower blood sugar (as the following ones), I would like to know if blood sugar is lowered by adding to coffee generous amounts of cinammon, nutmeg, or the sweetener stevia. Also, does adding lemon to tea lower blood sugar? In other words, would these additives negate the blood-raising effects of caffeine?
Posted by Ed S | Jun 15, 2008 at 12:16 pmI rarely drink coffee anymore but have been drinking reg & green tea, both decaf. I have found that even “decaf” raises my blood sugar. The dietician said that even decaf has a small amount of caffeine.
Posted by Sue T | Jun 20, 2008 at 10:17 amDear Sir
Posted by john sugar | Jul 01, 2008 at 9:01 pmI have type 2 diabetis I AM 74 Years old
I use accu-chek device to monitor GI.
Blood test evening 01.07.08 7. mmol
Blood test morning after one mug instant coffee
8.8 mmol
Jhon Sugar
I do not have diabetes. However, I work at a rehab agency for people with vision impairment, and interact with people who have diabetes, both Type I and II. My understanding of diabetes is that blood glucose levels need to stay within an acceptable range, and that people who use oral meds. or insulin to control blood glucose need to be concerned both with readings that are too high, and also too low. Could people with diabetes (and the rest of us!) be using caffeine to raise blood glucose levels at times of the day when glucose levels are sinking unacceptably low? I am thinking that many people tend to drink caffeinated substances at mid-morning and mid-afternoon. Might this possibly be a healthier way to deal with mildly low blood glucose levels than a sugary snack?
Posted by Leslie B. | Dec 08, 2008 at 3:50 pmLeslie B.,
Caffeine is not an approved treatment for hypoglycemia (low blood glucose), and trying to use it as such could be dangerous. As you can see just from reading the comments here, caffeine can have different effects on different people, and even if it does raise a person’s blood glucose level, it may take an unpredictable amount of time to do so.
You may want to check out our article “Understanding Hypoglycemia,” which lays out the protocol for treating low blood glucose. Many different sources of fast-acting carbohydrate — such as milk, juice, or fruit — can be appropriate if a person wants to avoid candy or other “sugary snacks.”
Posted by Tara Dairman, Web Editor | Dec 08, 2008 at 5:27 pm02/08/2009:
Posted by troben46 | Feb 08, 2009 at 7:56 pmI am a 62 year old white male Type 2 Diabetic. 12 years on oral meds. Now two weeks on Humalog (3-4 times daily before meals} and Lantus (10 units every evening). Still taking 2000 mg Metformin per day. I drink 8-10 cups coffee per day. My blood sugar definitely spikes. Example, this morning before breakfast my blood sugar tested 153 mg/dl. One hour later (still before breakfast)after a 24 ounce Dunkin’ Donuts Hazelnut coffee with milk my blood sugar tested at 188 mg/dl. This has been my continuing observation about the effect caffeine has on my blood sugar level. Time to quit.
I just found this site this morning. I rarely drink diet soda. I actually love water (sometimes with lime or lemon). I have just recently been diagnosed with Type II. I am on 500 mg. of metformin and having lost 8 pounds and moderately exercising most days of the week, I have gotten my BS down to normal levels. I have been keeping a log of what I eat, when, levels, etc…..last night we were visiting friends and I decided to drink diet Coke and then to top it off, I had a 1/2 cup of Blue Mountain regular coffee from Jamaica (since we had all just visited there last month). I did have a small piece of birthday cake…2″x2″ without all the frosting. I was so proud of myself….
This morning I took my BS on arising and to my dismay, it was 129!!!! I know that isn’t too out of range, but I have gone a whole month now with levels in the non-diabetic range.
This morning I told my husband that I wondered if caffeine could have had anything to do with that reading (at first I thought the testing was in error)….came here to look it up and sure enough. I don’t even like diet pop….so, for me, I am thinking that three smalls cans of diet coke and a cup of Blue Mountain reg. could have been the dirty little culprit! What do you think?
Posted by Chris | Mar 23, 2009 at 12:43 pmHy
I have just discovered this website.
Posted by Cordier Alain | Jun 11, 2009 at 5:19 amAwesome ! Thanks for all the news and comments. I’m 57, french and type 2 diabetic. I’m going to stop caffeinated beverages. A question: what do you think about chromium picolinate since your last article?
I am brand new to all of this. Approx 2 months ago my doc told me I was T2 Diabetic (BS was why high 200+). Since that time I’ve dropped 20lbs and my avg BS is below 120 (a couple of spikes to 160 have kept it up). I don’t know if that is good or not? My doc is not very imformative and I do not know anyone else w/T2D to chat with? Any insights would be appreciated, thanks.
Posted by John | Jun 25, 2009 at 5:07 pm