Is coffee good or bad for diabetes? Some studies show that coffee is protective, while others say it’s harmful. Some say decaf is better; others say it’s worse. Let’s try to sort this out.
For years, various studies have reported that coffee drinkers are less likely to develop Type 2 diabetes. A recent UCLA study found that “women who drink at least four cups of coffee a day are less than half as likely to develop diabetes as non-coffee drinkers.” Lead scientist Simin Liu said that coffee may improve the body’s tolerance to glucose by increasing metabolism or lowering insulin resistance.
In 2008, Diabetes Self-Management blogger Amy Campbell reported on several other studies showing benefits for coffee. A study published in Diabetes Care in 2006 followed about 900 adults, roughly 300 of whom had prediabetes, for eight years. The people who drank caffeinated coffee had a 60% lower risk of getting diabetes than those who didn’t drink coffee.
Another Diabetes Care study published the same year looked at more than 88,000 women in the Nurses’ Health Study II. It found that women who drank two or more cups of coffee daily had a lower risk (slightly more than half the risk) of getting diabetes than those who drank just one cup of coffee daily, or no coffee at all. And it didn’t matter whether the coffee was regular or decaf.
So right there you have a disagreement about caffeine. Meanwhile, other studies have shown that coffee, or the caffeine in coffee, raises after-meal (postprandial) blood glucose levels up to 20% in people with diabetes. These studies have not been large but have received a lot of attention. In the most-reported study, from Duke University, ten subjects, all with diabetes, were tested — given either caffeine capsules or a placebo (inactive treatment), then switched to the other type of capsules. All showed higher blood glucose levels on the days they took caffeine.
Lead researcher James Lane, PhD, wrote that “In contrast to nondiabetic subjects, our subjects demonstrated exaggerations of both glucose and insulin responses when caffeine was ingested with carbohydrates.”
In a survey on a Mayo Clinic diabetes blog, most readers reported that coffee raised their glucose, even if they had no cream, sugar, or any other food at the time. A reader named Sherri posted, “I drink one large cup in the morning (with flavored cream) before breakfast. [When I monitor], I find that my glucose level is already at high normal for two hours after a meal, and I didn’t even eat yet!”
So how can coffee protect against diabetes if it raises blood sugar? Is coffee good for preventing diabetes, but bad once you already have it? How could this be?
How Coffee Might Protect
First of all, what is going on in people’s bodies when they drink coffee? The UCLA researchers have found that a protein called sex hormone-binding globulin (SHBG) somehow lowers insulin resistance. Most coffee drinkers greatly increased levels of SHBG in the UCLA study. The people with higher SHBG were the ones who didn’t develop diabetes.
A 2009 study in The New England Journal of Medicine of over 800 women found that “higher plasma levels of SHBG were… associated with a lower risk of Type 2 diabetes.” The lowest SHBG group had twenty times the risk for Type 2 of the highest SHBG group.
This is pretty convincing evidence for SHBG, and since coffee is the first way anyone has found to raise SHBG, it might be very helpful stuff. But coffee is a complex substance, with hundreds of natural chemicals in it. How does it work, and what kind of coffee is best?
Is It the Caffeine?
If coffee is good for you, but caffeine is bad, then maybe decaf coffee is the answer? But the UCLA study found that decaf drinkers did not get the protective benefits of coffee. In the two Diabetes Care studies cited by Amy Campbell, one found that decaf or regular worked equally well, while the other found benefits only for caffeinated coffee.
Perhaps the mice have the answer. Reporting in the Journal of Agricultural and Food Chemistry, Fumihiko Horio and colleagues at Nagoya University in Japan fed either water or coffee to a group of laboratory mice engineered to be susceptible to diabetes. According to Science Daily, “Coffee consumption prevented the development of high blood sugar and also improved insulin sensitivity in the mice, thereby reducing the risk of diabetes. Coffee also caused a cascade of other beneficial changes in the…liver and inflammatory [chemicals] related to a reduced diabetes risk. Additional lab studies showed that caffeine may be ‘one of the most effective anti-diabetic compounds in coffee,’ the scientists say.”
So what’s the answer? It certainly seems that coffee protects against Type 2 diabetes, with more evidence for the caffeinated version than for decaf. For people with Type 2 diabetes, going with decaf would be safer, but it’s possible that regular might be more effective. Maybe the temporary glucose spikes, associated with drinking caffeinated coffee with meals, may be worth it in the long run. Or maybe not. People with Type 1 might be better off with decaf. We just don’t know, but with or without caffeine, coffee seems to be one of nature’s wonder drugs for many people. Of course, you should check your own blood glucose levels and see how it affects you personally.
I’d like us to conduct our own study here. Does coffee raise your glucose levels or lower them? What have you noticed about the effects of coffee drinking on your diabetes?
This is fascinating David.
Caffeinated coffee will definitely spike my BG at lot so it is hard to see caffeine being a good guy after you have developed D. Before D who knows? My wife who is well on her way to D is Swedish were coffee is a sacred ritual so it does not seam to have helped her. She has a BMI of 22 and has never eaten at American junk food establishments. She eats fairly low carb.
I am not 100% sure which type I am. I take a lot of insulin and I am very insulin resistant. I could be some sort of slow onset older type 1. Loosing weight and tonnes of exercise did not reverse the D. Avandia did not help. Nobody ever did a proper diagnosis.
Nevertheless the results above cannot be dismissed and might point the way for effective treatment when the biologists unravel all this and explain it to the Endos.
Aslo interesting in wiki. was the “transcortin” that binds to cortisol, corticosteroids and progesterone. I don’t know about progesterone but cortisol is very bad for diabetes one of the effects of Cushings is diabetes and corticosteroids are a blood sugar disaster when they are prescribed to diabetics.
Thanks a lot for the post.
Posted by calgarydiabetic | Mar 02, 2011 at 5:43 pmFascinating article. How complex it all is.
Posted by a.j. spero | Mar 02, 2011 at 6:58 pmI have type 2 diabetes and have just switched from Advandia 4mgs once a day to Metformin500mgs twice a day. I requested the change as taking the Advandia was getting to be stressful due to the bad publicity
Posted by Maria Huff | Mar 03, 2011 at 4:15 pmI was reading the other day about C-peptides and how they are not in the synthetic insulin that is given now.. they were in the old animal based insulin..
As for Coffee . I can not drink the ground stuff that comes in a can..
I grind my own beans and get along great.. it doesn’t seem to raise my blood sugar .I do limit my coffee to one cup in the morning..Also I can not use half-half in my coffee as my blood sugar is affected by the fat.
When I have had a few sips of coffee in the morning BEFORE taking any meds or eating, blood glucose spiks to 116 when it is normally 95
Posted by Annette Prickett | Mar 09, 2011 at 2:09 pmInteresting article. I have found that since giving up caffeine in coffee, my fasting blood sugar is better. I occasionally will have a drink with caffeine in it, but not often. I’ve also found that giving up diet soda has helped also!
Posted by Jean | Mar 09, 2011 at 2:48 pmI’ve had to convince my endocrinologist that coffee/caffeine does raise my blood sugar. When I do a fasting blood sugar, I’m fine. If I forget to bolus when I have coffee, my blood sugar really spikes. I bolus for the carbs in my half & half and what’s in my artificial sweetener. But I also need to add in some insulin to cover the caffeine.
Posted by Jaci | Mar 09, 2011 at 3:33 pmI have type 2 and love coffee: regular in AM and decaf in PM. Thank heaven for this study. I’ll take it as proof that they are both good for me. (My doctor is very happy with how well I am doing.)
Posted by Lawrence Wackerman | Mar 09, 2011 at 4:32 pmPlay it safe and end the studies before you find something bad about coffee!
I have found that with or without coffee sugars were no different. As a younger person I drank a lot of coffee even up to the time I was diagnosed with type 2 at the age of 55. I still feel that stress was the leading factor for me, along with heritage.
Posted by Tim Gimeno | Mar 09, 2011 at 5:08 pmMy blood sugar levels spike if I drink tea with caffiene as opposed to decaf tea. So It’s not just the coffee!
Posted by Rebecca | Mar 09, 2011 at 7:42 pmI am a type 1 diabetic and regular coffee definitely raises my blood sugar. I count 1 cup as 5g of carbs and take insulin to cover that.
Posted by Diane Fadley | Mar 09, 2011 at 8:14 pmI am a 64 year old man. I was diagnosed as a diabetic about 10 years ago after taking a glucose tolerance test. Both of my parents were Type 2 Insulin dependent. I have been able to control my diabetes with exercise and diet alone. I check my fasting glucose levels daily in the morning. It almost always 80 to 90 range. HgA1C is 5.7. I do not know if it has helped, but I drink 4 to 6 cups of decafinated coffee on a daily basis and have done so since 1987 when I suffered a closed head injury and was forced to become decafinated. Prior to that I would drink the same amount (4-6 cups) of coffee with the cafine intact. Although it is not scientificly suported, it is my opnion that coffee has most likely helped to control my glucose levels. Given my family history, I had expected to be medicated for diabetes by now.
Posted by John R. | Mar 09, 2011 at 8:37 pmMy mother could not get a foot ulcer to heal after I tried all my “health” tricks.
I finally told her she must stop drinking coffee, which I suspected for a long time but did not ask her to do so because she loved coffee.
But, I laid it on the line about amputation. She stopped drinking coffee and the foot ulcer finally began to show signs of healing on or about the 7th day.
I did nothing else but stop the coffee. So, that is why as a diabetic you should not drink coffee.
We also stopped drinking tea.
Posted by BimBam | Mar 09, 2011 at 9:45 pmMy mother who is diabetic could not get a foot ulcer to heal after I tried all my “health” tricks.
I finally told her she must stop drinking coffee, which I suspected for a long time but did not ask her to do so because she loved coffee.
But, I laid it on the line about amputation. She stopped drinking coffee and the foot ulcer finally began to show signs of healing on or about the 7th day.
She is fine now with no other foot problems have occurred since she quit drinking coffee and it has been several years. She had numerous severe foot problems before this last ulcer off and on.
I did nothing else but stop the coffee. So, that is why as a diabetic you should not drink coffee.
We also stopped drinking tea.
Posted by BimBam | Mar 09, 2011 at 9:47 pmI found when I was hypoglycemic that caffeine lowered my blood sugar - to the point of a hypoglycemic episode. About an hour after breakfast with coffee, I would start getting hungry, then would go hypoglycemic if I didn’t have something more to eat. When I was diagnosed with diabetes, I thought that would stop — but it didn’t. After 10 years as a diabetic, the same thing still happens — why?
Posted by Tabitha | Mar 10, 2011 at 12:03 amThis study fascinates me. I have been a Type 1 diabetic for 44 years. Coffee consumption is 2 large cups of coffee each morning with Coffeemate Lite. In the past 3 years, we mix caffeinated and decaf evenly. Even though I compensate the creamer calories/carbs with insulin, I’ve never been able to explain why my blood sugars are so high before lunch. Breakfast, if any, is lite yogurt or a single serving of sugar free applesauce.
Thank you “calgarydiabetic” for pointing out the possible connection between cortisol producing agents in coffee. That would definitely cause the glucose spike.
FYI, one cortisone shot will triple my insulin requirement for 3 full days.
Posted by Ginger Almy | Mar 10, 2011 at 2:12 amI drink a lot of coffee. Is tea better, if I switched?
Posted by Dave | Mar 10, 2011 at 2:37 amI find that if I don’t eat a little something say at least a slice of whole grain toast with my coffee I get a higher post prandle reading. I seem to need to have some food . I have one latte a day which I make at home with low fat milk. I do not use fat free milk because if you check the sugar content you will discover that fat free dairy contains more sugar than low fat dairy. For some reason food manufactures think they need to either add more sugar or more salt to fat free products. Milk and Dairy are the worst for that .. Also be aware that fat free cheese contains corn starch which breaks down into sugar.
Posted by Maria Huff | Mar 10, 2011 at 7:12 amA good spread for me is to take 1/2 olive oil and one half real butter and whip togeather . Usually I use a little cashew butter on my toast as I have a peanut alergy .
I also have a spike in blood sugar when I drink coffee, either regular or decaf. So whatever is responsible must not be the caffeine. I do not use any sweeteners or liquid coffee creamers, just a couple tablespoons of whole milk in a 16 oz travel cup in the morning. My sugar can spike 30-40 points after having just coffee - no food.
Posted by Bethany A Brown | Mar 10, 2011 at 9:44 amI drink a lot of coffee. Grind my own beans. It does nothing for my blood sugars, either up or down. It just makes me feel good. On the rare occasion I go to Starbucks and get a latte, though, my sugar goes way up and stays there. Too much extra stuff in it. I will continue to stick with my black coffee. Good article.
Posted by Cathy A. | Mar 10, 2011 at 1:28 pmI have been diabetic for about 19 years. I used to drink coffee when I was younger, then went through a period of caffeine free due to tachycardia. A couple of years ago I started drinking coffee again. It has had absolutely no affect on my blood sugar what so ever! I drink two cups a day (as I told my cardiologist :o) ). But they are huge cups!! So make that probably 4 usual size cups. And I use about one level teaspoon in each of the large cups, so 2 teaspoons. And half & half in each cup. All this before breakfast. Then test before I eat and blood sugar is still around 80. No spike at all! What I cannot do without adding insulin, is eat dry cereal!! Absolutely everything these days has way too much sugar and way too much salt added!! So most days I just have oatmeal! I cannot use artificial sweetener of any kind, I get migraines. So I either use regular sugar or honey, both in moderation.
Thank you for a very interesting article!!
Posted by Barbara Fiedler | Mar 10, 2011 at 5:38 pmI am a type 1 diabetic for 38 yrs. I drink 1 cup of coffee each am with stevia sweetener and half and half. My blood sugar jumps up 30 pts. My CDE told me to take an extra .25 units of insulin just for the coffee. She said she has found that coffee did raise her bg along with alot of other clients.
Helpful information!
Posted by Pam D | Mar 10, 2011 at 8:30 pmCoffee is my life blood and I can’t imagine mornings without several cups of the steaming caffeinated stuff. I’ve always drank my coffee black even before my diagnose almost 6 years ago and do not have a significant blood sugar increase.
Posted by Helen | Mar 13, 2011 at 12:02 amMy employer provides annual blood tests for $10 so needless to say, I participate each year. Over the years, I saw my blood sugar levels slowly climbing to the point where they fell just above the high level. I read somewhere that coffee could throw off the levels for some tests included in a basic blood workup. For me it didn’t make any sense because I always drink my coffee black with no sugar. I always fasted the night before my tests but would have 1 - 2 cups of coffee in the morning prior to the test thinking it would have no effect. I decided to check out the effects of eliminating my coffee and now for the past 3 years my blood sugar levels have dropped to median levels or below. Looking at some of the comments it looks like it affects some people while others not at all; similar to how different people’s bodies process foods high in cholesterol. Some see huge spikes; others very little. Who knows? =;<)
Posted by Bob | Mar 16, 2011 at 1:05 pmI find my glucose spikes after a cup of coffee. My theory is that I have always been kinda sensitive to caffeine anyway and I think it causes me to react by releasing stress hormones which causes me to spike and if I don’t eat something then I tend to go low after the spike. I am no doctor but it makes sense to me because when I am stressed my bg goes up. Strangely this does not happen with tea. I believe the caffeine in tea is released in the body at a slower rate. I will stick to my tea or decaf coffee.
Posted by Dan Bennett | Mar 16, 2011 at 2:37 pmI have found that coffee with caffine in it raises my blood sugar just a touch, but it doesn’t bother if it’s just a touch because I do like my coffee, But if I’m going to drink more than 3 or 4 cups I switch to decaff.
Posted by Holly Wirth | Mar 16, 2011 at 3:45 pmhave type 2 and drink decaf coffee. What impact does that have?
Posted by Ed Dauksz | Mar 16, 2011 at 5:26 pmI did a test this morning after reading this, and I could see no difference inblood sugar between before and after having a cup af coffee. However, I had nothing with that cup of coffee, so now this afternoon I’m going to do the test again with some nonsweet carb with it and see if having coffee with a carb influences the carb results. I find all this very interesting and if I do find a difference I will definitely make use of it in my diet.
Posted by Joye | Mar 16, 2011 at 6:44 pmeverything raises my blood sugar. i mean everything.
Posted by STEVEN | Mar 16, 2011 at 7:34 pmwatching tv, going to the bathroom(will raise it 25 points). i used to smoke cigars(quit 2006), the big ones raised it 150-200 points.
after i eat, it’ll be several hours before the level comes down to under 200.
my dr. wanted to put me on several different meds.
but i refused. al of the ones he wanted me on has since been taken off the market, for causing death by heart attact.
the more medicine i take for high sugar, the higher
my blood pressure goes. so i end up taking my sugar meds till my blood pressure starts going up, then quit till it comes back down.
i take glimpiride, and several vitamins for my blood sugar.
I am a diabetic (type 2).In my case black coffie lowers the goucose levels in the blood.
Posted by Henrech Lib | Mar 17, 2011 at 2:27 pmI was diagnosed as a diabetic 8yrs.ago.I control my prediabetes with exercise an diet alone.I just recently increased my coffee because ijust had a taste for some coffee.I checked my blood sugar the next morning an it had dropped 10-12 points.I thought about what i had done different the day before.I drink 3 mugs of coffee with regular an caffine mixed every morning.I had increased 3mugs of decafinated around 4pm.I have done this for four days now.My glucose readings in the morning an at night [before & after meals]are still 89-90 range.I also exercise from 10min.-15-20-minutes twice to three times daily.Moderate speed.I changed my last exercise time to 8pm.So,i don’t know if its the combination of both or if its the coffee.
Posted by julia vaughn | Mar 17, 2011 at 9:37 pmI have to cover my coffees’ w/ 2 uhumalog and if its w/ cream ck the carbs which is usually 2 but how many tblspn.. so coffeemate sugar free is best.. I am type 1..took a long time to figure this out just a problem when your itching for an ice coffee and didnt calculate Im not on a pump..
Posted by christine | Mar 21, 2011 at 5:18 pmI am a Type 1 of 37 years. Over the
Posted by Sarah | Mar 21, 2011 at 5:49 pmlast 10 years, I can drink only coffee
(often 50-50)in the morning and have
my sugar spike up to 50 points
especially when I am not being very
active though sometimes it just spikes
regardless of activity. However, most
times it is less than 30 points and
since I am heading into a walk and
low-carb breakfast I do not dose.And,
it doesn’t happen every day.
Glad you covered this topic.
Well, it’s still a mystery to me. Most people seem to have some kind of spike with coffee, with or without caffeine, with or without carbs. But some people don’t.
So how to explain the coffee’s protective effect against Type 2? Is it possible that coffee could raise short-term blood sugar levels but still be good for diabetes in the long term? And would this apply to Type 1 as well?
Thanks to everyone who has posted. Perhaps we can get to the bottom of this.
Posted by David Spero RN | Mar 22, 2011 at 11:17 amI am a type II diabetic. My blood sugar will
Posted by Pam S | May 27, 2011 at 6:49 amspike 50 points after two cups of coffee. Then
after a little exercise, I will drop very rapidly so that I become hypoglycemic. Coffee really has
an effect on my blood sugar.
As one who has liver issues making too much glucose and shutting doen with metformin; I do not see these issues with spiking and have two cups of regular percolated coffee every morning.
I am not fan of decaff as the process to remove caffene involves using carbon tetrchloride - dry cleaning fluid to remove the caffiene. That does not impress me consuming residue of carbon tet.
Posted by jim snell | May 27, 2011 at 3:46 pmone other key issue. Are you drinking coffee black - no canned creme, creme, milk, coffeemate
etc.
Coffeemate because it has corn syrup solids in it and NO sugar; the corn syrup solids do jump the BG.
Once I drank black - then no noticeable jump.
Type 2 diabetics - and I am one of those where any hint of sugar, corn syrup solids will jump the BG in early am. Once system up and running not much issue for this person.
Posted by jim snell | May 27, 2011 at 5:51 pmwhen i tested this morning my sugar level was 105 then i had coffee with coffemate and i measured my blood sugar levels at 11am after breakfast and it was 305 can you imagine my shock. i have type 2 diabites, the only other items i had to eat was a bowl of bran flakes and some milk plus mabey 6-8 grapes. thats when i started to investigate coffee mate. i will monitor this for a few days and see if there is any difference without drinking coffe or without drinking coffee with coffeemate.
Posted by kathleen Kadron | Sep 21, 2011 at 4:45 amI am like Steven above that says no matter what he does his blood sugar goes up. I have just recently gone insulin I take Levemir in the mornings and Novalog during my biggest meal my sugar stills runs over 200 and into the 3’s I just dont know what to do. I am fixing to have the lapband surgery done and the nutrition says I have to stop drinking caffeine? I really dont understand why but I am just wondering why caffeine is so bad…I did notice that caffeine coffee did spike my sugar level even though I hadnt eat..So to all this can you give me any type of information so my mind can be at ease and hopefully help me in some way?
Posted by Mary | Nov 11, 2011 at 8:32 amazhar gil from pakistan.i am 44 and diabetese since 10 years.im feeling much better after starting coffee one cup caffinated daily,
Posted by AZHARGILL | Nov 23, 2011 at 11:13 amHere we go again; are we drinking coffee black?
Coffee mate ia NOT SUGAR FREE as the corn sugar/starches are in the bloody stuff and even the “sugar Free” versions and when I questioned the folks on that - they pointed out the small star on the sugar solids on the label in the sugar free stuff that always spiked me in am. Apparently the FDA lets em get away with this con job.
If you are drinking black and then claim about spiking BG on coffee drinking may be valid.
Posted by jim snell | Nov 25, 2011 at 3:41 pmI recently found out I have pre-diabetes. I have a glucose meter, so I have been monitoring my blood sugar for about a week. This morning my fasting glucose level was 108. For breakfast I had two cups of strong black coffee and 1 oz of cheese which, according to the label, had zero carbohydrates. Two hours later my blood glucose was 118! It went up 10 points after 2 cups of coffe and 1 oz of cheese? How can that be?
Incidentally, when I say black coffee, I mean absolutely no sweeteners or creamers, just plain coffee.
Posted by Carrie | Jan 16, 2012 at 4:37 pmTo drink or not to drink (coffee).
I have been diagnosed type 2 diabetic for 7 years.
I always drank coffee like there was no tommorrow.
Coffee definately contributed to my condition.
I can now only drink the cheap chicory/coffee mixtures as normal coffee makes me feel so ill if I have it for a few days then go back to the cheap stufff.
Even the coffee/chicory stuff is now affecting me so that will also have to go in place for decaf.
So I believe coffee contributes to carb cravings, adrenal stimulation and ultimately unstable blood sugar.
Andrew. southafrica
Posted by Andrew | Feb 14, 2012 at 9:53 amAfter reading meany of these posts, it seems to me that there appears to be a pretty good correlation between drinking coffee (caffeinated or decaf) and folks that exercise and non-exercisers. While we know that diet and exercise are the key to avoiding and/or controlling type 2 diabetes, it is obvious that exercisers do not seen to have as much a problem with the bg spikes from drinking coffee.
Penny for your thoughts on this….
Posted by Donna | Feb 23, 2012 at 5:40 pmI am an insulin dependent diabetic (insulin pump/novolog last a1c was 5.9) and have been for ~18 years (since I was 13). Years ago I noticed that after a cup of coffee (maybe 8-10 oz, the smaller styro cups in waiting rooms/etc)even though I only used non-dairy creamer (powder) and sweet&low, my glucose levels would reach the 200’s. This always puzzled me and I never even thought about the caffeine. Now, I’m 99% sure that’s the problem either from the caffeine allowing my liver to release glucose or decreased sensitivity to insulin for a short period.
Now trying to come up with an appropriate bolus in anticipation of coffee consumption, that should be fun! Are we bolusing the amount of coffee, the amount of caffeine, does freshness effect rises, how about temp….?
Obviously its a person to person case but this is interesting for sure. The conflicting studies do have me puzzled and im not sure where to place my trust.
Posted by bsmith | Apr 21, 2012 at 11:25 am