Diet Soda and Diabetes

In reply to my recent blog entry “Stopping Diabetes Medicines,” Patsy wrote: “I have stop[ped] drinking Diet Cokes, or anything with artificial sweeteners. I can’t tell you what a difference that has made! … I am overweight and have lost 14 pounds. My blood sugar has gone down, too.”


How could this be? How could diet sodas, which have essentially no carbohydrates and no calories, raise blood glucose and weight? Or is the whole thing an illusion?

Four studies in the last decade have raised concerns about diet soda. In 2005, University of Texas researchers reported that people who drank diet soda were more likely to gain weight than those drank regular soda. Fewer calories = more weight! Strange…

In 2006, Dartmouth scientists found that people with diabetes who drank one or more cans of diet soda a day raised their A1C levels by an average of 0.7%, compared to those who didn’t.

In 2007, the American Heart Association found that those who drank either regular or diet soda had a higher risk of “metabolic syndrome,” which includes diabetes, high blood pressure, high levels of LDL (“bad”) cholesterol, and obesity, compared to nondrinkers. This is just a correlation; it doesn’t show cause, but it’s still interesting.

In the January 16, 2009 issue of Diabetes Care, a group of analysts reviewing the Multi-Ethnic Study of Atherosclerosis found that “Daily consumption of diet soda was associated with… a 67% greater relative risk of… Type 2 diabetes compared to non-consumption.” They said the increased diabetes was not due to increased weight, although that happened too. “Associations between diet soda consumption and Type 2 diabetes were independent of baseline measures of adiposity or changes in these measures,” they wrote. The data was adjusted for “lifestyle and dietary differences.”

The Internet is full of anecdotal reports saying similar things, that people felt better and had better blood glucose levels when they stopped the artificially sweetened drinks. But what is going on here?

Some skeptics believe that the effect is an illusion. “It may be that many people who drink diet soda, do so because they realize they are becoming fat,” wrote the Web site “However, the basic habits that cause obesity (lack of exercise, over eating) still exist.” I don’t buy this theory.

Another explanation is that artificial sweeteners may confuse the body about how much energy it is consuming. They could make you feel your blood glucose is low when it’s not, so you seek out food and eat more.

It could also be the taste buds that are thrown off. Most artificial sweeteners are even sweeter than sugar. Compared to them, real foods don’t taste very sweet, so we are tempted to sweeten them or eat more of them to meet caloric needs.

Animal studies seem to support this idea. Purdue University researchers have shown that rats eating food sweetened with saccharin took in more calories and gained more weight than rats fed sugar-sweetened food.

I haven’t seen studies on it, but I can imagine that artificial sweeteners might raise blood glucose by confusing the liver into thinking glucose levels are low, causing it to release sugar to keep us from going low.

Certain sweeteners used in diet drinks could also cause other health problems. Diabetes Self-Management has a long article on these sweeteners here.

I’m not suggesting switching from diet sodas to regular ones. Although apparently that would be some improvement, it would seem that lemon water, sparkling water, or fruit juice diluted with water would be better. (I’m feeling really good lately with some unsweetened cranberry juice twice a day. Now that is seriously unsweetened! I mix a couple of ounces of juice in eight ounces of water to make it drinkable. But it seems to be helping my bladder function and energy level.)

I believe our bodies are so complicated, and so poorly understood, that we don’t want to put artificial anything in there unless we have to. The chemists and companies who brought us artificial sweeteners were probably trying to do something good, as well as make money. But perhaps they just didn’t know.

At any rate, I think we might be better off if we do like Patsy and cut the artificial sweeteners out.

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  • calgarydiabetic

    I dilute my diet pop 1:1 with water to make it less sweet. It is caffeine and phosphoric acid free. Caffeine disturbs sleep more if that is possible in the modern age. Phosphoric acid decalcifies the body.

    Still based on the above you wonder if total abstinance is better.

  • Beth

    II used to be very strict with myself about eating an all-natural diet, close to the form the food grew in. I cooked everything from scratch, ground my own grains, and at a plant-centered diet with only small amounts of animal products, mostly eggs and dairy. I got fat on that diet, which I think had very little to do with the type of food I was eating and a lot to do with having panic attacks at night that produces a voracious hunger.

    I have never been a pop-drinker, and still am not. In my all-natural time, I would never have used artificial sweeteners before — but now I make home-brewed teas, sweetened with a little sucralose. I neither gained weight nor lost weight. Overall, I do not think that using some sucralose has made me either more or less healthy, except that I think I may be better hydrated than I was.

  • PNWdiabetic

    I don’t believe that diet soda has any direct impact whatsoever.

    Fruit juices were a substantial cause for weight gain and metabolic syndrome for me.

    It was switching to diet soda that helped ease the transition to eating less.

    A dramatic increase in daily exercise was also required to reverse weight gain while building muscle mass.

    The single best advice for TypeII diabetics is to exercise much more. It may take a total of two hours of vigorous activity every day until excess weight has been eliminated. Then it may take an hour of the same every day for maintenance.

  • Jon

    Since I was diagnosed as a diabetic, I have switched from regular sodas to diet sodas. And I’ve seen a dramatic improvement in my weight and my blood glucose. At diagnosis I had an A1C over 7, and at my last check it was 5.4. My weight has dropped over 30lbs. So I’d say that artificial sweeteners work fine for me.

  • Lynn

    Perhaps there is a connection with the fact that people drink soda instead of water. Daily water intake is essential to good health and weight loss.

  • Mike Romm

    I just recently wrote to Crush to ask about their Diet version. I have been a Type 1 diabetic for decades. I noticed the other day while shopping at Wal-Mart that Diet Crush is the only diet soda that has high fructose corn syrup. Worse it is the second ingrediant listed right after water. It is also the only diet soda with that high a coloric value or that high a carbohydrate value. I am a brittle diabetic and have always been told to stay away from anything that has high fructose corn syrup. I have checked lots of labels of diet anything and they are the only ones that list high fructose corn syrup. They also bottle or make Diet Sunkist soda and HFCS is not part of it. What’s your opinion?

  • Mike

    I have been a type 1 diabetic since 1963 when the first diet sodas were introduced and have consummed approximately 24 ounces more or less a day. I have not noticed any side effects from drinking the diet soda, nor have I gained any weight. The diet soda (caffinated) I consume has not affected my sleep at night even when continuing to enjoy a soda late into the evening. Personal note: I am currently on pump therapy and use a continuous glucose monitor to help me maintain healthy glucose control.

  • Miki

    I feel if diabetes has to do with the liver not able to handle the amount of sugar and diet drinks are metabolized in the liver, the liver is unable to metabolize these drinks in addition to carbohydrates and as such the subject increase through weight gain. An individual who likes soda can probably drink one a day (over several hours and diluted with crushed ice) and this would lower the input of the regular soda The amount of crushed ice would raise the fluid in the system.

    Diet drinks may cause an individual to have diarrhea and as such cause dehydration. The body will try to retain fluid and as such increase the amount of wait–fluid gain. Persons with diabetes run the risk of renal failure and this could prematurely bring on renal disease.

    Of course there is nothing scientific to what I say, this is only why I feel in my own management of my own hard to control brittle diabetes.

  • S.Kaye

    This newsletter is the making me understand more clearly why my doctor has me on Symlin. Thanks for really explaining what it does and how it may help after meal spikes.

  • Mark Buse

    Blood sugar surges experienced by diet soda drinkers are most likely caused by
    1. high caffeine levels in fountain versions of diet soda
    2. drinking the soda chilled by ice, shocking the body into a cold response

    In my own experience, there is no impact on my Type II blood sugars from low-sodium, caffeine-free sodas.

  • David Spero RN

    Good comments. It seems different people react to different foods in different ways. Surprise!

    I really don’t get this “Diet Crush” thing with the HFCS. That sounds like a mistake or like highly misleading marketing.


  • jim snell

    Mark Buse is on my page. I see no issues on diet drinks and glucose control.

    Caffiene will be issue becase folks propbably drink more of stuff since it is diet version,

  • Sunny

    I think diet drinks have their place in the diabetic world. For someone who is a big soda drinker, yes, drinking diet soda is going to prevent you from adding 500 or 600 calories a day.

    I wonder though, if they have different effects on DM1 and DM2. Maybe studies should be done to compare the effects of artificial sweeteners between DM types. For me (DM2), they seem to cause more trouble than benefit. I definitely limit my aspartame intake.

    For stuff like ice cream or juices, I go for the “no added sugar” labels rather than the “diet” labels. I have noticed from time to time that “diet” foods and drinks have more calories than regular. Check out some yogurt labels and see for yourself. Gotta be a label reader. ūüôā

  • Ron Tillotson

    My wife has been a Type 1 for 49 years and loves to have an occasional diet soda, but chooses wisely. She has no problem with caffeine-free diet sodas like Hanes Diet Root Beer and Diet Rite Cola, both of which are sweetened with Splenda. She stays away from high fructose corn syrup, which everyone should do — diabetic or not — because studies have shown that it assimilates rapidly and can stress the pancreas.

  • ADigeon

    Many times when I am having a meal at a restaurant, I notice what people order for a drink with their meal. Most often tey order a diet soda of some sort after ordering a high caloric, high fat non-nutritious mean. I think that, for many people this is their way to cut calories. It may not be the diet soda that is affecting blood sugar but what is being eaten with it. As for me, I drink both diet and non-diet sodas and do not see a huge effect on my blood sugar. My diabetes (type 2) is controlled with metformin and byetta.

  • Rose

    i just try to watch what i eat, and what eating me. My problem is wehn I go out and eat with friends who are not diabetic. I have a huband who needs care and has trouble keeping his weight up and I must try and keep my weight down, and it can really be a problem. Thanks for sharing, Good information always helps. Rose

  • charlie c

    i drink diet soda to the pont that it was like a drug i had to have a drink. i did not louse weight i gain weight and start having aura headakes from the the postaisum in the diet caffeine free soda.

  • J Castillo

    There is nothing about any of the studies cited that shows that the diet soda (and/or artificial sweeteners) cause increased glucose levels! Period.

    People who drink diet soda…had these conditions, okay that is association, not cause. Those people, as is contemplated, might be eating too much, eating the wrong things (from a carb perspective) or not exercising enough.

    Drinking too much caffeine is also a problem as caffeine has a diuretic affect, fluid id expelled from your. Reduce the fluid in your blood, and guess what, the amount of glucose in your blood remains essentially the same, but it is more concentrated since there is less fluid and we measure glucose level relative to volume. So drinking too much caffeinated diet soda, even if the caffeine does not keep you awake (aka you are actually addicted to caffeine), can increase blood glucose because the caffeine leads to fluid reduction.

    This article, as written, is at best ambiguous and at worst potentially harmful.


  • AL Hernandez

    I’m a type 2 diabetic having been diagnosed about (5) yrs ago. About (2) yrs ago I discovered that whenever I’ve eaten something that causes my blood sugar to rise to (200) or above, if I drink a diet soda, w/in (30-45) min my sugar drops
    (30-40) points. I haven’t found out why this occurs.

  • Jerry Steege

    It’s become very obvious to me that whether it is diet soda or regular soda, the drawbacks of drinking them are much worse than the benefits of a tasty drink. If you read anything about High Fructose Corn Syrup you won’t want to drink a pop again. Thanks for the informative article.

  • Linda T

    thank you, David, for a review of the past literature. I drink 1-2 Diet Cokes a day. should I stop? I am cutting down so I usually only drink about half a can and throw the rest out. I do think that people who stop have a self-induced placebo effect -“look how well-inforned I am”. that can’t happen to me because I am a cynic. Nontheless, I drink 2 16 oz glasses of water a day, because I enjoy it. The fact that this issue keeps popping up in studies is interesting to monitor and I thank you for being a balanced voice on the subject. Linda

  • Connie Stuart

    I have been a type 1 diabetic for 54.5 years and during that time I have drank diet drinks sweetened with the various diet sweetners. The only time that I use a regular soda is if my glucose is too low. I will continue to use diet sodas. My favorite that I consider to be the best for me is Diet Rite with no sodium or caffeine.

  • Walden

    I am with diabeties type 11 since 1992
    Regular sodas(without artificial sweetners) are good for low occuring glucose levels.-A fact.
    For two years(since 2008-left kidney removal)I have used diet sodas and Homemade Lemonade( 1- cup lemon Juice plus 1-cup splender with 1- gallon of water).
    Kidney cancer seems to be in remission.All lemonade intake is boring(no fizz)
    After reading about diet sodas I want to change from the diet sodas and artificial sweetners to a healthy non-boring good-fizz tasting liquid Refresher.Teas and coffees require artificial sweetners.
    Anyone with any ideas that are inexpensive? The selzer waters are not in my budget.

  • acampbell


    I just wanted to respond to J Castillo’s comment about the effect of caffeine on blood glucose. The explanation is only in part correct. Caffeine may increase blood glucose in some people, possibly due to caffeine affecting the transport of glucose into cells or by stimulating adrenaline release, which, in turn, can raise glucose. However, caffeine in small to moderate amounts doesn’t lead to fluid loss or dehydration as is commonly thought.

  • RKeenan

    I am a type II diabetic who has struggled with weigh gain due to insulin. I take it, I gain weight; I stop it, I lose weight.
    This idea that diet soda causes or worsens diabetes is irrational to me. Some studies (and I’e read a lot of them) show some correlation; other studies do not. But none have proposed causation. In other words, diet sodas have not been shown to cause anything except a significant decrease in sugar intake from regular sodas. This has been my experience, also.

  • jim snell

    FRom one who has ended up watching my body/liver and metformin interaction; I find there are meds, foods, msg etc that cause my liver to ignore the metformin and cause excess glucose release. Give it 6 hours and the liver and met go back to work.

    I must confess that the reports here are far too general.

    WHich sweetners are you talking about.

    Diet coke with aspartame do not hammer me but I had to drop diet rootbeer as it would routinely cause a unwarranted liver dump to 278. I was unable to identfy offending agent.

    It would be far more helpful to have a fuller report listing names, sweetners, products etc.

    Truvia has not caused problems with me. Splenda gives me the trots. Aspartame seeems ok but not AW diet rootbeer which I like but forced to drop.

    I am always watching my foods and additional antibiotics for any sudden liver glucose release.

    The reports so far are not much better than wet fingers in the air.

    There are classes of products/salts, drugs and spices that kick livers butt and shutdown metformin and cause large unwanted glucose release. Others are completely benign or inconsequential.

  • rita

    My husband has been having diet cokes 2-3 a day. his blood sugar levels shot up to 33 fasting. that was a shock to us.

  • Eric Anderson

    I drank one 20 ounce A&W DIET root beer in 5 four ounce dodes with cream over a day and found my night tims blood sugar was 97 which is 15 points higher and NOT GOOD!

    Maybe this was a fluke but isuspect maybe aspertame? Maybe I’ll go back to heave cream and stevia with a root beer flavor. Eric

  • Marian

    I am a type2, diagnosed a little over 4 years ago. I’ve been on lantus and humalog, 3-4 shots daily. Over time I have been able (through lifestyle changes) to reduce the insulin while keeping my AIC’s in the 5.5-5.8 range.

    Here’s the fascinating part…I’ve been having horrible GI symptoms for months – and finally considered it might the the diet soda (I’d eliminated everything else I could!). I’d been drinking 1-2 liters a day.

    Within a week my GI symptoms were significantly improved and still getting better 2 1/2 weeks later. I am finally feeling more like myself. My insulin needs have plummeted. I first stopped taking long acting, and today absolutely no insulin at all. WEIRD. My bg #’s are fine – under 100 in am, under 120 2 hrs after meals. So what the heck is going on???? I can only assume it’s the removal of diet soda.

    I know – you’re skeptical. But what else explains it? I’m actually eating slightly more carb…the same calories…and nothing else has changed. I feel confused and – well…just confused! Any response would be appreciated!

  • David Spero RN

    Hey Marian,

    I’m glad you figured that out about how diet sodas affect you. As you can see from the comments above, they affect everyone differently. Do what’s right for you!


  • Joefh

    Ever since the Doctor told me that I was over the VA’s limit to be classified as diabetic just this year, I removed most sugars from my diet. Use sweet-n-low for my coffee and switched to Diet Sunkist which according to the label contains no sugar, carbohydrates, or calories. I also cut way back on the “nasties” in my eating habits. Albeit I struggle to cut out rice. My weight is in a nose dive and I rarely test above 120 on the pin prick test. It was hovering around the 180 – 225 mark. Now it tends to stay in the 105 to 118 range. I guess that is a good thing.

    I can’t say I buy this crusade against diet soda – it hasn’t proved to be anything but a benefit to me.

  • Olivia Gonzalezdepetrinidimonf

    I am borderline diabetic. I do a fasting glucose test every morning. Yesterday morning it was 106. Today, it was 137. The only thing I did different was that yesterday evening I had a small diet coke at Walmart. I am not a soda drinker; never have been…but I guess, the Texas heat beat me yesterday.

  • Kate

    I am not diabetic but I found this article while looking for information regarding the glycemic index of caramel coloring. I have found that a lot of diet drinks are full of things that provide no calories and no sugar but tend to have a high glycemic index. I was doing well losing weight and then I discovered Crystal Light. I didn’t gain weight but I also wasn’t losing any more so I researched each of the ingredients and found maltodextrin has an extremely high GI which means that it can affect your blood sugar. I have seen some “natural” sweeteners cut with maltodextrin as well (and marketed to diabetics!).
    I haven’t found any information on it but I am curious about the caramel coloring in the diet soda – it is derived from corn, the same as maltodextrin – it might make sense that also had a high glycemic index despite offering no calories.
    I am thinking about buying a blood sugar monitor to see if there is something that might affect my blood sugar as keeping those levels relatively even seems to be key for me during weight loss.
    Of course, each person is different and I am still losing weight drinking 1-2 diet sodas a day (bad mommy caffeine habit I still feed) but I still might be sabotaging in small ways. They actually seem to reduce my hunger because they are fizzy and filling.