#215 Is Diet Soda Bad for You?

Is Diet Soda Bad for You?

If you have been following the news, then the media probably had you convinced that diet soda causes strokes and dementia.  Is that really true?  In this article, I review this latest diet soda study and what we know about diet sodas.  I will also attempt to answer the question, is diet soda bad for you?

The Latest Diet Soda Study

In the latest diet soda study, Dr. Matthew Pase and colleagues from Tufts University in Boston, dug through the medical records of 2,888 people who were part of the legendary Framingham Heart Study.  The Framingham Heart Study stands out in that it included almost everyone who has ever lived in Framingham Massachusetts since 1948. It was from this Framingham Heart Study that we first learned what causes heart disease decades ago.

In this study, researchers collected data in the 1990s about how much diet soda almost everyone living in Framingham drank.  They then looked at the medical records of these Framingham residents to see who had a stroke and who suffered from dementia over the following 10 years.

Dr. Pase and his team found that drinking one diet soda a day was linked to a 3-fold higher risk of stroke and dementia.  For those Framingham people drinking less than one diet soda a week, their risk also seemed to be moving in the same direction.

Basically, their findings suggest that any diet soda is bad for you.  Interestingly, this study also found that you could drink all the sugar you wanted from sugary soda pop or fruit juice and not increase your risk of a stroke or dementia.

3 Reasons Why You Should Question This Study

Whenever you hear about a study in the news, you should question the validity of the study.  This study is no exception.

The problem with most studies looking at diet soda is that of reverse causality.  In other words, sicker people are more likely to drink diet soda.  Thus, the question then is did diet soda cause them to get sick or do sicker people drink diet soda because it is “less bad” for you?  Below are 3 good reasons why you should definitely question this study.

1. Most strokes happened in people with a history of high blood pressure.

As most strokes in Framingham happen to people with a history of high blood pressure, did diet soda cause high blood pressure or did people with high blood pressure drink diet soda because it is “less bad” for you?  This question was never answered in this study.

Interestingly, there is one big study linking diet soda to high blood pressure.  However, this same study also linked sugary soda to high blood pressure as well.

2. Dementia was mainly seen in people with diabetes.

Once again, did diet soda cause diabetes or did people with diabetes drink diet soda because of blood sugar issues?  As anyone suffering from diabetes could tell you, sugary sodas and fruit juice quickly shoot your blood sugar levels high.

Along the diet soda and possible diabetes link, studies do show that artificial sweeteners change the gut bacteria of mice thereby causing diabetes.  However, it is important to remember that only about 10% of animal studies apply to humans.

In humans, the link between diet soda and diabetes is tenuous at best.  One big study from the United Kingdom did show an association between diet sodas and diabetes.  However, this study also never answered the question, did diet soda cause diabetes or did people with diabetes switch to diet drinks?

3. Sugary sodas and fruit juice were totally safe in this study.

This finding alone really caused me to question the validity of the entire study.  In my mind, the only possible explanation for this finding is that people with a history of high blood pressure or diabetes  switched to diet drinks because of some perceived health benefit.

Given all that we know about sugar, most nutrition researchers and cardiologists now feel that sugar is one of the biggest causes of heart disease, obesity, diabetes, strokes, dementia, and an early death.  With this is mind, some studies show that fruit juice may be just as bad for you as sugary soda.

Take Home Message

The big take away is that diet soda, sugary soda, and fruit juice are not health drinks.  While diet soda may be less bad for you than sugary soda, it would be like using nicotine patches instead of cigarettes.  Personally, if an occasional diet soda helps you break the sugary soda pop addiction, then I am all for it.

I understand that the addiction to soda pop is real.  This is something that I suffer from as well. While it has been 10 years since I have had a sugary soda, I still have cravings for diet cherry Pepsi if I have been up all night.

Is diet soda bad for you?  Well, it definitely isn’t good for you.  The problem is that we really don’t know how bad it is for you.  Perhaps as we learn more about how artificial sweeteners affect gut bacteria, metabolism, and the brain we’ll have a clearer picture.

What is your take on diet soda?  Please leave your thoughts and questions below.  As always, I’ll do my best to answer any question posted below within 24 hours.

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  1. Thanks Dr John. My take is that food and drink artificially sweetened still makes you used to the sweet taste. Where as if you cut out the sweetness, your taste buds adjust and you no longer enjoy sweet food. (It tastes too sweet). What are your thoughts?

    • Hi Sue,

      I completely agree. This “sweetness theory” could explain how artificial sweeteners may somehow be tied to diabetes. Speaking from personal experience, since cutting out all added sugars to my diet, fruit far sweeter and more exquisite.

      Thanks for reading!


  2. A great and very useful article that explains very well some of the cautions that apply to evaluating any research findings. Thank you, Dr. Day.

  3. Doc,

    your take on it is kind of ambiguous: what type of sweetener, number of diet sodas per day,
    Is it bad or ins’t?
    Debating with your colleagues may be interesting but not adding a definitive conclusion to lay people isn’t very helpful.

    The acidity alone in cola and diet cola is enough to cause concern.

    Diabetics shouldn’t be drinking soda or fruit juice. And if they’re diabetic they’re probably also sedentary and overweight.
    You might want to add a caution about those factors, as well.

    • Hi Mark,

      You bring up some excellent points. The problem is that we are just starting to learn how artificial sweeteners affect the body. There is still so much that we don’t understand.

      Regarding your question, is it bad. My answer is simply that there are no studies saying it is good for you. The question really is, how bad is it for you. The studies seem to suggest that it probably isn’t as bad as sugary soda. Beyond that is pure speculation at this time…

      In this study, they used an average of one diet soda daily as their cut off. I’m sure drinking more would have had worse outcomes.

      Hope this helps!


  4. Great post! I love how balanced it is.

    I’ve got a funny question for you. I read your blog avidly, and am trying to make changes to more whole food choices. So I’m curious–are there any natural, whole foods that are just not really worth eating?

    • Hi Margot,

      Great question. Off the top of my head I’m not coming up with any unprocessed, natural, whole foods, that should be avoided…


  5. I recall one of your previous articles that said that people gain weight because the diet sodas make them feel hungry all the time. Is this still true?

    • Hi Bryce,

      The story on weight gain with diet sodas is a mixed bag. There are a number of studies which link diet sodas to diabetes and metabolic syndrome. But once again the question comes up, was it the diet soda or did people with these challenges turn to diet soda because it was “less bad” for them.

      Other studies show that when it comes to weight gain, diet soda is neutral. Then there are some reports that the sweetness of artificial sweeteners may somehow affect metabolism, brain processing of calories, or gut flora.

      The bottom line is that we really don’t fully understand the effect of diet soda. The currently available studies just don’t provide enough answers. Hopefully, our understanding will improve as more studies are done…

      Hope this helps!


  6. I wonder how the dementia risk from artificially sweetened soda compares with the risk from drinking artificially sweetened coffee. Are you aware of a comparable study?

    • Hi Cathy,

      I have not seen any studies yet looking at this issue. However, this type of a study would also be challenged in that was it the artificial sweetener that caused the dementia or did people who were at risk for dementia (obesity, diabetes, high blood pressure, etc.) turn to artificial sweeteners in the coffee because it was perceived as being “less bad?”


  7. The real issue besides aspartame, is the carbonation in sodas. I understand the acidic nature of carbonated beverages drives calcium from our bones and teeth to neutralize the acid. In my opinion way more important than sugar vs aspartame.
    Are we missing the point?

  8. Not mentioned in the study was the effect of artificial sweeteners on the release of insulin (if any). I was a bit surprised to come across studies suggesting it causes a surge when reading further on the article. (I was concerned as I had started drinking Crystal Lite in place of OJ in the morning.) As a type 2 diabetic, I’m concerned about the insulin issue as well.