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,