A Study Found That Diet Coke Is Healthier Than Water (in Some Ways).
I’m sure you’ve seen the studies that pop up from time to time showing that diet sodas may be somewhat harmful to health . (The evidence is never very compelling.) But have you seen the new study that found that diet soda is better than water for people with type 2 diabetes? Not only is it a real study, but it’s also well-designed, and we should pay attention to it, according to an epidemiologist I spoke with who wasn’t involved in the study.
That epidemiologist is Gideon Meyerowitz-Katz of the University of Wollongong, who wrote about it here . When I asked him whether it was a good thing that this study went largely unnoticed by the media, he replied, “It’s a much more compelling study than most scientific papers that get media coverage.” The study was not sponsored by any commercial beverage company.
What the study showed
In a study with the amusing name SODAS (Study Of Drinks with Artificial Sweeteners), researchers from the University of California, Irvine, and the University of Minnesota, Minneapolis, recruited adults with type 2 diabetes who habitually consumed drinks with artificial sweeteners (including, among other things, my one true love, Diet Coke). The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health.
Half of the participants were asked to switch to drinking water, while all were given three servings per day of either a diet drink of their choice or a water of their choice (including unsweetened sparkling water). The study lasted 24 weeks. It involved 181 participants, of whom 179 completed the study, which is considered a relatively large group for a study of this type. (This is twice the size of the earlier study, which I will compare it to below.)
The main indicator studied by the researchers was the level of glycated hemoglobin ( HbA1C ), measured by a blood test. This is a common test used to monitor glucose levels in people with diabetes or at risk for developing it. The higher your HbA1C level, the higher your blood glucose levels are likely to have been over the past three months.
Results: HbA1C levels improved slightly in the artificial sweetener group, from 7.19% to 7.14%. In the water group, they worsened , from 7.20% to 7.44%.
To complete the picture, the researchers collected several other parameters. Fasting glucose, fasting insulin, and “time in target range” measured with a continuous glucose monitor showed better results in the diet drink group. People in the diet drink group lost a small amount of weight (an average of two pounds), while those in the water group maintained their weight. The researchers called this difference in weight loss “statistically significant but not clinically significant.” In other words, it was probably real, but too small to be meaningful.
The bottom line: Study participants saw no real benefit from switching from diet soda to water; in fact, it may have even caused some harm to their health.
What does this mean for you and your Diet Coke habit?
Okay, maybe I’m talking about myself and my Diet Coke habit. I fully acknowledge my bias, but it’s a valid opinion. I like Diet Coke. I’ve also been following the research on artificial sweeteners for years, and while I wouldn’t necessarily defend my soda as healthy, nothing has ever convinced me that it’s bad for me. (Sugar-laden sodas are a different story; we should probably all avoid them.)
We now have a fairly large, well-designed, and independent study showing that artificially sweetened beverages may be healthier than water. I haven’t seen any news reports about this yet, although a study was published a few years ago with contrary results . That study involved 81 women with diabetes undergoing weight loss, and their HbA1C levels improved slightly when drinking water compared to diet sodas. However, one expert interviewed by Everyday Health said he “believes the health risks of diet sodas are overstated.” (Incidentally, the authors of the latest study point out that comparing that study to theirs is not entirely fair, as that was a weight-loss study, and this is not.)
It’s important to remember that any study on a specific food product typically focuses on a specific disease or population group. We tend to remember them as “Diet Coke is good for you” or “Diet Coke is bad for you,” but each study only provides a piece of the puzzle, not a generalization. For example, this study says nothing about the effects of Diet Coke on people with poorly controlled diabetes or no diabetes at all; and it says nothing about outcomes other than those related to blood sugar levels. It didn’t even specifically study Diet Coke, though it was likely one of the most popular drinks among the participants.
To be clear, it’s entirely possible that this isn’t a genuine effect, and that water and diet drinks are generally equivalent in terms of blood glucose levels and health outcomes. Meyerowitz-Katz says this is probably the most likely explanation, but we can’t rule out the possibility that diet sodas may help control glucose levels in type 2 diabetes. Perhaps they satisfy sweet cravings and help people avoid other sugary snacks, for example.
The researchers write that their main conclusion is that “maintaining normal [artificially sweetened] beverage consumption may be a tool for further control of type 2 diabetes if glycemic control is maintained and stable.” Meyerowitz-Katz agrees: “At worst, there is no difference between diet soda and water in terms of diabetes control. At best, diet drinks may be slightly better.”