Reference: Diabetes Care 2025 Dec 10 early online
Practice Point: Diet drinks may not actually be worse than water for patients with diabetes.
EBM Pearl: The realities of human behavior make studying the health effects of dietary changes particularly challenging. Limitations like lack of objective adherence measures and inadequate accounting of participants’ diets during the study period can limit the ability to confidently interpret the results.
Artificially sweetened beverages like diet sodas or sugar-free sports drinks, lemonades, and iced teas are favorites of people trying to satisfy their sweet tooth without the health risks of sugary drinks. This is especially true for people with diabetes, who are the highest consumers of diet drinks in the United States. The American Diabetes Association (ADA) recommends diet drinks as a reasonable alternative to sugar-sweetened drinks for people who don’t prefer plain water to help them consistently cut sugar without feeling deprived.
Conventional wisdom has long held the idea that water is better for you than diet drinks, and the ADA still recommends water as the primary beverage of choice. Diet drinks have been linked in observational studies to higher risks of obesity, hypertension, cardiovascular disease, and type 2 diabetes. The thought behind the mechanism is that diet drinks could result in more cravings for, and ultimately more consumption of sweets. But does replacing diet drinks with water actually improve health? Until now, randomized trial data to answer that question were scarce.
The Study of Drinks with Artificial Sweeteners in People with Type 2 Diabetes (SODAS) trial, published in Diabetes Care addressed the question directly and found surprising results that challenge the conventional wisdom. The trial included 181 adults with long-standing type 2 diabetes who regularly consumed commercial diet drinks. Participants were randomly assigned to drink 24 ounces (the equivalent of 2 soda cans) of either their preferred commercial diet drink or unflavored still or sparkling water daily for 24 weeks. Participants in the water group were instructed to avoid consuming any artificially sweetened beverages during the study period.
After 24 weeks, the participants assigned to the diet drinks group had a tiny decrease in HbA1c, while the participants assigned to the water group had a tiny increase in HbA1c, resulting in a total of 0.29% higher HbA1c on average in the water group (p = 0.013). Other glycemic outcomes, including fasting glucose and insulin levels and percentage time in range of glycemic targets, also slightly but nonsignificantly favored the diet drinks group. Based on these data, it appears that, surprisingly, substituting diet drinks with water in people with type 2 diabetes who regularly consume them may not substantially improve diabetes-related outcomes and might even make them slightly worse.
In studies investigating diet changes, one of the biggest challenges is always accounting for the complexities of human behavior, especially adherence to the assigned intervention. In some ways, this study did well in that regard. The authors made a great effort to maximize adherence: They let participants choose their preferred drink within the group they were assigned to, they provided the drinks and had them shipped to the participants’ homes, they allowed participants in the water group to replace any caffeine they usually consumed from diet drinks with caffeine from another source, and they financially compensated participants several times throughout the study when they completed follow-up assessments. Over 90% of the participants in both groups successfully adhered to the intervention (defined as being at least 90% adherent over the course of the 24 weeks).
However, in some ways the study design missed the mark. Adherence was only self-reported without independent verification by the researchers, so there is the possibility that participants were not 100% truthful or accurate in their reporting about their beverage consumption during the 6-month-long study. Additionally, the study did not control for or analyze compensatory behaviors in the water group; that is, changing dietary habits to compensate for missing the regularly-consumed sweet beverage. For example, a participant in the water group craving their usual daily diet soda might have replaced it with a sugary snack. It is also worth noting that there were some differences in baseline characteristics between the two groups that could be clinically meaningful, including an average of 3.5 years’ longer duration of diabetes and a higher prevalence of lipid therapy use in the water group.
It’s always interesting and noteworthy when the results of a study are contradictory to long-established clinical guidelines, and the SODAS trial is no exception. While this study has its limitations, it suggests that diet drinks might not be much worse than water for people with type 2 diabetes who are trying to meet their glycemic goals. One study isn’t likely to change clinical guidelines any time soon, and future research will need to dig deeper before there is a clear answer. But in the meantime, clinicians may want to reconsider pushing patients who rely on diet beverages to switch to water, as it may not necessarily deliver the benefits we might expect.
For more information, see the topic Dietary Considerations for Adults With Type 2 Diabetes in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Claire Symanski, PhD, Medical Editor and Team Lead for ENT at DynaMed. Edited by Katharine DeGeorge, MD, MS, Executive Editor at DynaMed and Associate Professor of Family Medicine at the University of Virginia; Alan Ehrlich, MD, FAAFP, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School; McKenzie Ferguson, PharmD, BCPS, Senior Clinical Writer at DynaMed; Rich Lamkin, MPH, MPAS, PA-C, Clinical Writer at DynaMed; Michael Butler, PhD, Medical Writer at DynaMed; Matthew Lavoie, BA, Senior Medical Copyeditor at DynaMed; Hannah Ekeh, MA, Senior Associate Editor II at DynaMed; and Jennifer Wallace, BA, Senior Associate Editor at DynaMed.