Diet Drinks or Water? New Diabetes Study Finds a Surprising Result

For years, water has been widely considered the healthiest beverage choice, while drinks containing artificial sweeteners, such as Coke Zero, have often been viewed as a less desirable alternative. But a new study published in the scientific journal Diabetes Care challenges the assumption that replacing diet drinks with water necessarily leads to better blood sugar control for people with type 2 diabetes.

What Happened When Diet Drinks Were Replaced With Water?

The study included 181 adults age 35 and older with type 2 diabetes who regularly consumed diet beverages. Participants were divided into two groups and followed for 24 weeks.

One group continued drinking approximately 710 milliliters, or about 24 fluid ounces, of diet beverages each day. The other group replaced that same amount with plain water or unflavored sparkling water.

Throughout the study, researchers monitored participants’ blood sugar levels, body weight, and other measures of metabolic health.

The findings were unexpected. Among participants who continued consuming diet beverages, HbA1c, an important measure of average blood sugar levels over the previous few months, decreased slightly from 7.19% to 7.14%.

By comparison, HbA1c among participants who switched to water increased from 7.20% to 7.44%. The difference between the two groups was statistically significant, favoring those who continued drinking artificially sweetened beverages.

Other measurements, including fasting blood sugar, insulin levels, and continuous glucose-monitoring data, also showed no clear benefit from replacing the diet beverages with water.

Participants in the diet-beverage group also experienced slightly greater weight loss, although researchers noted that the difference was not large enough to be considered clinically significant.

Does This Mean Diet Drinks Are Healthier Than Water?

Not necessarily.

The researchers stressed that the results should not be interpreted as evidence that water is unhealthy or that artificially sweetened beverages are generally healthier than water.

Instead, the study examined a much narrower question: If people with type 2 diabetes who already regularly drink diet beverages replace those drinks with water, will their blood sugar control and other metabolic measures improve?

Over the 24-week study period, the researchers found no evidence that making this switch produced better results. In fact, HbA1c outcomes slightly favored the group that continued consuming diet beverages.

The findings suggest that for people with type 2 diabetes who are already accustomed to drinking artificially sweetened beverages, continuing to consume them may not negatively affect blood sugar control in the way some might expect.

However, this is one study, and the findings should be viewed in the context of the broader body of research on artificial sweeteners and long-term health. Further studies will be needed before the results could lead to changes in official dietary or medical recommendations.