Does drinking two diet beverages a day increase your diabetes risk?

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Overview

A new study has found that drinking diet beverages doubles your risk of diabetes, according to CNN, the Telegraph, the Daily Mail, and others. The study analyzed survey data from almost 3,000 Swedes, 357 of which had latent autoimmune diabetes in adults (LADA) and 1136 of which had type 2 diabetes. The rest were controls who had neither disease.

LADA, also known as diabetes type 1.5, is a form of type 1 diabetes that occurs in adults and has a slower course of onset compared to childhood type 1 diabetes. Insulin is usually not needed until several months after diagnosis, but it is estimated that over 50% of adults diagnosed with non-obesity-related type 2 diabetes may have LADA instead. The symptoms of LADA may include unusual thirst, frequent urination, weight loss, nausea, blurred vision, and others according to Lehigh Valley Health Network.

Methods

The researchers analyzed data from the ESTRID (Epidemiological Study of Risk Factors for LADA and Type 2 Diabetes) study, which was initiated in 2010 to track and characterize all new diabetes cases within the Swedish county of Scania. A questionnaire was used to determine the participants’ routine food intake during the previous year. In particular, the participants were asked to report their average number of 200mL servings of “cola, other soft drinks/soda, diet cola and other diet soft drinks/soda” per day or per week (a typical can of soda is 355mL). The survey also collected information about possible confounding variables.

The results were calculated using three methods. The first model had its data adjusted for age and sex. The second model had its data adjusted for age, sex, and a wide variety of variables, including education, family history of diabetes, physical activity, smoking, alcohol, and other intake levels. The third took into account all previous variables, and in addition BMI. Odds ratios (ORs) were calculated for the data and the paper interpreted them as incidence rate ratios due to the low natural incidence of LADA.

Results

Despite an embarrassing autocorrection of the value 10/18 to the current date (seen below), the study found an OR for LADA of 1.99 for consumers of more than two servings of sweetened drinks daily overall compared to non-consumers. The OR for sugar-sweetened beverages, 2.20, was slightly higher than that of artificially sweetened beverages, 1.90. The OR for type 2 diabetes for >2 servings consumers was 2.39 and, according to the researchers, “was seen across subgroups of sex, age, family history of diabetes and BMI.”

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However, each odds ratio found had a broad 95% confidence interval. For the OR of 1.99, the confidence interval was 1.11–3.56, with a value of 1 signifying no change between high sweetener consumers and non consumers. The OR for type 2 diabetes had a confidence interval of 1.39–4.09, and these wide ranges are consistent across the study.

How did the media do?

The Telegraph reported this study with the headline “Two diet drinks a day could double the risk of diabetes, study finds” and made several claims in their article, including that “those who consumed at least two 200ml servings of soft drinks daily were 2.4 times as likely to suffer from a form of type 2 diabetes.” The article also clarifies that the increased risk was the same for diet drinks and non-diet drinks, something they did not specify in the headline.

However, the article fails to even mention or explain LADA and how it differs from type 2 diabetes. The author also failed to acknowledge the faults of the study, namely recall bias since participants were asked to report food intake from the past year. In addition, the study details another explanation for their results: high sugar or artificial sweetener intake is simply a marker of an overall poor lifestyle, since high consumers had the largest BMI and weight gain.

Overall, while the Telegraph article missed important points about LADA and the limitations of the study, the author did a good job of conveying the information presented by the study.

Unprofessional Opinion

The media seems to love stories about soda impacting long term health. In this case, most articles focused on the fact that diet sodas didn’t seem to reduce the risk of developing diabetes compared to sugar-sweetened drinks, missing the articles focus on latent autoimmune diabetes in adults.

As for the study, while there is evidence in the literature that sweetener heavy drinks impact diabetes risk, the large confidence intervals and many confounding variables don’t assure me that drinking almost two cans of soda doubles your risk of type 2 diabetes or LADA. The study did a good job trying to account for these variables by including BMI and lifestyle analysis into their results but does admit that “the suggested positive association between artificially sweetened beverages and diabetes risk remains to be further explored.”

With high confidence intervals and confounding variables, I am fairly confident that a link exists between high sugar or sweetened drink intake and risk of developing LADA or type 2 diabetes, though the “doubled risk” reported by most media sources may be misleading.

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