Drinking just two diet drinks per day doubles the risk of diabetes.
There is no convincing science to support the claim that drinking two diet drinks per day increases the risk of diabetes.
Last year the media sensationalized the results of a research study and claimed that diet drinks increase the risk of diabetes. The research study in question was conducted in Sweden and published in the European journal of endocrinology (1). The history behind the study is that in 2010 Swedish researchers carried out a clinical study on diabetes. This original study was a population based study and not a randomized clinical control trial.
All patients from the original study who were diagnosed with a specific type of diabetes called latent autoimmune diabetes in adults [LADA] and a random sample of patients diagnosed with type 2 diabetes were enrolled in the new controversial follow-up study. A random selection of patients enrolled in the new study and matched control were invited to participate in a self-administered questionnaire by mail.
The follow-on study found that a high intake of sweetened beverages was associated with a higher risk of LADA and type 2 diabetes. Both sugar sweetened and diet or artificially sweetened drinks were associated with a higher risk of diabetes.
There is a very significant difference between causation and association. Association [which is all that was demonstrated in this study] means that people with LADA or type 2 diabetes were more likely to drink sweetened beverages as opposed to controls. It does not prove causation. This means that it does not prove that sweetened drinks actually caused any form of diabetes.
The study authors acknowledge many limitations of the study. Firstly, the participants were asked to record their dietary habits for the year prior to the diagnosis of diabetes. This raises the possibility of recall bias. Study participants may not accurately remember their food intake prior to the diagnosis of diabetes. Secondly, polydipsia or increased thirst is an symptom of diabetes which may have lead to an increased intake of drinks including sweetened beverages. Finally, the higher intake of sweetened beverages may just reflect an overall unhealthy lifestyle, which would be an independent risk factor for diabetes.
In summary there is no reliable clinical evidence to support the claim that diet drinks increase the risk of diabetes.