Drinking more than 2 soft drinks a day doubles the risk of developing two types of diabetes, a study in the European Journal of Endocrinology has found.
Researchers say this applies to soft drinks that are artificially sweetened as well as those containing sugar.
Types of Diabetes
Type 2 diabetes is the most common form of the condition in which a person's blood sugar (glucose) levels become too high because their body can't produce or use insulin properly.
Type 1 diabetes is less common and occurs when special cells in the pancreas are mistakenly destroyed by the body's immune system, meaning that insulin can't be produced. This autoimmune disease usually starts in childhood.
There is, though, a third type of diabetes called Latent Autoimmune Diabetes of Adulthood (LADA). It shares some of the characteristics of type 1 and some of the characteristics of type 2 – and for that reason it is sometimes referred to as type 1.5 diabetes.
It is estimated that LADA is found in between 6% and 10% of diabetes cases. However, this may be as high as 25% of cases in people diagnosed with diabetes under the age of 35.
Sweetened and Diet Drinks
The latest study by the Karolinska Institute in Sweden examined the effect of drinking sugary or artificially sweetened drinks on the risk of developing type 2 diabetes or LADA.
The study of 2,864 Swedish adults was based on questionnaires detailing what they ate and drank. Around half of the group had either type 2 diabetes and LADA, with the remaining individuals being free of diabetes.
The researchers found that people who drank 2 or more 200ml glasses of soft drinks a day were 2.4 times as likely to develop type 2 diabetes as those who did not drink these beverages.
Also, this amount of soft drinks doubled the risk of developing LADA.
The risk increased in line with consumption. So, those who had 5 glasses a day of soft drinks – whether sugary or artificially sweetened – had more than 10 times a higher risk of type 2 diabetes and more than 4 times a higher risk of LADA than those who did not.
Josefin Edwall Löfvenborg, who led the research team, comments in a statement: "In this study we were surprised by the increased risk in developing autoimmune diabetes by drinking soft drinks." However, there was no evidence that increasing consumption increased the autoimmune response in LADA patients. "This could mean that the increased risk of developing LADA in relation to soft drink consumption isn't directly caused by the immune response killing beta cells – which is what we see in type 1 diabetes," she explains.
One theory is that artificially sweetened, or 'diet', drinks, may stimulate appetite and lead to weight gain – a known risk factor for type 2 diabetes.
The researchers acknowledge that one drawback to their research technique was that participants were asked to record what they ate and drank a year in the past.
Consequence or Cause?
Several experts have commented on the findings in statements.
Dr Nita Forouhi, from the University of Cambridge urges caution about the results. "Increased thirst is a classical feature of diabetes onset, so higher intakes of beverages in the period leading up to a diagnosis of diabetes is to be expected," she says. "Therefore the higher beverages intake may well be the consequence rather than the 'cause' of diabetes onset."
Christine Williams, professor of human nutrition at the University of Reading, observes: "A most interesting finding was that the higher risk was the same for both sweetened and artificially sweetened beverages, suggesting that greater risk of diabetes was not directly related to higher calorie intake, or adverse metabolic effects of sugar (in the form of sucrose) from the sweetened drinks."
Dr Elizabeth Robertson, director of research at Diabetes UK, comments that "participants who drank more sweetened drinks also led unhealthier lifestyles in general, meaning a number of other factors like diet and exercise may have affected the results."
Sweetened beverage intake and risk of latent autoimmune diabetes in adults (LADA) and type 2 diabetes, J Löfvenborg et al, European Journal of Endocrinology
Press release, European Society of Endocrinology
Science Media Centre