Drinking two sweetened drinks a day could double the risk of diabetes, new study suggests.

Research from the Karolinska Institute in Sweden found that consuming over 200 ml of carbonated drinks a day could double an individual's risk of developing type-2 diabetes. As the standard 12-ounce soft drink can contain more than 300 ml, this suggests that drinking merely one and a half of these beverages per day will increase the risk.

The study also highlights that even diet drinks could have the same effect, as the level of risk remains regardless if whether the drinks contain sugar or artificial sweeteners.

"Not all studies have been able to look at sugary and artificially beverages separately," Josefin Edwall Löfvenborg, a nutritionist at Karolinska Institute and one of the authors of the study, said in a report by CNN. "[But] it's getting more and more established that soft drinks increase risk of type 2 diabetes."

The researchers also found that drinking more than five 200ml sweetened drinks per day results in 10 times more risk of developing type-2 diabetes compared with individuals who do not drink sweetened beverages.

In the study, the researchers analyzed the levels of soft drink consumption of over 2,800 Swedish adults with type-2 diabetes who are reported to be drinking sweetened drinks. The researchers also studied subjects with latent autoimmune diabetes (LADA), a condition that shares the same characteristics of both type-1 and type-2 diabetes where the pancreas could not produce enough insulin and at the same time, the body becomes resistant to insulin.

"In this study, we were surprised by the increased risk in developing autoimmune diabetes by drinking soft drinks," Löfvenborg said in a report by Huffington Post. According to Löfvenborg, LADA is not routinely diagnosed, and because of this, experts find it difficult to estimate the prevalence of this condition.

The reason behind the increase in type-2 diabetes risk is not yet clear. But the researchers suspect that because these drinks are high in calories, the likelihood of obesity also increases. Obesity, in turn, is a risk factor for diabetes.

However, in terms of developing LADA, Löfvenborg thinks that the increase in risk is due to the spike in sugar levels caused by sweetened beverages. Excessive spikes could "wear out" the cells that produce insulin and could also make individuals less sensitive to insulin.