A new study challenges a longstanding perception that people with type-2 diabetes always need to avoid eating potatoes, and other high Glycemic Index (GI) foods.
The findings, published in the journal Clinical Nutrition, showed that Glycemic Index is not an accurate surrogate for an individual's glycemic response (GR) to a food consumed as part of an evening meal.
"These findings are contrary to that of observational research and traditional dietary guidance that has led some to believe potatoes are not an appropriate food choice for people with type-2 diabetes," said corresponding author of the study Brooke Devlin from Australian Catholic University in Melbourne.
"Our study shows high GI foods, like potatoes, can be consumed as part of a healthy evening meal without negatively affecting GR -- and while delivering key nutrients in relatively few calories, which is essential for people with type-2 diabetes."
The controlled clinical trial involved 24 adults with type-2 diabetes.
Participants were provided the same breakfast and lunch, but they were randomly assigned to one of four dinners, each including either skinless white potatoes (test meal) prepared in three different ways (boiled, roasted, boiled then cooled then reheated) or basmati rice (control meal).
Participants repeated the experiment, with a nine-day break in between each trial, to cycle through all test meals and the control.
In addition to having blood samples collected regularly (both immediately after the meal and again every 30 minutes, for two hours), participants also wore a continuous glucose monitor overnight to track changes in blood sugar levels while sleeping.
There were no differences between meals in glucose response following the dinner that contained any of the potato dishes or basmati rice.
Moreover, participants' overnight glycemic response was more favourable after eating the evening meal that included any of the potato side dishes compared to low basmati rice, said the study.
Although the potatoes' impact on long-term glycemic control was not assessed in the study, the researchers concluded that "potatoes are a vegetable that is sustainable, affordable and nutrient-dense, and thus, they can play an important role in modern diets irrespective of metabolic health status."
However, people with diabetes should continue to follow the diet suggested by their physician, the study authors cautioned.