Potato Based Diet Doesn't Affect Blood Sugar Control

Researchers from the Australian Catholic University in Melbourne have discovered in a rigorously controlled clinical trial that people with diabetes don't need to avoid potatoes. It was previously thought that potatoes with a high glycemic index should be avoided by diabetics as they may adversely affect blood sugar. But the recent study indicates that the glycemic index is not an accurate surrogate for an individual's glycemic response (GR) to food consumed as part of an evening meal.

People with type-2 diabetes (T2D) are frequently told to avoid eating potatoes, and other high glycemic index (GI) foods, because of the longstanding perception that these foods make it difficult to control blood sugar levels. This is especially problematic during the night when blood sugar tends to spike.

In the study, the 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 9-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 GR was more favorable after eating the evening meal that included any of the high GI potato side dishes compared to low GI basmati rice. "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 T2D," says Dr. Brooke Devlin, Ph.D., the primary investigator, at 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 T2D."

Findings from this study demonstrate how other factors, such as the time of day or food pairings, need to be considered when investigating the GR of mixed meals in individuals with T2D, adds Devlin.

Although this study followed a rigorous methodology, the potatoes' impact on long-term glycemic control was not assessed. Despite such limitations, 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.