Potatoes have long been considered the most basic of basic foods, a no-frills staple for the everyman or everywoman. One reason potatoes have earned this distinction is, no doubt, their low cost, but another may be their basic nutritional qualities: They are fat-, sodium-, and cholesterol-free, and a medium-size potato contains just 110 calories. Nevertheless, the reputation of potatoes has taken a hit lately due to their relatively high glycemic index, which means that the carbohydrate in them is quickly converted to glucose when digested. Many people with diabetes take glycemic index into account when deciding what foods to incorporate into their diet.
So how good or bad are potatoes when it comes to weight control and glucose tolerance? A study examining these topics was published earlier this month by the Journal of the American College of Nutrition. According to an article on the study in the Daily Mail, the effect of potatoes on weight control may be modestly positive. Researchers assigned 90 overweight participants to one of three groups. Two of these groups were taught how to reduce their daily caloric intake by 500 calories, but one group was taught how to do this by eating mostly high-glycemic-index foods, and the other by eating mostly low-glycemic-index foods. The third group was not told to change anything about the caloric or glycemic-index composition of their diet. All three groups were told, however, to consume 5–7 servings of potatoes per week.
After 12 weeks of following their prescribed diets, there were no significant differences between the groups in terms of weight loss or body composition changes. All three groups, however, experienced modest weight loss and improvements in body composition. Since the only dietary change that all three groups had in common was consuming potatoes regularly, it’s plausible that the potatoes were responsible for this weight loss. But since the study had no control group that changed nothing at all in their diet, it’s impossible to say for sure. After 12 weeks, there were no significant changes seen in participants’ triglycerides, glucose tolerance, insulin levels, or insulin sensitivity.
One reason why it’s difficult to come to any conclusions on the role potatoes play in glucose control is that they may have very different effects depending on how they’re prepared. As shown by a search for “potato” at GlycemicIndex.com, different varieties of potatoes have different glycemic indexes that are also affected by how they’re cooked. The numbers range from 58 (low-medium glycemic index) for a boiled Nicola potato to 111 (extremely high) for a baked Russet Burbank potato. This range in numbers doesn’t even take into account the reality that potatoes are often combined in dishes with other ingredients, which can have an enormous effect on their glycemic impact. Adding ingredients containing fat, protein, and fiber can greatly lower the glycemic index of a food, leading to a more moderate and consistent release of glucose into the bloodstream.
What’s your take on potatoes — have you found that they spike your blood glucose, or that your body tolerates them just fine? Have you noticed any differences in your blood glucose behavior depending on how potatoes are prepared and served? Have you found that adding fat to lower the glycemic index of potatoes is problematic for weight control? Have you found any easy alternatives to potatoes in your diet? Leave a comment below!