Recommendation to eat potatoes questioned in study linking them to gestational diabetes

Researchers with the Eunice Kennedy Shriver National Institute of Child Health and Human Development and Harvard University question the wisdom of including in the US Dietary Guidelines potatoes as a healthy food in the vegetable category after they found women who eat potatoes at least once a week were 21% more likely to develop gestational diabetes.

The relative risk increases the more potatoes women eat – rising to 34% increased risk after two to four servings a week and 62% for five or more servings a week compared to women who do not eat potatoes, according to the study published Jan. 12 in The BMJ​.

The relative risk falls slightly when adjusted for body mass index, but otherwise the association did not differ by other factors for gestational diabetes, which is a common pregnancy complication that increases long term cardiometabolic risk for mothers and children, according to the study.

The researchers uncovered the potentially dangerous association by analyzing the dietary patterns of women who became pregnant while participating in the Nurses’ Health Study II. The study captured 854 cases of gestational diabetes out of 21,693 pregnancies in a 10 year period.

Results supported by previous findings​

While the researchers were quick to point out the study did not causally connect the two factors, they did note that the results are in line with those of previous studies that linked eating potatoes to an increased risk of type 2 diabetes.

Despite prior findings, the US Dietary Guidelines and the United Kingdom’s national dietary guidelines advise people to eat plenty of potatoes. The main difference between the two guidelines is the US categorizes potatoes as a vegetable and the UK categorizes them as a starch.

“Findings from the present study raise concerns about such guidance,”​ which have been the source of “long standing debates,”​ given the broader inconclusive evidence on the health effects of potatoes, the authors write.

A “biologically plausible”​ explanation​

A “biologically plausible”​ explanation for the association between gestational diabetes and potatoes is the high level of rapidly absorbed starch in the food that can cause a sharp rise in post prandial blood glucose levels, induce oxidative stress in pancreatic β cells followed by dysfunction and exhaustion, according to the study. In contrast, it adds, other vegetables, legumes and whole grains have low glycemic indexes.

Along with the starch, potatoes offer Americans high amounts of vitamin C, dietary fiber and some phytochemicals, which likely is why the food won the recommendation in the guidelines. But these benefits also can be obtained from other sources not connected to gestational diabetes, the researchers note.

With this in mind they recommend women substitute two servings of potatoes per week with other vegetables, legumes and whole foods, which they found reduced the risk of gestational diabetes 9-12%.

Specifically, whole grains offered the highest risk reduction at 12% followed by 10% for legumes and 9% for other vegetables.