Eating Potatoes Linked to Gestational Diabetes

A new study suggests that eating potatoes before you get pregnant or when trying to conceive is linked with a higher chance of gestational diabetes.

Eating Potatoes Linked to Gestational Diabetes Kseniia Perminova/Shutterstock

Doesn't the list of what you should and shouldn't consume during, and even before, pregnancy seems so long? Well, you might want to add another food to the list: the seemingly harmless potato. In a recent study published in The BMJ, researchers found a connection between eating the starchy veggie pre-pregnancy and a greater risk for gestational diabetes (GD) while expecting.

Potato, potato?

Researchers looked at more than 15,000 women who became pregnant over a ten-year period. Through self-reported surveys, the scientists tracked the women's food intake and compared it with which ones were diagnosed with gestational diabetes (also called gestational diabetes mellitus, or GDM), a condition marked by high blood sugar, during pregnancy. They found that the women who ate more potatoes, including baked, boiled, mashed and fried, had a higher rate of gestational diabetes during pregnancy—even after they took into account other factors like weight and overall diet quality. "Pre-pregnancy potato consumption was significantly and positively associated with the risk of GDM," the study's senior author Cuilin Zhang, M.D., Ph.D., a senior investigator at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), tells Fit Pregnancy.

This is the first study to look at potatoes' effect on the development of GDM. Although it didn't identify a specific threshold over which it's unhealthy to eat potatoes, "our data indicated that the more potato women consumed before pregnancy, the greater their risk," Dr. Zhang says. "In particular, consuming five or more than five servings per week was related to more than 50 percent increased risk as compared to less than one serving/week."

Although this new research proves there is a link, it didn't prove cause and effect, so we can't say for sure that eating potatoes leads to gestational diabetes. But even so, the study authors think it's time to revise the US's dietary guidelines, which categorizes potatoes as a vegetable and advises people to eat plenty of them. Because potatoes are high in starch, they raise blood sugar levels. This, in turn, could lead to a greater chance of developing gestational diabetes, as was seen in the study. "Our data suggested that women who are planning for pregnancy may want to be cautious about greater potato intakes," Dr. Zhang says.

Fries are a vegetable, right?

And if you think you're being healthy by having a baked potato instead of fries, you might want to think again. The researchers broke down the results by type of potato preparation, lumping together baked, boiled and mashed, and comparing that with french fries. The increased rate of gestational diabetes was the same for both types of taters—although women who ate baked, boiled or mashed were also more likely to eat fries, and vice versa. "Regardless of the way of cooking, greater potatoes consumption was related to higher GDM risk," Dr. Zhang says. "In our study, we found higher consumption of boiled, mashed, baked and fried were all related to a greater risk of GDM."

Switching out two servings of potatoes a week with other foods, though, could lower the risk of gestational diabetes nine to 12 percent, according to the findings. "We found replacing potatoes with whole grains such as whole grain bread, legumes [like beans and lentils] and other vegetables such as green leafy vegetables or cauliflower, was related to a lower GDM risk," Dr. Zhang says. Although the study didn't specifically address sweet potatoes, that veggie is lower on the glycemic index, which measures how foods raise blood sugar, so it is likely also a healthier choice. In addition, sweet potatoes have more advantages like antioxidants, beta-carotene, and lots more vitamin C and A than white potatoes.

Should you stop eating potatoes?

This study only looked at women's diets pre-pregnancy, but it stands to reason the same rules would apply while pregnant. "We do not have data on potato consumption during pregnancy, but given the biological plausibility, women may want to avoid frequent potato consumption during pregnancy to lower their risk of GDM," Dr. Zhang says. But, you probably shouldn't cut out potatoes completely—at least not before talking with your doctor—because they do have some nutritional value. "Potatoes contain vitamin C, potassium and fiber as well," Dr. Zhang says. And although the study gives potatoes a bad rap, it is possible that some other factor is at play—women who eat more potatoes, for example, may gain more weight during pregnancy, which is itself a risk factor for GD.

Overall, a balanced diet is most important in pre-pregnancy and pregnancy health, and all foods prepared well and eaten in moderation—especially natural, whole foods like potatoes—can have their place on the table.