Past research on potatoes’ ties to type 2 diabetes has been mixed, with some studies showing greater risk with greater consumption, and others pointing to a protective effect.In this study, the rate of type 2 diabetes increased by 20% and 5% with every increment of three servings weekly of French fries or total potato, respectively.Choosing whole grains instead of French fries three times per week may cut type 2 diabetes risk by 19%.
Eating French fries multiple times a week was associated with a higher risk of type 2 diabetes, though this wasn’t the case for baked, boiled, or mashed potatoes, researchers said.
For every increment of three servings weekly of French fries, the rate of type 2 diabetes increased by 20% (95% CI 1.12-1.28), and for every increment of three servings weekly of total potato, the rate increased by 5% (95% CI 1.02-1.08), reported Walter Willett, MD, of the Harvard T.H. Chan School of Public Health in Boston, and colleagues.
However, consumption of combined baked, boiled, or mashed potatoes was not significantly associated with risk of type 2 diabetes (pooled HR 1.01, 95% CI 0.98-1.05), they noted in The BMJ.
“Importantly, our substitution analysis showed that replacing all forms of potatoes — especially fries — with whole grains was linked to a lower risk of type 2 diabetes, whereas swapping them for white rice was associated with the opposite effect,” co-author Seyed Mohammad Mousavi, PhD, also of the Harvard T.H. Chan School of Public Health, told MedPage Today. “This reinforces that it’s not just about the potato itself, it’s about how it’s prepared and what foods it’s replacing in the diet.”
Of note, replacing three servings weekly of total, non-fried, and fried potatoes with whole grains was estimated to lower the risk of type 2 diabetes by 7%, 5%, and 17%, respectively.
“Are potatoes back on the plate? Well, it depends,” wrote Daniel Ibsen, MSc, of Aarhus University in Denmark, and Yanbo Zhang, PhD, of the Albert Einstein College of Medicine in the Bronx, New York, in an accompanying editorial. “Two key considerations are important when guiding the public or informing policy: the food should be defined clearly (e.g., the method of potato preparation), as should be the type of carbohydrate rich food to be replaced by minimally processed potatoes.”
Cooking Up a Better Potato Analysis
Past research on potatoes’ ties to type 2 diabetes has delivered mashed results. Some studies showed greater risk as potato consumption rose, while others either came up empty or even pointed to a protective effect. That earlier research often failed to distinguish between how potatoes were prepared, Mousavi said, or to consider what replaced potatoes in people’s diets.
To address those shortcomings, the researchers analyzed data from the Nurses’ Health Study (72,712 women), Nurses’ Health Study II (90,232 women), and the Health Professionals’ Follow-up Study (42,163 men). They assessed links between potato consumption and diabetes development, and studied how replacing potatoes with foods such as whole grains and non-starchy vegetables might impact diabetes risk. They also conducted a meta-analysis of 10 prospective studies to clarify potential links between specific potato preparations, whole grains, and diabetes risk.
The current analysis included participants who had completed the three longitudinal studies’ food frequency questionnaires and had no prior diagnoses of type 2 diabetes, cancer, myocardial infarction, stroke, angina, or coronary artery bypass grafting.
During 5,175,501 person-years of follow-up in the three cohorts, there were 22,299 documented diagnoses of type 2 diabetes. The participants in all three studies ate baked, boiled, or mashed potatoes more often than French fries. Those reporting greater total potato consumption tended to be less active, had a greater total energy intake, and were less likely to take supplements.
Increased potato consumption showed a linear relationship with type 2 diabetes risk. Those who ate five or more servings of French fries every week saw a significant, adjusted 27% greater risk compared with those who almost never ate them (P<0.001 for trend). Boosting total potato intake to at least seven weekly servings pushed risk up a significant 12% (P<0.001 for trend). In contrast, eating potatoes baked, boiled, or mashed, even seven times or more each week, delivered a small but significant 1% lower risk.
French fries weren’t exonerated even after controlling for intake of trans fatty acids and confections, body mass index, and polygenic risk scores. Despite adjusting for those factors, the increased type 2 diabetes risk linked to French fries remained significant.
Assessing Dinner Plate Alternatives
The researchers estimated that choosing whole grains instead of three weekly servings of baked, boiled, or mashed potatoes would likely drop the risk of diabetes by 4%. Go with whole grains instead of French fries three times per week, and risk would fall 19%.
Swap in non-starchy vegetables instead of French fries, and risk would drop 17%. Doing the same for baked, boiled, or mashed potatoes, however, would do nothing to dent risk.
That substitution health halo didn’t hold for white rice, however. Replacing all baked, boiled, or mashed potatoes with white rice was linked to a significantly greater risk of developing type 2 diabetes (HR 1.19, 95% CI 1.14-1.25). Brown rice didn’t excel as a substitute, either. Subbing in brown rice for any potato other than French fries delivered no risk advantage.
I’m Not Bad — I’m Just Cooked That Way?
Potatoes’ high, rapidly absorbed starch content can lead to a high glycemic index and load. Eating them in large amounts can spike blood glucose and insulin levels, potentially stressing pancreatic beta cells and eventually contributing to insulin resistance. But the potato preparations’ dissimilar diabetes risks suggest a more complex nature-versus-nurture story, the researchers cautioned.
“Complexities in glycemic response and metabolic impact could partly explain inconsistent associations for non-fried potatoes compared with the stronger relation seen with French fries,” Willett and colleagues wrote. Fried potatoes “not only have a high glycemic index but also contain added fats that have varied over time, salt, and potentially harmful products due to preparation at high temperatures.”
The Takeout, er, Takeaway Messages
For clinicians, the message is that not all potatoes are equal in terms of diabetes risk, Mousavi told MedPage Today. “French fries are the main concern — they’re calorie-dense, high in sodium, and often fried in unhealthy oils, which can increase risk even at moderate intake levels,” he said.
For patients who enjoy potatoes, “encourage them to prepare potatoes in healthier ways, like baking or boiling, and to prioritize whole grains as their main carbohydrate source,” Mousavi noted. “It’s also worth stressing that food swaps matter — replacing potatoes with whole grains can lower risk, while replacing them with white rice may not help.”
The study’s largest limitation may be its participant populations. “Most of our participants were white health professionals,” Mousavi said. “We need more high-quality data in diverse populations to ensure these findings — and the dietary recommendations based on them — are relevant across different racial and ethnic groups. This is especially important because type 2 diabetes disproportionately affects some communities, including Black and Hispanic Americans.”
Dining and Cooking