Scientists Reveal Potato Dish That Raises Diabetes Risk

Eating French fries just three times a week was linked to a 20 percent higher chance of developing type 2 diabetes, according to a study published in The BMJ. In contrast, eating the same amount of potatoes prepared in other ways (boiled, baked, or mashed) did not show a meaningful increase in risk.

The research also found that replacing any kind of potatoes with whole grains was tied to a lower risk of type 2 diabetes, while swapping them for white rice was linked to a higher risk.

Potatoes provide beneficial nutrients such as fiber, vitamin C, and magnesium, but they are also high in starch, which gives them a high glycemic index. This has been associated with a greater likelihood of developing type 2 diabetes.

Until now, studies had not examined how cooking methods or the specific foods that potatoes replace in the diet might influence their overall health effects.

To explore this, researchers analyzed how different preparations of potatoes (boiled, baked, or mashed compared with French fries) related to the risk of type 2 diabetes. They also studied the effects of replacing potatoes with other carbohydrate-rich foods, including whole grains and rice.

The analysis drew on data from more than 205,000 U.S. health professionals who took part in three large studies between 1984 and 2021. All participants were free of diabetes, heart disease, and cancer at the start and completed detailed dietary questionnaires every four years.

During almost 40 years of follow-up, 22,299 people were diagnosed with type 2 diabetes.

After adjusting for lifestyle and dietary factors related to diabetes risk, the researchers found that for every three weekly servings of total potatoes, the rate of type 2 diabetes increased by 5% and for every three weekly servings of French fries, the rate increased by 20%. However, similar intake of baked, boiled, or mashed potatoes was not associated with a significantly increased risk.

Replacing three weekly servings of total potatoes with whole grains lowered the type 2 diabetes rate by 8%. Substituting baked, boiled, or mashed potatoes with whole grains lowered the rate by 4%, and replacing French fries lowered the rate by 19%.

In contrast, replacing total potatoes or baked, boiled, or mashed potatoes with white rice was associated with an increased risk of type 2 diabetes.

This is an observational study, so no firm conclusions can be drawn about cause and effect, and the researchers can’t rule out the possibility that other unmeasured factors may have influenced their results. Most participants were also health professionals of European ancestry, so findings may not apply to other populations.

Nevertheless, they conclude: “Our findings underscore that the association between potato intake and type 2 diabetes risk depends on the specific foods used as replacement. The findings also align with current dietary recommendations that promote the inclusion of whole grains as part of a healthy diet for the prevention of type 2 diabetes.”

So, are potatoes back on the plate? Well, it depends, say researchers in a linked editorial, who note that it is important to consider preparation method and replacement food when guiding the public or informing policy.

They point out that with their relatively low environmental impact and their health impact, baked, boiled, or mashed potatoes can be part of a healthy and sustainable diet, though whole grains should remain a priority, but say future studies from more diverse populations that account for both preparation methods and substitution analysis are needed.

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