A study published in The BMJ on August 6 has found that eating three servings of French fries a week is linked to a 20% higher risk of developing type 2 diabetes.
In contrast, eating similar amounts of potatoes prepared by boiling, baking, or mashing does not appear to significantly raise the risk.
The research also showed that replacing any form of potatoes with whole grains was associated with a lower risk of type 2 diabetes, while swapping them for white rice was linked to an increased risk.
Potatoes contain important nutrients such as fiber, vitamin C, and magnesium, but their high starch content and high glycemic index have raised concerns about their role in diabetes risk.
To better understand this link, researchers examined data from over 205,000 health professionals in three large U.S. studies conducted between 1984 and 2021.
All participants were free of diabetes, heart disease, and cancer at the start, and they completed detailed food questionnaires every four years. During nearly 40 years of follow-up, 22,299 participants were diagnosed with type 2 diabetes.
After adjusting for lifestyle and dietary factors, the team found that every three weekly servings of total potato intake increased diabetes risk by 5%, and the same frequency of French fries increased the risk by 20%. However, baked, boiled, or mashed potatoes were not significantly linked to higher risk.
Substituting three weekly servings of total potatoes with whole grains reduced diabetes risk by 8%. Replacing baked, boiled, or mashed potatoes with whole grains lowered the risk by 4%, and replacing French fries with whole grains reduced the risk by 19%. Conversely, replacing any type of potato with white rice increased the risk of type 2 diabetes.
The authors caution that this was an observational study, so no firm conclusions about cause and effect can be made. They also noted that most participants were health professionals of European ancestry, meaning the findings may not apply to all populations.
In a linked editorial, experts stressed that preparation method and replacement foods should be taken into account when making dietary recommendations.
They noted that baked, boiled, or mashed potatoes can be part of a healthy, sustainable diet—especially when combined with whole grains—but more diverse studies are needed to confirm these results.
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The study is published in BMJ.
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