A new study from Harvard T.H. Chan School of Public Health shows that eating French fries regularly may increase your risk of developing type 2 diabetes.
However, eating other kinds of potatoes—like baked, boiled, or mashed—does not seem to raise the risk.
The study also found that replacing potatoes with whole grains can help lower the chance of getting type 2 diabetes.
The study will be published on July 30 in the medical journal BMJ. It followed over 205,000 men and women in the U.S. for more than 30 years. These people were part of three big long-term health studies: the Nurses’ Health Study, the Nurses’ Health Study II, and the Health Professionals Follow-up Study.
Every few years, participants answered detailed questions about what they ate and whether they had developed any new health conditions, including type 2 diabetes.
Over the study period, 22,299 participants said they had developed type 2 diabetes. When the researchers looked closely at what these people ate, they found that those who ate French fries three times a week had a 20% higher chance of getting diabetes.
But people who ate baked, boiled, or mashed potatoes did not show a higher risk. This suggests that how potatoes are cooked plays an important role in health.
The researchers also looked at what would happen if people replaced potatoes with other foods. They found that swapping French fries for whole grains—like whole grain bread, pasta, or farro—could lower the risk of diabetes by 19%.
Even replacing French fries with regular white bread or pasta (called refined grains) could reduce the risk. If people replaced baked, boiled, or mashed potatoes with whole grains, the diabetes risk could drop by 4%.
The study’s lead author, Dr. Seyed Mohammad Mousavi, explained that this research helps us ask better questions—not just “Are potatoes good or bad?” but “How are they cooked, and what are we eating instead?”
To strengthen their results, the researchers also reviewed earlier studies that followed over 500,000 people across four continents. These studies showed similar results: eating whole grains instead of potatoes, especially French fries, helps lower diabetes risk.
One of the senior researchers, Dr. Walter Willett, said the message is simple: small diet changes can make a big difference. Choosing whole grains instead of French fries can help reduce the risk of type 2 diabetes.
He also said that health guidelines should focus not only on types of food but also on how the food is prepared. Not all carbohydrates are the same, and not all potatoes are the same either.
This study offers important advice for anyone looking to eat healthier. French fries should be eaten less often, while baked or boiled potatoes are safer options. Best of all, switching to whole grains is a simple way to protect your health.
If you care about diabetes, please read studies about Why diabetes drug metformin can help increase longevity and findings of This drug could manage type 2 diabetes for a long time.
For more about diabetes, please read studies about Potatoes: friend or foe in the battle against diabetes? and findings of This blood pressure drug may protect kidney health in people with diabetes.
The study is published in BMJ.
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