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Potatoes have long had a bad rap for being high in carbohydrates. A new study backs that concern—at least in part.
That weekly french fry habit could be setting you up for diabetes decades down the road.
Research found that eating french fries just three times per week may significantly raise Type 2 diabetes risk—but surprisingly, other potato preparations showed no increased risk at all.
“Our findings suggest it’s not fair to put all potatoes in the same basket,” lead author Seyed Mohammad Mousavi told The Epoch Times.
How You Like Your Potatoes Matters
The study, led by Harvard T.H. Chan School of Public Health, tracked more than 205,000 adults across three major U.S. observational health studies for 30 years. Participants regularly reported what they ate, along with details about their health and lifestyle.
The study found that every three extra servings of potatoes per week was associated with a 5 percent increase in Type 2 diabetes risk. For french fries, that jump was even higher—20 percent per three servings.
In contrast, eating baked, boiled, or mashed potatoes was not associated with an increased risk, suggesting that french fries are the main driver behind the link between potatoes and diabetes.
French fries are often loaded with salt, which can raise blood pressure and trigger inflammation, increasing the risk of Type 2 diabetes. However, it’s more than just the fat and salt content driving the diabetes risk.
“French fries are typically deep-fried at very high temperatures, which can produce harmful compounds,” Mousavi said. One such compound is acrylamide, which is formed during browning and linked to inflammation, insulin resistance, and blood vessel damage.
“Due to their deep-fried nature, [fries] are also much higher in calories than baked or mashed potatoes,” said Melissa Mitri, a registered dietitian-nutritionist and owner of Melissa Mitri Nutrition, who was not involved in the study.
The large amounts of oil used in frying also introduce trans fats, which further increase insulin resistance and inflammation. Combined with the high-temperature cooking that breaks down resistant starches, french fries become a perfect storm for blood sugar chaos.
Potatoes and Type 2 Diabetes
Even aside from french fries, people who ate seven or more servings of potatoes per week had a 12 percent higher risk of developing Type 2 diabetes. The risk rose with greater intake.
While preparation plays a key role in how potatoes affect diabetes risk, it’s worth noting that they still have a high glycemic index, meaning that they can rapidly raise blood sugar.
Potatoes are a common source of carbohydrates, especially starch, which the body quickly breaks down into sugar. Because of this, eating potatoes can cause a sharp rise in blood sugar levels soon after a meal.
Frequent blood sugar spikes force the pancreas to release more insulin repeatedly. Over time, this constant demand can cause insulin-producing cells to wear out or stop working properly. This contributes to insulin resistance and reduced insulin production—both key drivers of Type 2 diabetes.
The glycemic index ranks how quickly and how much different foods raise blood sugar levels after eating. A higher glycemic diet is associated with an increased risk of developing Type 2 diabetes, as high glycemic foods cause a rapid and significant rise in glucose levels.
A potato’s glycemic index depends on how it is prepared. Mashed and boiled potatoes have higher glycemic indexes because cooking breaks down the potato’s structure and makes the starch easier to digest, leading to faster spikes in blood sugar.
Deep-frying also softens the starch inside, but the hot oil forms a crust with some resistant starch that slows digestion. The fat in fries also helps slow down how quickly sugar is absorbed, making the glycemic index of french fries a bit lower than that of mashed or instant potatoes.
Using different food preparation methods can reduce potatoes’ risks:
- Chill potatoes after cooking to increase their resistant starch content, slowing digestion and causing a more balanced rise in blood sugar.
- Bake or boil potatoes with the skin to retain more fiber and micronutrients.
- Boil, bake, or roast potatoes with minimal oil instead of frying to avoid added fats.
- Air-fry potatoes to reduce the formation of harmful compounds produced by deep-frying.
The study found that replacing potatoes with other carbohydrates reduced Type 2 diabetes risk. Swapping mashed, boiled, or baked potatoes for whole grains such as pasta, bread, or farro lowered diabetes risk by 4 percent, while replacing french fries cut it by 19 percent. Substituting fries with whole grains, legumes, brown rice, or vegetables also reduced risk by 19 percent.
The only swap that increased risk was white rice, which was linked to a 3 percent higher risk of Type 2 diabetes. This may be because white rice has a high glycemic index.
“White rice is stripped of fiber and nutrients, digests quickly, and causes sharper spikes in blood sugar,” Mousavi said.
Whole grains have fiber that slows digestion and causes smaller blood sugar spikes.
Effects Surface Years Later
Perhaps most concerning, the study found that potato intake 12 to 20 years before diagnosis had the strongest association with diabetes risk—suggesting that dietary choices in your 20s and 30s could determine your health in your 50s and 60s.
Type 2 diabetes develops gradually, with insulin resistance and inflammation starting decades before symptoms appear.
Who’s Most at Risk
Even after adjusting for genetics, diet, and lifestyle, the link between french fries and diabetes remained strong. It was especially pronounced in people with a higher body mass index (BMI) and in white participants.
Mitri noted that excess weight is tied to inflammation.
“Someone with a higher BMI may have more difficulty responding to insulin,” she said, noting that this can worsen insulin resistance.
Mousavi said, “For people with higher BMI, the same amount of potatoes may have a bigger impact on diabetes risk.”
The study also found that people who ate more potatoes were often less physically active and took in more calories, sugary drinks, and red meat—factors that can raise diabetes risk.
https://www.theepochtimes.com/health/french-fries-versus-baked-potatoes-one-raises-diabetes-risk-20-percent-the-other-doesnt-5897553
