A salty twist: Diabetes risk study says french fries are a culprit

NBC News

5 days ago

Craving french fries? Dunking your spuds in a deep fryer might be a recipe for elevating your risk of Type 2 diabetes.
According to a study published Wednesday in the journal BMJ, swapping out your weekly dose of frites for boiled, baked or mashed potatoes could lower your risk of this chronic condition.
The authors examined the diets of more than 205,000 adults in the U.S. who responded to questionnaires about what they ate over nearly four decades. Among those who consumed potatoes, the authors looked at which people developed Type 2 diabetes, a disease that leads to persistently high blood sugar levels.
Eating three weekly servings of french fries, they found, was associated with a 20% increased risk of Type 2 diabetes. But consuming the same amount of boiled, baked or mashed potatoes did not appear to be linked to the disease.
The vast majority of the 1 in 10 people with diabetes in the U.S. have Type 2. The condition can increase the risk of heart attacks, strokes or kidney damage.
The findings underscore that the way foods are prepared is key to their overall health risks or benefits, said Seyed Mohammad Mousavi, the study's lead author and a postdoctoral research fellow at the Harvard T.H. Chan School of Public Health.
'Not all potatoes are created equal,' he said. 'Even a small amount of french fries, less than one serving in the week, is associated with a higher risk of Type 2 diabetes.'
Unlike boiled or baked potatoes, french fries are deep-fried in oils that usually contain trans or saturated fats. The way the body metabolizes those fats can contribute to insulin resistance — when cells don't respond properly to insulin, a hormone that helps regulate blood sugar. Regular consumption of fried foods can also lead to obesity and inflammation, both of which raise the risk of Type 2 diabetes.
'When you fry the potatoes, the energy content — calories — increases because of the fat they absorb. If you eat many servings of french fries, it predisposes [people] to weight gain,' said Candida Rebello, the director of the nutrition and chronic disease program at Louisiana State University, who wasn't involved in the study.
The study relied on data collected between 1984 and 2021, when several different frying methods were popular. Most fast-food chains today prepare fries using vegetable oils like canola, sunflower, soybean or peanut oil. But during the 1980s, beef tallow was common. And in the early 1990s, restaurants shifted to partially hydrogenated oils. (The oils were a major source of trans fat in the U.S. diet and were largely phased out of the food industry by 2018.)
Health and Human Services Secretary Robert F. Kennedy Jr. has said the seed oils used today are 'poisoning' Americans and contributing to high levels of obesity in children. He has advocated for restaurants to switch back to beef tallow, a recommendation that isn't backed by scientific research.
'Beef tallow is high in saturated fats and other harmful fats. We definitely don't recommend that,' Mousavi said.
One limitation of Mousavi's study is that it did not account for people adding unhealthy ingredients to their boiled, baked or mashed potatoes.
'What do people add to baked potatoes? Butter, bacon, cheese, sour cream,' said Shannon Galyean, an assistant professor of nutritional sciences at Texas Tech University, who wasn't part of the research. 'Then we also don't know, did they eat it with the skins?'
Galyean said potato skins contain nutrients such as fiber, which helps with blood sugar control. And potatoes, when they aren't deep-fried or slathered in butter, can be a useful source of potassium, which helps regulate blood pressure.
'Definitely, potatoes can be considered a healthy food when you don't fry it, or when you don't add lots of fat to it,' Galyean said.
Mousavi said baking french fries at home with a healthier oil, such as olive or avocado oil, could help lower one's diabetes risk compared to eating them from fast-food restaurants. Swapping out potatoes with whole grains, such as farro or whole-grain bread or pasta, could make an even bigger difference. These foods have a lower glycemic index, meaning they're less likely to spike blood sugar levels.
His study found that whole grains, when compared to all types of potatoes, were less likely to elevate one's diabetes risk. White rice, on the other hand, had a stronger association with Type 2 diabetes than either of these foods.
Megan Mulcahy, the director of communications at Potatoes USA, a marketing and research organization that supports potato consumption, said fries can 'absolutely be part of a healthy eating pattern when enjoyed in moderation.'
Galyean said it's important to consider a person's overall diet, which has a greater impact on their health than any individual food. Nutritionists generally recommend a colorful plate with a variety of fruits, vegetables, whole grains and healthy proteins such as fish, beans or nuts.
'People don't eat just one thing, they eat meals,' Galyean said.