Harvard study links this popular vegetable to a rising diabetes risk, but there's a catch; and a healthier alternative too

In a world that increasingly glorifies healthy eating and clean diets, vegetables are often hailed as heroes on our plates. But a new study suggests that when it comes to type 2 diabetes risk, not all vegetables are created equal — especially when deep fryers are involved.

While potatoes are a staple in many cuisines and diets around the globe, the way they are cooked might determine whether they help or hurt your health. The humble spud, it turns out, has a dark side when sliced, fried, and salted.

A Troubling Link
According to a recent study published in The BMJ and reported by Prevention, people who consume French fries at least three times a week may increase their risk of developing type 2 diabetes by up to 20%. This alarming connection emerged from a long-term analysis of more than 205,000 participants over a 30-year period across three major U.S. health studies.

The lead author, Dr. Seyed Mohammad Mousavi, a postdoctoral research fellow at Harvard T.H. Chan School of Public Health, emphasized the dose-dependent nature of this risk. “Surprisingly, the increase starts with even less than one serving per week,” he said. “By the time consumption hits three servings a week, the risk is about 20% higher.”

It’s important to note that this risk wasn’t found with other forms of potatoes. When consumed boiled, baked, or mashed, potatoes did not significantly raise the risk of type 2 diabetes — a vital distinction that shifts the focus from the vegetable itself to how it is prepared.

What Makes French Fries Riskier?
Experts suggest that the risk likely comes down to how French fries are cooked and consumed. “Frying potatoes makes them energy-dense and high in saturated fat, while also stripping away much of their natural fiber,” said Dr. Katherine N. Balantekin, assistant professor at the University at Buffalo. These nutritional changes can disrupt blood sugar levels and contribute to weight gain, both of which are linked to insulin resistance.

Frying at high temperatures — especially in certain oils — may also promote inflammation and impair insulin sensitivity, further compounding the risk.

Additionally, French fries rarely appear on their own. They're typically part of high-calorie, low-nutrient meals such as fast food combos, which collectively lower overall diet quality and increase disease risk.

The Whole Grain Advantage
Interestingly, the study also found that replacing French fries with whole grains like quinoa, oats, or whole wheat pasta led to a 19% reduction in type 2 diabetes risk. Even swapping out boiled or mashed potatoes for whole grains showed a 4% drop in risk.

Why are whole grains better? According to Dr. Mousavi, “Whole grains digest more slowly and are packed with fiber, vitamins, and plant compounds that help keep blood sugar stable.” Unlike fries, these foods release glucose gradually, preventing the sharp spikes associated with diabetes development.

Should Potatoes Be Off Your Plate?
Not necessarily. Both Mousavi and Balantekin agree that potatoes can still be part of a healthy diet — it just depends on preparation and portion size. “Potatoes should not be your main source of carbohydrates, but baking or boiling them with the skin on can retain fiber and reduce negative impact,” Balantekin advised.

Medical News Today also reports that while potatoes are a starchy vegetable, they do not need to be eliminated entirely from a diabetic diet. The glycemic index (GI) of potatoes varies based on how they are cooked, and pairing them with lean proteins, healthy fats, and low-GI vegetables can moderate blood sugar responses.

It's All in the Cooking
This research underscores a critical point: the nutritional value of a food is not just about what it is, but how it’s made and what it’s eaten with. While potatoes themselves are nutrient-rich and versatile, frying them in oil transforms them into a food that could harm long-term health.

As Balantekin summed up, “It’s all about balance and making thoughtful choices.”

So the next time you’re tempted by a serving of fries, remember — a boiled or baked potato might not be as trendy, but it could be far better for your long-term health. Not all vegetables are equal, after all, and this one has a catch.