Does eating potatoes raise your risk of type 2 diabetes?
It depends entirely on how they are cooked. In this study of more than 205,000 US adults, eating French fries three times a week was linked to a 20% higher risk of type 2 diabetes. Baked, boiled, and mashed potatoes showed no meaningful link to the disease.
This is good news for potato lovers who do not fry them. The problem is not the potato itself. The problem is what happens to it in hot oil. When researchers separated fried potatoes from other forms, the risk gap between them was striking, and as I explain below, I suspect the oil it is cooked in matters more than the starch.
What the data show
Researchers pooled data from three large groups: the Nurses’ Health Study, the Nurses’ Health Study II, and the Health Professionals Follow-Up Study. Together these covered more than 205,000 US adults followed for nearly four decades. Over that time, 22,299 people developed type 2 diabetes.
Every three weekly servings of total potatoes raised the risk of type 2 diabetes by about 5%. But that small overall number hides a sharp split. The increase was driven almost entirely by French fries. Eating fries three times a week was tied to a 20% higher risk, while baked, boiled, or mashed potatoes carried no significant risk at all.
The study also looked at what happens when you swap potatoes for other foods. Replacing potatoes with whole grains was estimated to lower diabetes risk. The biggest benefit, about 19%, came from replacing French fries with whole grains.
Dr. Kumar’s Take
I like this study because it answers a question people actually ask me. Patients often think they have to give up potatoes to protect their blood sugar. That is not what the data say. The form matters far more than the food. A boiled or baked potato behaved very differently from a serving of fries in this analysis.
What stands out to me is the size and length of the work. Following hundreds of thousands of people for nearly forty years is rare and valuable. Still, this is observational research. It can show a strong link, but it cannot prove that fries directly cause diabetes. People who eat a lot of fries may share other habits that raise risk. I read this as one more reason to treat fried foods as an occasional choice, not a daily one.
Here is the part I keep coming back to, and it is my own opinion rather than something this study set out to prove. If glycemic load were the whole story, then baked, boiled, and mashed potatoes, which still raise blood sugar, should have moved the needle too. They did not. To me, the cleanest explanation for why fries stand apart is not the carbohydrate. It is the oil. French fries are almost always cooked in industrial seed oils, the kind I talk about often on the podcast. When these oils are heated to high temperatures and reused for hours, they become highly oxidized, and when we eat them they drive oxidation and inflammation in the body. I increasingly think of metabolic risk less in terms of glycemic load alone and more in terms of these oxidative and inflammatory inputs. A baked potato and a French fry start as the same vegetable. What separates them is what we do to that potato in the fryer. If I had to bet on the real driver of this risk gap, I would bet on the oil, not the starch. When I want fried foods at home, I reach for stable fats like ghee, tallow, or coconut oil rather than seed oils.
How the studies were done
These were prospective cohort studies, which means researchers tracked people forward in time and recorded what they ate and who later developed diabetes. This design is stronger than a one-time snapshot because it follows habits over many years before disease appears. The team also ran a substitution meta-analysis, which models what might happen if one food were swapped for another.
The strength here is scale and consistency across three separate groups. The main limit is that diet was self-reported and people were not randomly assigned to eat fries or not. So the findings show a strong and believable pattern, but they stop short of proving cause and effect.
Who should pay attention
This matters most for anyone who eats fried potatoes often or who already has risk factors for type 2 diabetes, such as a family history or extra weight around the middle. The message is not to fear potatoes. It is to look closely at fries specifically and at how often they show up on your plate.
Practical Takeaways
- Treat French fries as an occasional food rather than a weekly habit, since eating them three times a week was tied to a 20% higher diabetes risk in this study.
- Choose baked, boiled, or mashed potatoes when you want potatoes, as these forms showed no meaningful link to type 2 diabetes.
- Swap French fries for whole grains like brown rice, quinoa, or whole wheat when you can, since this swap was estimated to lower diabetes risk by about 19%.
- Watch the cooking method across all your foods, because this study suggests how a food is prepared can matter as much as the food itself.
Related Studies and Research
- Association of weekday sleep duration and estimated glucose
- Mediterranean diet plus exercise cuts diabetes risk by 31%
- PPIs increase fracture risk by 30%: meta-analysis of 11 studies
- Short sleep and poor diet: a double hit for type 2 diabetes risk
FAQs
Are baked or boiled potatoes safe for people worried about diabetes?
In this study, baked, boiled, and mashed potatoes showed no significant link to type 2 diabetes. That suggests they can fit into a balanced diet for most people watching their blood sugar. The risk signal came from fries, not from potatoes prepared without deep frying. As always, portion size and what you eat alongside the potato still matter for your overall blood sugar response.
Why would French fries raise diabetes risk more than other potatoes?
The study did not test the exact reason, so this is informed reasoning rather than proven fact. My own view is that it is less about glycemic load and more about the oil. Fries are cooked at high heat in industrial seed oils, which become heavily oxidized when heated and reused, and that drives oxidation and inflammation in the body. Notice that baked, boiled, and mashed potatoes still raise blood sugar yet did not raise diabetes risk here, which argues against carbohydrate alone being the culprit. Frequent fried-food eaters also tend to have other diet patterns that raise risk. The clear takeaway is that the frying process, not the potato, appears to drive the higher risk.
What should I eat instead of French fries?
This study found that swapping French fries for whole grains was estimated to lower diabetes risk by about 19%, the largest benefit of any swap tested. Whole grains include foods like brown rice, oats, quinoa, and whole wheat bread. These foods are digested more slowly and tend to cause smaller blood sugar spikes. If you still want potatoes, a baked or boiled version is a reasonable choice based on this research.
Bottom Line
The way you cook a potato may matter more than whether you eat one at all. In this nearly four-decade study of over 205,000 adults, French fries three times a week were linked to a 20% higher risk of type 2 diabetes, while baked, boiled, and mashed potatoes were not. Swapping fries for whole grains was tied to a meaningful drop in risk. You do not have to give up potatoes, but cutting back on the fried form is a simple, evidence-based step.
