French fries have long been criticized as an unhealthy food choice, but new research suggests they may be more deserving of that reputation than other potato dishes.
A large-scale study published in BMJ They found that eating three servings of fries a week increased your risk of developing type 2 diabetes by 20%. In contrast, consuming the same amount of potatoes prepared in other ways, such as boiling, baking, or mashing, was not associated with a significantly increased risk of diabetes.
The study also found that alternatives to potatoes are important in people’s diets. They found that replacing potatoes with whole grains reduced the risk of type 2 diabetes, while replacing potatoes with white rice increased the risk.
Look beyond just potatoes
Potatoes contain important nutrients such as fiber, vitamin C, and magnesium. However, it is also rich in starch and has a relatively high glycemic index, which can cause blood sugar levels to rise rapidly. For this reason, previous studies have often linked potato consumption to an increased risk of type 2 diabetes.
However, the researchers noted that two important factors have often been overlooked. Firstly, potatoes can be cooked in very different ways. Second, the health effects of potatoes may depend on what foods people eat instead.
To explore these questions, scientists looked at whether the risk of diabetes differed between fried potatoes and potatoes prepared by boiling, baking, or mashed. They also evaluated the potential effects of replacing potatoes with other common carbohydrate-rich foods such as whole grains and rice.
40 years of health data
The study drew on data from more than 205,000 U.S. health care professionals who participated in three major longitudinal studies conducted between 1984 and 2021.
At the start of the study, participants did not have diabetes, heart disease, or cancer. The researchers completed a detailed dietary questionnaire every four years, allowing researchers to track their eating habits over time.
During nearly 40 years of follow-up, 22,299 participants developed type 2 diabetes.
After taking into account lifestyle and dietary factors that can influence diabetes risk, the researchers found that for every three servings of potatoes a week eaten, the overall chance of developing type 2 diabetes increased by 5%.
However, the strongest association involved french fries. It was found that for every three times a week, there was a 20% increase in the incidence of type 2 diabetes. Similar intakes of baked, boiled, or mashed potatoes were not associated with statistically significant increases.
Whole grains have benefits
Researchers also looked at what happens when you replace potatoes with other foods.
Replacing three servings of potatoes each week with whole grains reduced the incidence of type 2 diabetes by 8%. Replacing baked, boiled, or mashed potatoes with whole grains lowered that rate by 4%. When french fries were replaced with whole grains, that percentage decreased by 19%.
The results were different when I replaced the potatoes with white rice. It was found that replacing total potato intake or baked, boiled, or mashed potatoes with white rice was associated with higher rates of type 2 diabetes.
Important notes
Because this is an observational study, it cannot prove that French fries directly cause diabetes. The researchers acknowledged that other factors not measured in the study may have contributed to the results.
Additionally, participants were primarily medical professionals of European descent, so the findings may not apply equally to all populations.
Still, the researchers say, “Our findings highlight that the association between potato consumption and risk of type 2 diabetes depends on the specific food substitute used. The findings are also consistent with current dietary recommendations that promote whole grain intake as part of a healthy diet to prevent type 2 diabetes.”
Are potatoes back on the menu?
In an accompanying editorial, the researchers argued that potatoes should not be viewed as a single category when considering health effects.
They emphasized that both cooking methods and food alternatives are important factors in shaping dietary recommendations and public policy.
According to the editorial, baked, boiled and mashed potatoes have a relatively low environmental impact and high overall nutritional value, making them compatible with a healthy and environmentally sustainable diet. However, the authors noted that whole grains should remain the preferred food choice for reducing diabetes risk.
They also called for future studies with more diverse populations and analyzes that continue to examine both cooking methods and food alternatives.
