Eating fries this many times a week raises diabetes risk

By Stephen Beech

Eating fries three times a week raises the risk of diabetes by 20%, warns new research.

But scoffing similar amounts of boiled, baked or mashed potatoes is not associated with such a "substantial" increase, say scientists.

The study, published by The BMJ, found that eating three servings of French fries a week is associated with a 20% increased risk of developing type 2 diabetes.

The American research team also found that replacing any form of potatoes with whole grains was associated with a lower type 2 diabetes risk.

But swapping spuds for white rice was linked to an increased diabetes risk.

Study author Dr. Seyed Mohammad Mousavi said: "Potatoes contain several nutrients, including fibre, vitamin C, and magnesium, but they also have a high starch content and therefore a high glycemic index, so they have been linked to a higher risk of developing type 2 diabetes.

"But neither the preparation method for potatoes nor specific foods that potatoes would replace have been considered, both of which are key to evaluating the overall health impact of potatoes."

The researchers investigated the association between intake of potatoes prepared by different methods - boiled, baked, or mashed compared to frying - and the risk of type 2 diabetes.

They also looked at the impact on well-being of replacing potatoes with other major carbohydrates, including whole grains and rice.

The findings are based on more than 205,000 health professionals from three large American studies carried out between 1984 and 2021.

Participants were free of diabetes, heart disease or cancer and completed detailed food questionnaires every four years.

During almost 40 years of follow-up, 22,299 people were diagnosed with type 2 diabetes.

After adjusting for lifestyle and dietary factors related to diabetes risk, the researchers found that for every three weekly servings of total potatoes, the rate of type 2 diabetes increased by 5% and for every three weekly servings of French fries, the rate increased by 20%.

But similar intake of baked, boiled, or mashed potatoes was not associated with a significantly increased risk.

Replacing three weekly servings of total potatoes with whole grains lowered the type 2 diabetes rate by 8%.

Substituting baked, boiled, or mashed potatoes with whole grains lowered the rate by 4%, and replacing French fries lowered the rate by 19%.

But replacing total potatoes or baked, boiled, or mashed potatoes with white rice was associated with an increased risk of type 2 diabetes.

The researchers said that it was an observational study, so no firm conclusions can be drawn about cause and effect, and they can’t rule out the possibility that other unmeasured factors may have influenced their results.

But Dr. Mousavi, a research fellow at Harvard T.H. Chan School of Public Health in Boston, added: “Our findings underscore that the association between potato intake and type 2 diabetes risk depends on the specific foods used as replacement.

"The findings also align with current dietary recommendations that promote the inclusion of whole grains as part of a healthy diet for the prevention of type 2 diabetes.”

Experts say, in a linked editorial, that it is important to consider preparation method and replacement food when guiding the public or informing policy.

Professor Daniel Ibsen, of Aarhus University in Denmark, pointed out that with their relatively low environmental impact and their health impact, baked, boiled, or mashed potatoes can be part of a "healthy and sustainable" diet.

But he said whole grains should remain a "priority" for health and well-being.