High intake of veggies, but not fried potatoes, improves T2D markers

Individuals with type 2 diabetes (T2D) may benefit from eating green leafy vegetables, which may enhance glucose tolerance and insulin sensitivity. However, higher consumption of potatoes prepared in an unhealthy way, such as fries and chips, may worsen T2D markers, reports a study.

A total of 8,009 participants (median age 52 years) were included in the analysis, with a vegetable intake of 132 g/day. Higher intake of total vegetable, green leafy, yellow/orange/red, and moderate intakes of cruciferous vegetables contributed to a decrease in postload plasma glucose (PLG). [J Clin Endoc Metab 2025;110:e1068-e1083]

Notably, greater consumption of green leafy vegetables resulted in lower homeostasis model assessment of β-cell function (HOMA2-%β) and serum insulin. Additionally, a moderate intake of cruciferous vegetables was associated with a 25-percent reduction in the risk of T2D at the end of the 12-year follow-up.

On the other hand, higher intakes of potato fries or chips significantly correlated with higher fasting plasma glucose (FPG), HOMA2-%β, serum insulin, and lower HOMA2 of insulin sensitivity (HOMA2-%S).

“Our findings suggest a nuanced relationship between vegetable subgroups and their impact on glucose tolerance,” the investigators said.

Cooking method

The positive association between potatoes and diabetes is heavily influenced by their preparation and cooking methods, as well as the dietary pattern of individuals who regularly eat potatoes. [BMJ 2019;366:2368; Diabetes Care 2023;46:286‐296]

“In line with our previous findings that intakes of potatoes were not associated with incident T2D, the current investigation found that a higher intake of potatoes (excluding fries/chips) was not associated with markers of glucose tolerance, β-cell function, and insulin sensitivity,” the investigators said.

“Conversely, a higher intake of potato fries/chips was associated with significantly higher serum insulin and HOMA2-%β but a lower HOMA2-%S, suggesting adverse physiological impacts on glucose tolerance and insulin sensitivity with higher consumption of ‘unhealthy’ potatoes,” they added.

Potato fries/chips contain high amounts of unhealthy oil, salt, trans fat, and acrylamide, which contribute to greater body weight, insulin resistance, and T2D. [Diabetes Care 2020;43:1479‐1486; Sci Rep 2023;13:8235; Am J Clin Nutr 2001;73:1019‐1026; Nat Rev Endocrinol 2009;5:335‐344]

“The current findings align with our previous study and emphasize that potatoes, when prepared in a healthy way, may have a neutral impact on markers of glucose tolerance,” the investigators said. “However, their negative influence on these markers might be amplified if prepared in an unhealthy way, involving the addition of salt and fats.”

The current study used data from the Australian Diabetes, Obesity and Lifestyle Study to assess intakes of vegetable and potatoes via a food frequency questionnaire at baseline.

The investigators used generalized linear and Cox proportional hazards models to explore the associations of vegetable intake with FPG, 2-hour PLG, HOMA2-%β, HOMA2-%S, and fasting insulin levels at baseline, as well as with cumulative incident T2D at the end of follow-up.