Researchers from Harvard University analyzed data from 205,107 healthy adult men and women – free from diabetes, cancer or cardiovascular disease – in the long-term Nurses' Health Study (NHS), Nurses' Health Study II (NHSII) and Health Professionals Follow-up Study (HPFS). 

Across these studies, dietary intake and health outcomes were tracked for up to 36 years, with data collected between 1984 and 2021, and questionnaires and new information entered every two-to-four years. Over the course of this period, 22,299 cases of type 2 diabetes (T2D) were documented.

What they found was that while higher overall potato intake was associated with a modestly increased risk of developing T2D, this risk was almost entirely driven by French fries.