LCDs emphasizing plant protein, healthy fats, and high-quality carbohydrates were associated with a lower risk of developing T2DM, while animal-based and low-quality LCDs increased risk. The findings were published in Diabetes Care.

This prospective cohort analysis included 199,006 adults from the Nurses’ Health Study (1984–2018), Nurses’ Health Study II (1991–2019), and Health Professionals Follow-up Study (1986–2018), all free of diabetes, cardiovascular disease, and cancer at baseline. Diet was assessed every 2–4 years using validated food frequency questionnaires, and five LCD scores were developed based on macronutrient sources.

During 4,987,761 person-years of follow-up, 20,452 cases of T2D were identified. Higher overall and animal-based LCD scores were associated with increased T2D risk (hazard ratio 1.39–1.44), while vegetable-based and healthy LCD scores were linked to 6%–16% lower risk. The associations were more pronounced in participants with lower baseline body mass index and were partly mediated by weight change.

These results highlight that the quality of macronutrients in low-carbohydrate diets determines their metabolic impact. Emphasizing plant protein, unsaturated fats, and whole-grain carbohydrate sources may offer protection against diabetes.