LAWRENCE DE KONING, TERESA T. FUNG, ERIC B. RIMM, WALTER C. WILLETT, FRANK B. HU
The purpose of this study is to compare the associations of several low-carbohydrate diet scores with T2D risk.
Men from the Health Professionals Follow-up Study free of T2D, cardiovascular disease or cancer (n=41,212) in 1986 were followed for ≤ 20 years. Three low-carbohydrate diet scores were derived from food frequency questionnaires every 4 years: (1) a low-carbohydrate high-total protein/fat score, (2) a low-carbohydrate high-animal protein/fat score, and (3) a low-carbohydrate high-vegetable protein/fat score. Scores were calculated by summing decile ranks (1 to 10 for increasing intake) of protein and fat with inverted decile ranks of carbohydrate (10 to 1 for increasing intake). Each score had a maximum value of 30. Cox proportional hazard models were used to determine T2D risk across score quintiles.
During follow-up, 2761 cases of T2D were ascertained. After adjustment for age, smoking, physical activity, BMI, coffee intake, alcohol intake, family history of diabetes and total energy, the hazard ratio for T2D (top vs bottom score quintile) was 1.32 (95% CI: 1.16-1.50, p for linear trend < 0.0001) for the high-total protein/fat score, 1.41 (95% CI: 1.23-1.62, p < 0.0001) for the high-animal protein/fat score, and 0.93 (95% CI: 0.82-1.05, p = 0.44) for the high-vegetable protein/fat score. The high-total protein/fat score was not significantly associated with T2D after adjusting for animal protein and fat.
The high-animal protein/fat score was attenuated after adjusting for red and processed meat (HR: 1.19, 95% CI: 1.02-1.39, p = 0.01) but no changes were observed after adjusting for poultry (HR: 1.40, 95% CI: 1.22-1.61, p < 0.0001) or fish (HR: 1.42, 95% CI: 1.24-1.63, p < 0.0001). Associations were slightly stronger after adjusting for dairy (HR: 1.49, 95% CI: 1.30-1.72, p < 0.0001).
In conclusion, low-carbohydrate diets that are high in animal protein and fat may increase the risk of T2D, particularly if they contain large quantities of red and processed meat. Low-carbohydrate diets high in vegetable protein and fat are not associated with changes in T2D risk.