Associations Between Linoleic Acid Intake and Incident Type 2 Diabetes Among U.S. Men and Women

OBJECTIVE To investigate the association between intakes of n-6 polyunsaturated fatty acids (PUFAs) and type 2 diabetes risk in three prospective cohort studies of U.S. men and women. RESEARCH DESIGN AND METHODS We followed 83,648 women from the Nurses’ Health Study (NHS; 1980–2012), 88,610 women from NHSII (1991–2013, and 41,771 men from the Health Professionals Follow-Up Study (1986–2012). Dietary data was collected every 2–4 years by using validated food-frequency questionnaires. Self-reported incident diabetes, identified biennially, was confirmed by using a validated supplementary questionnaire. RESULTS During 4.93 million person-years of follow-up, 18,442 type 2 diabetes cases were documented. Dietary n-6 PUFAs accounted for 4.4–6.8% of total energy, on average, and consisted primarily of linoleic acid (LA; ≥98%). In multivariate-adjusted models, hazard ratios (95% CIs) of type 2 diabetes risk comparing extreme n-6 PUFA quintiles (highest vs. lowest) were 0.91 (0.85, 0.96; P trend = 0.002) for total n-6 PUFAs and 0.92 (0.87, 0.98; P trend = 0.01) for LA. In an isocaloric substitution model, diabetes risk was 14% (95% CI 5%, 21%; P = 0.002) lower when LA isocalorically replaced saturated fats (5% of energy), 17% (95% CI 9%, 24%; P trans fats (2% energy), or 9% (95% CI 17%, 0.1%; P = 0.047) lower for carbohydrates (5% energy). Replacing n-3 PUFAs or monounsaturated fats with LA was not significantly associated with type 2 diabetes risk. CONCLUSIONS Our study provides additional evidence that LA intake is inversely associated with risk of type 2 diabetes, especially when replacing saturated fatty acids, trans fats, or carbohydrates.