Monounsaturated fatty acids from plant or animal sources and risk of type 2 diabetes in three large prospective cohorts of men and women

Aims/hypothesis: Existing evidence on the relationship between intake of monounsaturated fatty acids (MUFAs) and type 2 diabetes is conflicting. Few studies have examined whether MUFAs from plant or animal sources (MUFA-Ps and MUFA-As, respectively) exhibit differential associations with type 2 diabetes. We examined associations of intakes of total MUFAs, MUFA-Ps and MUFA-As with type 2 diabetes risk.

Methods: We used data from 51,290 women in the Nurses' Health Study (1990-2016), 61,703 women in the Nurses' Health Study II (1991-2017) and 29,497 men in the Health Professionals Follow-up Study (1990-2016). Using food frequency questionnaires and food composition tables, we calculated MUFA-P and MUFA-A intakes every 4 years and modelled their associations with type 2 diabetes using Cox regression models.

Results: During 3,268,512 person-years of follow-up, we documented 13,211 incident type 2 diabetes cases. After multivariate adjustment, total MUFA intake was associated with higher type 2 diabetes risk, with HR for Q5 vs Q1 of 1.10 (95% CI 1.01, 1.22). MUFA-Ps and MUFA-As demonstrated divergent associations, with HRs of 0.87 (95% CI 0.81, 0.94) and 1.34 (1.23, 1.45), respectively. In substitution analyses, HRs were 0.92 (95% CI 0.86, 0.99) for replacing 2% of energy from trans fatty acids or 0.72 (0.66, 0.78) and 0.82 (0.77, 0.88) for replacing 5% from MUFA-As and 5% from the sum of saturated fatty acids and MUFA-As with MUFA-Ps, respectively. Substituting MUFA-As for saturated fatty acids and refined carbohydrates was associated with a 43% and 33% higher risk, respectively.

Conclusions/interpretation: Higher intake of MUFA-Ps was associated with lower type 2 diabetes risk, whereas increased intake of MUFA-As was associated with higher risk. Replacing saturated fatty acids, trans fatty acids and MUFA-As with MUFA-Ps may be beneficial for type 2 diabetes prevention.