Dietary marine ω-3 fatty acids and CRC risk

Immunomodulatory dietary marine ω-3 polyunsaturated fatty acids (PUFAs) are hypothesized to protect against the development of cancer, particularly colorectal cancer (CRC). Now, a large prospective cohort study has been conducted to test this hypothesis in 173,229 white individuals. After a follow-up duration of 2,895,704 person-years, 2,504 CRCs were reported, 614 of which were analysed for FOXP3+ regulatory T (T_reg)-cell infiltation. A daily marine ω-3 PUFA intake of ≥0.35 g versus <0.15 g was associated with a reduced risk of T_reg-cell-high CRC (multivariable HR 0.57; P_trend <0.001), but not T_reg-cell-low tumours (HR 1.14; P_trend = 0.77;): P_{heterogeneity} = 0.01. The suppressive role of T_reg cells on effector T cells was reduced by around twofold after treatment with a ω-3 PUFA in vitro. These findings support the immunopreventive role of dietary marine ω-3 PUFAs in CRC via modulation of T_reg cells.