Guidelines to restrict consumption of red meat to under 350 g/wk based on colorectal cancer risk are not consistent with health evidence

Abstract

BackgroundThe Nordic Nutrition Recommendations of 2023 (NNR2023) incorporate sustainability, health, and nutrition in their food-based dietary guidelines (FBDGs). NNR2023 recommends a consumption of ≤350 g/wk of unprocessed red meat (RM) based on association with colorectal cancer (CRC). This recommendation is lower than other FBDGs such as the World Cancer Research Fund (WCRF) recommendation it is based on (350–500 g/wk). ObjectiveTo evaluate the empirical evidence and models cited by the NNR2023 to support the RM guidance. MethodsWe fitted least-assumption (LA) dose-response (DR) models to the studies included in two systematic reviews (SRs) selected by NNR2023 on the RM and CRC association. We compared them against six parametric models reported in the two SRs. We evaluated the statistical significance of modeled relative risks (RR) at different consumption levels. ResultsTwenty-one studies (20,604,188 patient-years) were analyzed. We found no significant association (RR = 1.04, 0.99–1.09) between 350g/wk of RM and CRC using the LA models, in agreement with the least restrictive models reported by Lescinsky et al., 2022 (RR = 1.11[0.89–1.38]) and WCRF (RR= 1.01[0.96–1.07]). The association was significant at 350 g/wk only under restricting assumptions such as monotonicity RR=1.3[1.01–1.64], and linearity RR = 1.06 [1.00–1.12]. No significant empirical association is observed under 567 g/wk based on evidence used by NNR2023. ConclusionsThe sources cited by NNR2023 do not support a consumption restriction of ≤350 g/wk of RM due to CRC, and other studies omitted by NNR2023 do not support association between RM and CRC. We show that model assumptions rather than empirical evidence drive this recommendation. Model uncertainty should be explicitly incorporated in FBDGs.