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Available online 15 February 2024

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

Author links open overlay panelJane G. Pouzou, Francisco J. Zagmutt
https://doi.org/10.1016/j.nut.2024.112395

Highlights
•Model assumptions can strongly influence the results of dose-response meta analysis

•Quantitative health evidence is lacking for precise amounts as dietary guidelines

•Model and other types of uncertainty must be incorporated in dietary guidelines

Abstract
Background
The Nordic Nutrition Recommendations of 2023 (NNR2023) incorporate sustainability, health, and nutrition in their food-based dietary guidelines (FBDGs). NNR2023 recommends a consumption of ≤350 grams/week 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/week).

Objective
To evaluate the empirical evidence and models cited by the NNR2023 to support the RM guidance.

Methods
We fitted least-assumption (LA) DR models to the studies included in two systematic reviews (SRs) selected by NNR2023 on the RM-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.

Results
Twenty-one studies (20,604,188 patient-years) were analyzed. We found no significant association (RR=1.04, 0.99-1.09) between 350g/week 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/week 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/week based on evidence used by NNR2023.

Conclusions
The sources cited by NNR2023 do not support a consumption restriction of ≤350 grams/week 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.

A new devastating blow to the Nordic Nutritional Recommendations #NNR2023's call to restrict red meat to intake levels <350g/w:
- cherry-picking of sources
- conclusions not supported by the data
- "driven by model assumptions", rather than by empirical evidence