A Prospective Analysis of Red and Processed Meat Intake in Relation to Colorectal Cancer in the Black Women's Health Study

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

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 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).

OBJECTIVE

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

METHODS

We 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.

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/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.

CONCLUSIONS

The 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.

Weight-centric prevention of cancer

Background

The link between excess adiposity and carcinogenesis has been well established for multiple malignancies, and cancer is one of the main contributors to obesity-related mortality. The potential role of different weight-loss interventions on cancer risk modification has been assessed, however, its clinical implications remain to be determined. In this clinical review, we present the data assessing the effect of weight loss interventions on cancer risk.

Methods

In this clinical review, we conducted a comprehensive search of relevant literature using MEDLINE, Embase, Web of Science, and Google Scholar databases for relevant studies from inception to January 20, 2024. In this clinical review, we present systematic reviews and meta-analysis, randomized clinical trials, and prospective and retrospective observational studies that address the effect of different treatment modalities for obesity in cancer risk. In addition, we incorporate the opinions from experts in the field of obesity medicine and oncology regarding the potential of weight loss as a preventative intervention for cancer.

Results

Intentional weight loss achieved through different modalities has been associated with a reduced cancer incidence. To date, the effect of weight loss on the postmenopausal women population has been more widely studied, with multiple reports indicating a protective effect of weight loss on hormone-dependent malignancies. The effect of bariatric interventions as a protective intervention for cancer has been studied extensively, showing a significant reduction in cancer incidence and mortality, however, data for the effect of bariatric surgery on certain specific types of cancer is conflicting or limited.

Conclusion

Medical nutrition therapy, exercise, antiobesity medication, and bariatric interventions, might lead to a reduction in cancer risk through weight loss-dependent and independent factors. Further evidence is needed to better determine which population might benefit the most, and the amount of weight loss required to provide a clinically significant preventative effect.

Ameliorative potential of synbiotic combination of Lactobacillus sp. and polyphenols against Benzo[a]pyrene-induced toxicity in Caco-2 cell line

Exposure to benzo[a]pyrene (B[a]P), a major global food safety concern, is often associated with increasing incidence of colorectal cancers. This in-vitro study was focused on the identification of potential B[a]P-adsorbing Lactobacillus strains and evaluation of the ameliorative effect of synbiotic combination of selected Lactobacillus sp. and polyphenols (quercetin or resveratrol) against B[a]P-induced intestinal toxicity in Caco-2 cells. Preliminary studies lead to the selection of Lactiplantibacillus plantarum MTCC 25433 strain that showed 86% of B[a]P adsorption in 2 h as compared to L. rhamnosus GG that showed 74% of B[a]P adsorption. B[a]P adsorption by MTCC 25433 was reduced to 9%, 16% and 20% upon pre-treatment with SDS, NaIO4 and mutanolysin, attributing the involvement of cell wall proteins and polysaccharides in the adsorption. Additionally, peptidoglycan of both strains adsorbed >50% of B[a]P. In-vitro assays revealed that the selected LAB mitigated the B[a]P-induced epithelial cell damage. Among the polyphenols, quercetin, resveratrol and curcumin, varied in their potency to mitigate B[a]P-induced oxidative stress, with curcumin being least effective. Combinations of selected Lactobacillus sp. and polyphenols were more potent in averting B[a]P-induced toxicity via increase in GSH (17-30 %), SOD (50-88 %), catalase (19-45 %), and reduction in IL-8 secretion (14-28 %) and barrier dysfunction. Principal component analysis affirmed the superior potency of combination of L. plantarum MTCC 25433 and quercetin in averting B[a]P-induced toxicity. Overall, this study highlighted a novel promising strategy of synbiotic combination of Lactobacillus sp. and polyphenols (quercetin or resveratrol) in alleviating the B[a]P-induced toxicity in intestinal epithelial cells.

Association between Dietary Fatty Acid Patterns and Colorectal Cancer Risk: A Large-Scale Case-Control Study in China

Associations of dietary fatty acids with the risk of colorectal cancer (CRC) remain controversial. The objective of this study was to examine whether dietary-derived fatty acid patterns were related to CRC risk among Chinese people. A total of 2806 CRC patients and 2806 frequency-matched controls were interviewed in this case-control study between July 2010 and May 2021. A food frequency questionnaire was used to gather information on dietary intake. Four fatty acid patterns were identified using factor analysis. The even-long-chain fatty acid pattern had no statistically significant association with CRC risk (adjusted Odds ratio (aOR), 1.16; 95% confidence interval (CI), 0.97–1.39; ptrend = 0.129). However, significant inverse associations were found between the medium-chain and long-chain saturated fatty acid (SFA) pattern (aOR, 0.34; 95%CI, 0.27–0.42), the highly unsaturated fatty acid pattern (aOR, 0.73; 95%CI, 0.60–0.88), the odd-chain fatty acid pattern (aOR, 0.69; 95%CI, 0.57–0.83), and CRC risk. The interaction between fatty acid patterns and sex was observed, and the association between the highly unsaturated fatty acid pattern and CRC risk differed by subsite. In conclusion, increasing the intakes of foods rich in medium-chain SFAs, highly unsaturated fatty acids, and odd-chain fatty acids may be related to a lower risk of CRC.

Health effects associated with consumption of unprocessed red meat: a Burden of Proof study

Characterizing the potential health effects of exposure to risk factors such as red meat consumption is essential to inform health policy and practice. Previous meta-analyses evaluating the effects of red meat intake have generated mixed findings and do not formally assess evidence strength. Here, we conducted a systematic review and implemented a meta-regression-relaxing conventional log-linearity assumptions and incorporating between-study heterogeneity-to evaluate the relationships between unprocessed red meat consumption and six potential health outcomes. We found weak evidence of association between unprocessed red meat consumption and colorectal cancer, breast cancer, type 2 diabetes and ischemic heart disease. Moreover, we found no evidence of an association between unprocessed red meat and ischemic stroke or hemorrhagic stroke. We also found that while risk for the six outcomes in our analysis combined was minimized at 0 g unprocessed red meat intake per day, the 95% uncertainty interval that incorporated between-study heterogeneity was very wide: from 0-200 g d-1. While there is some evidence that eating unprocessed red meat is associated with increased risk of disease incidence and mortality, it is weak and insufficient to make stronger or more conclusive recommendations. More rigorous, well-powered research is needed to better understand and quantify the relationship between consumption of unprocessed red meat and chronic disease.

What Are the Factors Underlying Colorectal Cancer Health Disparities?

Black Americans have the highest colorectal cancer incidence and mortality rates of any U.S. racial/ethnic group. Warren Andersen and colleagues report that sociocultural, lifestyle, and healthcare factors did not explain the racial disparity in colorectal cancer incidence, but colorectal cancer screening lessened the disparity. While screening is a cornerstone of colorectal cancer prevention, an improved understanding of etiologic factors may inform additional strategies for primary prevention or risk stratification. As important "established" colorectal cancer risk factors have not been corroborated for Black Americans, this begs the question of what other etiologic factors are important for colorectal cancer development in Black American populations. See related article, p. 595.