Meat intake and non-Hodgkin lymphoma: a meta-analysis of observational studies

Purpose: High intake of meat has been inconsistently associated with increased risk of NonHodgkin Lymphoma (NHL). We carried out a meta-analysis to summarise the evidence of published observational studies reporting association between red meat and processed meat intake and NHL risk. Methods: Analytical studies reporting relative risks with 95% confidence intervals (95% CI) for the association between intake of red and/or processed meat and NHL or major histological subtypes were eligible. We conducted random-effects meta-analysis comparing lowest and highest intake categories and dose-response meta-analysis when risk estimates and intake levels were available for more than three exposure classes. Results: Fourteen studies (4 cohort and 10 case-control) were included in the meta-analysis, involving a total of 10121 NHL cases. The overall relative risks of NHL for the highest versus the lowest category of consumption were 1.14 (95%CI: 1.03, 1.26) for red meat and 1.06 (95%CI: 0.98, 1.15) for processed meat. Significant associations were present when the analysis was restricted to case-control studies but not when restricted to cohort studies. No significant associations were found for major NHL etiological subtypes. Dose response meta-analysis could be based only on 8 studies that provided sufficient data and, compared to no meat consumption, the overall NHL relative risk increased not linearly with increased daily intake of red meat. Conclusion: The observed positive association between red meat consumption and NHL is mainly supported by the effect estimates coming from case-control studies and is affected by multiple sources of heterogeneity. This meta-analysis provided mixed and inconclusive evidences on the supposed relationship between red and processed meat consumption and NHL.