Generated Summary
This document is a correspondence published in The Lancet, critiquing the Global Burden of Disease Study (GBD) 2019 analysis, specifically its findings on the health impacts of red meat consumption. The authors, Alice V Stanton, Frédéric Leroy, Christopher Elliott, Neil Mann, Patrick Wall, and Stefaan De Smet, raise concerns about the substantial changes in the GBD 2019 estimates compared to the GBD 2017 estimates, particularly the increased disease burden attributed to diets high in unprocessed red meat. The primary focus is on the significant discrepancy between the GBD 2019 findings, which indicate a much higher estimate of deaths attributable to red meat intake, and other recent systematic reviews and meta-analyses on the same topic. The correspondence examines the methodology used by the GBD 2019, highlighting issues with the data sources, the selection of the theoretical minimum risk exposure level (TMREL), and the overall conclusions drawn regarding the impact of red meat on health outcomes. The authors provide context by acknowledging the importance of GBD studies but emphasize the need for rigorous scrutiny of the methodology and transparency in reporting.
Key Findings & Statistics
- The GBD 2019 reported that a diet high in red meat was responsible for 896,000 deaths (95% uncertainty interval [UI] 536,000–1,250,000) and 23.9 million DALYs (15.6-32.0).
- The GBD 2017 analysis attributed 25,000 deaths (95% UI 11,000–40,000) and 1.3 million DALYs (0.5–2.3) to diets high in red meat.
- The estimates of deaths attributable to unprocessed red meat intake have increased 36-fold.
- Estimates of DALYs attributable to unprocessed red meat intake have increased 18-fold.
- The relative risk of suffering an ischaemic stroke, an intracerebral haemorrhage, or a subarachnoid haemorrhage for people aged 55-59 years who are consuming 50 g per day of red meat versus those consuming no red meat is 1.20, 1.20, and 1.20, respectively, according to the GBD 2019 analysis.
- The GBD 2019 Risk Factors Collaborators reported “sufficient evidence supporting the causal relationship of red meat intake with ischaemic heart disease, breast cancer, haemorrhagic stroke, and ischaemic stroke.”
- The GBD 2019 Risk Factors Collaborators performed or updated their own systematic reviews for each dietary risk and its related outcomes.
- The TMREL for red meat changed from 22.5 g per day to 0 g per day.
Other Important Findings
- The authors note that the GBD 2019 analysis significantly changed the estimated disease burdens attributable to various dietary risk factors.
- The GBD 2019 analysis included additional outcomes (ischaemic heart disease, breast cancer, haemorrhagic stroke, and ischaemic stroke) to the list of red meat-related health risks.
- The findings of the GBD 2019 are not in agreement with other recently conducted systematic reviews and meta-analyses.
- The authors cite the NutriRECS consortium, which found low to very low certainty evidence that diets lower in unprocessed red meat might result in very small reductions in risk of cardiovascular disease, stroke, myocardial infarction, type 2 diabetes, and overall lifetime cancer mortality.
- The authors point out a considerable disparity between the relative risk curves of GBD 2019 and the dose-response curves of peer-reviewed cohort studies.
- The authors highlight the importance of the GATHER statement and the PRISMA guidelines for accurate and transparent health estimates reporting.
- The authors are puzzled by the reference to more empirical standardised methods for selecting the TMREL for risk factors in GBD 2019.
- The assumption of a red meat TMREL of zero is counterintuitive, given the role of meat in evolutionary diets and in contemporary hunter-gatherer populations.
- The authors also mention the substantial influence of GBD reports on worldwide nutritional policy decision-making.
Limitations Noted in the Document
- The GBD 2019 analysis provides little information concerning their updated systematic reviews, making it difficult to assess the quality of the data and methods used.
- The authors cannot find any reporting of GATHER items 3-6, which pertain to how the data from each source were identified and accessed.
- The GBD 2019 systematic reviews and meta-analyses are not reported according to the PRISMA 2009 guidelines.
- The authors are concerned about the lack of empirical evidence for the change in the red meat TMREL from 22.5 g per day to 0 g per day.
- The authors question whether the totality of nutritional effects of red meat have been considered in the meta-regressions.
Conclusion
The authors express serious concerns about the GBD 2019 estimates, particularly regarding the substantial increase in deaths attributed to red meat consumption. They underscore the need for the GBD 2019 Risk Factors Collaborators to clarify their methodology and provide supporting evidence for the changes in the TMREL and the updated dose-response curves. The authors emphasize that the GBD 2019 estimates should undergo critical scrutiny and be based on rigorous and transparent evidence. They are concerned that the current public health message advising moderate consumption of red meat may be replaced by a message that any intake of red meat is harmful, which could have negative consequences. The authors believe that it would be inappropriate and imprudent for the GBD 2019 dietary risk estimates to be used in any national or international policy documents, nor in any regulatory nor legislative decisions, unless the new or updated systematic reviews and meta-analyses pertaining to all dietary risk factors are published and have undergone comprehensive independent peer review. The authors call on the GBD 2019 Risk Factors Collaborators to address two key concerns, namely, the lack of comprehensive reporting of the updated systematic reviews and the evidence for the changes in the dose-response curves and the TMREL. The conclusion is that, given the influence of the GBD reports on policy decisions, it is vital that the underlying methodology and data are transparent, and the findings are supported by robust evidence.