Experts criticise health research on red meat

An international team of experts has called on the influential Global Burden of Diseases, Injuries and Risk Factors Study (GBD) to publish the evidence behind its most recent report linking the consumption of unprocessed red meat to certain diseases.

In a letter published in The Lancet, six leading academics raise concerns about the dramatic differences in estimates of disease burdens (as measured by deaths and disability-adjusted life-years [DALYs]) attributable to unprocessed red meat cited in GBD 2019 compared to the GBD 2017 study.

In the GBD 2019 report, a diet high in red meat was reported to be responsible for 896 000 deaths and 23.9 million DALYs. It was considered the fifth leading dietary risk factor for attributable DALYs. By contrast, the GBD 2017 analysis only attributed 25 000 deaths and 1.3 million DALYs to diets high in red meat, and red meat intake was the least important of 15 dietary risk factors.

“Hence, by comparison with previous estimates, the 2019 estimates of deaths attributable to unprocessed red meat intake have increased 36-fold, and estimates of DALYs attributable to unprocessed red meat intake have increased 18-fold,” the experts pointed out and added that the marked increase in the 2019 estimates depended on two assumptions: that the optimal intake of red meat is zero; and that risk rises sharply even with moderate consumption of red meat.

According to the scientists, a theoretical minimum risk exposure level (TMREL) of zero for red meat was “counterintuitive given the role of meat in evolutionary diets and in contemporary hunter-gatherer populations, in which cardiometabolic diseases were and still are uncommon,” and added that one of the largest multinational studies - the Prospective Urban Rural Epidemiology study also could not find consistent evidence of an association between unprocessed red meat intake and negative health outcomes such as cardiovascular disease.

The authors further elaborated that “if the TMREL is assumed to be zero, red meat would then de facto be presented as an inherently harmful food. This assumption would ignore the well documented nutritional benefits with respect to the supply of essential nutrients and bioactive components.”The authors criticised that the GBD 2019 findings were not backed by other recently conducted systematic reviews and meta-analyses and found it “problematic that the GBD 2019 analysis provides little information concerning their updated systematic reviews,” and added that it was “of considerable importance that the GBD estimates are subject to critical scrutiny and that they continue to be rigorously and transparently evidence-based,” due to the substantial influence of the GBD report on worldwide nutritional policy decision making.

The letter further recommends that the GBD 2019 dietary-risk estimates are not used in national or international policy documents until comprehensive independent peer reviews of the evidence underpinning the revised estimates have been conducted.

The letter’s authors are led by Prof Alice Stanton of RCSI University of Medicine and Health Sciences, Dublin. The co-authors are Prof Chris Elliott (Queen’s University Belfast); Prof Frederic Lerory (Vrije Universiteit Brussels); Prof Neil Mann (University of Melbourne); Prof Patrick Wall (University College Dublin); and Prof Stefaan De Smet (Ghent University).