“Very odd things are going on” with one of the world’s major scientific references for health and disease risk, a team of six scientists has found, after its authors failed to produce the data required to defend claims villifying red meat.

After the authors of the influential “Global Burden of Disease” study failed to respond to their latest deadline last Wednesday, The Lancet medical journal agreed to publish a letter from the six scientists outlining their concerns about the study this week.

In 2017, the influential Global Burden of Disease study, a biannual report published in The Lancet, listed red meat as the “least important” of 15 dietary risk factors.

Yet, just two years later, the authors of the 2019 version of the study substantially escalated the estimated risk factor of red meat, suggesting a 36-fold increase in just two years, and re-ranking red meat as the fifth leading dietary risk factor for disease.

Concerned about the reliability of the claims, a team of six international scientists – Alice Stanton, Ireland; Frederic Leroy, Brussels; Christopher Elliot, Ireland; Neil Mann, Australia; Patrick Wall, Ireland and Stefaan De Smet, Belgium – conducted a forensic review of the science in the 2019 study and concluded that it contained “considerable disparities” and major contradictions with available evidence.

Both the 2017 and 2019 studies also failed to report existing major studies documenting nutritional benefits of red meat.

The scientists requested the authors of the GBD 2019 study to produce the evidence they used to support the reported 36-fold increase in global deaths linked to red meat.

However the authors have apparently refused, missing multiple deadlines to do so in recent months, including most recently last Wednesday.

After months of raising their concerns with The Lancet, the medical journal this week published a letter in full from the six scientists, documenting their concerns under the headline: 36-fold higher estimate of deaths attributable to red meat intake in GBD 2019: is this reliable?

The Lancet’s response falls short of the full retraction of the GBD 2019 report the scientists believe is necessary, based on their concerns about misleading information shaping national and global health policies.

Since publication, the GBD 2019 study has been cited by 635 documents, including 351 scientific papers and nine policy documents, including the UK National Food Strategy.

“If the current public health messaging advising moderate consumption of red meat is replaced by the message that any intake of red meat is harmful, this change will probably adversely affect iron deficiency anaemia, sarcopenia and child and maternal malnutrition,” the letter states.

“These conditions and their associated risk factors are already responsible for considerably greater global disease burdens than a diet high in red meat, particularly in low-income and middle-income countries.”

They are now appealing to other members of the scientific community to bring more pressure to bear on the authors of the GBD 2019 to retract their own paper, or for The Lancet to do that.

Non-adherence to best practice ‘deeply concerning’

The letter notes that all previous GBD risk factor analyses prior to 2019 used data from published peer-reviewed, systematic reviews and meta-analyses, as well as the World Cancer Research Fund criteria for determining theoretical minimal risk exposure level (TMREL).

The GBD 2019 analysis differed from this in that the authors performed or updated their “own systematic reviews” to report “sufficient evidence” of causal relationships of red meat intake with “ischaemic heart disease, breast cancer, haemorrhagic stroke, and ischaemic stroke”, and added these outcomes to previously identify relationships with diabetes and colon cancer.

“These findings of additional causal relationships for red meat are not in agreement with other recently conducted systematic reviews and meta-analyses,” the scientists wrote, then going on to list numerous peer-reviewed studies which had produced conflicting results.

It was “problematic”, the scientists wrote, that the GBD 2019 analysis “provides little information concerning their updated systematic reviews.

The report’s non-adherence to agreed best practice was “deeply concerning”.

“Given the substantial influence of GBD reports on worldwide nutritional policy decision making, it is of considerable importance the GBD estimates are subject to critical scrutiny and that they continue to be rigorously and transparently evidence-based.”

The scientists are calling on the authors of the GBD 2019 report to address two key concerns:

– First, to produce the peer-reviewed evidence upon which their new “systematic reviews” which claim abrupt increases in the risk of red meat are based, and

– Second, to clarify if the additional deaths and DALYs it claims from iron deficiency anaemia, sarcopenia, and child and maternal malnutrition that would result from the imposition of a red meat TMREL of zero have been included in the GBD 2019 estimates.

“Unless, and until, all new or updated reviews and meta-analyses pertaining to all dietary risk factors are published, having undergone comprehensive independent peer review, we think it would be highly 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.”

One of the scientists who signed the letter, Prof Frédéric Leroy of Vrije Universiteit in Brussels,has tweeted his concerns, stating:

“Very odd things are going on, incl. the assumption every bite of red #meat is harmful (?!).

In this letter to The Lancet we are asking to see the evidence.”

‼️📢 The #GlobalBurdenOfDisease (GBD) study is used globally in health policies. Very odd things are going on, incl. the assumption that every bite of red #meat is harmful (?!) In this letter to The Lancet 👇 we are asking to see the evidence. https://t.co/r72ua4LsUi

— Frédéric Leroy (@fleroy1974) February 25, 2022

Earlier article: Authors of ‘unreliable’ anti-red meat report miss deadline to defend their data