A revised vision for the Planetary Health Diet from The Lancet

In 2019 The Lancet - EAT Commission published a paper describing the Planetary Health Diet (PHD), which proved to be somewhat controversial and generated considerable discussion. Their recent follow up edition, produced, as the authors comment, in a significantly changed post-Covid global environment, is certain to attract similar attention and this article will present a brief VetSalus perspective on the new paper [1]. And that is no simple task, as the publication runs to seventy six pages and lists nearly six hundred references.

The basis of the paper, which is the work of an impressive list of senior academics from many of the world’s leading universities, posits that it is theoretically possible to feed a nutritious and healthy diet to the world’s growing population, in a just and equitable manner, without transgressing boundaries which compromise the environmental future of the planet. In assessing this the authors have divided the paper into several sections which examine key questions, including: ‘What is a healthy diet?’ and ‘Sustainable Food Systems within Planetary Boundaries.’

This concept of Planetary Boundaries is explored in some depth, with nine being recognised:

• Biosphere integrity

• Land System Change

• Freshwater Change

• Biogeochemical Flows

• Ocean Acidification

• Atmospheric Aerosol Loading

• Stratospheric Ozone Depletion

• Novel Entities 

• Climate Change

The 2019 paper assessed only five of these and concluded that food systems exerted significant pressure on all five. The authors have extended this work to assess the impact of food production on all nine, and while they note that reliable criteria have not yet been established to permit a complete analysis, they provide a logical basis for proceeding and present conclusions which will be of concern to all. 

Of these boundaries, it is the ‘Novel Entities’ category that is of greatest interest to VetSalus, as it includes antimicrobial usage, and veterinarians involved in food production have major influence here. The authors limit their analysis in this Novel Entities section to the application of pesticides and the rate of antimicrobial use; the latter is assessed at 73 - 130 kilotonnes annually and one might have hoped for a more clearly defined range from which to measure future progress. Few veterinarians will argue with the conclusion that halting prophylactic use is vital to the overall reduction, with significant progress already seen in many countries including the U.K., New Zealand and Denmark. In acknowledging the importance of the Novel Entities boundary it does appear, to this author at least, to be the least clearly defined of all nine boundaries analysed.

It is far beyond the scope of this review to critique their conclusions on what constitutes a healthy diet but few will argue that reduction in the ingestion of high quality protein, including red meat, and an increase in the consumption of whole grains and vegetables would benefit many, particularly those inhabiting first world countries. The paper claims that widespread adoption of the PHD would avert 27% of world deaths annually, some 15 million people. The cynic might note that all of these people will eventually die, (there are no claims to immortality attached to the PHD!) and that they will increase the requirement for global food production until they do. But as the world population accelerates towards 9.6 billion in 2050, a few million more surviving for a few more years is probably not that material. However a reduction in the spread of communicable diseases, which is one claimed benefit arising from improved global nutrition, will be of interest to all in this post pandemic environment.

The strong linkages between the increased ingestion of red meat and conditions such as Diabetes Type 2 is fully referenced, but whether this is causative or correlated is not explored. The insistence, as is to be expected, on a largely plant based diet remains at the core of the paper. Hence, it is interesting to note that dairy emerges with a relatively healthy review; fermented foods such as yoghurts are supported and the value of milk in infant nutrition is emphasised. While widespread adoption of the diet is predicted to reduce livestock populations by a massive 26%, only a 4% reduction in dairy animals is envisaged. 

The contribution of livestock to methane emissions has been well noted before, with this paper stating that 53% of all non CO₂ emissions arise from livestock; that they choose to remain with CO₂ equivalents when assessing this, rather than a more accurate metric, will not be explored on these pages today but remains a concern. 

One quote from the paper will emphasise much that VetSalus aims to achieve:

“Meeting rising food demands must be achieved with less land, and with food production methods that generate—rather than degrade—ecological functions. Sustainable intensification entails achieving important reductions in environmental impacts through increased efficiency, reduced losses, and reduced pollution.”

VetSalus has long emphasised the importance of increasing productivity and reducing losses in food production from animals, and veterinarians have a major role to play in achieving this. While recognising the obvious, that the envisaged reduction of livestock numbers has the potential to reduce methane output by 22%, the authors comment on the potential for improved ruminant management to mitigate further methane admissions. The social impact of this massive reduction in livestock numbers is not explored, nor is there any significant analysis of changes to carbon sequestration from declining grazing systems. The reduced land usage envisaged implies increased intensification but will such an approach be possible without increased further ecological degradation? 

Social justice, including the requirement that everyone on this planet has a basic right to consume a healthy diet, is also fully explored in a section that is necessarily less science based and more idealistic. The paper also develops a long list of potential solutions and required actions. Detailed trajectories for the required reductions of items like methane, phosphorus, nitrate and red meat (to mention those of most interest  to veterinarians) are presented. In concluding, there is a call for urgent, global action and concern that the current political environment will not permit the required transitions.

This is an enormous piece of work and this review can only scrape over the surface of the detailed data contained therein. Any veterinarian interested in the future sustainability of food production from animals should access this paper and read, at the very least, the Executive Summary. The wealth of information within the paper, some of it undoubtedly contentious, will take many more hours to assimilate but there can be little doubt that such study will bring rewards and furnish the student with numerous discussion points.