Moving to diets with fewer animal-sourced foods would have major health benefits (Fig. 1A). Compared with the reference scenario, we project that adoption of global dietary guidelines (HGD) would result in 5.1 million avoided deaths per year [95% confidence interval (CI), 4.8–5.5 million] and 79 million years of life saved (CI, 75–83 million) (Fig. 1Aand SI Appendix). The equivalent figures for the vegetarian (VGT) diet are 7.3 million avoided deaths (CI, 7.0–7.6 million) and 114 million life years saved (CI, 111–118 million) and for the vegan (VGN) diet 8.1 million avoided deaths (CI, 7.8–8.5 million) and 129 million life years saved (CI, 125–133 million).
The value-of-statistical-life approach led to much higher estimates of the economic benefits associated with dietary change (Fig. 2). For the HGD scenario, we estimate that the monetized value associated with diet-related changes in mortality amount to 21 trillion (or 1012) US dollars per year ($21 trillion⋅y−1) in 2050 with a range (again reflecting uncertainties in the methodology) of $10–31 trillion⋅y−1. The values we obtain for the VGT diet are $28 trillion⋅y−1 ($14–42 trillion⋅y−1), and for the VGN diet $30 trillion⋅y–1 ($15–46 trillion⋅y−1).
The benefits were greater for diets with fewer animal-sourced foods: for VGT, $511 billion⋅y−1 ($194–1,589 billion⋅y−1) and, for VGN, $570 billion⋅y−1 ($217–1,773 billion⋅y−1). As a percentage of expected world GDP in 2050, the benefits amounted to 0.10% (0.04–0.32%) for HGD diets, 0.22% (0.08–0.69%) for VGT diets, and 0.25% (0.09–0.77%) for VGN diets.
In relation to an emissions pathway that is believed to be likely to limit global temperature increase to below 2 °C (32), we project that the ratio of food-related GHG emissions to GHG emissions from all sources increases from 16% in 2005/2007 to 52%, 37%, 19%, and 15% in 2050 in the REF, HGD, VGT, and VGN scenarios, respectively (SI Appendix, Fig. S6 and section SI.3).
The above study is recent, but these benefits have long been known and supported by the balance of scientific evidence. On top of which we have long since known it is not philosophically justifiable to harm sentient beings for reasons of pleasure (or habit, tradition, etc). (Reasons of pleasure include: we think they taste good or that they look good decorating our bodies – ie leather shoes, belts – etc.)