Summary

  • Food production is a big contributor to greenhouse gas emissions, water and land use, and dietary choice contributes to increased death from lifestyle diseases.
  • A plant-based diet provides the greatest reduction in greenhouse gas emissions and land use in comparison to 13 other sustainable diets.

Take Home Message

A plant-based diet provides the greatest benefit for reductions in greenhouse gas emissions, land use and human death compared to other ‘sustainable’ diets.

Paper's Stats

First up, ‘vegan diet’, is their term not mine. I’ll refer to it as a plant Boxplot graph showing impact of different sustainable diets on landuse.based diet from here on.

I’m sure you’ll shocked to learn that it seems a plant based diet is better for the environment and possibly our health . Before you shrug and say ‘what’s new’, it’s important to note that this is a review of lots of scientific evidence. That means it holds more weight and is more convincing than your average study.

Given the increasingly desperate need to reduce our environmental impacts on the earth some researchers from the UK thought they’d look at how our diets can help. They also looked at health impacts as a bonus. To do this they reviewed a bunch of scientific literature on the environmental and health impact of shifting to a more sustainable diet.

The environmental impacts they evaluated were greenhouse gas emissions, land use and water use. To be included in the study a record had to compare the difference between the environmental impact of the average population-level dietary intake and a proposed sustainable diet. In regards to health, most studies evaluated the reduction in ‘all-cause mortality rate’ (i.e. risk of dying).
The researchers included 63 records in their review (peer reviewed papers and grey literature), which contained 210 scenarios of shifting diets. This included 14 different sustainable diets, with 11 of these also having evidence related to health. A plant based diet was one of the sustainable diets identified, and that’s what we’ll talk about.

So, the results…

Well a plant based diet saw the greatest reduction in greenhouse gas emissions and land use when compared to any other ‘sustainable’ diet. For greenhouse gas emissions this meant a median reduction of 45%, and for land use a median reduction of 55%. This is 12% and 4% better than the next most sustainable diet; vegetarian. In terms of water use, only one study evaluated the effect of a vegan diet and showed a 107% INCREASE in water use! This seems pretty weird so that particularly paper is probably well worth checking out.

In regards to health, a plant based diet showed the greatest change in all-cause mortality rate when compared to any other diet. Though it’s important to note this was from a single study, so more work is needed here.

Despite the encouraging results for a plant based diet the authors suggested that having people go plant based is unrealistic (WTF). This is a common sentiment in the scientific literature when it comes to plant based diets. They are rarely recognised as a viable tool for driving positive environmental and health impacts, which is a real shame. I am not sure whether it’s the reserved nature of scientists or simply their own values and attitudes influencing their opinions. Either way we need to challenge this view, especially given the potentially great benefits we could gain.

As with any literature review there are several limitations to this study, all of which you can find in the discussion of the paper (it’s free so check it out!). The review highlights some important opportunities for future research. A clear one is more scientific investigations into the impact of a plant based diet on water use, that certainly needs to be cleared up.

It would also be good to investigate the significant variation seen within the plant based diet impacts on environment. What is causing this variation? What assumptions are being made and how are they impacting the outcome? How does this affect our conclusions?
I think this review is a valuable addition to the vegan knowledge base. It will be a very useful piece to share with our environmentally minded friends and to show that the evidence is clear.

One final thing, the authors forgot to mention the other significant impact that a plant based diet has, and is much greater than other sustainable diets, it’s positive benefit for the non-human animals (in before Mike Archer’s tired old argument!)

Title: The Impacts of Dietary Change on Greenhouse Gas Emissions, Land Use, Water Use, and Health: A Systematic Review

Authors: Lukasz Aleksandrowicz, Rosemary Green, Edward J. M. Joy, Pete Smith, Andy Haines

Journal: PLOSone

Date Published: November 3, 2016

URLhttp://journals.plos.org/plosone/article?id=10.1371/journal.pone.0165797

Paper Access

Free full-text access

Research Type

Peer-reviewed research