Take home message: “Your shopping list is a ballot paper and your lunch is your immediate opportunity for action”

The Offspring declared August as "Sustainability & Environmental" Awareness Month. We are continuing with a contribution by Evelyn Medawar, a doctoral researcher from the MPI for Human Cognitive and Brain Sciences, Leipzig. She is writing about the concept of a "planetary health diet" and her doctoral project in which she assesses wether plant based diets influence our decisions of what we would like to eat.  For more about this you can follow Evelyn on Twitter @EvelynMedawar.

by Evelyn Medawar

See our other articles of the Environmental & Sustainability Awareness Month.
Closing the gaps in Europe’s nature protection network by Anke Müller more

The concept of “planetary health diet”

Public and scientific interest for plant-based eating patterns has been consistently increasing over the last 20 years, in particular for vegetarian and vegan diets, which partly or completely avoid animal-based products. Today, estimates propose that 5-10% of Germans are vegetarian or vegan1,2. Reasons for changing one’s diet can be multi-fold, including animal welfare, health, climate and religion among others.

The term “planetary health diet” was coined by the EAT-Lancet Commission with the aim to define guidelines for sustainable diets meeting both human health requirements and environmental sustainability3. As a proof of concept, it has been shown that following the suggested 14 guidelines for a sustainable diet (e.g. doubling the intake of fruit, vegetables, legumes and nuts and reducing the intake of meat and sugar by 50%), is linked to lower risk for ischaemic heart disease and diabetes in the cross-sectional data of the EPIC-Oxford study4.

“But what’s the link to climate – do plant-based food items really emit less CO2?”

Supply chains in the animal industry make up to 14.5% of global anthropogenic greenhouse gas emissions5, 22% of the global groundwater footprint6  and 38% of global land use (FAO, 2003). Completely or partly avoiding animal-based products can have substantial positive effects of human behaviour on climate: 50-80% of diet-related anthropogenic greenhouse gas emissions and land use demands7,8, about 50% of individual diet-related water consumption8, between 14-21% of global water use9 and a significant reduction of the global nitrogen footprint10 could be avoided by adopting a plant-based diet. The ecological benefits of plant-based diets become apparent when comparing the resources needed for 1kg of beef compared to 1kg of a non-animal-based alternative: land use is 10-fold, greenhouse gas emissions 30-fold and nitrogen use is 17-fold higher for producing beef 11.


“Ok, and practically, what does that mean for my individual CO2 footprint and aren’t there actions with higher climate impact?”

Plant-based eating can save up to 1t CO2/year compared to an omnivorous Western diet, fourth in line for high impact actions that can decrease one’s personal CO2 footprint behind having one fewer child (60t CO2/year), living car-free (2.4t CO2/year) and avoiding one round-trip transatlantic flight (1.6t CO2/year) 12.

Inspired to pursue my PhD on the topic of plant-based diets

I am in the second year of my PhD with the aim to assess whether plant-based diets, i.e. a high-fiber diet, influence our decisions of what we would like to eat. We postulate that potential effects are mediated by the gut microbiome. In a literature review, I summarized benefits and risks of following a plant-based diet for the body and in particular for the brain (Medawar et al. 2019, in press). Further, in a large cross-sectional study of the Leipzig population10 I am investigating the interplay between plant-based eating patterns, weight status measured as body-mass-index, emotional health and personality traits. Two observational studies placed in the German student cafeterias (Mensen des Deutschen Studentenwerks - click here if you want to participate live in Berlin/Leipzig/Jena/Halle or nation-wide via an app) are currently running with the aim to investigate the effect of a single meal choice on well-being and satiety. We want to find out what effect the nutrition value of the meal has, and which other variables may play a role for mood after a meal, e.g. social contact, smartphone use etc.

To investigate neural patterns of food choices, we examine whether a 2-week high-fiber dietary intervention affects food wanting and memory performance. Participants come four times to our institute with brain scans (magnetic resonance imaging = MRI), extensive lab examination, stool samples, food diaries and cognitive testing. We want to find out whether our gut bacteria do have a say in what we choose to eat.

Stay tuned for the results via Twitter @EvelynMedawar and @AgingObesity

Big thank you to my group for running the studies with me!

Feeling motivated? Next steps:

  • choose the meat-free option for lunch
  • eat locally (choose ingredients from your local region or from Germany)
  • reduce waste: avoid plastic wrappings (bring your own mug, take your Tupperware to transport leftovers)
  • get in touch with your institute’s Sustainability Group or if there is none yet, get a group of motivated people and create one
  • find info on how to eat greener within MPI canteens see here


  1. VEBU Deutschland & Joy, S. Anzahl der Veganer und Vegetarier in Deutschland. Stand 31, 2016 (2015). https://vebu.de/veggie-fakten/entwicklung-in-zahlen/anzahl-veganer-und-vegetarier-in-deutschland/
  2. Mensink, G., Barbosa, C. L. & Brettschneider, A.-K. Verbreitung der vegetarischen Ernährungsweise in Deutschland. (2016). https://edoc.rki.de/bitstream/handle/176904/2488/JoHM_2016_02_ernaehrung1a.pdf?sequence=4&isAllowed=y
  3. Willett, W. et al. Food in the Anthropocene: the EAT–Lancet Commission on healthy diets from sustainable food systems. Lancet (2019). https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(18)31788-4/fulltext
  4. Knuppel, A., Papier, K., Key, T. J. & Travis, R. C. EAT-Lancet score and major health outcomes: the EPIC-Oxford study. Lancet (2019). https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)31236-X/fulltext
  5. Gerber, P. J. et al. Tackling climate change through livestock. (2013). http://www.fao.org/3/a-i3437e.pd
  6. Hoekstra, A. Y. & Mekonnen, M. M. The water footprint of humanity. Proc. Natl. Acad. Sci. 109, 3232–3237 (2012). https://waterfootprint.org/media/downloads/Hoekstra-Mekonnen-2012-WaterFootprint-of-Humanity.pdf
  7. Hallström, E., Carlsson-Kanyama, A. & Börjesson, P. Environmental impact of dietary change: a systematic review. J. Clean. Prod. 91, 1–11 (2015). https://www.sciencedirect.com/science/article/pii/S0959652614012931?via%3Dihub
  8. Aleksandrowicz, L., Green, R., Joy, E. J. M., Smith, P. & Haines, A. The impacts of dietary change on greenhouse gas emissions, land use, water use, and health: a systematic review. PLoS One 11, e0165797 (2016). https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0165797
  9. Jalava, M., Kummu, M., Porkka, M., Siebert, S. & Varis, O. Diet change—a solution to reduce water use? Environ. Res. Lett. 9, 74016 (2014). https://iopscience.iop.org/article/10.1088/1748-9326/9/7/074016
  10. Eshel, G., Shepon, A., Makov, T. & Milo, R. Land, irrigation water, greenhouse gas, and reactive nitrogen burdens of meat, eggs, and dairy production in the United States. Proc. Natl. Acad. Sci. 111, 11996–12001 (2014). https://www.pnas.org/content/111/33/11996.long
  11. Wynes, S. & Nicholas, K. A. The climate mitigation gap: education and government recommendations miss the most effective individual actions. Environ. Res. Lett. 12, 74024 (2017). https://mahb.stanford.edu/wp-content/uploads/2017/07/Wynes_2017_Environ._Res._Lett._12_074024.pdf
  12. Loeffler, M. et al. The LIFE-Adult-Study: objectives and design of a population-based cohort study with 10,000 deeply phenotyped adults in Germany. BMC Public Health 15, 691 (2015). https://bmcpublichealth.biomedcentral.com/articles/10.1186/s12889-015-1983-z 

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