One day vegan…

One day veganWhat is the positive impact of eating a plant-based (vegan) diet for one day? A person with an omnivorous diet spends just a few minutes a day consuming animal products. But those few minutes cause a lot of harm. Replacing those animal products with animal-free, plant-based, vegan alternatives avoids those harms. So I have made some calculations of the harms avoided when an average omnivore (in Western-Europe) becomes a vegan for 1 day and replaces red meat with protein-rich soy beans and leguminous vegetable products, fish with omega-3 rich linseed, walnuts and seaweeds, eggs and poultry with vegetables and seeds, cheese with vegan nut cheese and milk with soy-milk. Replacing these animal products with their alternatives results in an optimal healthy diet (if supplemented or enriched with vitamins B12 and D).

How much harm is caused by just those few minutes of consuming animal products in an omnivore’s day?  What is avoided each day by being vegan? Below are the results. Adding together the avoided harm over 365 days in a year, several years of your life, the total positive impact becomes enormous.

Short summary: a vegan day saves 1 week of animal suffering in captivity, 1,5 hours of a consumer’s life due to less chronic diseases (cardiovascular diseases, cancers and diabetes), 0,5 hours of someone else’s life due to less health impact from global warming, malnutrition, antibiotic-resistant bacteria and new infectious diseases, and 10 hours of an average species lifespan.

Note 1: these results assume a high elasticity close to 1, which means a decrease of demand with one unit results in the decrease of production quantity with one unit. For animal products, more realistic elasticity values are around 0,7, because a decrease in demand by one person results in a decrease in price which results in a small increase in consumption by other people. Taking this lower elasticity into account, the results should be reduced with 30% .

Note 2: for each result I also give my epistemic status, i.e. my level of confidence in the results.

Note 3: see also similar calculations for one day car free.

Harm to the animals

The death of 1 sentient animal (vertebrates, crustaceans and cephalopods, including sea animals killed as bycatch or used as fish meal). [Epistemic status: low] This corresponds with 1 week of animal suffering in captivity. [Epistemic status: moderate]

Harm to the environment

The emissions of 2 kg CO2 and other greenhouse gases, the equivalent of 1 minute traveling by plane or 15 minutes driving by car. [Epistemic status: high] These emissions contribute to climate change and generate a health cost on future generations (diarrhea, malnutrition due to harvesting loss, cardiovascular disease due to heat waves, malaria due to the spread of mosquitoes by higher temperatures and floods due to extreme weather events and sea level rise), resulting in an expected 4 minutes shortening of someone else’s life in the near future. [Epistemic status: very low]

Addendum: The agricultural land for livestock could be used for planting trees to absorb CO2. This land occupation of livestock farming has a carbon opportunity cost of 4 kg CO2. Hence, one day vegan means a total avoidance and absorption of 6 kg CO2.

The use of 1 m³ fresh water, as much as 2 hours non-stop showering. [Epistemic status: high]

The occupation of 700 m² highly fertile land for one day, used as cropland to grow animal feed. [Epistemic status: moderate] Combined with other environmental impacts that harm biodiversity, this results in an expected 10 hours shortening of the natural lifespan of an average species. [Epistemic status: very low]

Harm to the human population

The conversion of 600 grams of edible crops into inedible manure, which means the waste of one meal. [Epistemic status: moderate]

The malnutrition of 1 person for 5 hours. (5 people eating vegan means 1 person no longer malnourished). This also corresponds with an expected 7 minutes shortening of someone else’s life.  [Epistemic status: almost zero]

The use of 20 mg antibiotics, which increases the risk of microbial resistance, resulting in an increased mortality and hence an expected 3 minutes shortening of someone’s life in the near future. [Epistemic status: very low]

The shortening of someone else’s life with 15 minutes due to increased mortality from new infectious diseases (e.g. viruses such as avian flu, swine flu,…). [Epistemic status: very low]

Harm to your health

The consumption of 20 grams saturated fat. [Epistemic status: high] Combined with other harmful chemicals in animal products this amounts to a 10% higher risk of dying prematurely, or an expected 1,5 hours shortening of your life due to chronic diseases (cardiovascular diseases, cancers and diabetes). [Epistemic status: low]

Harm to the economy

The loss of 8 euro economic wealth due to environmental and health costs. This includes the social costs of climate change (0,15 euro), the extra health care costs due to chronic diseases (0,17 euro), the costs due to loss of labour activities (0,07 euro) and the willingness to pay for mortality reductions (7,3 euro). If everyone adopts a vegan diet, the increase in economic wealth corresponds to an increase in income of 8 euro per person per day. [Epistemic status: very low]

Calculations and sources

-Consumption levels, kg per day (average Belgian person):

FOD Economie bevoorradingsbalans vlees 2013,

FAO Food Balance Sheets 2013 Belgium (,

Flemish food survey.

-Animals killed and hours suffering per kg product:

Saja. K (2012). The moral footprint of animal products. Agriculture and Human Values. 30:193-202.

Fish killed for fish meal: FAO Fishstat, FishCount ( and Counting Animals (

-Greenhouse gas emissions per kg product:

Nederlandse consumptie van eiwitrijke producten. Gevolgen van vervanging van dierlijke eiwitten anno 2008. Blonk Milieu Advies, Gouda.

CE Delft (2011). Life Cycle Impacts of Protein- rich Foods for Superwijzer. Delft.

CE Delft (2010). Milieuanalyses voedsel en voedselverliezen. Delft.

Springmann M. e.a. (2016). Analysis and valuation of the health and climate change cobenefits of dietary change. Proc Natl Acad Sci. 113(15):4146-51.

-Carbon opportunity cost of livestock:

cropland 700 m².day + grazing land that can be reforested 700 m².day = 4 m².year. Global Footprint Network (2015) National Footprint Accounts.

Planting 1m² of forest absorbs 1 kg CO2 per year. Turning agricultural land into forest absorbs 4 m².year x 1 kg CO2/m²/year = 4 kg CO2.

This is a bit lower than another global average estimate of the carbon opportunity cost of livestock. Total area of grazing lands reverted to forests due to global veganism: 20 million km². Carbon sequestered in reverted lands at maturity: 1000 Gigaton CO2. Yearly carbon sequestration (50 years at maturity): 20 Gigaton CO2. World population: 7.5 billion. Carbon sequestration for 1 person 1 day vegan: 20 Gigaton CO2/7.5 billion/365 = 7 kg CO2.

-Health cost due to climate change, per unit CO2 emitted: 3,5 DALYs (disability adjusted life years) per 1000 ton CO2 (according to egalitarian perspective)

Goedkoop M. e.a. (2009). ReCiPe 2008. A life cycle impact assessment method which comprises harmonised category indicators at the midpoint and the endpoint level. Report I: Characterisation. Ministry of Housing, Spatial Planning and Environment, the Netherlands.

-Fresh water use per kg product:

Mekonnen, M.M. and Hoekstra, A.Y. (2010) The green, blue and grey water footprint of crops and derived crop products, Value of Water Research Report Series No.47, UNESCO-IHE, Delft, the Netherlands.

Mekonnen, M.M. and Hoekstra, A.Y. (2010) The green, blue and grey water footprint of farm animals and animal products, Value of Water Research Report Series No.48, UNESCO-IHE, Delft, the Netherlands.

Pahlow M e.a. (2015). Increasing pressure on freshwater resources due to terrestrial feed ingredients for aquaculture production. Science of the Total Environment 536 (2015) 847–857.

-Occupation of land (agricultural cropland footprint per kg product):

Global Footprint Network (2015) National Footprint Accounts

-Shortening of lifespan of species:

De Vos J. e.a. (2015) Estimating the normal background rate of species extinction. Conservation Biology 29(2):452–462

Stehfest E. e.a. (2008). Vleesconsumptie en klimaatbeleid. Nederlands Planbureau voor de Leefomgeving (PBL).

Each year an expected 1 in 10.000 species go extinct, which is 1000 times higher than the background extinction rate. There are about 10 million species, which means 1000 extinctions per year. A species has an average life expectancy of 10 million years, which means the current premature extinction of a species causes a shortening of 5 million years of a species lifespan. About 1/3 of the biodiversity loss is due to livestock farming (in particular due to the higher land occupation of an omnivorous diet compared to a vegan diet), which means the worldwide consumption of animal products instead of plant-based alternatives causes 1 species extinction per day, or the loss of 5 million species years. An average Western-European person consumes a share of 1 in 3 billion of the total livestock production (per capita consumption of animal products in Europe is twice as high as the world average). This means the omnivorous diet of an average Western-European causes the loss of 10 hours of a species lifespan, relative to a vegan diet.

-Conversion of edible crops (grains, soy and other edible products used as animal feed per kg product):

Global Footprint Network (2015) National Footprint Accounts


Lusk J & Norwood B. (2009) Some Economic Benefits and Costs of Vegetarianism. Agricultural and Resource Economics Review 38/2:109–124.

1 day vegan reduces demand of edible crops (mostly grains) with 600 gram. Total world cereal production is 7 Mton. A 1% decrease in production of cereal (corn) implies a 2% decrease in price (Lusk & Norwood 2009). A 2% decrease in cereal prices correlates with a 3,2% decrease in number of people malnourished (between 2009 and 2016 cereal prices dropped with 14% and number of malnourished people dropped with 22% from 1020 million ton 790 million). Hence, 1 day vegan means 0,2 people less malnourished for one day, or 1 person less malnourished for 5 hours.

If a vegan day means 0,2 people less malnourished for one day and 11% of people are malnourished, a vegan day saves 7 minutes of life because 0,56% of global deaths are due to protein-energy malnutrition (, there are 3 deaths per 100.000 persons per day and an early death means an average of 2 million minutes of life lost.

Note: the assumption that increasing food prices results in increasing malnutrition is likely to be wrong. The correlation between the drop in food prices between 2009 and 2016 and the drop in the number of malnourished people does not imply a causal relationship, or only implies a causality in the short run. In the medium and long run, food price increases are likely to reduce poverty. See Ivanic M. & Martin W. (2014) Short- and Long-Run Impacts of Food Price Changes on Poverty. Policy Research Working Paper; No. 7011. World Bank Group

-Antibiotic use

Center for Global Development (2017) A Global Treaty to Reduce Antimicrobial Use in Livestock, CGD Policy Paper 102

Each year an expected 1 in 10.000 people die due to infections from antibiotic resistant bacteria. More than 70% of antibiotics are used in livestock in developed countries. 60% of those livestock antibiotics (about 50% of total antibiotic use) are also given to humans. That means an estimated 1 in 20.000 people per year die because of livestock antibiotic use. One death corresponds with an average 40 years of life lost. Multiplying these factors results in 3 minutes shortening of someone’s life.

-New infectious diseases

Jones e.a. (2008) Global trends in emerging infectious diseases. Nature 451, 990–993

15% of new (infectious) diseases come from global livestock (Jones e.a. 2008). Per capita consumption of livestock products in Europe is twice as high as world average. Assume that the mortality rate of new infectious diseases equals mortality rate of diarrhea, lower respiratory and other common infectious diseases. These diseases contribute 9% to total deaths. Total mortality rate is 1% per year (1 in 100 people die per year). One death means the loss of 40 years of life (21 million minutes).  Multiplying these factors (15% x 2 x 9% x 1% x 21 million minutes / 365 days per year) results in 15 minutes shortening of someone’s life.

-Saturated fats per kg product:

-Hours loss of healthy life per kg product:

Spiegelhalter D. (2012). Using speed of ageing and “microlives” to communicate the effects of lifetime habits and environment, Britisch Medical Journal, 345:e8676.

Springmann M. e.a. (2016). Analysis and valuation of the health and climate change cobenefits of dietary change. Proc Natl Acad Sci. 113(15):4146-51.

Replacing 1 kg of red meat with 1 kg of plant-based protein sources increases expected lifespan with 5 hours (Spiegelhalter, 2012).  Also the replacement of 1 kg of cheese, eggs and poultry meat with 1 kg of vegetables saves 5 hours. At the daily consumption levels of a European person, this means 1,5 hours of life saved per day.

This estimate corresponds with two other estimates: a vegan world reduces early mortality (causes of death) with 10% (for a vegan diet according to Springmann e.a. 2016) to 16% (for a diet high in fruits, vegetables, legumes, whole grains, nuts and seeds and low in red and processed meat according to At an average mortality rate of 1% per year and an average loss of 40 years or 350.000 hours per early death, this results in 1 – 1,5 hours of life saved per day.

-Loss of economic wealth

Springmann M. e.a. (2016). Analysis and valuation of the health and climate change cobenefits of dietary change. Proc Natl Acad Sci. 113(15):4146-51.

Total extra costs in 2050 in the scenario where everyone has an omnivorous diet rich in animal products, compared to the scenario where everyone eats vegan is 31 trillion dollars (27 trillion euro), including environmental costs (social cost of carbon), health costs and willingness to pay for mortality reductions. This is divided by 9 billion people in 2050.


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