Food for Thought

Food for Thought

It’s well known that meat production generates more greenhouse gas emissions compared to vegetable farming. This #OpenAccess study attempted to quantify the difference in emissions for people with different diets. Based on their findings, the study concluded that “It is likely that reductions in meat consumption would lead to reductions in dietary GHG emissions.”

Originally shared by Rakesh Yadav

Dietary greenhouse gas emissions of meat-eaters, fish-eaters, vegetarians and vegans in the UK

This is one of those days when I get quirky and read stuff about the stuff we eat. I found an interesting paper (http://goo.gl/Y8WwEC; open access) whose title is mentioned above. The paper tries to put some numbers on the greenhouse gas (GHG) emissions from different dietary practices, in UK. The following summary is mostly a copy-paste job with some paraphrasing here and there.

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Introduction

When measured by consumption food is responsible for approximately one fifth of all GHG emissions attributable to the UK. There is considerable variation in the amount of GHG emissions related to different food groups, with animal-based products generally having much greater emissions than plant-based products per unit weight. Substantial reductions in GHG emissions can only be achieved through changes in consumption patterns and reduction in food waste. We use data on actual diets of vegans, vegetarians, fish-eaters and meat-eaters to estimate the difference in dietary GHG emissions attributable to these four diet groups. Previous estimates of dietary GHG emissions for self-selected dietary groups have not compared meat consumers with those who abstain from meat.

Methods

The analysis is based on data from participants in the EPIC-Oxford cohort, which consists of 65,000 (12,666 males and 42,838 females) participants generally aged 20 and over at recruitment between 1993 and 1999.

Diet groups:

High meat-eaters, 8286 people: those who consume >=100 g/day

Medium meat-eaters, 11971: meat consumptions 50 to 99 g/day

Low meat-eaters, 9332: meat consumption <50 g/day

Fish-eaters, 8123

Vegetarians, 15751

Vegans, 2041

A food-frequency questionnaire (FFQ) that estimates intake (frequency of consumption) of 130 different food items over the previous 12 months was completed at recruitment by most participants. Nutritional analysis of 130 food-item FFQ were based on nutritional data for 289 food codes taken from UK food composition tables. We estimated the GHG emissions associated with these 289 food codes. Carbon dioxide, methane and nitrous oxide emissions were incorporated. The data includes the life cycle of food commodities from the earliest stages of production to the retail distribution centre. We did not account for the cooking process (either at the industrial stage or at home) for any of the food codes.

Results

Generally, there were significant trends towards lower total fat, saturated fat and protein consumption and higher carbohydrate, total sugar, fibre and fruit and vegetables consumption as animal-based food consumption decreased.

The highest dietary GHG emissions were found in high meat-eating men and the lowest dietary GHG emissions were found in vegan women. The mean observed values of dietary GHG emissions for meat-eaters (results reported for women and then men) was 46 % and 51 % higher than for fish-eaters, 50 % and 54 % higher than for vegetarians and 99 % and 102 % higher than for vegans. The results showed highly statistically significant differences in dietary GHG emissions between the six diet groups, with progressively higher emissions for groups with greater intakes of animal-based products.

Discussion

After adjustment for sex and age, an average 2,000 kcal high meat diet had 2.5 times as many GHG emissions than an average 2,000 kcal vegan diet. Assuming that the average daily energy intake in the UK is 2,000 kcal, then moving from a high meat diet to a low meat diet would reduce an individual’s carbon footprint by 920kgCO2e every year, moving from a high meat diet to a vegetarian diet would reduce the carbon footprint by 1230 kgCO2e/year, and moving from a high meat diet to a vegan diet would reduce the carbon footprint by 1560 kgCO2e/year. For context, an individual travelling on an economy return flight from London to New York has an addition to their carbon footprint of 960kgCO2e. A family running a 10 year old small family car for 6000 miles has a carbon footprint of 2440 kgCO2e, roughly equivalent to the annual carbon saving of two high meat eating adults moving to a vegetarian diet.

Caveats

Although the nutrient intakes estimated by the FFQ have been validated against food diaries and some biomarkers, the GHG emissions have not. Throughout the analysis presented here we have assumed that GHG emission related to food wastage is reasonably similar across all food groups, but this may not be the case. Estimates of food wastage in the UK suggest that wastage of fruit and vegetables is higher than for meat products, which could reduce the difference in GHG emissions between the dietary groups.

Conclusions

Analysis of observed diets shows a positive relationship between dietary GHG emissions and the amount of animal-based products in a standard 2,000 kcal diet. This work demonstrates that reducing the intake of meat and other animal based products can make a valuable contribution to climate change mitigation. Other work has demonstrated other environmental and health benefits of a reduced meat diet. National governments that are considering an update of dietary recommendations in order to define a ‘healthy, sustainable diet’ must incorporate the recommendation to lower the consumption of animal-based products.

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I hope this motivates people to read further about what they eat.

ScienceSunday  #sciencesunday

Rajini Rao  Robby Bowles  Buddhini Samarasinghe  Allison Sekuler

Image taken from the cover of “Changing

what we eat” by the Food Climate Research Network.