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Which Diet Has the Least Environmental Impact on Our Planet? A Systematic Review of Vegan, Vegetarian and Omnivorous Diets

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The food that we consume has a large impact on our environment. The impact varies significantly between different diets. The aim of this systematic review is to address the question: Which diet has the least environmental impact on our planet? A comparison of a vegan, vegetarian and omnivorous diets. This systematic review is based on 16 studies and 18 reviews. The included studies were selected by focusing directly on environmental impacts of human diets. Four electronic bibliographic databases, PubMed, Medline, Scopus and Web of Science were used to conduct a systematic literature search based on fixed inclusion and exclusion criteria. The durations of the studies ranged from 7 days to 27 years. Most were carried out in the US or Europe. Results from our review suggest that the vegan diet is the optimal diet for the environment because, out of all the compared diets, its production results in the lowest level of GHG emissions. Additionally, the reviewed studies indicate the possibility of achieving the same environmental impact as that of the vegan diet, without excluding the meat and dairy food groups, but rather, by reducing them substantially.
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sustainability
Review
Which Diet Has the Least Environmental Impact on
Our Planet? A Systematic Review of Vegan,
Vegetarian and Omnivorous Diets
Bingli Clark Chai, Johannes Reidar van der Voort, Kristina Grofelnik , Helga Gudny Eliasdottir,
Ines Klöss and Federico J. A. Perez-Cueto *
Design & Consumer Behaviour Section, Department of Food Science, Faculty of Science,
University of Copenhagen, Rolighedsvej 26, 1958 Frederiksberg C, Denmark
*Correspondence: apce@food.ku.dk
Received: 11 July 2019; Accepted: 24 July 2019; Published: 30 July 2019
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Abstract:
The food that we consume has a large impact on our environment. The impact varies
significantly between dierent diets. The aim of this systematic review is to address the question:
Which diet has the least environmental impact on our planet? A comparison of a vegan, vegetarian
and omnivorous diets. This systematic review is based on 16 studies and 18 reviews. The included
studies were selected by focusing directly on environmental impacts of human diets. Four electronic
bibliographic databases, PubMed, Medline, Scopus and Web of Science were used to conduct a
systematic literature search based on fixed inclusion and exclusion criteria. The durations of the
studies ranged from 7 days to 27 years. Most were carried out in the US or Europe. Results from
our review suggest that the vegan diet is the optimal diet for the environment because, out of
all the compared diets, its production results in the lowest level of GHG emissions. Additionally,
the reviewed studies indicate the possibility of achieving the same environmental impact as that
of the vegan diet, without excluding the meat and dairy food groups, but rather, by reducing
them substantially.
Keywords:
omnivorous; vegan; vegetarian; sustainable; diet; GHG; LCA; carbon; environment;
footprint; systematic review
1. Introduction
According to the United Nations, the world’s population will grow to 9.8 billion people by 2050 [
1
].
This corresponds to an increase of almost 30% from the current population of 7 billion [
2
]. Demographic
changes and population growth imply an increasing demand for animal products, particularly meat,
dairy products and crops, which suppliers need to fulfil [
2
]. It is expected that by 2050, milk and
meat production will increase 58 and 73 percent, respectively [
3
]. Concerns about animal welfare
have been an issue for centuries, but climate change and greenhouse gas emissions (GHGEs) have
recently started to become a point of interest [
4
]. Modern food systems, especially the agriculture
sector, have a highly unsustainable impact on the environment. Using natural resources (land, water
and fossil energy) to raise livestock and produce crops increases environmental degradation day by
day. Agriculture alone is responsible for fully 10–12% of global GHGEs. It is estimated that GHGEs
will rise by up to 150% of current emission levels by 2030 [
5
]. For this reason, finding ways to mitigate
the negative impact of climate change and the environmental footprint of the current food system’s
environmental footprint is becoming more and more urgent. A sustainable diet is one with production
that has little environmental impact, is protective and respectful of biodiversity and of ecosystems,
and is nutritionally adequate, safe, healthy, culturally acceptable and economically aordable [
6
,
7
].
Sustainability 2019,11, 4110; doi:10.3390/su11154110 www.mdpi.com/journal/sustainability
Sustainability 2019,11, 4110 2 of 18
Animal husbandry requires a large number of inputs. At the same time, it generates undesirable
by-products that aect the environment. While there is no universally accepted system for measuring
these eects quantitatively, a widely used method is the Life Cycle Impact Assessment technique
(LCAs) [
8
]. LCAs can estimate the environmental impacts of production, transport, processing, storage,
waste disposal and other life stages of food production [
9
]. This paper will use an LCA approach to
frame and systematically review the literature as related to the eects of food production on three main
indicators: GHGEs, land use and the water footprint. We will evaluate variations in these eects that
are associated with production for three diets, which dier mainly by their consumption of animal
based products: vegan diets do not include any products from animal origin; lacto-ovo-vegetarian
diets (LOV) include milk, dairy products and eggs, but no animal meat; and omnivorous diets (OMN)
includes all animal-based food products, including meat, dairy and eggs.
2. Methods
2.1. Literature Search Strategy
In order to find articles relevant to the research question, the electronic bibliographic databases
PubMed, Medline, Scopus and Web of Science were searched. The literature search took place on 9 April
2019. The specific search strategy and careful selection of the terms (environment* AND diet* AND
(footprint OR sustain* OR impact) AND (“greenhouse gas*” OR vegetarian* OR vegan OR omnivorous)
AND diet* AND (footprint OR sustain* OR impact) AND (“greenhouse gas*” OR vegetarian* OR vegan
OR omnivorous) AND (water) AND (land)) AND (vegetarian OR vegan) AND (Life cycle analysis))
were entered and 1246 hits were obtained. The language was restricted to English. In order to include
relevant articles from older years, no time restriction was set. Moreover, no citation-based search of
prior references to relevant articles was used. That is, the literature search strategy was limited to a
direct database search. In addition to work identified through this process, two additional articles
provided by a senior researcher have been included in the review. The keywords used in the literature
search are based on a joint agreement between the junior and senior authors.
2.2. Inclusion and Exclusion Criteria
The included studies were selected by focusing directly on keywords related to the environmental
impacts of diets, rather than on special nutritional dierences and health eects for the human body.
Some of the reviewed articles combine health aspects and the environmental footprint. Only articles
about human dietary patterns were included. Scientific papers on specific dietary patterns such as:
the New Nordic Diet, the Mediterranean Diet or the Atlantic Diet have been excluded, because it is
dicult to classify these diets as fully omnivorous, vegetarian or vegan. Articles that report research
performed on a very specific target group (e.g., Carbon footprint and land use of conventional and
organic diets in Germany, Treu Hanna et al., 2017.) were also excluded. Moreover, articles that focused
on technological improvements in agriculture, economic analyses on food systems and sociological
aspects behind food choice/consumer behaviour were excluded.
2.3. Screening
After the initial list was generated, duplicates were removed using Excel. Next, the titles of all
studies were screened by five reviewers, to avoid reflexivity bias; titles that did not fulfil the inclusion
criteria were removed. Further screening was conducted by reading each full-text article, focusing on
our criteria.
2.4. Data Extraction
In order to extract relevant data from the selected 34 articles, a predetermined grid was created
and served as a tool to organize an overview of all relevant information. Two tables were created,
one for all studies and the other for all reviews. Each table was split up into the following categories:
Sustainability 2019,11, 4110 3 of 18
author, publication year, country, diet comparison, quality assessment, main outcome, and magnitude.
The table of studies also included space for a description of the study design and for duration. These
data are presented here as Tables 1and 2.
2.5. Quality Assessment
Methodological and reporting quality assessment was performed in order to evaluate the
robustness of the conclusions of the review. The quality assessment was done by checking
each of the used research articles and reviews according to a predetermined set of criteria
(Tables 3and 4)
and following Research Connections Quantitative Quality Assessment Tool (https:
//www.researchconnections.org/content/childcare/understand/research-quality.html, retrieved at 16
January 2019) and National Heart, Blood and Lung Institute Study Quality Assessment Tool
(https://www.nhlbi.nih.gov/health-topics/study-quality-assessment-tools, retrieved 16 January 2019).
Additionally, all authors had to achieve consensus on the final mark. Articles and reviews were
managed by using the software Mendeley. The papers were categorized in low quality, medium quality
and high quality. This leads to 9 low quality papers, 9 medium quality papers and 16 high quality
papers, with a total of 34 papers.
Sustainability 2019,11, 4110 4 of 18
Table 1. Characteristics of the included studies.
Authors/Year Country Study Design Description of Intervention Duration Diet Comparison Quality Assessment Main Outcome
Harwatt,
H./2017 USA LCA
Simple analysis, which
replacement of food could be a
contributor to achieve GHGEs
reduction.
N/A
comparing
omnivorous diet and
plant-based diet
Medium
Replacing beans for beef in general
diets could achieve a reduction of
cropland by 42% and 46%–74%
reduction of GHGEs need by the 2020
target in the US.
Hyland,
J./2016 Ireland Descriptive
Analysis
Using data from the National
Adult Nutrition Survey in
Ireland to analyze GHGEs for
the total population and
various categories
2008–2010
comparing
omnivorous,
vegetarian and
plant-based diet
High
Highest contributor to GHGEs was
meat with 1646 g COs-eq. The second
largest daily emissions were dairy
and starchy products with 732 g
COs-eq and lowest were vegetables,
fruits and legumes with 647 COs-eq.
Pradhan,
P./2016 Global Global data
analysis
Global analysis of 16 dierent
global dietary patterns 1961–2007
16 dietary patterns
based on energy
content of these diets
Medium quality
Highlighting the changes in food
consumption over the past 50 years
and their regionality.
Rosi, A./2017 Italy LCA
Real-life context. Controlled
intervention among 3 designed
diets groups.
7 consecutive
days
omnivorous, vegan,
lacto-ovo-vegetarian High quality
It shows a pattern that vegan diet is
better than omnivorous diet in terms
of environmental footprint.
Ulaszewska,
M.M./2017. Italy LCA
Comparison of Mediterranean
and New Nordic diet in terms
of GHGEs
N/AMediterranean and
New Nordic diet Low quality
GHGEs for high-protein and
vegetable/fruit group in
recommendations is comparable
and similar
Tyszler,
M./2016 Netherlands LCA and
questionnaire
Eect of dierent variations of
the current diet on the
environment with comparison
with vegetarian and vegan diet
N/A
Vegan, vegetarian,
current and closest
healthy diet
Medium quality
There is a diet, not much dierent
from the current Dutch diet, that has
the same eect on the environment as
the vegan diet
Arrieta,
E.M./2018 Argentina Scenario
analysis
Estimating the GHGEs of
dierent diets in Argentina
through a scenario analysis
N/A
National diet, diet
with no ruminant
meats, LOV and vegan
diet
Low quality
Least GHGEs from vegan diet,
highest GHGEs from national
Argentinian diet.
Meier,
T./2013 Germany LCA
Comparison of environmental
impact of 4 dietary scenarios in
the period between 19851989
and 2006.
N/AD-A-CH UGB
LOV vegan High quality
All the indicators of environmental
impact are lower in 2006, compared
to 1985–1989. because of the change
in diet
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Table 1. Cont.
Authors/Year Country Study Design Description of Intervention Duration Diet Comparison Quality Assessment Main Outcome
Blackstone,
N.T./2018 USA LCA
Comparing dierent diets and
estimating their
environmental impact
N/A
Healthy US diet, healthy
Mediterranean diet and
healthy vegetarian diet
Low quality
A healthy vegetarian diet has 84–42%
lower climate impacts than the
healthy US diet and Mediterranean
diet with the exception of water use
which was the same.
Seconda,
L./2018 France Questionnaire
Evaluating dierent dietary
patterns to assess their
environmental impact and
characterizing consumer
dietary patterns
N/AConsumer dietary
patterns High quality
Dietary patterns among the
consumers were not seen as
sustainable and more sustainable
diets contained less meat and less
processed food.
Corrado
et al./2019 Italy LCA
Evaluating dierent LCA
associated with three
dietary patterns
N/AVegan, vegetarian and
omnivorous Medium quality
A reduction in the GHG emission
would be attained by changing the
dietary patterns to vegan and
vegetarian under certain limits
Esteve-Llorens
et al./2019 Spain LCA
Evaluating the carbon footprint
through life cycle by analyzing
the Atlantic diet
N/AOmnivorous and
Atlantic diet Medium quality
Atlantic dietary is beneficial from
both health and environmental
perspective
Green
et al./2018 UK
GHGEs and
water footprint,
LCA
Evaluating the environmental
footprint in agriculture (India) N/AOmnivorous, vegan,
fruitirism, vegetarian Medium quality
Environmental impact of certain diets
in India are relatively low compared
with high income countries
Van Dooren,
C./2014
Netherlands/global
LCA
Analyzing six dierent dietary
patterns to assess their
nutritional value and
environmental impact
N/A
Average Dutch diet,
recommended Dutch
diet, semi-vegetarian,
vegetarian, vegan and
Mediterranean
Medium quality
High health scores of diets are linked
to high sustainability scores. The
vegan diet has the highest
sustainability score while the
Mediterranean diet has the highest
health score.
Weber,
C./2008 USA Method:
IO-LCA
LCA of GHGEs associated with
distribution N/AN/A No comparison High quality
Transport contributes to only 11% of
GHGEs. Delivery from producer to
retail contributes only with 4%
Scarborough,
P./2014. UK FFQ
Are there dierences in dierent
diets contribution to GHGEs N/AOmnivorous, vegan,
vegetarian, fish-eaters High quality GHGEs are twice as high in meat
eaters as those in vegans
Sustainability 2019,11, 4110 6 of 18
Table 2. Characteristics of the included reviews.
Author/Year Country Description of Review Diet Comparison Quality Assessment Main Outcomes
González-García,
S./2018 Spain Systematic analysis of 21
Peer-Review Studies
Examines 66 dietary scenarios
and their carbon footprint,
including vegetarian, vegan
and omnivorous diet patterns
High quality
Dietary choices have higher carbon
footprints if they are meat-rich; reducing
animal products is advantageous for
the environment
Wanapat, M./2015 Global Dierent feed additive practices
for ruminants No comparison High quality
Decrease of methane production from
ruminants will contribute to reduction of
global methane production
Garnett, T./2013 Global
How to make food production
more environmentally sustainable
and resilient while feeding more
people more eectively
No comparison Low quality
The priority for the future should be a
nutrition-driven food system that sits within
environmental limits.
Pimentel, D./2003 USA
Comparison between meat-based
diet and lacto-ovo-vegetarian diet
in terms of
environmental footprint.
Meat-based diet and
lacto-ovo-vegetarian diet Low quality
In the long term, both diets are not
sustainable. However, the meat-based diet
uses more resources than
lacto-ovo-vegetarian diet. Therefore,
between them, lacto-ovo-vegetarian diet is
more sustainable.
Reijnders, L./2003 USA
Quantitative evaluation of dierent
types of protein sources.
Comparison of dierent types of
protein and their emissions.
Vegetarian and non-vegetarian. High quality
Encouraging individuals to eat more
eciently on the food chain where they
consume less meat and more plant-based,
will reduce the environmental cost of food
production.
Ridoutt, B./2017 Australia Environmental impact of
dierent diets
Vegetarian, vegan and
non-vegetarian. High quality
In general, average diets have a higher
emission on environmental aspects than
recommended diets.
Sabaté, J./2014 Global
Comparison of plant-based and
animal-based diets in terms of
environmental impact
Plant-based and
animal-based diet Medium quality Implementing plant-based diet is the best
option for sustainable future
Friel, S./2009 UK Agricultural strategies to reduce
emissions by 80% till 2050 No comparison Medium quality
Formulation of policies that consider
equitable distribution and reduction of
livestock production is needed
Aleksandrowicz,
L./2016. Global Dierent diet types and their eect
on GHGEs, land and water use
Comparison of plan-based
diets, omnivorous diets and
their variations
High quality
Shift to more sustainable diet variations can
show reduction of 50% water use and 70%
land use and GHGEs
Sustainability 2019,11, 4110 7 of 18
Table 2. Cont.
Author/Year Country Description of Review Diet Comparison Quality Assessment Main Outcomes
Jones, A.D./2016. Global
What are the components of
sustainability and how are
they measured
Comparison of diets
considered sustainable High quality 3 dierent approaches for defining
sustainable diets
Heller, M.C./2013 USA
Need to combine nutrition
assessment and life
cycle assessment
No comparison of diets High quality Nutritional quality indices
Hess, T./2015 UK
Dierent GHGEs and water use for
dierent starchy
carbohydrate sources
No comparison of diets Low quality Rice has the biggest impact on the
environment, followed by pasta and potatoes
Niles, M.T./2018 Global
Review on the possibilities for
mitigating climate change in the
food chain
No comparison of diets Low quality Non-ruminant meat consumption will lead
to lower GHGEs.
Van Kernebeek,
H.R.J./2014 Global
Review of 12 LCA studies to study
the environmental impact of
human diet
Human diets with varying
degrees of animal-source
food products
High quality
Higher intake of animal products led to a
higher intake of protein and higher intake of
animal-based protein has a bigger
environmental impact
John Reynolds,
C./2014 Global
Review of dietary advice from the
World Health Organization and its
environmental impact.
Diets with, reduced fat
consumption, reduced
animal-based food
consumption and increased
fruit and vegetable
consumption
High quality
Reducing animal-based food consumption
and increasing fruit and vegetable
consumption decreases the environmental
impact of consumption. Decreasing the
amount of dietary fat has little to no eect on
the environmental impact.
Cleveland, D./2017 USA What is the contribution of
plant-based diets to climate change.
Vegan, lacto-ovo-vegetarian
and omnivorous diet Low quality
Most plant-based diets have a much lower
GHGE than omnivorous diets, they are
important in preventing climate change. The
food industry needs to change and
motivating diet change is a huge challenge.
Tilman, D./2014. Global
Quantification of global diets in
connection with
environmental impact
Vegetarian, pescatarian,
Mediterranean and
omnivorous diet
Low quality Oer of dierent scenarios that could help
lower environmental impact of diets.
Gerber, P.J./2013. Global
What is contribution of livestock
production to global emission
of GHGs
No diets compared High quality
By improving technology, emissions coming
from livestock production could be reduced.
There is a need to make strategies for
developing countries.
Sustainability 2019,11, 4110 8 of 18
Table 3. Quality assessment criteria of included studies.
Low Quality Medium Quality High Quality
POPULATION AND SAMPLE:
No description of the sample selection procedure
No information on response rate or
participation rate
Sample size smaller than similar study or sample
size not given
POPULATION AND SAMPLE:
Non-random selection
Sample size the same as similar studies
Moderate to low response rate (less than 65%)
Population represents a limited, atypical or
selective subgroup of the population of interest
POPULATION AND SAMPLE:
Randomized control studies
Sample size larger than similar studies
Participation response rate high (65–100%)
Eligible population include entire population of
interest or a substantial portion of it
Valid (internal/external/construct)
MEASUREMENT:
Main variables or concepts are not defined
No discussion of variable operationalization
MEASUREMENT:
Poor definition of main variables/concepts or it
cannot be matched
Measurement of key concepts with variables that
do not make sense
MEASUREMENT:
Description is accurate and can be matched
Measurement of key concepts with variables that
make sense
ANALYSIS:
No presentation of means and
standards deviations
No discussion on missing data
No explanation of statistical techniques
ANALYSIS:
Standard deviations are not presented but
means are
Cases with missing data are removed from
the analysis
Explanation of statistical techniques, no inclusion
of the reasons to choose this technique
ANALYSIS:
Errors presented of means and standard
deviations/standard
Description of number of cases with missing data
and strategy to handle missing data
Explanation of statistical techniques, reason of
choosing and caveats
Following Research Connections Quantitative Quality Assessment Tool (https://www.researchconnections.org/content/childcare/understand/research-quality.html, retrieved at 16 January
2019).
Sustainability 2019,11, 4110 9 of 18
Table 4. Quality assessment criteria of included reviews.
Low Quality Medium Quality High Quality
No adequate formulation/description of
research question
No comprehensive literature search strategy
No adequate description of selected study designs
and justification of excluded articles
No performing of study selection/data extraction
in duplicate
No appropriate methods for statistical
combination of results
Missing report of potential sources of conflict
of interest
No discussion about the heterogeneity of the
studies in the results
Not well-defined description of research question
Literature search strategy is not comprehensive
Exclusion/inclusion criteria are not specific
Not well-defined study selection
Methods used for statistical combination of results
not adequately defined.
Conflict of interest is not well assessed
Insucient discussion of any heterogeneity
observed in results of review
Adequate formulation and description of
research question
Specific and predefined exclusion/inclusion criteria
Comprehensive/systematic literature search
strategy (if systematic review)
Independent review of titles, abstracts and
full-text articles
Using a standard method to appraise internal
validity of included studies
Assessment of publication bias and heterogeneity
List and description of included studies
Appropriate methods for statistical combination
of results
Following National Heart, Blood and Lung Institute Study Quality Assessment Tool. (https://www.nhlbi.nih.gov/health-topics/study-quality-assessment-tools, retrieved 16 January 2019).
Sustainability 2019,11, 4110 10 of 18
2.6. Data Analysis
Meta-analysis was not conducted in this systematic review because the measurement units and
eect sizes from dierent papers were not comparable. Some results from the papers are mentioned in
this review but no graphs, forest plots or pictures are presented here. Instead, a narrative synthesis has
been chosen.
3. Results
3.1. Selection of Articles and Studies
From four databases, 1246 results were obtained through the systematic literature research
(see Section 2.1). After removing 352 duplicates, 894 article titles were screened for relevant content,
yielding 68 articles deserving of closer reading were identified. After the full-text reading of these,
34 articles were excluded because their focus turned out to be tangential to our criteria. Thus, 34 articles
have been included in our systematic review. The screening process can be seen in Figure 1.
Sustainability 2019, 11, x FOR PEER REVIEW 10 of 18
Figure 1. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) diagram
showing the screening process. (http://www.prisma-statement.org)
3.2. Characteristics of Relevant Articles and Studies
Both the LOV and vegan diets will be referred to below as plant-based diets.
3.3. Environmental Impact of an Omnivorous Diet
The environmental impact of OMN production can be measured in several ways, of which we
focus on three: GHGEs, land use and water footprint.
3.3.1. Greenhouse Gas Emissions
Regarding the carbon footprint, red meat production normally generates 23% of agriculture-
related GHGEs [10]. Nitrous oxide (NO2), methane (CH4) and carbon dioxide (CO2) are considered as
GHGEs. GHGEs from agriculture induce changes in land use, especially deforestation, and are
expected to increase [11]. Therein, NO2 and CH4 from livestock account for 80% of all agricultural
GHGEs [2]. In the US, about 31% of CH4 emissions are generated from enteric fermentation (primarily
cows) and manure management. Emission per unit of livestock product varies with animal types.
Apparently, GHGE emission is much greater for ruminant animals such as cattle, sheep and dairy,
than for pigs or poultry [2]. It is estimated that about 44% of total global methane emissions are from
livestock, and that the output is dominated by beef production. On average, 43 kg of GHGEs released
during the production of each kg of beef. Of these 43 kg, approximately 22 kg are methane emissions.
This result does not include the GHGEs from the beef carcass [12].
Records identified through
database search (n = 1246)
Additional records identified
through other sources (n = 2)
Records after duplicates
removed
n = 894
Titles screened; records
included
(
n = 68
)
Full-text articles assessed for eligibility (n = 34)
Final selected
p
a
p
ers
(
n = 34
)
Duplicate records excluded (n = 352)
Full-text articles excluded (n = 34)
Nutrition- and health-
specific
Animal diets
Other types of diets
Farming specific
Microorganisms
Records excluded on the basis of title
(n = 826)
Figure 1.
Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) diagram
showing the screening process (http://www.prisma-statement.org).
3.2. Characteristics of Relevant Articles and Studies
Both the LOV and vegan diets will be referred to below as plant-based diets.
Sustainability 2019,11, 4110 11 of 18
3.3. Environmental Impact of an Omnivorous Diet
The environmental impact of OMN production can be measured in several ways, of which we
focus on three: GHGEs, land use and water footprint.
3.3.1. Greenhouse Gas Emissions
Regarding the carbon footprint, red meat production normally generates 23% of agriculture-related
GHGEs [
10
]. Nitrous oxide (NO
2
), methane (CH
4
) and carbon dioxide (CO
2
) are considered as GHGEs.
GHGEs from agriculture induce changes in land use, especially deforestation, and are expected to
increase [
11
]. Therein, NO
2
and CH
4
from livestock account for 80% of all agricultural GHGEs [
2
].
In the US, about 31% of CH
4
emissions are generated from enteric fermentation (primarily cows) and
manure management. Emission per unit of livestock product varies with animal types. Apparently,
GHGE emission is much greater for ruminant animals such as cattle, sheep and dairy, than for pigs or
poultry [
2
]. It is estimated that about 44% of total global methane emissions are from livestock, and
that the output is dominated by beef production. On average, 43 kg of GHGEs released during the
production of each kg of beef. Of these 43 kg, approximately 22 kg are methane emissions. This result
does not include the GHGEs from the beef carcass [12].
A great share of GHGEs are produced while food is in the supply chain, prior to final consumption.
Meat production generates far more GHGEs than production for vegan and LOV diets [
13
]. Another
study shows that, for each gram of beef protein consumed in the human diet, beef production requires
42 times more land use, 2 times more water use and 4 times more nitrogen, while it generates 3 times
more GHGEs than the staple plant foods [
12
]. Finally, a study from India indicates that mutton and
milk production contribute up to 23% and 35% of total local agricultural GHGEs, while all other food
production combined contribute 16% of it [14].
The production of livestock contributes heavily to the GHGEs. These GHGEs are responsible
for climate change and represent a real threat to our planet [
2
]. Another study estimates that meat
and dairy production processes account for 80% of all GHGEs from the food sector and 24% of total
GHGEs [2]. Meat and cheese production contribute around 40% to daily GHGEs [7].
It has been reported that ruminant animals emit the largest GHGs content per gram of protein and
kcal. Methane comprises the largest part of GHGs. Based on self-reported dietary patterns in the UK,
high meat consumers were responsible for 1.9 times and average meat consumers were responsible for
1.5 times more GHGEs than people on LOV diets [
12
], and 2.5 and 2 times more GHGEs, respectively,
than vegan consumers [
12
]. One study concludes that, if the beef, dairy, pork, poultry and eggs
consumed in an average European diet were reduced by 50% of and replaced with a 50% higher bread
intake, the amount of GHGEs emitted could be reduced by over one-third [15].
Dierences in the type of meat consumed can also be seen with multiple studies supporting an
increase in GHGEs in diets with high amounts of ruminant meat consumption [
16
,
17
].
Walker et al.
shows a comparison between environmental impact and the quality of the diet. It suggests that
a reduced consumption of animal-based products, and an increased vegetable intake show lower
GHGEs [
18
]. This statement is supported by multiple other studies with diets having an increased
environmental impact when increasing the animal-based food intake [
15
,
19
]. Diets with low meat and
low processed food consumption have lower GHGEs than their counterparts [20].
3.3.2. Land Use
Beef production requires a vastly larger amount of resources than the staple plant foods such as
rice, beans, and potatoes. One study [
2
] calculates that each kg of beef requires 163 times more land
use, 18 times more water use, 19 times more nitrogen and 11 times more CO
2
than 1 kg of rice or I kg
of potatoes. A second study [
7
] points out that meat production accounts for 39% of land use related to
human diet [
7
]. Moreover, compared to a LOV diet, the inputs needed to produce a non-vegetarian
diet are: 2.9 times more water, 2.5 times more primary energy, 13 times more fertilizer and 1.4 times
Sustainability 2019,11, 4110 12 of 18
more pesticides [
7
]. Furthermore, livestock farming uses 70% of agricultural land overall and a third of
arable land. As such, it plays a major role in CO
2
release and biodiversity loss from deforestation [
21
].
Not all types of meat have the same protein conversion eciency: chicken broilers have a
conversion eciency of 18%, while pork and beef have 9% and 6%, respectively [
22
]. This leads to a
dierence in land requirements between the animal-based protein sources, as more feed is required for
the same amount of animal-based protein. Compared with soybean as a protein source, it becomes
clear that land requirements are 6–17 times higher for animal-based protein [22].
3.3.3. Water Footprint
Livestock farming also generates water shortage. It largely uses finite irrigation water to supply
the increasing demand for livestock products [
21
]. It is reported that animal production accounts for
12% of all groundwater and surface water used for irrigation. Therefore, the total water footprint
equals 29% of the global agricultural production. One study determined that a diet containing a lower
volume of livestock products would result in reduced global water consumption. Water input depends
on the season and annual fluctuations in rainfall. More water is used for meat production than for plant
protein production. One study finds that the dierence between water inputs for animal protein vs.
plant protein is normally around a factor of 26; even when intensive irrigation is needed for plant-based
protein, animal protein production requires 4.4 times as much water [
22
]. A second study supports this
finding, stating that production for LOV diets has increased the water-scarcity footprint by 26% [
15
].
Nevertheless, it is dicult to make general scientific claims, since studies regarding metrics of water
use are based on very limited evidence [
23
]. Producing each kg of consumable beef requires about
13 kg of grain and 30 kg of hay, which in turn require 105,400 L of water [
24
]. Furthermore, 500–2000 L
of water are required to produce one kilogram of crop [
24
]. In terms of fossil energy used in the whole
process, the input needed to produce 1 kcal of plant protein is 2.2 kcal. For instance, one kg of protein
obtained from a plant-based source requires approximately 100 times less water than one kg of protein
from an animal origin [12].
3.4. Environmental Impact of a Vegetarian Diet
Gonz
á
lez-Garc
í
a et al. have studied variations in dietary patterns, including within vegetarian
diets, around the world. They note that some LOV diets include fish (pesco-vegetarian diet also found
in Denmark) and even meat on rare occasions (e.g., the “semi-vegetarian diet,” which is found in
India), and they find that the major dierences between these diets are associated with calorie intake,
specific food choice and national dietary guidelines [
8
]. Our review is limited to studies of LOV, which
does not include any type of meat, but does include animal products such as milk, cheese and eggs.
3.4.1. GHGE Impacts for Production of LOV Diets
It is widely believed today that plant-based diets (such as vegetarian and vegan) have a positive
impact on the environment and health, and they are indeed shown to have many benefits: safety for
human consumption, waste management, storage options and lower GHGEs than the animal-based
diets [
8
]. Although proteins from plant-based sources are considered to be of lower quality than
proteins from animal origin, a well-planned plant-based diet can be both nutritionally sucient and
environmentally sustainable [
25
]. Preferred sources of plant-based proteins are quinoa, amaranth,
wheat, pulses and soy-based products such as tofu and tempeh [
8
]. Milk, dairy products and eggs are
another important source of proteins in LOV diets. A study in Sweden compared beef with soybeans
and reports that per gram of protein, beef requires 18 times more energy and produces 71 times more
CO
2
than soybeans [
12
]. A study of dierent dietary patterns in the UK determined that OMN had
causes 4 times higher GHGEs per kcal than LOV. A vegan diet was not studied separately, but the
authors conclude that dairy accounts for about 40% of GHGEs associated with production for LOV
diets [12].
Sustainability 2019,11, 4110 13 of 18
Vegetarians often use meat substitutes, but the dierent substitutes carry very dierent
environmental implications. Depending on what substitute is used, the associated reduction in
meat consumption can result in no positive eect on the environment at all or even trigger a negative
trend [
7
]. One study indicates that, despite the likelihood that more consumers of vegetarian diets
will lead to reduced GHGEs, this outcome is not guaranteed. For instance, substituting cheese for
chicken in a diet could result in higher aggregate GHGE production if the energy and nutrient content
is not considered and production of the vegetarian substitute is associated with higher GHGEs [
26
].
Other important factors are transportation (especially long-distance), deep-freezing, and some specific
horticultural practices, all of which can lead to higher environmental damage than locally produced
organic meat [22].
One of the most important issues in environmental studies are GHGEs, most notably carbon
dioxide. Estimates of CO
2
emissions vary widely from study to study. The carbon footprint in Italy
was found to be 2.60
±
0.62 kg CO
2eq
per person, per day [
27
]. Another study presented carbon dioxide
in terms of calories and calculated that the total amount produced by vegetarians and semi-vegetarians
for average calorie intake of 2000 kcal was 3.81 kg CO
2eq
[
7
]. Nitrogen gasses are also very important
factor. Nitrogen is usually added through fertilizers to improve crop yields. Its negative impact
results in acid rain, biodiversity loss, stratospheric ozone depletion, climate change, eutrophication and
smog [
25
]. Reported nitrogen footprint for the vegetarian diet is 18.3
±
2.4 kg per capita per year [
25
].
3.4.2. Land Use for Production of LOV Diets
The land used to produce protein from plants is much lower than the production of proteins
from animals. For example, for soybean production, the requirements are a factor of 6–17 larger for
production of meat proteins (depending on the type of meat) [
22
]. In previous years, about 0.5 hectare
(ha) of cropland was used in omnivorous diet and less than 0.4 ha for vegetarian-based diet [
24
].
It should be taken into account that, in order to produce meat, animals need to be fed plants. Another
important thing is how much of animal-based products are incorporated in the vegetarian diet. If the
diet is high-fat, more land is required [
27
]. A study from the USA by Blackstone et al. found that the
vegetarian diet has the lowest GHGEs and is favorable when it comes to sustainability [28].
Overall, the consumption of animal products which presents a secondary production is much less
ecient than eating plants which directly convert solar energy to food energy (primary production) [
12
].
3.4.3. Water Impact of LOV Diets
The water-related eects of agricultural production for LOV diets essentially parallel the discussion
in Section 3.3.3 above, and need not be repeated here.
3.5. Environmental Impact of a Vegan Diet
Multiple studies have shown that diets rich in vegetables have a better influence on the environment
than those rich in meat. It is therefore proposed, both as a conclusion of this systematic review and
of several studies reviewed herein, that the vegan diet is the most sustainable diet in terms of
environmental footprint e.g., [8].
One analysis shows that high meat eaters in the UK had 1.9 times and medium meat eaters had
about 1.5 times more of GHGEs than an LOV, and that the food consumed by high meat eaters is
associated with 2.5 times more GHGEs that that consumed by a vegan, and even average meat eaters
are responsible for twice as many GHGEs [12]. A second study reports similar conclusions, based on
the number and composition of 2000 kcal consumed in various diets: 7.19 kg for high meat eaters
(100 g of meat per day or more), 5.63 kg for medium meat-eaters (50–99 g of meat per day), 4.67 kg for
low meat-eaters (less than 50 g per day), 3.81 kg for vegetarians, and 2.89 kg for vegans [7,29].
Most studies demonstrate that, in general, vegan diets are the most environmentally sensitive.
However, this some authors would disagree and would suggest that 100% plant-based food consumers
may need larger volumes of food than vegetarians to achieve the same energy intake [
27
]. The main
Sustainability 2019,11, 4110 14 of 18
reason, however, is that many vegans replace animal-based products with processed plant-based meat
and dairy substitutes (e.g., seitan burger and soy yoghurt) instead of consuming the unprocessed,
plant-based nutritious foods that are relatively favored in many LOV diets. For example, one study
finds that vegetarians in the USA substitute meat mostly with dairy products and, to a lesser extent,
with fruits, vegetables and oil [
12
], that is, with the foods that, aside from meat, have the most
deleterious environmental impacts. These choices are described as the main reason why GHGEs
associated with plant-based diets are not as low as they should be, and also highlights the importance
of reducing dairy consumption in all diets. When dairy is reduced or eliminated, as it is LOV and
vegan diets, these two diets produce 33% and 53% lower emissions for the same number of calories
(2000 kcal) as the average US diet [
12
]. The production of vegan cheese-like spread (lupine-based
cheese) requires one-fifth of the land required for cheese from cow’s milk: 0.02 ha of land per 100 kg,
compared with 0.1 ha of land per 100 kg of cow-milk-based cheese [
22
]. Consuming legumes for
protein instead of meat has a beneficial environmental impact, and it is also a lot cheaper [25].
A life cycle assessment analysis suggests that, if beans were substituted for beef, then 692,918 km
2
of US cropland could be freed up for other uses and GHGEs from this land would decrease by 74% [
30
].
Perignon et al. states that if a replacement of all meat and dairy products by plant-based food would
take place, land use could be reduced by 50% [7].
A large part of plant-based diets consists of fruits and vegetables. The origin and mode of
transport of fruits and vegetables has a big impact on their contribution to GHGEs, which can vary a
lot. Whether they are produced in heated greenhouses or not has a huge eect on their GHGEs [
31
].
Locally grown and sold fruits and vegetables have been assumed to be more environmentally friendly.
However, it has been shown that this might not be the case. A study shows that when customers in the
UK choose to drive more than 7.4 km to buy locally grown fruits and vegetables, the GHGEs would be
higher than if a large-scale delivery system transported the food closer to the customer [12].
Nonetheless, one study estimates that a complete switch to a vegan diet could result in reductions
of 17% for CO
2
, 21% for NO
2
and 24% for CH
4
[
2
]. Among the three diets, the vegan diet makes the
lightest demands on the global water supply, requiring 14.4% less freshwater and 20.8% less ground
water than the omnivorous diet [12].
4. Discussion
The general outcome that can be concluded from this review is that the more plant-based a diet is,
the more sustainable. However, in some cases, the vegan diet may not have a lower environmental
footprint than LOV. The reason for this is that vegans tend to replace animal-based products in their
diet by industrially, highly processed plant-based meats and dairy substitutes [27].
This literature review looked into three main indicators of the environmental impact caused by
three types of human dietary patterns: GHGEs, the use of land and the water footprint. The studies
reviewed here were selected by use of a specific inclusion and exclusion process, which is explained
in the Methods section. Studies that focus directly on environmental impacts of human diets were
considered most relevant for this review.
This research involves some limitations. First of all, the method used allowed for only one
search, with the same keywords in each database. As a result, certain articles that are relevant to
the subject of the paper may have been overlooked. The choice of search words could also have
placed undesired limits on the results generated. Keywords such as ‘environmental assessment’ and
‘life cycle assessment’ for example, have not been included in the literature search. For this reason,
some high-quality studies are inevitably missing from this paper. Secondly, all papers that survived
through the title screening were carefully examined by all authors before the final exclusion took
place, to ensure no loss of data (see Section 3.1). Still, the possibility remains that the collective
view of the authors might be dierent from that of a reader. Besides these technical limitations, this
review is limited to assessing the relationship between three diets and only three among the many
environmental factors that are aected by dietary choices. We justify this choice on the basis of our
Sustainability 2019,11, 4110 15 of 18
claim that GHGEs, land stress and water supply are the biggest causes of environmental damage,
broadly understood. Obviously, more environmental factors could have been taken into account, but
doing so would have risked drawing attention away from our main purpose. A final notable limitation
is the geographic scope of the papers included. Most of the papers are from high-income countries, and
several others including global data. Thus, we are unable to assess the environmental consequences of
food production in low-income countries. We are sensitive that, due to variations in input intensity and
production eciency, for example, these consequences may dier markedly from those in high-income
countries [31].
A quality assessment table for the included studies can be found in the method section. This table
shows what terms each report needs to meet in order to be classified as low, medium or high quality.
The assessed quality of each paper is listed in Tables 1and 2. The quality assessment further allows
to state that the narrative synthesis performed in this paper is sustained by a majority of papers and
reviews with high or medium quality.
Although it was not the main focus of this research, food waste is another important contributor to
climate change, as the production of every kg of unconsumed food entails has the same environmental
impact as a kg of consumed food. As with consumption, plant-based diets are also more climate
friendly when they are wasted. One study, conducted in the US, finds that fruits and vegetables which
comprise 33% of food waste, account for only 8% of carbon dioxide emissions. Animal-based foods,
by contrast, account for 33% of food waste by mass and 74% of carbon dioxide emissions. Ruminant
meat accounts for 3% of waste by mass and 31% of emissions from waste. Thus, in order to prevent
increased agricultural expansion, must be reduced [
12
]. Besides food waste, it is also important to note
that food miles contribute heavily to the GHGEs associated with a specific diet. A plant-based diet that
requires products from all over the world will have a footprint equivalent to a moderate meat eater.
Reduction of GHGEs per household on a fully local diet is equivalent to 1600 km/year driven and
therefore an important factor in mitigating GHG from diets [
4
]. A British study on the environmental
impact of food transport, in this case on the eect of potatoes, rice and pasta on GHGEs and water use,
shows that the environmental impact of transporting food products from the same group can vary
significantly [32].
According to the results presented here, it is very clear that the vegan diet has the least
environmental impact in comparison with LOV and OMN diets. Vegans do not consume any animal
products and thus are able to avoid all the negative environmental impacts that these animal-based
products bring. It is very important to note that vegan products that are highly processed, high in fat, or
have to be transported long distances may have considerably larger environmental footprints. Possible
negative impacts of LOV and vegan diets on human health should also be assessed. Insuciencies
of vitamin B12, calcium, iron and other nutrients could appear if diets are not well balanced [
33
].
Still, a 2014 study demonstrates that synergies can be developed between a healthy diet and an
environmentally sustainable food pattern [34].
Healthy OMN diets come in many forms; some currently popular variations include the Atlantic
diet, the Mediterranean diet and the Nordic diet. All of these diets dier—both from each other
and from other OMN diets that include a higher proportion of beef products—in their animal-based
protein sources and the amount of animal-based protein consumed. This complicates eorts to estimate
precisely the environmental impact of the OMN diet conceptualized as a discrete entity. Results show
that the OMN diet has the highest environmental footprint mainly due to the consumption of animal
flesh, dairy products and eggs. In very rare cases it is possible for an OMN consumer to be more
sustainable than a consumer following a LOV, e.g., when a LOV diet including large amounts of highly
processed foods, imported from afar is compared with an OMN diet that follows national dietary
recommendations that urge moderate meat, dairy and eggs consumption mostly from local sources.
If consumers would follow current dietary recommendations e.g., for Mediterranean and Nordic
diets, their corresponding weekly GHGEs resulting of the consumption of food rich in protein (meat,
legumes, milk, etc.) would have a comparable and similar impact on the environment as consumption
Sustainability 2019,11, 4110 16 of 18
of vegetables and fruits [
1
]. Additionally, adherence to recommendations will have similar impact to
plant-based diets (vegan or vegetarian) as the common denominator for all recommendations is to
increase consumption of foods of plant origin while reducing those of animal origin [
35
] or highly
processed [36].
Even though results of this systematic review point to a 100% plant-based diet such as the vegan
diet as the best solution for the future, such changes are hard to achieve at population level if the
recommendations clash with cultural expectations and norms. For example, linear programing can be
used to identify a dietary pattern that is healthy and similar in its environmental impact to the vegan
diet, but based on the current foods consumed by the population. This method could identify possible
diets with the same impact on the environment as vegan diet but with lesser change from the original
diet in other cultural contexts [25,37].
5. Conclusions
The present review based on 16 papers of high quality, 9 of medium quality and 9 of low
quality, shows a consistent and clear dierence between the environmental impacts of dierent diets.
The GHGEs dier considerably per diet, with a vegan diet having the lowest CO
2eq
production per
2000 kcal consumed.
The environmental impact on land and water also diers among the three diets. Water use is
higher in LOV and OMN diets, due to the use of animal-based proteins. In short, the more animal
protein consumed in a diet, the higher the water use will be. A diet pattern based only of foods of
plant origin oers the greatest potential for reduced global water consumption. Furthermore, livestock
farming uses 70% of agricultural land overall and a third of arable land. On this account, a vegan diet
has the lowest land use and water use of the three dierent diets.
In conclusion, a 100% plant-based diet (e.g., vegan) has the least environmental impact. Therefore,
this review further supports the wealth of existing evidence supporting a transition to a more sustainable
food system and food consumption. Still, it is important to note that, in order for a 100% plant-based
diet to be sustainable, local products that minimize the environmental impact of transport should be
preferred. Further research should focus on the GHGEs from dierent types of plant-based foods, and
modified omnivorous diets with the same environmental impact as the impact from vegan diet.
Author Contributions:
Conceptualization, all authors; methodology, B.C.C., J.R.v.d.V., K.G., H.G.E., I.K.; software,
B.C.C.; formal analysis and data extraction, B.C.C., J.R.v.d.V., K.G., H.G.E., I.K.; writing—original draft preparation,
B.C.C., J.R.v.d.V., K.G., H.G.E., I.K.; writing—review and editing, B.C.C., F.J.A.P.-C.; visualization, B.C.C., F.J.A.P.-C.;
supervision, F.J.A.P.-C.
Funding: This research received no external funding.
Conflicts of Interest: The authors declare no conflicts of interest.
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2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
article distributed under the terms and conditions of the Creative Commons Attribution
(CC BY) license (http://creativecommons.org/licenses/by/4.0/).
... The cultivation of plants for food products has relatively low environmental impact and is considered more sustainable than animal products (Pimentel and Pimentel, 2003), (Chai et al., 2019), although processed plant-based foods can have high environmental impact, especially relative to their nutritional content (Clune et al., 2017), (Berardy, 2020), (Smedman et al., 2010), species and type of farming (Clune et al., 2017), (Leinonen and Kyriazakis, 2016), (Lynch, 2019), (Samuel-Fitwi et al., 2013), (Eriksson et al., 2005). ...
... For example, the lectins in soybeans were found to harm intestines of salmonids (Dersjant-Li, 2002), (Hendriks et al., 1990). Highly processed plant-based foods for human consumption can exhibit a larger environmental impact than animal products, especially relative to their nutrient content (Chai et al., 2019), (Smedman et al., 2010), (González et al., 2011). Further options to expand the sustainability of fish feed could include the use of technologies such as genetic manipulation of plants to minimize their anti-nutritive content, reduce pesticide reliance, and increase resistance to extreme weather (Kwon et al., 2001), (Šamajová et al., 2013), , (Muzquiz et al., 2012), (Grover u. a., 1998). ...
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Fish from aquaculture has the ability to meet consumer demand for a healthy and sustainable diet. The environmental footprint of fish farming depends largely on the method of production. Trout production in the temperate climate zone in open flow-through systems using the natural hydraulic gradient of streams as freshwater supply is energy efficient relative to more intensive systems. To investigate the possibility of reducing global warming potential, eutrophication potential, acidification potential, and ozone layer depletion associated with rainbow trout (Oncorhynchus mykiss) production in southern Germany, a comprehensive dataset collected under the typical farm framework was analyzed and a cradle-to-gate life cycle assessment was conducted. The impact of feed source (plant- and fish-based) was analyzed, as well as that of photovoltaic panels installed over the production area. Calculated emissions per kg fish live weight were 1.18 kg CO2eq, 7.89e⁻⁸ kg CFC11eq, 0.00552 kg SO2eq, and 0.0257 kg PO4eq. Full covering of the production area with photovoltaic panels, compared to the current ∼40% coverage, was estimated to provide a reduction of 1.04 kg CO2eq, resulting in emissions of 0.773 kg CO2eq per kg fish live weight. Feeds containing 35% and 61.8% fishmeal were associated with lower emissions compared to 100% plant-based, with a reduction in GWP of 0.79 kg CO2eq in the 61.8% fishmeal variant. Results showed that the use of photovoltaic panels can significantly reduce rainbow trout culture impact on the analyzed environmental impact categories. Feed containing fishmeal has a lower impact on the analyzed environmental impact categories. Alternatives such as insect meal and sustainable plant alternatives should be the focus of future research.
... Likewise, the EU's Farm to Fork Strategy explicitly includes the promotion of sustainable diets, in addition to the objective of promoting sustainable practices in production and food processing [7]. The more a diet is based on plant-based rather than animal-based products, the lower that diet's carbon footprint (CF) [8,9]. When comparing protein sources, all plant-based foods were found to underscore GHGEs of animal-based products [6]. ...
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The food system plays a crucial role in mitigating climate change. Even if fossil fuel emissions are halted immediately, current trends in global food systems may prevent the achievement of the Paris Agreement's climate targets. The high degree of variability and uncertainty involved in calculating diet-related greenhouse gas emissions limits the ability to evaluate reduction potentials to remain below a global warming of 1.5 or 2 degrees. This study assessed Western European dietary patterns while accounting for uncertainty and variability. An extensive literature review provided value ranges for climate impacts of animal-based foods to conduct an uncertainty analysis via Monte Carlo simulation. The resulting carbon footprints were assessed against food system-specific greenhouse gas emission thresholds. The range and absolute value of a diet carbon footprint become larger the higher the amount of products with highly varying emission values in the diet. All dietary pattern carbon footprints overshoot the 1.5 degrees threshold. The vegan, vegetarian, and diet with low animal-based food intake were predominantly below the 2 degrees threshold. Omnivorous diets with more animal-based product content trespassed them. Reducing animal-based foods is a powerful strategy to decrease emissions. However, further mitigation strategies are required to achieve climate goals.
... A vegan diet has less environmental impact than vegetarian and omnivorous diets [79]. Greater consumption of animal-derived food products has a more significant estimated impact on the environment than consuming plant-derived products with a lower estimated environmental impact [80]. ...
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Global warming is a problem that threatens humanity, with livestock being one of the causes. A systematic literature review was carried out by using some appropriate elements of the PRISMA statement to identify disciplines that work to mitigate the effects of the livestock industry by organizing them according to their approach to addressing this problem. The main objective is to find information and classify the disciplines, papers, literature review methodologies, research gaps, authors, and journals developing the management of the cattle supply chain. This paper could analyze and mitigate the adverse effects on society and the environment generated by the industry, organizing them according to their approach. Twenty databases were consulted between March and May 2020, from which 146 review documents were chosen. The papers reviewed were published between 2003 and 2020. The eligibility criteria for selection were open access to the full text, publication in an indexed journal, and a focus on any discipline related to cattle. The unselected papers did not have DOIs or duplicates, and those focused on other types of meat and book chapters. Subsequently, the information in the selected papers was described and consolidated, and these papers had 602 authors and were from 99 journals. Next, a discipline categorization was proposed. The results were organized, showing that among all the analysis criteria, the category of veterinary medicine had the best results in terms of indicators; therefore, additional research is needed on the other disciplines, especially in culture, technology, management, quality control, tanneries, and transportation, as there was less research within these disciplines. It is recommended that research on a mix of the different proposed disciplines be conducted. The proposed categorization’s main contribution is to identify and group the cattle supply chain’s different disciplines and the definition of research gaps organized under a structure organizational management model. Finally, a multicriteria selection methodology must be used that prioritizes the discipline categories proposed in this review to guide future research.
... corresponds to a portion of just 10.9 g of beef, or 49.0 g of pork. Thus, our analysis aimed to assess the magnitude of food selections among different food items within the same food category on final environmental impact, finding a non-negligible effect on final CF, but largely corroborated the wider literature supporting the lower CF associated with more plant-based diets, in comparison to more meat-based ones [37,38]. The present study has some strengths worth noting. ...
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The definition of a healthy and sustainable diet is nowadays considered pivotal, but data related to environmental outcomes are still debated. In this study, we compared the carbon (CF) and water footprints (WF) of an Italian-Mediterranean (EAT-IT) dietary pattern designed on the “Planetary diet”, with a pattern based on the Italian Dietary Guidelines (IDG). The influence of different food categories and food choices on environmental impact was assessed. To this aim, weekly dietary patterns were developed, considering food categories and related portions and frequencies of consumption. Results show that the EAT-IT dietary pattern, compared to the IDG, had a significantly lower CF (2.82 ± 1.07 and 3.74 ± 0.92 kg CO2/day, respectively) but not WF. Protein-rich foods were the main contributors to CF and WF in both dietary patterns. The increased substitution of frozen instead of fresh foods, imported instead of local fruits, greenhouse-grown instead of seasonal vegetables, and processed legume-based foods instead of unprocessed legumes caused an increasing worsening of the CF in both patterns, but with different magnitudes. Our analysis indicated that the EAT-IT dietary pattern can be considered sustainable for CF, but individual choices are likely to largely affect the final environmental outcomes.
... We built our study on a specific environmental challenge: meat consumption. Given that meat consumption explains a significant part of greenhouse gas emissions due to human activity (Tukker and Jansen, 2006;Aubin, 2014), reducing our dietary intake of meat would contribute considerably to the fight against climate change (Salonen and Helne, 2012;Chai et al., 2019). In France and most western societies, however, diets with low or no meat intake are rare (Sanchez-Sabate and Sabaté, 2019) and there is often a strong national fightback when it is the case (Cholez, 2021;Schittly, 2021). ...
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A large body of research has explored opportunities to mitigate climate change in agricultural systems; however, less research has explored opportunities across the food system. Here we expand the existing research with a review of potential mitigation opportunities across the entire food system, including in pre-production, production, processing, transport, consumption and loss and waste. We detail and synthesize recent research on the topic, and explore the applicability of different climate mitigation strategies in varying country contexts with different economic and agricultural systems. Further, we highlight some potential adaptation co-benefits of food system mitigation strategies and explore the potential implications of such strategies on food systems as a whole. We suggest that a food systems research approach is greatly needed to capture such potential synergies, and highlight key areas of additional research including a greater focus on low- and middle-income countries in particular. We conclude by discussing the policy and finance opportunities needed to advance mitigation strategies in food systems.
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In light of the considerable pressure exerted by food production on the environment, the assessment of the environmental burdens of dietary choices has recently gained interest among the scientific community. Several studies based on life cycle thinking approach agreed that a transition from an omnivorous to either a vegan or vegetarian diets would reduce the environmental impact associated with food consumption. The majority of the studies set the system boundaries up to the retail, excluding the consumption phase and generally do not account for uncertainties. The aim of the present study was to assess how personal consumption choices and behaviour can affect the greenhouse gas emissions generated by three balanced dietary patterns (omnivorous, vegetarian and vegan), defined on the basis of nutritional recommendations for an average Italian man. It took into consideration the uncertainties associated with three elements, namely the greenhouse gas emissions due to the production of the food items, the emissions associated with cooking and the food wasted by consumers. The results of the study highlighted that, despite the higher share of greenhouse gas emissions of the supply chain stages prior to consumption (66%–74% of the total emissions), domestic behaviours have an important influence of the total greenhouse gas emissions of the diet, which can offset the lower GHG emissions due to the choice of vegetable-origin foods. In fact, 15%–21% of the total emissions are associated to the cooking phase and 11%–13% to the food waste generation. Therefore, this study remarks the importance of adopting a cradle to grave perspective when assessing the environmental burden of dietary patterns and emphasises the central role of consumers in the definition of low GHG-emitting dietary patterns.
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Production and consumption of food has a significant effect on climate change. The effect of different consumption habits on the environment should not be under estimated, as there are different studies that mention the environmental impact associated with different foods, especially those of animal origin. The analysis of the Atlantic diet (AD), as the most common dietary pattern in Northwestern Spain, serves as an example of a diet with a high consumption of local, fresh and seasonal products, home cooking and low-processed foods. The evaluation was carried out by quantifying the carbon footprint following the Life Cycle Analysis methodology and identifying its nutritional quality according to the value of the Nutrient-rich Dietary index (NRD9.3.). According to the main results, the consumption of livestock products and shellfish is responsible for most GHG emissions (70% of the total). The basic ingredients of the AD, such as vegetables and legumes, make a relatively minor contribution (with an impact of 30% of the total) to the total carbon footprint of 3.01 kg CO2eq·person-1·day-1. As regards nutritional quality, AD has a high nutritional score (474), mainly due to the low intake of sodium, added sugars and saturated fats (nutrients to be limited in healthy diets). In general, both the carbon footprint and the nutritional index score are consistent with those of other studies on the Mediterranean diet, which has been recognised as beneficial. Therefore, it can be concluded that the AD may be recommended from a nutritional and environmental point of view, mainly due to the high intake of fish and vegetables. The communication of this valuable environmental and nutritional information to consumers should be taken into account when considering strategic actions for the adoption of healthy and sustainable dietary patterns.
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Apart from industrial activities, our eating habits also have a significant environmental cost associated with crop cultivation, manufacturing processes, packaging, refrigeration, transport cooking and waste management. In a context of growing social awareness of the role of different dietary choices in the environment, the review of different alternatives on the road to a healthy and sustainable diet should integrate relevant information on the nutritional quality of different eating habits. Since dietary choices have an effect on environmental sustainability and human health, a literature review on different dietary choices has been conducted to determine the differences in carbon footprint and nutritional quality identifying the main hotspots trying to give advice towards the identification of sustainable diets. After applying a set of criteria for reference selection, 21 peer-reviewed studies have been analysed in detail, allowing the comparison of 66 dietary scenarios. We identified that the so-called Mediterranean and Atlantic diets present high nutritional scores and low carbon footprints. On the contrary, the dietary choices identified in northern and Western Europe, as well as in the United States, have the highest carbon footprints, highlighting the contribution of dairy products as a basic source of high-quality nutrients and protein. Broadly speaking, dietary choices rich in vegetables (e.g., vegan, vegetarian as well as Indian and Peruvian) have a better environmental profile than those rich in meat (mainly ruminant meat). In line with these findings, the shift in meat consumption habits from beef and veal to chicken, pork and poultry, the introduction of alternative foods to animal protein (e.g. quinoa) and the consumption of olive oil as a major source of vegetable oil may be compatible with a healthier and more environmentally friendly diet. However, the complete elimination of meat and dairy products from the daily diet may not be feasible in case the supply of some micronutrients (e.g., calcium and vitamin D) is not guaranteed. Limitations were identified in the consulted studies related to the consideration of the different system boundaries, as well as underlying uncertainties related to data sources. Therefore, efforts should be made to develop consistent and agreed-upon methods for estimating both the carbon footprint and nutritional quality scores.
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Diets have become an increasingly important driver of environmental pressures due to greenhouse gas emissions (GHGE), land use and other indicators of environmental impact associated with food production. In the present study we analyse the GHGE and the potential climate change mitigation through dietary changes in a country with high beef consumption, to contribute to the debate on what constitutes a healthy and sustainable diet. Data collected in the National Survey of Household Income and Expenditure 2012/2013 was used to estimate the composition of the current diet in Argentina, and four dietary scenarios were developed following the nutritional recommendations of the National Dietary Guidelines (NDG). We found that the GHGE related to the current Argentinian diet are very high (5.48 ± 1.71 kg CO2-eq/person/day), with beef production contributing to the largest share of emissions (71%). The NDG suggest a 50% reduction of total daily intake of meats compared to current consumption, which, if adopted, would reduce GHGE in 28%, to 3.95 ± 0.96. Further reductions in GHGE appear possible while maintaining a healthy and balanced diet. The scenarios with non-ruminant meats and lacto-ovo vegetarian lead to similar GHGE, 2.11 ± 0.41 and 1.73 ± 0.37 kg CO2-eq/day/person, respectively; and the vegan diet results in the lowest, 1.47 ± 0.34 kg CO2-eq/day/person. Indicators for nutrient efficiencies were also developed. All nutrient efficiencies decreased in diets with bovine meat with respect to the non-ruminant, vegetarian and vegan ones. The results of this study therefore indicate that a set of dietary changes would significantly contribute to lower GHGE. Argentina's NDG should include the environmental impacts of food consumption with the aim of raising consumer awareness.
Chapter
Diet change toward more plant-based diets is very likely critical for avoiding catastrophic environmental damage, including climate change. This is primarily because animal foods contribute such a large proportion of food system climate impacts, which in turn contribute a large portion of the total human impact. However, our understanding of the details of the impact of different diets is also limited due to lack of data, uncertainty, and differences in methodology. We address three key questions that need to be answered for an informed discussion of the climate impact of plant-based diets: How can diets be measured to assess their climate impact? How can climate impact be measured and attributed to diet? What do we know about the relative climate impact of different plant-based diets?.