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Plant-Based Meats, Human Health, and Climate Change


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There is wide scale concern about the effects of red meat on human health and climate change. Plant-based meat alternatives, designed to mimic the sensory experience and nutritional value of red meat, have recently been introduced into consumer markets. Plant-based meats are marketed under the premise of environmental and human health benefits and are aimed appeal to a broad consumer base. Meat production is critiqued for its overuse of water supplies, landscape degradation, and greenhouse gas emission, and depending on production practices, environmental footprints may be lower with plant-based meat alternatives. Life-cycle analyses suggest that the novel plant-based meat alternatives have an environmental footprint that may be lower than beef finished in feedlots, but higher than beef raised on well-managed pastures. In this review, we discuss the nutritional and ecological impacts of eating plant-based meat alternatives vs. animal meats. Most humans fall on a spectrum of omnivory: they satisfy some nutrient requirements better from plant foods, while needs for other nutrients are met more readily from animal foods. Animal foods also facilitate the uptake of several plant-derived nutrients (zinc and iron), while plant nutrients can offer protection against potentially harmful compounds in cooked meat. Thus, plant and animal foods operate in symbiotic ways to improve human health. The mimicking of animal foods using isolated plant proteins, fats, vitamins, and minerals likely underestimates the true nutritional complexity of whole foods in their natural state, which contain hundreds to thousands of nutrients that impact human health. Novel plant-based meat alternatives should arguably be treated as meat alternatives in terms of sensory experience, but not as true meat replacements in terms of nutrition. If consumers wish to replace some of their meat with plant-based alternatives in the diet (a “flexitarian approach”) this is unlikely to negatively impact their overall nutrient status, but this also depends on what other foods are in their diet and the life stage of the individual.
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published: 06 October 2020
doi: 10.3389/fsufs.2020.00128
Frontiers in Sustainable Food Systems | 1October 2020 | Volume 4 | Article 128
Edited by:
Carla Pinheiro,
New University of Lisbon, Portugal
Reviewed by:
Ali Saadoun,
UDELAR, Uruguay
Jean-Francois Hocquette,
INRA UMR1213 Herbivores, France
Stephan van Vliet
Specialty section:
This article was submitted to
Agroecology and Ecosystem Services,
a section of the journal
Frontiers in Sustainable Food Systems
Received: 23 April 2020
Accepted: 22 July 2020
Published: 06 October 2020
van Vliet S, Kronberg SL and
Provenza FD (2020) Plant-Based
Meats, Human Health, and Climate
Front. Sustain. Food Syst. 4:128.
doi: 10.3389/fsufs.2020.00128
Plant-Based Meats, Human Health,
and Climate Change
Stephan van Vliet 1
*, Scott L. Kronberg 2and Frederick D. Provenza 3
1Duke Molecular Physiology Institute, Duke University Medical Center, Durham, NC, United States, 2Northern Great Plains
Research Laboratory, USDA-Agricultural Research Service, Mandan, ND, United States, 3Department of Wildland
Resources, Utah State University, Logan, UT, United States
There is wide scale concern about the effects of red meat on human health and climate
change. Plant-based meat alternatives, designed to mimic the sensory experience and
nutritional value of red meat, have recently been introduced into consumer markets.
Plant-based meats are marketed under the premise of environmental and human health
benefits and are aimed appeal to a broad consumer base. Meat production is critiqued
for its overuse of water supplies, landscape degradation, and greenhouse gas emission,
and depending on production practices, environmental footprints may be lower with
plant-based meat alternatives. Life-cycle analyses suggest that the novel plant-based
meat alternatives have an environmental footprint that may be lower than beef finished
in feedlots, but higher than beef raised on well-managed pastures. In this review, we
discuss the nutritional and ecological impacts of eating plant-based meat alternatives vs.
animal meats. Most humans fall on a spectrum of omnivory: they satisfy some nutrient
requirements better from plant foods, while needs for other nutrients are met more
readily from animal foods. Animal foods also facilitate the uptake of several plant-derived
nutrients (zinc and iron), while plant nutrients can offer protection against potentially
harmful compounds in cooked meat. Thus, plant and animal foods operate in symbiotic
ways to improve human health. The mimicking of animal foods using isolated plant
proteins, fats, vitamins, and minerals likely underestimates the true nutritional complexity
of whole foods in their natural state, which contain hundreds to thousands of nutrients
that impact human health. Novel plant-based meat alternatives should arguably be
treated as meat alternatives in terms of sensory experience, but not as true meat
replacements in terms of nutrition. If consumers wish to replace some of their meat with
plant-based alternatives in the diet (a “flexitarian approach”) this is unlikely to negatively
impact their overall nutrient status, but this also depends on what other foods are in their
diet and the life stage of the individual.
Keywords: plant-based meat, sustainability, meat, nutrition, diet, climate change, vegetarian and non-
vegetarian diet
Novel plant-based meat alternatives such as the ImpossibleTM Burger and Beyond Burger R
are becoming increasingly popular with consumers and have attracted considerable financial
investments, media coverage, and research attention. Their success has led other food companies
to produce their own versions of these products. The plant-based meat market is growing rapidly
van Vliet et al. Plant-Based Meat Alternatives and Meat
and is expected to be worth more than $30 billion by 2026
(Statista, 2020.1). Meat alternatives, formulated to mimic the
taste and sensory experience of red meat, are marketed for
their ecological and health benefits compared to red meat.
While ingredients vary amongst plant-based meat products,
the new generation of alternatives is formulated specifically
to mimic the sensory experience and macronutrient content
of meat by using plant proteins (e.g., soy, pea, potato,
rice, wheat, and/or myocprotein), fats (e.g., canola, coconut,
soybean, and/or sunflower oil), and other novel ingredients
(e.g., soy leghemoglobin, red-colored vegetable extracts, and/or
flavoring agents). Additionally, various vitamins and minerals
that are naturally found in meat (e.g., zinc, iron, and B-
vitamins) are increasingly added to plant-based meats (Curtain
and Grafenauer, 2019). By doing so, novel plant-based meat
alternatives are able to closely mimic the Nutrition Facts
panels of meat (Figure 1). Plant-based meats may also reduce
apprehensions regarding the effects of red meat on human health
and climate change, and fit with recommendations for dietary
transitions toward reduced meat consumption and increased
plant-based diets, particularly in Western civilization (Godfray
et al., 2018; Graça et al., 2019). Moreover, the novel meat
alternatives are particularly targeted at flexitarians—omnivores
who are looking to eat less animal foods. Given the close
resemblance of novel plant-based meat alternatives to meat, we
will discuss the nutritional and ecological impacts of eating plant-
based meat alternatives vs. animal meats, while also providing
a broader discussion of the ecological and health effects of
replacing animal foods with plant foods.
Omnivory or Optionality?
A core question in discussions of replacing animal foods with
plant-based substitutes is whether plant-based substitutes can
adequately satisfy nutrition requirements. As omnivores, humans
tend to satisfy some nutrients more readily from plant sources
while other nutrient requirements are generally better satisfied
by consumption of animal foods. For example, our vitamin C
and magnesium requirements are much more readily fulfilled
by plant than animal foods. In addition, plant-based diets are
often higher in folate, manganese, thiamin, potassium, and
vitamin E (Davey et al., 2003). Plant foods also provide a wide
array of phytochemicals that have important regulatory roles in
human health (Briskin, 2000). The findings of extensive in vitro
and in vivo experimental data, furthermore, suggest that plant
compounds can antagonize some of the deleterious effects of
compounds found in cooked red meat (e.g., heterocyclic amines,
nitroso compounds, malondialdehyde, advanced glycation end
products etc.) (Pierre et al., 2003; Vulcain et al., 2005; Gorelik
et al., 2008; Hur et al., 2009; Li et al., 2010; Van Hecke et al.,
These findings may represent a mechanistic explanation—but
certainly not the only one—for why high quality omnivorous
1Statista (2020).
diets (also rich in plants) do not show the typical associations
between red meat consumption and negative health outcomes
(Key et al., 2003; Schulze et al., 2003; Kappeler et al., 2013; Lee
et al., 2013; Roussell et al., 2014; Wright et al., 2018; Deoula et al.,
2019) that are often observed in population studies of individuals
consuming a typical Standard American/Western Diet (Wang
and Beydoun, 2009; Chan et al., 2011; Pan et al., 2011; Micha
et al., 2012; Abete et al., 2014), though more work is needed to
firmly establish this hypothesis.
On the other hand, vitamins A (retinol), B12 (adenosyl- and
hydroxocobalamin), D (cholecalciferol), K2(menaquinone-4),
minerals such as iron and zinc, and long-chain polyunsaturated
fatty acid (PUFAs) (e.g., docosahexaenoic acid [DHA] and
eicosapentaenoic acid [EPA]) are more readily, or exclusively,
obtained from animal sources as opposed to plant sources.
These nutrients play essential roles in tissue development
and regeneration (Georgieff, 2007; van Vliet et al., 2018).
While plant foods often contain precursors to these nutrients,
considerable portions of the population experience a poor in vivo
enzymatic conversion of plant-precursors into forms usable by
the human body (Brenna, 2002; Burdge, 2006; Tang, 2010). For
example, the conversion of carotenoids (provitamin A) to retinol
(vitamin A) is in the range of 3.5 to 28%, depending on the
genetic variability between individuals, and highlights that “poor
converters” are unable to obtain sufficient retinol when relying
on plant foods only. Retinol deficiency is especially prevalent in
the developing world, particularly in young children and women
of childbearing age, who largely depend on the consumption of
provitamin A (primarily β-carotene) in vegetables and fruit to
satisfy their vitamin A needs, with many failing to do so (Sommer
and Vyas, 2012).
Of course, individual genetic differences related to nutrient
metabolism (Brenna, 2002; Burdge, 2006; Stover and Caudill,
2008; Tang, 2010), at the same time, also explain why some
individuals can thrive on plant-based diets, while others
following a vegan/vegetarian diet report health problems
associated with nutrient deficiencies. For example, there
are five times more former vegans/vegetarians than current
vegans/vegetarians in the US, of which 53% reported that they
followed the diet <12 months (Faunalytics, 2015). While many
factors contribute to the difficulties in adhering to plant-based
diets (including social factors and food options), intra-individual
differences in nutrient metabolism (Brenna, 2002; Burdge, 2006;
Stover and Caudill, 2008; Tang, 2010; van Vliet et al., 2015) make
it highly unlikely that everyone can thrive on a plant-based diet.
The same is likely true for those on “carnivorous” diets (mostly or
exclusively animal foods) (Mcclellan and Du Bois, 1930), though
more work is needed to confirm this hypothesis.
While human omnivory should arguably not be interpreted
as true optionality for either plant or animal foods, concerns
regarding the negative effects of animal foods on human and
environmental health have led to widespread suggestions to
replace traditional animal foods with plant-based foods to meet
the vast majority of our nutritional needs (Godfray et al., 2018;
Willett et al., 2019). The shift toward replacing animal foods
with plant substitutes is, furthermore, enabled by modern food
technologies that allow for the production of plant-sourced
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van Vliet et al. Plant-Based Meat Alternatives and Meat
FIGURE 1 | Nutrition Facts panels of 4 oz. (113 grams) of novel plant-based meat alternatives and ground beef. Food sources in their natural state contain thousands
of compounds that are capably of impacting human health, the vast majority not appearing on consumer Nutrition Facts panels (Barabási et al., 2019). Despite
comparable Nutrition Facts panels, important nutritional differences are expected between beef and the plant-based meats due to differences in their predominant
originating source (bovine vs. soy vs. pea-derived). At present, novel plant-based meat alternatives should arguably be treated as meat alternatives in terms of sensory
experience, but not per se as true nutritional replacement for meat. It is expected that both beef and plant-based meats will have a have a significant role to play in our
future food supply (Godfray, 2019). *A popular soy-based alternative is fortified with iron (from soy leghemoglobin), riboflavin, niacin, vitamin B6, vitamin B12, and zinc,
while a popular pea-based alternative is not fortified. Created with
foods that are able to match the macronutrient, vitamin
and mineral content of animal foods by using isolated plant
proteins, bioengineered ingredients, and/or synthetic vitamins
and minerals (Figure 1).
Moreover, a potential reason why the novel plant-based
meats that look, feel, and taste like meat are of interest to
consumers is that they may be able to better satisfy the “intrinsic
desire” that humans have for eating meat (Piazza et al., 2015).
For example, despite an aversion in vegetarians toward animal
foods at the subjective level, the intrinsic motivational salience
(desire for meat) was preserved on the neural level similar to
that of omnivores (Giraldo et al., 2019). Noteworthy, is that
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van Vliet et al. Plant-Based Meat Alternatives and Meat
this “subconscious motivation for eating meat” was observed
already after a single overnight fast, which is far from a
starvation-like state. Given the close resemblance of novel plant-
based meat alternatives to meat, in the following section we
address the following question: Can plant-based alternatives
meet the nutritional requirements traditionally fulfilled by eating
animal foods?
The recommended dietary allowance (RDA) for protein in
adults is 0.8 g protein/kg bodyweight per day (56 g for a 70 kg
individual) (Institute of Medicine, 2005). However, this amount
should be viewed as the minimum to prevent deficiency in young
adulthood rather that an amount that promotes optimal health
(Wolfe and Miller, 2008; Phillips et al., 2016). Furthermore, the
protein RDA is considered too low for middle-aged and older
adults (>50 y) (Bauer et al., 2013; Deutz et al., 2014), and for
adults who seek to maximize cellular adaptations from regular
physical activity/exercise (Kato et al., 2016; Morton et al., 2018).
Animal foods such as meat are often recommended to
meet protein needs because they provide dietary protein at a
modest caloric load, and are considered of higher protein quality
when compared to plant sources (FAO/WHO/UNI, 2011). The
protein digestibility-corrected amino acid score (PDCAAS) and
digestible indispensable amino acid score (DIAAS) are the two
major standards used to evaluate the quality of dietary protein
sources. Plant proteins often have lower scores (ranging from 0.4
to 0.9) than animal proteins (>0.9). The lower PDCAAS/DIAAS
of plant sources is, in part, due to their reduced digestibility
as a result of the presence of “anti-nutrients”—phytates and
trypsin inhibitors that interfere with digestion and absorption
of protein (Sarwar Gilani et al., 2012). The advantage of novel
meat alternatives is that they use concentrates and/or isolates
of soy, pea, and other plant proteins. These purified protein
sources are lower in anti-nutritional factors and, therefore, have
comparable PDCAAS/DIAAS to most animal proteins including
meat (Rutherfurd et al., 2014; Hodgkinson et al., 2018).
Based on their respective PDCAAS/DIAAS, one could expect
that isolated plant proteins would result in a similar anabolic
response when compared to animal sources. However, a number
of studies have demonstrated that purified plant proteins have
a lower skeletal muscle anabolic response when compared
to isonitrogenous amounts of animal proteins with similar
PDCAAS/DIAAS (Wilkinson et al., 2007; Tang et al., 2009;
Phillips, 2012; Yang et al., 2012; Gorissen et al., 2016). Plant
proteins tend to be particularly low in either lysine or methionine
as well as leucine, which are essential amino acids that cannot be
synthesized in vivo and need to be obtained through the diet (van
Vliet et al., 2015). For instance, both soy and pea protein, the most
commonly used protein sources in novel plant-based alternatives,
are particularly low in methionine when compared to beef, in
addition to being slightly lower in lysine as well (Figure 2).
The issue of an unbalanced amino acid profile can be solved
by combining isolated plant proteins that are lower in lysine
yet higher in methionine (e.g., wheat, rice, hemp, and maize)
with plant proteins that are higher in lysine yet lower in
methionine (e.g., soy, potato, and pea) in a single product or
FIGURE 2 | Methionine (A) and lysine (B) content of beef and plant proteins
commonly used in plant-based meat alternatives. Human muscle is provided
as a reference standard. 1From Burd et al. (2012).2From Tang et al. (2009).
3From Khattab et al. (2009).
by adding crystalline amino acids to the product (van Vliet
et al., 2015). While a popular pea-based alternative contains some
isolated rice protein, which is complementary to pea protein,
it is unlikely (based on the listed order of ingredients) that the
amount is sufficient to increase the methionine content of the
product. Similarly, a popular soy-based alternative has a limited
amount of potato protein (<2% of total ingredients), but potato,
like soy, is low in methionine and high in lysine. While we
have previously theorized that blending different complementary
plant sources is a promising strategy to improve the skeletal
muscle anabolic response to ingested plant protein (van Vliet
et al., 2015), no studies have yet determined if this brings
the muscle anabolic response from plant sources up to the
level of animal proteins. Of note is recent work that showed
that consumption of complementary plant proteins still resulted
in 30–40% lower circulating essential amino acid availability
when compared to a leucine-matched amount of whey protein
(Brennan et al., 2019). These data suggest that, despite the
blending of plant-based sources to make a complete amino
acid profile, the anabolic potential may still be reduced when
compared to animal-based protein.
A potential alternative strategy to overcome the lower anabolic
effects of plant vs. animal proteins is to simply eat more
plant proteins. Consuming 40 g of soy protein results in a
similar muscle anabolic response as 20 g of whey protein (Yang
et al., 2012). Adding a high dose of rice protein (48 g) to an
omnivorous diet is also as effective as a protein-matched amount
of whey protein in augmenting resistance-exercise induced gains
in muscle mass. This is in contrast to studies that show a superior
training-induced skeletal muscle gains after consuming lower
doses of animal vs. plant proteins (ranging from 17.5 to 25 g)
(Hartman et al., 2007; Volek et al., 2013). Nonetheless, it may
reasonably be expected that the consumption of plant-based meat
alternatives as part of an omnivorous diet is unlikely to negatively
impact skeletal muscle mass or affect protein requirements.
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van Vliet et al. Plant-Based Meat Alternatives and Meat
Vitamin B12
The cobalamins (vitamin B12) are the best-known members
of the group of compounds collectively known as corrinoids.
Cobalamin (vitamin B12) is an essential nutrient that plays
a role in DNA synthesis, myelin formation, red blood cell
production, and maintenance of central nervous system function
(Yamada, 2013). Humans must obtain vitamin B12 from the
foods they eat or via supplementation. While gut bacteria in
our large intestine still produce some corrinoids, including small
amounts of active forms of cobalamin (Kirmiz et al., 2020),
evolutionary pressures likely resulted in preferential absorption
of B12 in the small intestine as a result of regular animal
consumption (Seetharam and Alpers, 1982). This has resulted
in a dependence on exogenous B12 that has likely persisted for
at least 1.5 Ma (Dominguez-Rodrigo et al., 2012). Indeed, the
receptors necessary for absorbing B12 are found only in the small
intestine in modern-day humans, upstream of the site of bacterial
corrinoid production (Seetharam and Alpers, 1982).
Biologically active B12 is found predominantly as adenosyl
cobalamin in animal flesh (Czerwonka et al., 2014) and as
hydroxocobalamin in eggs and dairy (Matte et al., 2012).
These active forms of vitamin B12 bioaccumulate in animal
products predominantly through microbial synthesis in the gut
of ruminants, through consumption of soil and feces in non-
ruminant herbivores, and through phytoplankton consumption
in aquatic animals (Watanabe and Bito, 2018). A common
misperception is that the majority of cattle receive supplemental
B12 and that humans are essentially consuming B12 supplements
via a “middle-man.” While there is some evidence that high-
producing dairy cows need more B12 than their microbes
produce (Girard and Matte, 2005; Akins et al., 2013), the reality
is that B12 is seldom fed to cattle, which is likely due to its high
cost and limited benefits for production (Akins et al., 2013).
Although limited amounts of B12 are also found in some
plant foods, such as mushrooms and fermented vegetables, the
majority of B12 in plants are biologically inactive corrinoids (i.e.,
B12 analogs) (Stupperich and Nexø, 1991) that may compete with
transport of biologically active B12, thus potentially aggravating
a B12 deficiency (Dagnelie et al., 1991). Several plant-based foods,
particularly those meant to replace animal foods—cereals, non-
dairy milks, vegan spreads, and plant-based meat replacements—
are often fortified with supplemental B12 to counteract deficiency.
The common supplemental form of B12 used in these products is
cyanocobalamin which is relatively inexpensive to produce and
has stability to heat exposure (Goldstein and Duca, 1982).
Cyanocobalamin is a man-made form of Vitamin B12 that
normally occurs only in trace amounts in human tissue,
particularly in smokers (Paul and Brady, 2017). While all forms
of vitamin B12—naturally occurring adenosylcobalamin and
hydroxycobalamin and the man-made form cyanocobalamin—
are absorbed with similar efficiency (Paul and Brady, 2017),
a potential concern with meeting B12 requirements through
cyanocobalamin is that its tissue retention rates, and subsequent
metabolic activity, are reduced compared to naturally occurring
forms of B12 (Glass et al., 1961; Hertz et al., 1964; Okuda
et al., 1973; Paul and Brady, 2017). Additionally, the B12
found in animal foods is protein-bound and therefore partially
protected from light degradation (Linnell and Matthews, 1984).
Nonetheless, eating cyanocobalamin-fortified foods or ingesting
cyanocobalamin supplements can improve vitamin B12 status in
adults (Tucker et al., 2000, 2004; Damayanti et al., 2018) and
children (Sheng et al., 2019), which is also why fortifying meat
alternatives with B12 is encouraged. This is especially important
for vegans and vegetarians, and the elderly (even omnivores) who
often have low B12 status (Herrmann et al., 2003a,b; Andrès et al.,
2004), and rely on food fortification and/or supplementation to
meet B12 needs. It is important to highlight that only less than
a quarter of plant-based meat substitutes are fortified with B12
(Curtain and Grafenauer, 2019).
Dietary iron is found as heme iron in animal foods, particularly
in red meat, and as non-heme iron in plant foods, particularly
in pulses, grains, green leafy vegetables, and certain fruits. Heme
iron is 5-10-fold more bioavailable than non-heme iron (Hurrell
and Egli, 2010), and explains why omnivores often have higher
serum ferritin levels (a marker of iron status) (Haider et al.,
2018). The uptake of iron, particularly non-heme iron, is limited
by several plant compounds such as phytates, polyphenols, and
calcium, present in both plants and dairy (Hurrell and Egli, 2010).
In contrast to most plant foods, which predominantly contain
non-heme iron as part of their natural food matrix, the iron in a
market leading soy-based alternative is heme iron purified from
yeast that is genetically engineered to express the leghemoglobin
protein normally found in the root nodules of soy plants (i.e.,
soy leghemoglobin) (Fraser et al., 2018). While the amino
acid sequence of leghemoglobin is vastly different from animal
heme counterparts, iron uptake of leghemoglobin had similar
bioavailability as bovine hemoglobin in a human epithelial cell
culture model (Proulx and Reddy, 2006). Importantly, initial
studies regarding safety of yeast-derived soy leghemoglobin
show little concern for genotoxicity and immunogenicity in in
vitro and short-term (28-day) in vivo animal studies (Fraser
et al., 2018; Jin et al., 2018). Future work should confirm
the bioavailability and long-term safety of yeast-derived soy
leghemoglobin consumption in vivo in humans, and particularly
in children where soy allergy is more common (Savage et al.,
2010). While some concern exists with consumers regarding the
use of genetically modified ingredients in food products (Scott
et al., 2018), a recent consumer survey suggests that the presence
of soy leghemoglobin in a popular soy-based meat alternative
does not appear to be a barrier to consumption or perceived
healthfulness of the product (International Food Information
Council, 2020).
A market leading pea-based meat alternative contains non-
heme iron naturally present in peas (Figure 1). While the
bioavailability of non-heme iron is reduced compared to heme,
non-heme iron can still represent an important dietary source
of iron (Young et al., 2018). Vitamin C, and ironically meat,
are main enhancers of non-heme iron absorption (Hurrell
and Egli, 2010), which is why adding meat to plant-based
meals improves uptake of non-heme iron from plants (Bjorn-
Rasmussen and Hallberg, 1979; Kristensen et al., 2005). Vitamin
C also enhances iron uptake by acting as a chelator in the gut
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van Vliet et al. Plant-Based Meat Alternatives and Meat
(Conrad and Umbreit, 1993). Important to note is that a market
leading soy-based meat alternative is supplemented with sodium
ascorbate (vitamin C), which presumably counteracts some of the
inhibitory effects of the phytates, found in soy protein, on iron
absorption (Hurrell et al., 1992).
Despite increased awareness, iron deficiency remains one of
the most common nutrient deficiencies in both developed and
developing countries, and population groups such as children,
adolescent females, and older individuals are particularly at risk
for deficiency (Patel, 2008; Beck et al., 2014; Gibson et al., 2014).
On the other hand, excessive heme iron intake is increasingly
linked to the promotion of cardiovascular disease (CVD) (Fang
et al., 2015). The association of heme iron intake and CVD is
particularly prevalent in US cohorts, but is inconsistent in cohorts
outside of the US (Fang et al., 2015). Interestingly, even in the
US the association between high heme iron intake and risk of
CVD was absent in the first cohort of NHANES, which was
studied during the 1970s (Liao et al., 1994) when red meat intake
was higher compared to present day (Daniel et al., 2011). This
heterogeneity between studies likely suggests that the background
diet in which red meat is consumed may be an important
modulating factor. In particular, the deleterious effects of red
meat consumption may be perpetuated when meat is consumed
as part of the Standard American Diet, rich in processed foods
and inadequately counterbalanced with whole food plant sources.
For example, polyphenols, phytates, calcium, and fibers inhibit
heme iron absorption (Hurrell and Egli, 2010; Ma et al., 2010),
and this may explain why some epidemiolocal studies find that
risk of heme iron intake and CVD disappears with extensive
adjustment for diet quality (i.e., diets also high in whole plant
foods) (Galan et al., 2009; de Oliveira Otto et al., 2012; Kaluza
et al., 2014).
Similar to iron, zinc deficiency can be a concern in both
developed and developing countries (Alloway, 2008), and those
who restrict animal foods often have lower zinc status (Foster
et al., 2013; Foster and Samman, 2015). Uptake of zinc from
plant sources can be lower as a result of the presence of anti-
nutrients such as phytates, lectins, and certain fibers (Harland
and Oberleas, 1987; Welch, 1993). Similar to iron, zinc uptake
from plants can be improved when consumed in conjunction
with animal foods (Sandström et al., 1989). While soy protein
contains limited amounts of zinc, a popular soy-based alternative
is fortified with zinc gluconate to bring its level up to that of
beef (Figure 1). Nevertheless, zinc absorption from fortified plant
foods, at equal zinc content of beef, is lower than that for beef
(Zheng et al., 1993; Etcheverry et al., 2006). We note that a well-
planned vegan diet rich in legumes, nuts, seeds, and other zinc-
rich plant foods can potentially provide adequate amounts of
zinc (Eshel et al., 2019). Of further consideration when meeting
zinc (and iron) requirements with supplementation is that this
practice may reduce the absorption of other minerals such
as copper (Yadrick et al., 1989), thus increasing their dietary
requirements. The latter can be mitigated by consuming copper-
rich (plant) foods (e.g., nuts, seeds, and leafy greens).
Essential Fatty Acids
The ω-6 fatty acid linoleic acid (C18:2, LNA) and the ω-
3 fatty acid alpha-linolenic acid (C18:3, ALA) are essential
fatty acids that cannot be synthesized in vivo by humans and
must be obtained from dietary sources (Barcelo-Coblijn and
Murphy, 2009). ALA is the parent precursor to the long-
chain polyunsaturated fatty acids (LCPUFA) eicosapentaenoic
acid (C20:5 n-3, EPA) and docosahexaenoic acid (C22:6 n-3,
DHA). ALA and LNA are commonly found in plant foods
but can also be found in limited quantities in animal foods,
while DHA and EPA are found exclusively in animal foods and
certain algae.
While ALA can be converted to DHA and EPA through a
series of elongation and desaturation steps, this conversion is
poor and often <1% (Su et al., 1999; Brenna, 2002; Pawlosky
et al., 2003). Moreover, this conversion efficiency also depends
on the presence of co-factors such as selenium, zinc, iron and
vitamin B6(Brenner, 1981), which are less bioavailable from
plant foods. For these reasons, vegetarians can have lower levels
of DHA and EPA when compared to omnivores (Rosell et al.,
DHA and EPA have been studied extensively for their
importance in cardiovascular function, immunomodulation,
vision, and cognitive function (Swanson et al., 2012). DHA is
a major constituent of the brain phospholipid membrane (30–
40% of total fatty acids), and low circulating levels are associated
with accelerated brain aging (Tan et al., 2012; Otsuka et al.,
2014). Nonetheless, as studies suggest that the human brain only
requires 5 mg of DHA per day (Rapoport et al., 2007; Umhau
et al., 2009), it is estimated that 1,200 mg of ALA can provide
these minimum requirements (Barcelo-Coblijn and Murphy,
2009), though this minimum amount is not considered optimal
for health. While no official daily recommended intakes exist for
DHA and EPA, numerous studies demonstrate that combined
intakes of DHA and EPA ranging from 250 to 1000 mg/day
improve cognitive function and other health parameters (Yurko-
Mauro et al., 2015; Derbyshire, 2018), and such amounts are
therefore often recommended by various health organizations
(WHO, 2008; EFSA, 2012).
The ω-3 fatty acid ALA is found in substantial amounts in
certain vegetable oils, such as flax seed oil (53 % ALA), chia seed
oil (64% ALA), perilla oil (60% ALA), and camelina oil (38%
ALA), though consumption of the latter two oils is generally
restricted to Asian and Nordic countries, respectively (Barcelo-
Coblijn and Murphy, 2009). While the amount of ALA necessary
to ensure minimum DHA requirements in the human body can
be obtained with modest intake of these oils, the majority of
vegetable oils consumed in industrialized countries is in the form
of ω-6 LNA-rich seed oils such as soybean, corn, sunflower, and
canola oil, which contain <10% ALA. For instance, sunflower
oil and canola oil—the main oils in the novel plant-based meat
alternatives—contain only 1% (sunflower oil) and 10% (canola
oil) ALA. Given the already low conversion rates of ALA to EPA
and DHA, respectively, plant-based meat alternatives in their
current state likely will not provide meaningful amounts of very
long-chain PUFAs in the diet.
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Another potential issue is that the ω-6 fatty acids such
as LNA directly compete with ALA for enzymes involved in
elongation and desaturation, which further diminishes the ability
to obtain DHA and EPA from ALA (Sprecher et al., 1999).
This is particularly problematic when one considers that the
increased consumption of high LNA seed oils in the modern
Western Diet has resulted in an ω-6-to-ω-3 fatty acid ratio of
16:1 (Simopoulos, 2002), whereas historical intakes puts this ratio
closer to 1:1 (Eaton et al., 1998; Simopoulos, 2002). This high ω-
6-to-ω-3 fatty acid ratio is considered an important underlying
cause for the increasing incidence of metabolic disease and
all-cause mortality in Western countries (Das, 2006; Zhuang
et al., 2019). Experimentally substituting ω-6-rich LNA oils
with ω-3-rich ALA oils reduces inflammation (Rallidis et al.,
2003; Bemelmans et al., 2004), which represent a mechanistic
explanation for why consuming ω-3-rich ALA oils may be
cardioprotective. Thus, a suitable improvement to the novel
plant-based meat alternatives could be to consider the use of
high ALA oils, rich in ω-3, instead of high LNA oils rich in
ω-6 fatty acids. An important consideration is that high ALA
oils are more prone to lipid oxidation (and perhaps represents a
reason why high LNA oils are typically used in meat substitutes);
however, the addition of natural anti-oxidants (Wang et al.,
2018; Lu et al., 2020) as well as entrapment of high ALA
oils with isolated plant proteins (Karaca et al., 2013; Bajaj
et al., 2015) represent worthwhile opportunities to explore for
producers of plant-based meat substitutes that consider the use
of high ALA oils in their products, which potentially increases
their healthfulness.
It is often stated that ω-3 fatty acids are present in such
modest amounts in land animal-sourced foods, such as beef, that
they do not represent a valuable dietary source of these essential
fatty acids. However, this notion fails to take into account the
abundance of the ω-3 fatty acid docosapentaenoic acid (C22:5,
DPA) in beef, particularly pasture-raised beef, which raises
platelet EPA and DHA levels as a result of in vivo conversion
(McAfee et al., 2011). While DHA can also be directly obtained
in substantial amounts from offal cuts of meat—for instance,
100 g of grass-fed beef liver provides 80 mg of DHA (Enser
et al., 1998)—the consumption of organ meat is not as common
anymore in Western diets and marine sources account for the
majority of dietary intake of the ω-3 fatty acids DHA and EPA
(Bauch et al., 2006; Papanikolaou et al., 2014).
Secondary Nutrients
While we have highlighted several important individual nutrients
thus far, foods in their natural state are considerably more
complex than their essential fatty acid, amino acid, vitamin, and
mineral content would suggest. Food sources contain hundreds-
to-thousands of biochemicals that are important to human
metabolism (Barabási et al., 2019). While many of these nutrients
are considered non-essential or conditionally-essential based
on life-stages, and are often less appreciated in discussions of
human nutritional requirements, their ability to impact human
metabolism should not be ignored.
For example, creatine has been studied extensively for its
ability to enhance athletic performance (Cooper et al., 2012), but
creatine also plays an important role in cognition (Avgerinos
et al., 2018). As creatine is found only in animal foods, vegans
and vegetarians often have lower bodily stores (Burke et al.,
2003), and vegetarians provided with supplemental creatine
showed substantial improvements in memory tasks (Benton and
Donohoe, 2011). Similarly, the antioxidants anserine, carnosine,
and taurine are found (almost) exclusively in animal foods (Hou
et al., 2019). Increased anserine and carnosine intake provide
neurocognitive protection in humans (Szczesniak et al., 2014;
Rokicki et al., 2015).
Taurine is an amino acid found almost exclusively in animal
foods and though small amounts may be found in some plant
foods such as cereals, legumes, and grains (a thousand times
less when compared to animals foods) (Pasantes et al., 1989),
these amounts are insufficient to meet human requirements
(Laidlaw et al., 1990). It is often stated that since taurine
can be synthesized in vivo from methionine and cysteine via
cysteinesulfinic acid decarboxylase (CSD), taurine requirements
can be met by consumption of plant proteins that are rich
in methionine and cysteine, which can be found in adequate
amounts in several legumes and grains (van Vliet et al., 2015).
However, CSD levels in the human body, which allows for
the conversion of taurine from methionine and cysteine, are
insufficient to maintain tissue concentrations over time (Ripps
and Shen, 2012). Taurine impacts nearly every vital organ in
the body and plays vital roles in eye health (Froger et al.,
2014), brain function (Kilb and Fukuda, 2017), mitochondrial
functions (Suzuki et al., 2002), skeletal muscle cell differentiation
(Miyazaki et al., 2013), and cardiovascular health (Waldron et al.,
2018). Future studies are needed to better understand how these
differences in secondary nutrients between plant-based meat
alternatives and meat impacts short- and long-term health.
Fortifying Foods to Mimic the Natural Food
A recurring concern is that natural whole foods are extremely
complex and the reductionist approach of trying to “mimic”
whole food sources (whether it be meat or other foods) by
combining several isolated nutrients likely underestimates the
true complexity and health benefits of eating whole foods
(Lichtenstein and Russell, 2005; Jacobs and Tapsell, 2007). In
particular, fortification of a low-meat diet with zinc and other
minerals found in meat did not result in similar zinc status as
when these minerals were provided in the diet as part of the
natural matrix of meat (Hunt et al., 1995). Moreover, adequate
intakes of zinc, copper, and vitamins A and D were associated
with decreased risk of cardiovascular disease and all-cause
mortality when obtained from foods, but not from supplements,
in a recent large population-based study (Chen et al., 2019).
Similarly, carotenoid-containing foods are associated with a
decreased risk of various cancers (van Poppel and Goldbohm,
1995), retinopathies (Goldberg et al., 1988; Seddon et al., 1994),
and cardiovascular disease (Kritchevsky, 1999). However, the
results of interventional and epidemiological studies suggest
that carotenoid and/or vitamin A supplements do not decrease
the risk of cancer or cardiovascular disease, and might even
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van Vliet et al. Plant-Based Meat Alternatives and Meat
raise the risk for some sub-populations (The Alpha-Tocopherol
Beta Carotene Cancer Prevention Study Group, 1994; Omenn
et al., 1996; Druesne-Pecollo et al., 2010; Bjelakovic et al.,
2012). Similar findings have been made in studies of calcium
that show a potential for increased cardiovascular disease risk
with supplementation (Bolland et al., 2011; Li et al., 2012),
but not when calcium is obtained from food (Xiao et al.,
2013). Finally, similar findings have been made for vitamin C
and selenium supplements that show no benefits on mortality
in a systematic review of RCTs comprised of nearly 300,000
individuals (Bjelakovic et al., 2012). Thus, it appears that simply
ingesting these nutrients outside of their natural food matrices
may not be an optimal solution for promoting health. Thus,
obtaining nutrients from whole food sources as opposed to
supplemental forms is emphasized regardless of the individual’s
diet (Jacobs and Tapsell, 2007; van Vliet et al., 2018).
The plant vs. meat controversy takes on other dimensions
when assessing environmental degradation and climate change,
both of which adversely affect human health and are crucial
considerations when making recommendations on diets for
livestock and humans. Meeting requirements of nutrients with
plant foods (e.g., folate, manganese, thiamin, copper, and
β-carotene) may come at a lower environmental footprint (i.e.,
less greenhouse gas emissions) than when these nutrients are
met with animal foods (Eshel et al., 2019). Nonetheless, it
has been suggested that similar amounts of protein, iron, and
vitamin A can be obtained from carefully selected plant-based
diet at a lower carbon footprint when compared to omnivorous
diets/animal foods (González et al., 2011; Eshel et al., 2019);
however, such comparisons do not take into account the reduced
bioaccessibility and bioavailability of plant sources for these
nutrients (Stover and Caudill, 2008; Tang, 2010; van Vliet et al.,
2015). Moreover, when footprints—land use for production and
as greenhouse gas emissions (GHGE)—are calculated to consider
amino acid content and nutrient density (e.g., iron, vitamin B12,
zinc, retinol, and amino acids), the footprint of animal foods may
be more similar to plant foods (Drewnowski et al., 2015; Tessari
et al., 2016) because animal foods can more readily meet our
needs for these specific nutrients.
The lower carbon footprint of plant-based meat alternatives
is touted as a main reason for choosing plant alternatives over
beef. Recent life-cycle analysis (LCA) of the Beyond Burger R
and the ImpossibleTM Burger demonstrates a smaller carbon
footprint (+3.2 and 3.5 kg CO2-eq emissions/per kg product,
respectively) compared to US beef finished on total-mixed rations
in feedlots (Heller and Keoleian, 2018; Quantis International,
2019a), which ranges from +10.2 to +48.5 kg CO2-eq per kg
product, depending on the model used, the geographical location
where the cattle are raised, and the inclusion of GHGE potential
of retail, distribution, restaurant or at home use, and end-of-life
FIGURE 3 | Comparison of possible greenhouse gas emissions impacts of
various beef production systems and meat alternatives. All values include
cradle-to-distribution LCA, but excludes GHGE potential of retail, restaurant or
at home use, and end-of-life stages. 1From Stanley et al. (2018) assuming an
edible yield of 60 and 55% carcass weight for feedlot-finished and
“regenerative grazed” (adaptive multi-paddock grazed) beef, respectively with
an addition of +0.3 CO2-eq per kg product as published in Asem-Hiablie et al.
(2019) to account for the lack of inclusion of GHGE potential of packing, which
is taken into account in the LCA of the meat alternatives. 2From Quantis
International (2019b).3From Heller and Keoleian (2018). CO2-eq, Carbon
dioxide equivalent; GHGE, Greenhouse gas emissions; LCA, Lifecycle analysis.
stages (Heller and Keoleian, 2018; Stanley et al., 2018; Asem-
Hiablie et al., 2019; Rotz et al., 2019) (Figure 3).
While meat alternatives may have a lower environmental
impact when compared to feedlot-finished beef, well-managed
pasture-based livestock systems fix at a minimum all the GHG
they emit (and sometimes more) even when taking into account
all aspects of the production process (Allard et al., 2007; Teague
et al., 2016; Stanley et al., 2018). Pastured beef systems that use
land management practices such as rotational grazing—where
lands are allowed to properly recover after a grazing period—
and/or cover crop grazing suggest that the amounts of carbon
sequestered in the soil more than offsets the ruminants’ GHGE,
resulting in a net negative carbon footprint (Allard et al., 2007;
Teague et al., 2016; Stanley et al., 2018). By having livestock
participate in carbon cycling by spending their lives on well-
managed pastures—grooming and fertilizing vegetation and soil
(Reeder and Schuman, 2002)—such production systems have the
potential to help mitigate climate change (or in the very least not
exacerbate it further) while ensuring a degree of food security
(Teague et al., 2016).
Well-managed grasslands, especially in more mesic areas,
can act as carbon sinks in a variety of geographical locations
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van Vliet et al. Plant-Based Meat Alternatives and Meat
worldwide and depending on geographical locations, may be
more reliable carbon sinks than forest (Dass et al., 2018; Viglizzo
et al., 2019). It must be noted that the two (forests and livestock)
are not mutually exclusive to begin with, as demonstrated
by successful implementation of silvopastoralism—a type of
agroforestry integrating trees, forage, and livestock—in forested
areas across the globe as a strategy to enhance carbon
sequestration, soil health, and food security for those inhabiting
such areas (Kumar and Nair, 2011). Thus, considerations
regarding livestock-production systems should be tailored to
fit the geophysical landscape instead of attempting—often at
great expense—to change the environment to fit the production
system. For example, it would be suitable to practice silvopasture
techniques with locally adapted animals in landscapes such as
the Amazon rather than attempting to convert its forests to
pasturelands (Nair et al., 2011).
It must be noted though that not all pasture-based (grass-fed)
operations are per se regenerative or neutral, and depending on
management practices, grass-fed beef systems can have a higher
carbon footprint than some feedlot systems (Pierrehumbert and
Eshel, 2015; Lynch, 2019). It is also important to highlight that
the amount of carbon sequestered with well-managed grazing
of livestock on carbon-depleted soils is initially more rapid and
diminishes over time as soil health is restored (Godde et al.,
2020), which is not surprising once equilibrium of ecological
systems are reached. This notion should be considered in the
discussions below.
By performing an ISO-compliant partial LCA of pasture-
raised (grass-fed) beef in the Midwest US, Stanley et al. (2018)
found a net negative carbon footprint of ∼−3.5 CO2-eq/per kg
beef (assuming a 55% edible yield of hot carcass weight). We note
that the value from the pasture-finished beef LCA assessment
excludes the GHGE of getting the product case-ready, which is
included in the plant-based meat LCAs. This is expected to add
+0.3 kg CO2-eq/kg product (Asem-Hiablie et al., 2019) which
would put the LCA analysis from so-called regenerative, grass-
fed beef at 3.2 CO2-eq/per kg beef (Figure 3). This means that
over the lifecycle of the animal more carbon was sequestered
than emitted.
Notably, the same company (Quantis International) that
demonstrated a +3.5 CO2-eq emissions/per kg product in
the LCA analysis of the Impossible BurgerTM (Quantis
International, 2019b) also demonstrated a 3.5 CO2-eq/per
kg beef produced using regenerative livestock grazing practices
(Quantis International, 2019a). While these reports are not peer-
reviewed, it is encouraging that the values reported by Quantis
International are close to those reported in peer reviewed work
on so-called regenerative beef (Stanley et al., 2018) and the
work performed on plant-based meat alternatives by academic
scientists (Heller and Keoleian, 2018).
Nonetheless, the LCAs performed on meat alternatives and
pasture-finished beef both exclude GHGE potentials of retail,
and restaurant or at home preparation, end-of-life stages, and
other localized or indirect impacts. Acknowledging the difficulty
in assessing all aspect of environmental footprints, future work
should confirm these LCA analysis with full accounting for all
GHGE to provide for even-handed assessments (Halpern et al.,
Greenhouse gasses are often lumped together under the
umbrella of CO2-eq, which equates different GHGs to carbon
dioxide (CO2) (Allen et al., 2018). However, different gasses have
different global warming potentials (GWP) and their exact values
depend on the CO2-eq metrics and the timescale (e.g., 20 or 100
years) that is used to express its GHGE contribution (Lynch,
2019). While livestock production also includes significant
emissions of CH4(methane), plant based-meat emissions mostly
consist of CO2from energy generation (Heller and Keoleian,
2018). Livestock add 14.5% to GHGE globally (Gerber et al.,
2013). Of that, 9.5% is producing feed for livestock, processing,
and transportation, while the remaining 5% is methane from
rumen (enteric) fermentation and manure. While methane is a
potent GHG, it is also temporary one; it lasts a decade before it
breaks down into CO2that can be sequestered in soil. With a
stable or slightly decreasing population of cattle in the US, though
not globally, the methane belched from cattle is not likely to add
new carbon to the atmosphere (Lynch, 2019). On the other hand,
once we put carbon dioxide in the atmosphere from burning
fossil fuel—whether from transportation or food production—it
persists for thousands of years. These nuances are important to
recognize in discussions on carbon footprints of different foods
and dietary patterns.
The carbon footprint of meat alternatives is likely lower than
the majority of beef consumed in the US, because that beef is
produced primarily from feedlots that rely on fossil fuel-intensive
methods (Poore and Nemecek, 2018) (96% of all beef in the
US is finished in feedlots). Some suggest that with increased
conversion to pasture-based beef production systems in the US,
domestic beef consumption will have to be reduced by about
40% due to unavailability of land-provided roughage feed is
used to supplement cattle on pasture (Hayek and Garrett, 2018).
These estimations do not take into account the potential for
increased carrying capacity from multi-species grazing with little
dietary overlap, for instance mixing cattle with sheep or goats,
which improves productivity of both animals and vegetation
when compared to grazing of either animal alone (Walker, 1994;
Celaya et al., 2008; Anderson et al., 2012; Ferreira et al., 2013).
Moreover, properly management multi-species grazing can also
maintain plant diversity and thus improve ecological resiliency
and pasture health (Anderson et al., 2012). This would obviously
mean that we would have to diversify our meat and milk intake
to include products from other livestock, including sheep, goats
and perhaps smaller mammals such as ducks and rabbits.
Another opportunity to further increase the carrying capacity
of a pasture-based livestock, which is often not taken into
account in discussions on the carrying capacity of pasture-based
production systems, is to strategically supplement livestock on
pasture with edible by-products (Sunvold et al., 1991; Macdonald
et al., 2007). Ruminants have the unique capacity to upcycle
by-products from industrial and agricultural production (Mottet
et al., 2017). For example, when corn is used to make ethanol,
only the starch portion is used and its by-product (the outer shell,
oil, and germ) can be made into a high-fat, high-protein cake fed
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to cattle. Crop residues such as straws, stover, and sugar-cane tops
as well as phytochemically-rich byproducts of fruit and vegetable
processing such as leaves, pomace, peels, rinds, pulp, seeds, stems
etc. to livestock (Sruamsiri, 2007; Wadhwa and Bakshi, 2013;
Nwafor et al., 2017) provide similar opportunities to upcycle
these nutrients. Offering these byproducts to cattle on pasture
can potentially mitigate some nutritional deficits, enhance use
of unpalatable vegetation, reduce the risk of overgrazing, and
mitigate issues of reduced land availability (Provenza et al., 2003).
Offering by-products on pasture, as opposed to feeding
them to cattle in feedlots, would also mitigate some of the
animal welfare issues associated with feedlots such as unfamiliar
environments, inability to self-select their diet, and the ability
to express natural behavior (Atwood et al., 2001; Villalba and
Manteca, 2019). Offering by-products to cattle on pasture may
represent a worthwhile opportunity for the livestock industry
to improve consumer perception while maintaining the ability
to upcycle by-products to meet customer demand. It will be
important to use only industrial by-products that would have
been produced anyway, rather than growing feed with the specific
intent of giving it to livestock.
Recent studies also show that the mixture of forages animals
eat on pasture influences how long it takes them to reach
slaughter weight. Compared with grazing a monoculture of grass,
cattle eating diverse mixtures of plants, some of which contain
tannins, gain weight more efficiently and can reach finish body
condition nearly as quickly as animals in feedlots—and they do so
with less GHGE (Villalba et al., 2019). Providing ruminants with
forages that contain secondary compounds such as tannins and
terpenes also decreases nitrogen in urine and increases nitrogen
in tannin-rich manure that builds soil organic matter (Villalba
et al., 2019).
Finally, discussions on whether pasture-based productions
systems can sustain meat consumption revolve around the ability
of pasture-based systems to support the consumption of popular
retail cuts (i.e., steaks, roasts, beef). For instance, Hayek and
Garrett (2018) assume a 60% edible yield in their calculations on
the carrying capacity of pasture-based beef production systems
to support US consumption. While this number is justifiable,
another 20% of the animal is entirely suitable for human
consumption and includes organs, bones, and tallow (USDA,
2015). For example, increased consumption of organ meats—
often much denser in vitamins and minerals (e.g., 10–1000 fold
higher in retinol, iron, copper and vitamins B6, B12, and K2) than
muscle meat (USDA, 2016)—was recently found to reduce meat
intake-associated GHGE by 14% (Xue et al., 2019).
While not a panacea for saving the planet from climate
change, agricultural practices that integrate regenerative livestock
grazing practices with plant farming are an important step in
the right direction to reduce the carbon footprint and land
use of animal agriculture. Of 80 ways to mitigate climate
change evaluated in Project Drawdown, regenerative practices—
farmland restoration, conservation agriculture, agroforestry,
silvopastoralism, and managed grazing—jointly rank number
one as a way to sequester GHG (Hawken, 2017). Furthermore,
by integrating livestock grazing with plant farming, one can
also improve crop yield and soil fertility (Maughan et al., 2009;
Bell et al., 2014). The symbiotic relationship between plants
and herbivores, which each system strengthening the other, are
important to appreciate in discussions on whether we displace
livestock production.
When the projected increase to nearly ten billion people is
combined with an increase of 32 percent in per-person-emissions
from global shifts to ultra-processed diets by 2050, the net
effect is an estimated 80 percent increase in GHGE (Tilman and
Clark, 2014). Alternatively, GHGE may not increase if diets were
vegetarian, pescatarian, or Mediterranean that include whole
food sources of fruit, vegetables, seafood, grains, eggs, dairy, as
well as limited amounts of beef, lamb, and poultry (Tilman and
Clark, 2014). For example, the high carbon footprints in an urban
Japanese population was largely explained by confectionary
consumption, dining out, and alcohol consumption, whereas
consumption of meat and vegetables contributed much less to the
footprint—meat only contributed to 9% of the difference between
low and high dietary carbon footprints (Kanemoto et al., 2019).
Findings along similar lines were made recently in an Australian
cohort, where “discretionary foods” (sugar-sweetened beverages,
alcohol, confectionary, and other ultra-processed foods) made up
the largest share of the environmental footprint (Ridoutt et al.,
2020). Future studies should confirm this hypothesis in European
and American households, but similar results can reasonably
be expected due the prevalent consumption of the Standard
Western/American diet.
Moreover, biophysical simulation of various diet patterns
suggests that a healthy omnivorous diet—rich in whole-food
plant and animal sources—has the greatest carrying capacity
for feeding populations in diverse regions throughout the world
(Peters et al., 2016). Vegan and vegetarian diets have a greater
carrying capacity than the Standard Western Diet—high in
processed foods (Peters et al., 2016). On this basis, some make a
case for adoption of a plant-based diet, but a diet that contains
only plant foods does not integrate farming and grazing to
improve the fertility of soil—which synergistically strengthens
both plant (Maughan et al., 2009; Bell et al., 2014) and livestock
farming systems (Teague et al., 2016)—nor does it efficiently
use land that could otherwise feed more people (Peters et al.,
2016; Van Zanten et al., 2016). The latter point is significant
because two-thirds of earth’s land mass, which is unsuitable for
crop production (FAO, 2020), is home to billions of people who
depend on managed livestock grazing for their livelihood. In
discussions of dietary transitions towards plant-based substitutes
it is, therefore, crucial that no policies are set into place that
threaten the health and livelihood of the world’s poorest.
Another important point to consider is that most crops are
grown in monocultures where life below and aboveground is
sacrificed by chemical and/or mechanical means. While eating
roots of carrots, seeds from almonds, or plant-based meat
alternatives from peas or soy does not directly involve killing
animals, indirectly it does. The habitats of other plants and
animals are destroyed. One large and visible example is grassland
birds who have lost more than 50% of their populations in
North America in the last 50 years due to large-scale farming
practices be it plant or animal farming (Rosenberg et al., 2019).
Another clear example is found in the Southern Peninsula of
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Malaysia and Borneo where replacing native forests with oil palm
plantations has contributed to a reduction in the total number
bird and butterfly species by 80% (Koh and Wilcove, 2008) and
Orangutans by 85% (Ancrenaz et al., 2016).
There is considerable difficulty in estimating the number of
animals killed as part of “collateral damage” in agriculture (i.e.,
animals not killed for consumption) (Fischer and Lamey, 2018);
however, conservative yearly estimates in the US put this number
in the tens of millions and includes mammals, fish, reptiles, and
other amphibious creatures. In particular, Fischer and Lamey
(2018) put this number at roughly 127.5 million field deaths
per year in the US with a lower bound of 63.75 million per
year, though it must be noted that considerable uncertainty
exists regarding this number due to absence of systematic data
collection on field deaths. For perspective, 40 million cattle and
120 million pigs are estimated to be slaughtered for consumption
each year in the US (Fischer and Lamey, 2018). Whether intended
deaths (through animal consumption) are morally equivalent to
“unintended” deaths (through plant agriculture including those
for human consumption and animal feed) is beyond this review
[see Fischer and Lamey (2018) for a further discussion]. It
serves the point that in food systems, life consumes life to live.
Nonetheless, that improvements must be made in plant farming
and livestock production methods in ways that enhance the
welfare of livestock and wildlife is something arguably most agree
on (meat and plant-eaters alike).
The ecological impacts of human diets are not as simple as
plant vs. meat discussions might suggest. The global food system
is far too diverse and contingent on unique environmental and
socioeconomic circumstances to allow for one-size-fits-all policy
recommendations. As the latest IPCC Report points out, mixed
plant farming-livestock grazing systems can heal damage done
by years of continuous arable cropping reliant on mechanical and
chemical inputs (IPCC, 2019). In the process, we may increase the
number of animals grazing phytochemically rich landscapes that
nuture animals, soil, plants, and people, and provide food that
is biochemically richer and arguably more nourishing for Homo
sapiens and the planet.
Humans satisfy requirements for certain nutrients much better
from plant foods, while needs for other nutrients are met more
readily from animal foods. Plant nutrients (i.e., phytochemicals)
often protect against potentially harmful compounds in cooked
animal foods (Van Hecke et al., 2017b), while animal foods also
facilitate the uptake of several plant nutrients (e.g., zinc and non-
heme iron) (Sandström et al., 1989; Hurrell and Egli, 2010). Thus,
plant and animal foods interact in symbiotic ways to improve
human health.
While plant-based diets are being promoted for human
and environmental health reasons (Eshel et al., 2019; Willett
et al., 2019), this may put large portions of the population at
greater risk for nutrient deficiencies and accompanying health
issues (Payne et al., 2016). This may especially be the case for
vulnerable populations such as children, elderly, and nursing
mothers who are at increased risk for nutritional deficiencies.
Some suggest that in order to meet requirements for several
key nutrients with plant foods (vitamins A, B3,6,12 , choline,
zinc, iron, and selenium), more plants should be ingested
to overcome their reduced bioavailability and supplements
should be taken if deficiencies arise (vitamin B12 would
have to be supplemented regardless). However, intra-individual
differences in nutrient metabolism (Brenna, 2002; Burdge,
2006; Stover and Caudill, 2008; Tang, 2010) may preclude
portions of the population to thrive on vegan/vegetarian diets,
regardless of how well the plant-based food or diet may
be “designed.”
Many scientists are concerned about the reductionist
approach of simply adding isolated forms protein, vitamins,
and minerals to foods, or diets in general, and designating
them as nutritionally adequate (Lichtenstein and Russell, 2005;
Jacobs and Tapsell, 2007). As whole foods contain hundreds-
to-thousands of compounds that act synergistically to impact
human health (Barabási et al., 2019), adding synthetic nutrients
to food sources often does not confer similar benefits compared
to when these nutrients are ingested as phytochemically and
biochemically-rich whole foods—whether it be plant or animal
foods (Lichtenstein and Russell, 2005; Jacobs and Tapsell, 2007).
Scientists who operate in the realms of nutrition and
ecology, those in companies that produce plant-based meat
alternatives, and the general public arguably share similar
concerns about the influence of agriculture on climate change.
Where groups differ is in their solution to the challenge. There
are many whole-foods dietary options that could substantially
improve human and ecological health (Tilman and Clark,
2014)—whether they be vegetarian, pescatarian, or omnivorous.
We contend that an omnivorous diet rich in whole foods,
produced using sustainable agricultural practices that integrates
plants and animals in agroecological ways (i.e., in harmony
with natural systems), is most likely to benefit human and
ecological health.
At present, novel plant-based meat alternatives should
arguably be treated as meat alternatives in terms of sensory
experience, but not per se as true nutritional replacement for
meat. If consumers wish to replace some meat in their diet with
plant-based alternatives (a “flexitarian approach”), this is unlikely
to negatively impact their overall nutrient status; however, this
also depends on what other foods are routinely consumed and the
life stage of the individual (e.g., infancy, pregnancy, or advancing
age). That said, it is important for future work to compare
human health outcomes in response plant-based vs. animal meat
consumption. Such studies can ensure, and potentially improve,
the healthfulness of plant-based meat alternatives and meat itself,
as it is likely that both will have a have a significant role to play in
our future food supply.
SV and FP wrote the first draft of the manuscript. SK
critically revised the text and made substantial contributions
to the manuscript. All authors approved the final version of
the manuscript.
Frontiers in Sustainable Food Systems | 11 October 2020 | Volume 4 | Article 128
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Conflict of Interest: SV reports a grant from the North Dakota Beef Association
to study the impact of diet quality on the relationship between red meat and
human health and has not accepted personal honoraria from any organization to
prevent undue influence in the eye of the public. FP reports receiving honoraria
for his talks about behavior-based management of livestock.
The remaining author declares that the research was conducted in the absence of
any commercial or financial relationships that could be construed as a potential
conflict of interest.
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