Banning flavoured vaping liquids? A very bad idea.

Banning flavoured vaping liquids? A very bad idea.


  • In response to the increase in the number of young vapers, Health Canada recently proposed to ban most flavouring ingredients in vaping liquids.
  • Data collected in San Francisco, where a ban on the sale of flavoured vaping liquids has been in effect since 2018, shows a significant increase in the number of young people who have smoked cigarettes after the introduction of this measure, which raises serious doubts about the effectiveness of this approach.
  • In addition, the ban on vaping flavours will deprive several thousand adult smokers of the best tool available to quit smoking, as documented by several recent clinical studies.
  • The plan to eliminate vaping flavours from the market therefore seems ill-advised and we believe that its application should at the very least be delayed pending a better determination of its impact on smoking rates, both among young people and adults.

Health Canada recently sought comments on proposed regulations to ban most flavouring ingredients in vaping liquids, with the exception of a limited number of ingredients to impart tobacco or mint/menthol flavour.

This proposal is based on four assumptions:

  • There is apparently a “vaping epidemic” among young Canadians.
  • Flavoured liquids are believed to be one of the main factors contributing to the rapid increase in vaping among young people.
  • Vapers will develop a nicotine addiction and start smoking cigarettes. In other words, vaping would be a stepping stone to tobacco, what is colloquially called the “gateway effect”.
  • As a result, eliminating flavours from vaping liquids will discourage e-cigarette use and thus help prevent youth smoking.

The goal of protecting young people from tobacco is obviously laudable, but a careful examination of the data accumulated over the past few years raises several doubts about the effectiveness of banning flavoured vaping liquids to achieve this. In addition, this project completely ignores the potentially devastating effect of such a ban on adults who use flavoured electronic cigarettes to quit smoking. Before eliminating vaping flavours from the current market, we believe it is important to take a step back and examine the potential negative impacts of this ban, both among young people and adult smokers.

Youth smoking is at an all-time low. First of all, it is important to mention that we have made spectacular progress in the fight against youth smoking. Surprisingly, very little is said about it, but the number of high school students who smoke cigarettes regularly is currently at an all-time low, with only 3% of young smokers aged 15–19 in 2020 in Canada, compared to more than 30% in the late 1990s. A similar phenomenon is observed in most industrialized countries: in New York, for example, there are only 2.4% of smokers in high school compared to 27% in 2000. In concrete terms, this means that over the last 20 years, we have reduced the proportion of young smokers by 90%, which is phenomenal.

Of course, we may wish to reduce this number even further, but we must nevertheless admit that the efforts of recent years in the fight against tobacco have borne fruit and that we have collectively succeeded in making smoking a marginal and old-fashioned behaviour, rejected by the vast majority of young people. Given that more than 90% of adult smokers started smoking as teenagers, this means that the next generation of adults will be overwhelmingly non-smokers and consequently much less affected by the health problems caused by smoking (especially lung cancer) than previous generations. The current status quo therefore represents an unprecedented victory in the fight against tobacco.

Few young people vape regularly and those who do are smokers or ex-smokers. The number of young people who vape has actually increased in recent years. The latest statistics show that in 2019, around 41% of 16–19 year-olds had tried these products at least once, compared to 29% in 2017. On the other hand, it should absolutely be mentioned that this number of vapers is artificially inflated by including young people who have only experimented with electronic cigarettes on a few occasions. When we restrict the analysis to those who use e-cigarettes at least 20 times per month, the data is much less spectacular, with 5.7% regular vapers (see our article on this). In addition, the vast majority of these regular vapers are smokers or ex-smokers, with barely 1% who have never smoked cigarettes. Strictly speaking, there is therefore no vaping epidemic, especially since the latest US data indicates that the proportion of young vapers has decreased by 50% in the last two years, which could indicate that vaping is much more of a passing fad than a lasting transformation in the habits of young people.

Could this vaping among young people, even if it does not reach truly epidemic proportions, still erase this progress and lead to an upsurge in youth smoking? Tobacco control organizations seem to think so and that is why they want to eliminate flavours from vaping liquids to make e-cigarettes less appealing to young people. In other words, it is a question here of making electronic cigarettes “ugly” to reduce their attractiveness and social acceptability and thus prevent exposure to a nicotine-based product from causing young people to turn to tobacco (gateway effect).

This fear of a stepping stone to tobacco is in a way similar to the old mentality of the war on drugs. At the time (towards the end of the 1960s), it was believed that drug users were irremediably attracted by increasingly dangerous products. According to this belief, a cannabis smoker was at a very high risk of becoming a heroin addict, as if people who were attracted to one drug were unable to control themselves and were doomed to always want to go further, even if it meant destroying themselves. We now know that these fears were completely unwarranted and that just because people enjoy the effects of a recreational drug does not mean that they will become irrational. The legalization of cannabis reflects this change in perception of soft drugs.

The same reasoning can be applied to vaping: why would a young person who likes vaping decide to “go further” and turn to a source of nicotine known to be harmful, less appetizing, more expensive, and completely rejected by society like cigarettes? The data accumulated in recent years indicate that this is indeed unlikely and that far from being a stepping stone to tobacco, electronic cigarettes could instead represent a substitute for traditional cigarettes.

Vaping does not lead to smoking. First of all, it should be pointed out that the hypothesis of the gateway effect is completely incompatible with the current situation of youth smoking. Even though electronic cigarettes have been available for several years, the reality is that the proportion of young people who smoke tobacco cigarettes continues to decrease year after year. The arrival of the “pod mod” type electronic cigarettes (Juul, for example), which are even more efficient in terms of nicotine absorption, did not affect this downward trend in smoking among young people and, on the contrary, even accelerated it. In other words, the “vaping epidemic” among young people, so much decried by anti-tobacco organizations, has not led to an increase, but rather a marked decrease in youth smoking, something that would obviously be impossible if vaping led young people to smoke cigarettes.

The claim that vaping is a gateway to tobacco is based on a misinterpretation of studies that have addressed this issue. These studies show that electronic cigarette use is indeed associated with an increased risk of cigarette smoking, which may seemingly validate the existence of a gateway effect. In reality, however, it is impossible to establish a direct cause and effect link between the two behaviours due to what is called “common liabilities”: young people attracted by nicotine will experiment with several forms available, without this meaning that trying one will push them toward another.

In practice, studies show unequivocally that the vast majority of vapers are smokers or ex-smokers, with less than 1% of regular vapers who have never smoked. This suggests that if there is a gateway effect, it is rather in the opposite direction (and positive in terms of reducing tobacco damage), i.e. from cigarettes to vaping.

Vaping is a substitute for smoking. Like it or not, nicotine has long been a recreational drug that attracts significant numbers of young people. For a long time, tobacco was the only available source of this drug, and it is for this reason that rates of youth smoking reached worrying highs until the early 2000s. However, this is no longer the case today, at least in industrialized countries. The electronic cigarette now competes directly with tobacco and represents in practice a much more attractive alternative for nicotine users.

In addition to a better taste (because of the flavours added to vaping liquids) and being devoid of the defects of smoked tobacco (the smell, in particular), a marked advantage of the electronic cigarette is that it is a lot less harmful to health than traditional cigarettes. While the combustion of tobacco generates several thousand highly toxic and carcinogenic compounds that dramatically increase the risk of developing a host of pathologies, in particular cardiovascular disease and lung cancer, the amount of most of these compounds is reduced by 99% in the vapour emanating from electronic cigarette devices (see our article on this subject). According to several major scholarly associations (Public Health England, Académie française de médecine, National Academies of Science, Engineering and Medicine of the United States), electronic cigarettes are at least 20 times less harmful than smoked tobacco.

Vaping therefore has several competitive advantages over smoked tobacco, and it is for this reason that this new technology is establishing itself as a substitute for tobacco cigarettes among nicotine users. Economic analyses also confirm this role of substitution, since an increase in the tax on one of the products (tobacco or electronic cigarettes) leads to a decrease in the consumption of the taxed product for the benefit of the other. For example, one study showed that an increase in the tax on electronic cigarettes was associated with a reduction in vaping and a parallel increase in the sale of tobacco cigarettes. Conversely, an equivalent increase in the tobacco tax leads to an increase in the number of vapers. The two products are therefore substitutes from an economic point of view, which is why a decrease in the competitiveness of the electronic cigarette due to a higher price results in an increase in smoking. It has been estimated that for each cartridge (pod) of vaping liquid that is not purchased due to a tax increase, an additional 6 packs of tobacco cigarettes will be sold. Since a ban on flavoured vaping liquids will also decrease the competitiveness of e-cigarettes, there is concern that a similar phenomenon could occur (see next sections).

Overall, these observations suggest that the electronic cigarette can in a way be considered as a disruptive technology, i.e. an innovation that has the potential to compete with tobacco and even possibly replace it as the main source of nicotine consumed by the population (e.g. digital cameras that have eliminated film cameras).

This is very interesting, since there is usually no going back when one technology supplants another. To take a simple example, streaming has made DVD movie rental clubs a thing of the past, just as DVDs had previously driven VHS tapes out of the market. It is unthinkable that we will ever go back to these old technologies, just as we can be sure that the dial telephone will never take the place of our current cellphones. The electronic cigarette therefore has the potential to eliminate tobacco cigarettes in the medium and long term, a product which, it should be remembered, is responsible for nearly 8 million premature deaths each year. The multinational tobacco companies are perfectly aware of this evolution of the market and it is for this reason that they are gradually turning away from traditional cigarettes to develop less harmful electronic versions, and even anticipate the outright disappearance of traditional cigarettes in the next 10 to 15 years.

Banning flavours could lead to an increase in youth smoking. The main fear invoked to justify the ban on flavoured vaping liquids, namely a massive migration of young vapers to traditional cigarettes, therefore seems unjustified and one can wonder about the relevance of changing the current status quo. Especially since it is necessary to consider that the ban on flavours could have effects contrary to those sought. Since it appears increasingly obvious that the electronic cigarette is a substitute for tobacco cigarettes, isn’t there a risk that by discouraging vaping we push young vapers who are more addicted to nicotine toward tobacco? As Public Health England recently put it, “If an approach makes e-cigarettes less accessible, less palatable or acceptable, more expensive, less consumer-friendly, or less pharmacologically effective, then it causes harm by perpetuating smoking.

Given that the strategy of banning vaping flavours is fairly recent, it is not yet clear exactly how young people will react to the disappearance of these flavours. On the other hand, the preliminary data are very worrying; a study carried out in the San Francisco area, where a ban on the sale of flavoured vaping liquids has been in effect since 2018, recently showed a significant increase in the number of young people who smoked cigarettes after the introduction of this measure, while the smoking trend continues to decline in other parts of the United States where these flavours have not been prohibited (Figure 1).

Figure 1. Impact of a law banning vaping flavours on youth smoking. From Friedman (2021). Note the increase in the number of teenagers who smoked cigarettes following the implementation of the law banning flavours in 2018 (arrow).


A survey of young adults aged 18–34 paints a similar picture: When asked what they would do if vaping flavours were banned, 33.2% responded that they would likely use tobacco cigarettes as a source of nicotine. Therefore, there seems to be a significant proportion of young vapers who could make the jump to tobacco cigarettes in response to the disappearance of vaping flavours, which is obviously the reverse of the desired effect. In our view, if the objective of the project to completely ban flavoured vaping liquids is to prevent an upsurge in youth smoking, these observations should at least cause a delay in the application of this measure while waiting to be able to confirm or not this upward trend. In a sector where two products are in direct competition with each other, any attempt to make one of the two products less attractive (by taxing it or banning flavours, for example) is likely to strongly favour the other. Given the catastrophic health effects of tobacco, this is a huge risk that deserves careful consideration.

Vaping flavours play an important role in smoking cessation. Adult smokers are largely forgotten in the current debate on electronic cigarettes, even though they are by far the main users of these products. There is a lot of talk about the (very hypothetical) dangers of an upsurge in youth smoking caused by vaping, but the huge, clinically proven contribution of e-cigarettes as a smoking cessation aid is completely overlooked. In randomized clinical trials (the standard of excellence for clinical research), it is observed that electronic cigarettes are about twice as effective in leading to smoking cessation than traditional approaches (patches, gum). This is particularly true for heavy smokers, who are very dependent, where an even more impressive success rate is observed for electronic cigarettes, 6 times higher than with standard nicotine substitutes.

There is nothing abstract or theoretical about the effectiveness of electronic cigarettes in promoting smoking cessation: surveys reveal that at least 4.3 million Americans, 2.4 million Britons, and 7.5 million Europeans have quit smoking thanks to these devices, at the same time drastically reducing their risk of dying prematurely. There is therefore no doubt that electronic cigarettes have strongly contributed to the significant decline in adult smoking worldwide, from 23.5% in 2007 to 19% today.

The argument often invoked by opponents of vaping, namely that it is not proven that the electronic cigarette can help with smoking cessation, therefore does not correspond at all to the scientific reality and to that experienced by many ex-smokers for whom this new technology has literally saved their lives.

Flavoured vaping liquids are extremely important in enabling smokers to adopt e-cigarettes. Surveys on this subject show that adults much prefer fruit, dessert and candy flavours to that of tobacco. Flavours are therefore not only appealing to young people, because for a smoker looking to break their addiction to cigarettes, tobacco flavoured vaping liquids are often the last thing sought. Banning flavoured vaping liquids would therefore have the direct consequence of eliminating the main appeal of electronic cigarettes, consequently reducing the number of smokers who could adopt this method to break their addiction to cigarettes. In our opinion, this is a huge collateral damage to the proposed flavour prohibition, since the acceptability of a substitute for cigarettes is essential for quitting. In fact, a recent study showed that adult smokers who started vaping flavoured liquids (fruit, candy, chocolate, etc.) were more likely to be able to quit smoking than those who used tobacco flavours.

For all of these reasons, it seems to us that banning vaping flavours is a very bad idea. The effectiveness of this measure in stopping vaping among young people is questionable (flavours are only one of the factors that encourage vaping), and it is certain that it will have negative impacts on adult smokers by eliminating an alternative to tobacco. It should also be mentioned that a decrease in the number of adults who quit smoking has a negative impact on young people, not only because parental smoking is the main risk factor linked to the initiation of smoking in children and adolescents, but also because of the psychological trauma caused by the disease and/or death attributable to smoking in adults around them.

The disagreements over the issue of vaping reflect the evolution of two major schools of thought in the fight against tobacco. On the one hand, there is what we might call “abstentionists” or prohibitionists, for whom the only way to reduce smoking is to abstain completely from any product that contains nicotine, even when it is well documented that these products are much less harmful than smoked tobacco. Seeking to reduce the number of vapers by banning flavours, despite the fact that these products are much less dangerous than tobacco, is a good example of this “all or nothing” approach. In practice, we are no longer talking here only of the fight against tobacco, but rather of a more general fight against nicotine as a recreational drug, even if this drug has no major effects on health as such.

On the other hand, we find the “pragmatists” who are much more interested in concrete results (reduction in tobacco-related illnesses and mortality) than in the means to achieve them. In this approach, cigarettes remain the enemy to be defeated and anything that can reduce the damage caused by the combustion of tobacco is valued, especially when the experimental data clearly show a decrease in toxicity, as is the case for electronic cigarettes. The British are the leaders in this harm reduction approach and the public health agency of this country (Public Health England) strongly encourages all smokers to migrate to electronic cigarettes.

I firmly believe that this pragmatic approach to reducing the harm caused by tobacco is the best. Abstinence is a good virtue in theory, but the reality is that many smokers are extremely addicted to cigarettes and are absolutely unable to quit without a substitute allowing them to absorb an amount of nicotine equivalent to that found in tobacco. I can no longer count the number of my patients who had tried everything, without success, to overcome their addiction to tobacco, until the day they tried e-cigarettes and finally succeeded. A success that has been in many cases a true question of life and death, because there is no doubt that many of them would have died by now if they had not succeeded in quitting smoking. It would be extremely unfortunate if individuals who have to deal with a very heavy tobacco addiction were deprived of the best tool identified so far to quit smoking, namely vaping of flavours other than tobacco.





Will cultured meat soon be on our plates?

Will cultured meat soon be on our plates?


  • To preserve the planet’s environment and produce enough food to meet growing global demand, experts believe that in the future there will be a need to reduce livestock farming and conventional meat consumption.
  • Cultured meat is presented as a sustainable alternative to farmed meat for those who want to protect the environment but do not want to become vegetarians.
  • For cultured meat to be consumed on a large scale, production techniques and social acceptability will have to make significant progress.

Today there are 7.3 billion human beings on our planet, and it is expected that there will be 9 billion by 2050. The Food and Agriculture Organization (FAO) estimates that in 2050, 70% more food will be required to meet the demand of the growing population. This poses a great challenge because of limited resources and arable land. Meat production (especially beef and pork) is the most resource-intensive, and experts believe it would not be responsible, or even possible, to continue to produce more and more of these foods. Even though meat consumption is declining in developed countries, it is increasing globally because consumers in developing countries are getting richer and meat is seen by the new middle class in these countries as a desirable luxury food.

Among the solutions proposed to get out of this impasse is cultured meat (or lab-grown meat), which is presented as a sustainable alternative to farmed meat for those who want to protect the environment, but who do not wish to become vegetarians. It should be noted that some experts consider that cultured meat poses certain problems and that it would not be a viable alternative to conventional meat (see here and here). We will come back to this a little later in the text.

How is meat grown?
To grow meat, you must first obtain a muscle sample from a live adult animal (by biopsy, under anesthesia) and isolate a subpopulation of cells called “stem” or “satellite” cells. These stem cells participate in muscle regeneration and have the ability to differentiate into muscle cells themselves. The muscle stem cells are then cultured in bioreactors in the presence of a nutrient medium containing growth factors that induce rapid proliferation. The cells are then transformed into muscle cells that form structures called “myotubes” no larger than 0.3 mm in length and mechanically assembled into muscle tissue and ultimately into ground meat or artificial “steak”.

Problematic use of fetal calf serum and growth promoters
The best culture medium for growing cells contains fetal calf serum, obtained from fetal blood after slaughtering a pregnant cow. The procedure usually used (cardiac puncture of the still alive calf fetus) is considered cruel and inhumane by many. This is a problem since large numbers of calves would have to be produced to meet the demand for large-scale meat cultivation, and this use is unacceptable to vegetarians and those who follow a vegan diet or lifestyle. Fortunately, it is now possible, on a laboratory scale, to grow muscle cells without the use of fetal calf serum. However, the serum-free culture will need to be adopted on an industrial scale. To replace fetal calf serum, the industry will need to use growth factors and hormones that will need to be produced on an industrial scale. The use of growth promoters is prohibited in the European Union for conventional meat production; however, you cannot grow meat without using these growth factors and hormones. Overexposure to certain growth promoters can have harmful effects on human health, but this is a subject of debate and several countries approve the supervised use of stimulators in animal production.

From cell to steak
Real muscle (meat) is made up of muscle fibres organized into bundles, blood vessels, nerves, connective tissues, and adipocytes (fat cells). Simply producing animal muscle cells is therefore not enough to recreate meat. This is why in 2013 the first dish prepared from cultivated meat was a simple burger-type patty. Industries that develop cultured meat must now attempt to recreate a 3D structure that will resemble real meat as much as possible, a task that is proving difficult. It’s about recreating the taste experience associated with eating a steak, chicken thigh or shrimp.

Researchers have recently made progress and successfully created small samples of cultured meat that mimic real meat. Using a new approach, a Japanese research group succeeded in growing beef muscle cells in long filaments aligned in a single direction, a structure that closely resembles muscle fibres. When these cultured cells were stimulated by an electric current, the filaments contracted, similar to muscle fibres. Researchers at the University of Tokyo have so far managed to produce pieces of cultured meat weighing a few grams at most. The next challenge will be to successfully produce larger pieces of cultured meat, up to 100 g, and introduce other tissues (blood vessels, fat cells) to mimic meat more convincingly. It should be noted that the culture medium used in this study contained fetal calf serum, an ingredient that cannot be used industrially for ethical and economic reasons, as mentioned above.

Cultured chicken meat
Singapore’s food regulatory agency approved the sale of meat grown by the US company Eat Just in 2020. It was the first time that the sale of cultured meat had been permitted by a state. Eat Just grows chicken meat using a process that does not require antibiotics. This cultured meat is safe because it contains very low levels of bacteria, much less than conventional chicken meat. Cultured chicken meat contains a little more protein, has a more varied amino acid composition, and contains more monounsaturated fat than conventional meat. The muscle cells are grown in 1200-litre bioreactors and then combined with plant ingredients to make chicken nuggets. The Singapore-approved process uses fetal calf serum, but Eat Just plans to use a serum-free culture medium in their future productions.

Estimation of the environmental cost of cultured meat
Cultivated meat production offers many environmental advantages compared to conventional meat, according to a study published in 2011. It would reduce greenhouse gas (GHG) emissions by 78 to 96%, use 7 to 45% less energy and 82 to 96% less water, depending on the type of product. In contrast, a more recent and rigorous study suggests that in the long term, the impact of cultured meat on the environment may be greater than that associated with livestock farming. Cultivated meat production will certainly reduce global warming in the short term since less GHGs will be emitted compared to cattle farming. In the very long term however (i.e., several hundred years), models predict that this would not necessarily be the case, because the main GHG generated by livestock, methane (CH4), does not accumulate in the atmosphere, unlike CO2 which is practically the only GHG generated by cultivated meat. Another study based on data from 15 companies involved in the production of cultured meat concludes that it is less harmful to the environment than the production of beef, but that it has a greater impact on the environment than the production of chicken, pork and plant-based “meat”. In order for the environmental score of cultivated meat to be better than that of conventional products, the industry would have to use only sustainable energy.

Cost of cultured meat
The first cultivated beef burger was produced in 2013 by a Dutch laboratory at an estimated cost of US $416,000. In 2015, the cost of production (on an industrial scale) was reduced to around $12, and it is expected that the price could be the same as conventional meat within ten years. The cultured chicken nuggets produced by Just Eat each cost $63 to produce in 2019, so industries still have some way to go for cultured meat to become affordable enough for consumers to consume on a regular basis.

Cultured meat: an alternative for Canadians?
According to a 2018 Dalhousie University survey of 1,027 Canadians, 32.2% of respondents planned to reduce their meat consumption in the next 6 months. However, cultured meat is not very popular with Canadians as only 18.3% of those consulted said that this new type of “meat” represented an alternative to real meat for them. There is hope, however, as younger consumers (40 and under) seem more likely (34%) to view cultured meat as an alternative.

Will cultured meat one day replace conventional meat on our plates? Although there is still progress to be made before this is possible, both in terms of production and social acceptability, we can hope that the important efforts made will lead to results within a decade. Ideally, for our health and that of the planet, we should reduce our consumption of meat (of all kinds) and eat mainly plants, as is the case with the Mediterranean diet and other traditional diets.

Environmental impacts associated with food production

Environmental impacts associated with food production


  • Food production is responsible for about 25% of the greenhouse gases emitted annually, with half of these GHGs coming from animal farming, mainly in the form of methane.
  • The agricultural sector is also an important source of fine particles responsible for air pollution, with the majority of these pollutants coming from ammonia generated by livestock farming.
  • Overall, a reduction in the consumption of animal products, particularly those from cattle farming, is therefore absolutely essential to limit global warming and improve air quality.

The latest report from the Intergovernmental Panel on Climate Change (IPCC) confirms that, if nothing is done, the constant build-up of greenhouse gases (GHG) in the atmosphere will cause temperatures to increase by more than 1.5ºC above pre-industrial levels over the next century, namely the target set by the Paris Agreement to minimize the negative effects of global warming. There is therefore an urgent need to drastically reduce the emission of these gases if we want to prevent the consequences of this warming, already visible today, from becoming out of control and causing an increase in the incidence of extreme climatic events (droughts, heat waves, hurricanes, forest fires), disrupting life on Earth (extinction of species, fall in agricultural yields, increase in infectious diseases, armed conflicts) and increasing the incidence of several diseases linked to excessive heat.

Carbon dioxide and other greenhouse gases
The main greenhouse gas is carbon dioxide (CO2), which now has a concentration of 417 ppm, about twice as much as in pre-industrial times. However, it should be noted that other gases, even if they are present in smaller quantities, also contribute to global warming. These gases, such as methane or certain molecules used for industrial purposes, capture heat in a much greater way than CO2 and therefore have a higher global warming potential (GWP) than CO2. For example, a tonne of methane has a GWP 28 times greater than a tonne of CO2 over a 100-year period, while the GWP of some industrial gases such as sulfur hexafluoride can reach almost 25,000 times that of CO2 (Table 1). In other words, even if many of these gases are present in minute quantities, on the order of a few parts per billion (10-9) or even per trillion (10–12), their emission is several times that of CO2 and therefore significantly contributes to warming.

Table 1. Global warming potential of various greenhouse gases.1 Values are for the year 2018, except for CO2 which is for 2020. Derived from the United States Environmental Protection Agency (EPA).2 Calculated for a 100-year period. From Greenhouse Gas Protocol. *ppm (part per million or 10-6); **ppb (part per billion or 10-9); ***ppt (part per trillion or 10–12).

To calculate this contribution to global greenhouse gas emissions, the method generally used is to convert these emissions into CO2 equivalents (CO2eq) by multiplying their quantity in the atmosphere by their respective GWP. For example, 1 kg of SF6 is equivalent to 23,500 kg (23.5 tonnes) of CO2 (1 kg × 23,500 = 23,500 CO2eq), while it takes 1000 kg of methane to reach an equivalent amount of CO2 (1000 kg × 28 = 28,000 CO2eq). When this method is applied to all gases, it is estimated that 75% of greenhouse gas emissions are in the form of CO2, the remainder coming from methane (17%), nitrous oxide (6%), and various fluorinated gases (2%) (Figure 1).

Figure 1. Distribution of greenhouse gas emissions. Adapted from Ritchie and Roser (2020).

Emissions sources
The use of fossil fuels to support human activities (transport, electricity production, heating, various industrial processes) is the main source of greenhouse gases, accounting for around three quarters of total emissions (Figure 2). This enormous “carbon footprint” implies that the fight against global warming necessarily requires a transition to “cleaner” sources of energy, in particular with regard to transport and electricity production. This is especially true in a country like Canada, where we emit an average of 20 tonnes of CO2eq per person per year, which ranks us, along with the United States and Australia, among the worst producers of GHGs in the world (Quebec, for its part, does better, with about 10 tonnes of CO2eq per person per year).

Figure 2. Contribution of the food sector to the annual production of greenhouse gases. Adapted from Ritchie and Roser (2020).

Another industry that contributes significantly to greenhouse gas emissions, but that we hear much less about, is food production. It is estimated that around 25% of all these gases come from the production and distribution of food, a proportion that rises to 33% when food waste is taken into account. The food sector involved in animal protein production alone is responsible for half of these food-related GHG emissions, mainly due to methane produced by livestock and aquaculture (31%) (see box). Livestock farming also requires large spaces, created in some cases by massive deforestation (in the Amazon, for example), which eliminates huge areas of plants that can sequester COs. Livestock farming also requires large quantities of forage plants and therefore the use of nitrogen fertilizers to accelerate the growth of these plants. The CO2 and nitrous oxide released into the atmosphere during the production of these fertilizers therefore contribute to the GHG generated by livestock.

Where does methane come from?
Methane (CH4) is the end product of the decomposition of organic matter. Methanogenesis is made possible by certain anaerobic microorganisms from the archaea domain (methanogens) which reduce carbon, present in the form of CO2 or certain simple organic acids (acetate, for example), to methane, according to the following reactions:

CO+ 4 H2 → CH4 + 2 H2O


The methane generated by livestock comes mainly from the fermentation of carbonaceous products inside the digestive system of ruminants. In these animals, the digestion of plant matter generates volatile fatty acids (acetate, propionate, butyrate), which are absorbed by the animal and used as a source of energy, and lead in parallel to the production of methane, about 500 L per day per animal, most of it being released through the mouth of the animal. Globally, livestock is estimated to emit about 3.1 Gt of CO2-eq as methane, which represents almost half of all anthropogenic methane emissions.

Aquaculture is another rapidly expanding form of farming, now accounting for over 60% of the global supply of fish and seafood for human consumption. Although GHG emissions from this sector are still much lower than those associated with livestock, recent measurements nonetheless indicate a sharp increase in its global warming potential, mainly due to an increase in methane production. In these systems, the sediments accumulate food residues used for the growth of fish and seafood as well as the droppings generated by these animals. The transformation of this organic material leads to the production of methane, which can then be diffused into the atmosphere.

Finally, it should be noted that the majority of aquaculture systems are located in Asia, where they are often established in regions previously occupied by mangroves, ecosystems located along the coasts and deltas of tropical regions. The destruction of these mangroves (very often for shrimp farming) is very harmful to global warming, because mangrove forests collectively store around 4 billion tonnes of CO2 and their elimination therefore has a concrete impact on the climate.

A good way to visualize the impact of livestock farming on GHG production is to compare the emissions associated with different foods of animal and plant origin based on the amount of protein in these foods (Figure 3). These comparisons clearly show that products derived from livestock products, beef in particular, represent a much greater source of GHGs than plants. The production of 100 g of beef protein, for example, generates on average 100 times more GHGs than the same amount of protein from nuts or legumes. This is true even for beef produced in the traditional way, i.e., from animals that feed exclusively on grass: these animals grow more slowly and therefore emit methane for a longer period, which cancels out the benefits that could be associated with the sequestration of CO2 by the grass that they eat.

Figure 3. Comparison of GHG levels generated during the production of different protein sources. Based on Poore and Nemecek (2018), as modified by Eikenberry (2018).

These huge differences in GHGs associated with the production of everyday food therefore clearly show that our food choices can have a significant influence on global warming. Since the majority of GHG emissions come from livestock, it is evident that a reduction in the consumption of meat, and animal products as a whole, will have the most positive impact. These benefits can be observed even with a fairly modest reduction in meat intake, as in the Mediterranean diet, or simply by replacing products from ruminants (beef and dairy products) by other sources of animal protein (poultry, pork, fish) (Figure 4). Obviously, a more drastic reduction in meat intake is even more beneficial, whether through the adoption of a flexitarian diet (high intake of plants, but little meat and animal products), vegetarian (no animal products, with the exception of eggs, dairy products and sometimes fish), and vegan (no animal products). This remains true even if the plants consumed come from abroad and sometimes travel long distances, because contrary to popular belief, transport only accounts for a small proportion (less than 10%) of the GHGs associated with a given food.

Figure 4. Potential for mitigation of GHG emissions by different types of diets. Adapted from IPCC (2019).

It is impossible to completely decarbonize food production, especially in a world where there are over 9 billion people to feed daily. On the other hand, there is no doubt that the GHG footprint of food can be significantly reduced by reducing the consumption of products derived from ruminants, such as beef and dairy products. This is extremely important, because the status quo is untenable. According to recent models, even if GHG emissions from fossil fuels ceased immediately, we would still not succeed in reaching the target of a maximum warming of 1.5ºC due to emissions produced by the current food production system.

Another aspect that is often overlooked is how fast and significant this positive impact of a reduction in cattle breeding products can be. Even though methane is a GHG almost 30 times more powerful than CO2, its life in the atmosphere is much shorter, around 10–20 years vs. several thousand years for CO2. Concretely, this means that an immediate drop in methane emissions, for example following a drastic reduction in the consumption of beef and dairy products, can have measurable effects on GHG levels in the following years and therefore represents the fastest and most efficient way to slow global warming.

Pollution from food
In addition to contributing to global GHG emissions, another environmental impact of food production is its contribution to air pollution. This negative impact of the food sector should not be overlooked, because while the influence of global warming caused by GHGs will be felt above all in the medium and longer term, atmospheric pollutants have an immediate effect on health: air pollution is currently the 7th leading cause of premature death worldwide, being directly responsible for around 4 million deaths annually (Figure 5). In some countries, such as the United States, it is estimated that agriculture and livestock are responsible for about 20% of this air pollution-related mortality.

Figure 5. Leading causes of premature mortality worldwide. Note that air pollution is the only risk factor of environmental origin, not related to lifestyle. From GBD 2016 Risk Factors Collaborators (2016).

Fine particles of 2.5 µm and less (PM2.5) are mainly responsible for these negative impacts of air pollution on health. Due to their small size, these particles easily penetrate the lungs to the pulmonary alveoli, where they pass directly to the pulmonary blood vessels and then to all arteries in the body. They then produce an inflammatory reaction and oxidative stress that damage the vascular endothelium, the thin layer of cells that covers the inner walls of the arteries and ensures their proper functioning. The arteries therefore dilate less easily and tend to contract more, which interferes with normal blood circulation. For all these reasons, it is cardiovascular diseases (coronary heart disease and stroke) that represent the main consequence of exposure to fine particles, and alone are responsible for about 80% of all deaths caused by ambient air pollution (Figure 6).

Figure 6. Distribution of premature deaths (in millions) caused by fine particles PM2.5.
Note the predominance of cardiovascular disease as a cause of death linked to air pollution. Adapted from Lelieveld et al. (2015).

Primary and secondary particles
Fine particles can be emitted directly from polluting sources (primary PM2.5) or indirectly, following the combination of several distinct particles present in the atmosphere (secondary PM2.5) (Figure 7). Much of the primary PM2.5 is in the form of carbon soot, produced by the incomplete combustion of fossil fuels (diesel and coal, especially) or biomass (forest fires, for example). Carbon soot is also associated with various organic compounds (polycyclic aromatic hydrocarbons), acids, metals, etc., which contribute to its toxicity after inhalation. These particles can be transported aloft over very long distances and, once deposited, be resuspended in the wind. In urban areas, this resuspension also takes place under the action of road traffic. This turbulence associated with automobile traffic is also responsible for the production of another class of primary PM2.5 called fugitive road dust.

Secondary PM2.5, on the other hand, are formed from precursors such as sulfur dioxide (SO2), nitrogen oxides (NOx), various volatile organic compounds containing carbon (organic carbon) as well as ammonia (NH3). The chemical reactions that govern the interaction between these different volatile substances to form the secondary fine particles are extraordinarily complex, but let us only mention that it is well established that the presence of the ammonium ion (NH4+), derived from ammonia (NH3), neutralizes the negative charge of certain gases and thus promotes their aggregation in the form of fine particles (Figure 7). Consequently, the presence of NH3 in the atmosphere often represents a limiting step in the formation of these secondary fine particles and a reduction in these emissions can therefore have concrete effects on improving air quality.

Figure 7. Schematic representation of the mechanisms of formation of fine particles PM2.5.

It is this important role of ammonia in the formation of secondary fine particles that explains the contribution of the food production sector to air pollution. Agriculture and livestock are in fact responsible for almost all anthropogenic ammonia emissions, a consequence of intensive livestock farming, the spreading of manure and slurry, and the industrial production of nitrogen fertilizers.

An American study clearly illustrates this contribution of agricultural ammonia to the negative impacts of air pollution on health. In this study, the researchers show that of the approximately 18,000 deaths caused annually by pollution derived from the agricultural sector, the vast majority (70%) of these deaths are a consequence of ammonia emissions (and therefore secondary PM2.5), while the emission of primary PM2.5, from plowing, the combustion of agricultural residues, and machinery, is responsible for the rest. Since the vast majority of ammonia emissions come from animal faeces and the use of natural (manure and slurry) or synthetic fertilizers to grow food for these animals, it is not surprising that the production of food from livestock is the main cause of deaths attributable to pollution from agricultural sources (Figure 8).

Figure 8. Distribution of deaths caused annually by PM2.5 from the agricultural sector in the United States. Note that 70% of the mortality is attributable to livestock products, mainly due to the ammonia generated by the animals as well as by the spreading of manure, slurry and synthetic fertilizers for the cultivation of fodder plants (corn, soybeans). From Domingo et al. (2021).

When we compare the impact of different foods for the same quantity of product, we immediately see that the production of red meat is particularly damaging, being responsible for at least 5 times more deaths than that of poultry, 10 times more than that of nuts and seeds, and at least 50 times more than that of other plants such as fruits and vegetables (Figure 9).

Figure 9. Comparison of PM2.5-related mortality by food types. From Domingo et al. (2021).

In short, whether in terms of reducing GHG emissions or health problems associated with atmospheric pollution, all the studies unequivocally show that a reduction in environmental damage caused by food production necessarily involves a reduction in the consumption of products of animal origin, in particular those from cattle farming. A change that is all the more profitable as the reduction in the intake of food of animal origin, combined with an increase in the consumption of plants, is beneficial for health and could prevent about 11 million premature deaths annually, a decrease of 20%.