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.





Choosing the right sources of carbohydrates is essential for preventing cardiovascular disease

Choosing the right sources of carbohydrates is essential for preventing cardiovascular disease


  • Recent studies show that people who regularly consume foods containing low-quality carbohydrates (simple sugars, refined flours) have an increased risk of cardiovascular events and premature mortality.
  • Conversely, a high dietary intake of complex carbohydrates, such as resistant starches and dietary fibre, is associated with a lower risk of cardiovascular disease and improved overall health.
  • Favouring the regular consumption of foods rich in complex carbohydrates (whole grains, legumes, nuts, fruits and vegetables) while reducing that of foods containing simple carbohydrates (processed foods, sugary drinks, etc.) is therefore a simple way to improve cardiovascular health.

It is now well established that a good quality diet is essential for the prevention of cardiovascular disease and the maintenance of good health in general. This link is particularly well documented with regard to dietary fat: several epidemiological studies have indeed reported that too high a dietary intake of saturated fat increases LDL cholesterol levels, an important contributor to the development of atherosclerosis, and is associated with an increased risk of cardiovascular disease. As a result, most experts agree that we should limit the intake of foods containing significant amounts of saturated fat, such as red meat, and instead focus on sources of unsaturated fat, such as vegetable oils (especially extra virgin olive oil and those rich in omega-3s such as canola), as well as nuts, certain seeds (flax, chia, hemp) and fish (see our article on this subject). This roughly corresponds to the Mediterranean diet, a diet that has repeatedly been associated with a lower risk of several chronic diseases, especially cardiovascular disease.

On the carbohydrate side, the consensus that has emerged in recent years is to favour sources of complex carbohydrates such as whole grains, legumes and plants in general while reducing the intake of simple carbohydrates from refined flour and added sugars. Following this recommendation, however, can be much more difficult than one might think, as many available food products contain these low-quality carbohydrates, especially the entire range of ultra-processed products, which account for almost half of the calories consumed by the population. It is therefore very important to learn to distinguish between good and bad carbohydrates, especially since these nutrients are the main source of calories consumed daily by the majority of people. To achieve this, we believe it is useful to recall where carbohydrates come from and how industrial processing of foods can affect their properties and impacts on health.

Sugar polymers
All of the carbohydrates in our diet come from, in one way or another, plants. During the photosynthetic reaction, in addition to forming oxygen (O2) from carbon dioxide in the air (CO2), plants also simultaneously transform the energy contained in solar radiation into chemical energy, in the form of sugar:

6 CO2 + 12 H2O + light → C6H12O6 (glucose) + 6 O2 + 6 H2O

In the vast majority of cases, this sugar made by plants does not remain in this simple sugar form, but is rather used to make complex polymers, i.e., chains containing several hundred (and in some cases thousands) sugar molecules chemically bonded to one another. An important consequence of this arrangement is that the sugar contained in these complex carbohydrates is not immediately accessible and must be extracted by digestion before reaching the bloodstream and serving as a source of energy for the body’s cells. This prerequisite helps prevent sugar from entering the blood too rapidly, which would unbalance the control systems responsible for maintaining the concentration of this molecule at levels just sufficient enough to meet the needs of the body. And these levels are much lower than one might think; on average, the blood of a healthy person contains a maximum of 4 to 5 g of sugar in total, or barely the equivalent of a teaspoon. Dietary intake of complex carbohydrates therefore provides enough energy to support our metabolism, while avoiding excessive fluctuations in blood sugar that could lead to health problems.

Figure 1 illustrates the distribution of the two main types of sugar polymers in the plant cell: starches and fibres.

Figure 1. The physicochemical characteristics and physiological impacts of starches and dietary fibres from plant cells. Adapted from Gill et al. (2021).

Starches. Starches are glucose polymers that the plant stores as an energy reserve in granules (amyloplasts) located inside plant cells. This source of dietary carbohydrates has been part of the human diet since the dawn of time, as evidenced by the recent discovery of genes from bacteria specializing in the digestion of starches in the dental plaque of individuals of the genus Homo who lived more than 100,000 years ago. Even today, a very large number of plants commonly eaten are rich in starch, in particular tubers (potatoes, etc.), cereals (wheat, rice, barley, corn, etc.), pseudocereals (quinoa, chia, etc.), legumes, and fruits.

Digestion of the starches present in these plants releases units of glucose into the bloodstream and thus provides the energy necessary to support cell metabolism. However, several factors can influence the degree and speed of digestion of these starches (and the resulting rise in blood sugar). This is particularly the case with “resistant starches” which are not at all (or very little) digested during gastrointestinal transit and therefore remain intact until they reach the colon. Depending on the factors responsible for their resistance to digestion, three main types of these resistant starches (RS) can be identified:

  • RS-1: These starches are physically inaccessible for digestion because they are trapped inside unbroken plant cells, such as whole grains.
  • RS-2: The sensitivity of starches to digestion can also vary considerably depending on the source and the degree of organization of the glucose chains within the granules. For example, the most common form of starch in the plant kingdom is amylopectin (70–80% of total starch), a polymer made up of several branches of glucose chains. This branched structure increases the contact surface with enzymes specialized in the digestion of starches (amylases) and allows better extraction of the glucose units present in the polymer. The other constituent of starch, amylose, has a much more linear structure which reduces the efficiency of enzymes to extract the glucose present in the polymer. As a result, foods with a higher proportion of amylose are more resistant to breakdown, release less glucose, and therefore cause lower blood sugar levels. This is the case, for example, with legumes, which contain up to 50% of their starch in the form of amylose, which is much more than other commonly consumed sources of starches, such as tubers and grains.
  • RS-3: These resistant starches are formed when starch granules are heated and subsequently cooled. The resulting starch crystallization, a phenomenon called retrogradation, creates a rigid structure that protects the starch from digestive enzymes. Pasta salads, potato salads, and sushi rice are all examples of foods containing resistant starches of this type.

An immediate consequence of this resistance of digestion-resistant starches is that these glucose polymers can be considered dietary fibre from a functional point of view. This is important because, as discussed below, the fermentation of fibre by the hundreds of billions of bacteria (microbiota) present in the colon generates several metabolites that play extremely important roles in the maintenance of good health.

Dietary fibre. Fibres are polymers of glucose present in large quantities in the wall of plant cells where they play an important role in maintaining the structure and rigidity of plants. The structure of these fibres makes them completely resistant to digestion and the sugar they contain does not contribute to energy supply. Traditionally, there are two main types of dietary fibre, soluble and insoluble, each with its own physicochemical properties and physiological effects. Everyone has heard of insoluble fibre (in wheat bran, for example), which increases stool volume and speeds up gastrointestinal transit (the famous “regularity”). This mechanical role of insoluble fibres is important, but from a physiological point of view, it is mainly soluble fibres that deserve special attention because of the many positive effects they have on health.

By capturing water, these soluble fibres increase the viscosity of the digestive contents, which helps to reduce the absorption of sugar and dietary fats and thus to avoid excessive increases in blood sugar and blood lipid levels that can contribute to atherosclerosis (LDL cholesterol, triglycerides). The presence of soluble fibre also slows down gastric emptying and can therefore decrease calorie intake by increasing feelings of satiety. Finally, the bacterial community that resides in the colon (the microbiota) loves soluble fibres (and resistant starches), and this bacterial fermentation generates several bioactive substances, in particular the short chain fatty acids (SCFA) acetate, propionate and butyrate. Several studies carried out in recent years have shown that these molecules exert a myriad of positive effects on the body, whether by reducing chronic inflammation, improving insulin resistance, lowering blood pressure and the risk of cardiovascular disease, or promoting the establishment of a diversified microbiota, optimal for colon health (Table 1).

A compilation of many studies carried out in recent years (185 observational studies and 58 randomized trials, which equates to 135 million person-years) indicates that consuming 25 to 30 g of fibre per day seems optimal to benefit from these protective effects, approximately double the current average consumption.

Table 1. Main physiological effects of dietary fibre. Adapted from Barber (2020).

Physiological effectsBeneficial health impacts
MetabolismImproved insulin sensitivity
Reduced risk of type 2 diabetes
Improved blood sugar and lipid profile
Body weight control
Gut microbiotaPromotes a diversified microbiota
Production of short-chain fatty acids
Cardiovascular systemDecrease in chronic inflammation
Reduced risk of cardiovascular events
Reduction of cardiovascular mortality
Digestive systemDecreased risk of colorectal cancer

Overall, we can therefore see that the consumption of complex carbohydrates is optimal for our metabolism, not only because it ensures an adequate supply of energy in the form of sugar, without causing large fluctuations in blood sugar, but also because it provides the intestinal microbiota with the elements necessary for the production of metabolites essential for the prevention of several chronic diseases and for the maintenance of good health in general.

Modern sugars
The situation is quite different, however, for several sources of carbohydrates in modern diets, especially those found in processed industrial foods. Three main problems are associated with processing:

Simple sugars. Simple sugars (glucose, fructose, galactose, etc.) are the molecules responsible for the sweet taste: the interaction of these sugars with receptors present in the tongue sends a signal to the brain warning it of the presence of an energy source. The brain, which alone consumes no less than 120 g of sugar per day, loves sugar and responds positively to this information, which explains our innate attraction to foods with a sweet taste. On the other hand, since the vast majority of carbohydrates produced by plants are in the form of polymers (starches and fibres), simple sugars are actually quite rare in nature, being mainly found in fruits, vegetables such as beets, or even some grasses (sugar cane). It is therefore only with the industrial production of sugar from sugar cane and beets that consumers’ “sweet tooth” could be satisfied on a large scale and that simple sugars became commonly consumed. For example, data collected in the United States shows that between 1820 and 2016, the intake of simple sugars increased from 6 lb (2.7 kg) to 95 lb (43 kg) per person per year, an increase of about 15 times in just under 200 years (Figure 2).



Figure 2. Consumption of simple sugars in the United States between 1820 and 2016.  From Guyenet (2018).

Our metabolism is obviously not adapted to this very high intake of simple sugars, far beyond what is normally found in nature. Unlike the sugars found in complex carbohydrates, these simple sugars are absorbed very quickly into the bloodstream and cause very rapid and significant increases in blood sugar. Several studies have shown that people who frequently consume foods containing these simple sugars are more likely to suffer from obesity, type 2 diabetes and cardiovascular disease. For example, studies have found that consuming 2 servings of sugary drinks daily was associated with a 35% increase in the risk of coronary heart disease. When the amount of added sugars consumed represents 25% of daily calories, the risk of heart disease nearly triples. Factors that contribute to this detrimental effect of simple sugars on cardiovascular health include increased blood pressure and triglyceride levels, lowered HDL cholesterol, and increased LDL cholesterol (specifically small, very dense LDLs, which are more harmful to the arteries), as well as an increase in inflammation and oxidative stress.

It is therefore necessary to restrict as much as possible the intake of simple sugars, which should not exceed 10% of the daily energy intake according to the World Health Organization. For the average adult who consumes 2,000 calories per day, that’s just 200 calories, or about 12 teaspoons of sugar or the equivalent of a single can of soft drink.

Refined flour.  Cereals are a major source of carbohydrates (and calories) in most food cultures around the world. When they are in whole form, i.e., they retain the outer shell rich in fibre and the germ containing several vitamins and minerals, cereals are a source of complex carbohydrates (starches) of high quality and beneficial to health. This positive impact of whole grains is well illustrated by the reduced risk of coronary heart disease and mortality observed in a large number of population studies. For example, recent meta-analyses have shown that the consumption of about 50 g of whole grains perday is associated with a 22–30% reduction in cardiovascular disease mortality, a 14–18% reduction in cancer-relatedmortality, and a 19–22% reduction in total mortality.

On the other hand, these positive effects are completely eliminated when the grains are refined with modern industrial metal mills to produce the flour used in the manufacture of a very large number of commonly consumed products (breads, pastries, pasta, desserts, etc.). By removing the outer shell of the grain and its germ, this process improves the texture and shelf life of the flour (the unsaturated fatty acids in the germ are sensitive to rancidity), but at the cost of the almost total elimination of fibres and a marked depletion of several nutrients (minerals, vitamins, unsaturated fatty acids, etc.). Refined flours therefore essentially only contain sugar in the form of starch, this sugar being much easier to assimilate due to the absence of fibres that normally slow down the digestion of starch and the absorption of released sugar (Figure 3).

Figure 3. Schematic representation of a whole and refined grain of wheat.

Fibre deficiency. Fortification processes partially compensate for the losses of certain nutrients (e.g., folic acid) that occur during the refining of cereal grains. On the other hand, the loss of fibre during grain refining is irreversible and is directly responsible for one of the most serious modern dietary deficiencies given the many positive effects of fibre on the prevention of several chronic diseases.

Poor-quality carbohydrates
Low-quality carbohydrate sources with a negative impact on health are therefore foods containing a high amount of simple sugars, having a higher content of refined grains than whole grains, or containing a low amount of fibre (or several of these characteristics simultaneously). A common way to describe these poor-quality carbohydrates is to compare the rise in blood sugar they produce to that of pure glucose, called the glycemic index (GI) (see box). The consumption of food with a high glycemic index causes a rapid and dramatic rise in blood sugar levels, which causes the pancreas to secrete a large amount of insulin to get glucose into the cells. This hyperinsulinemia can cause glucose to drop to too low levels, and the resulting hypoglycemia can ironically stimulate appetite, despite ingesting a large amount of sugar a few hours earlier. Conversely, a food with a low glycemic index produces lower, but sustained, blood sugar levels, which reduces the demand for insulin and helps prevent the fluctuations in blood glucose levels often seen with foods with a high glycemic index. Potatoes, breakfast cereals, white bread, and pastries are all examples of high glycemic index foods, while legumes, vegetables, and nuts are conversely foods with a low glycemic index.

Glycemic index and load
The glycemic index (GI) is calculated by comparing the increase in blood sugar levels produced by the absorption of a given food with that of pure glucose. For example, a food that has a glycemic index of 50 (lentils, for example) produces a blood sugar half as important as glucose (which has a glycemic index of 100). As a general rule, values below 50 are considered to correspond to a low GI, while those above 70 are considered high. The glycemic index, however, does not take into account the amount of carbohydrate in foods, so it is often more appropriate to use the concept of glycemic load (GL). For example, although watermelon and breakfast cereals both have high GIs (75), the low-carbohydrate content of melon (11 g per 100 g) equates to a glycemic load of 8, while 26 g of carbohydrates present in breakfast cereals result in a load of 22, which is three times more. GLs ≥ 20 are considered high, intermediate when between 11 and 19, and low when ≤ 10.

PURE study
Results from the PURE (Prospective Urban and Rural Epidemiology) epidemiological study conducted by Canadian cardiologist Salim Yusuf have confirmed the link between low-quality carbohydrates and the risk of cardiovascular disease. In the first of these studies, published in the prestigious New England Journal of Medicine, researchers examined the association between the glycemic index and the total glycemic load of the diet and the incidence of major cardiovascular events (heart attack, stroke, sudden death, heart failure) in more than 130,000 participants aged 35 to 70, spread across all five continents. The study finds that a diet with a high glycemic index is associated with a significant (25%) increase in the risk of having a major cardiovascular event in people without cardiovascular disease, an increase that reaches 51% in those with pre-existing cardiovascular disease (Figure 4). A similar trend is observed for the glycemic load, but in the latter case, the increased risk seems to affect only those with cardiovascular disease at the start of the study.

Figure 4. Comparison of the risk of cardiovascular events according to the glycemic index or the glycemic load of the diet of healthy people (blue) or with a history of cardiovascular disease (red). The median glycemic index values were 76 for quintile 1 and 91 for quintile 5. For glycemic load, the mean values were 136 g of carbohydrates per day for Q1 and 468 g per day for Q5. Note that the increased risk of cardiovascular events associated with a high glycemic index or load is primarily seen in participants with pre-existing cardiovascular disease. From Jenkins et al. (2021).

The impact of the glycemic index appears to be particularly pronounced in overweight people (Figure 5). Thus, while the increase in the risk of major cardiovascular events is 14% in thin people with a BMI less than 25, it reaches 38% in those who are overweight (BMI over 25).


Figure 5. Impact of overweight on the increased risk of cardiovascular events related to the glycemic index of the diet. The values shown represent the increased risk of cardiovascular events observed for each category (quintiles 2 to 5) of the glycemic index compared to the category with the lowest index (quintile 1). The median values of the glycemic indices were 76 for quintile 1; 81 for quintile 2; 86 for quintile 3; 89 for quintile 4; and 91 for quintile 5. Taken from Jenkins et al. (2021).

This result is not so surprising, since it has long been known that excess fat disrupts sugar metabolism, especially by producing insulin resistance. A diet with a high glycemic index therefore exacerbates the rise in postprandial blood sugar already in place due to excess weight, which leads to a greater increase in the risk of cardiovascular disease. The message to be drawn from this study is therefore very clear: a diet containing too many easily assimilated sugars, as measured using the glycemic index, is associated with a significant increase in the risk of suffering a major cardiovascular event. The risk of these events is particularly pronounced for people with less than optimal health, either due to the presence of excess fat or pre-existing cardiovascular disease (or both). Reducing the glycemic index of the diet by consuming more foods containing complex carbohydrates (fruits, vegetables, legumes, nuts) and fewer products containing added sugars or refined flour is therefore an essential prerequisite for preventing the development of cardiovascular disease.

Refined flours
Another part of the PURE study looked more specifically at refined flours as a source of easily assimilated sugars that can abnormally increase blood sugar levels and increase the risk of cardiovascular disease. Researchers observed that a high intake (350 g per day, or 7 servings) of products containing refined flours (white bread, breakfast cereals, cookies, crackers, pastries) was associated with a 33% increase in the risk of coronary heart disease, 47% in the risk of stroke, and 27% in the risk of premature death. These observations therefore confirm the negative impact of refined flours on health and the importance of including as much as possible foods containing whole grains in the diet. The preventive potential of this simple dietary change is enormous since the consumption of whole grains remains extremely low, with the majority of the population of industrialized countries consuming less than 1 serving of whole grains daily, well below the recommended minimum (half of all grain products consumed, or about 5 servings per day).

Wholemeal breads are still a great way to boost the whole-grain intake. However, special attention must be paid to the list of ingredients. In Canada, the law allows up to 5% of the grain to be removed when making whole wheat flour, and the part removed contains most of the germ and a fraction of the bran (fibres). This type of bread is superior to white bread, but it is preferable to choose products made from whole-grain flour which contains all the parts of the grain. Note also that multigrain breads (7-14 grains) always contain 80% wheat flour and a maximum of 20% of a mixture of other grains (otherwise the bread does not rise), so the number of grains does not matter, but what does matter is whether the flour is whole wheat or ideally integral, which is not always the case.

In short, a simple way to reduce the risk of cardiovascular events and improve health in general is to replace as much as possible the intake of foods rich in simple sugars and refined flour with plant-based foods containing complex carbohydrates. In addition to carbohydrates, this simple change alone will influence the nature of the proteins and lipids ingested as well as, at the same time, all the phenomena that promote the appearance and progression of atherosclerotic plaques.

Modulation of the gut microbiota by dietary interventions to prevent cardiometabolic diseases

Modulation of the gut microbiota by dietary interventions to prevent cardiometabolic diseases


  • In a study of 307 participants, the Mediterranean-style diet was associated with a composition of the gut microbiota conducive to good cardiometabolic health.
  • In another study, intermittent fasting altered the gut microbiota and prevented the development of hypertension in rats that spontaneously became hypertensive as they aged.
  • The metabolism of bile acids modulated by the microbiota has been identified as a regulator of blood pressure.
  • Dietary interventions aimed at modifying the gut microbiota could be a viable non-pharmacological approach to prevent and treat high blood pressure and other conditions.

Cardiometabolic diseases including type 2 diabetes and cardiovascular disease are on the rise in Canada and around the world. These diseases, which reduce the quality of life and life expectancy of those affected and generate significant costs for society, can be prevented by maintaining good lifestyle habits, including a healthy diet and regular exercise.

Recent studies have linked microbial metabolism and immune interactions in the gut and the risk of cardiometabolic disease (see our articles on the subject herehere and here). Two new studies show that the type of diet and the frequency of meals have effects on the risk of metabolic disease, which are in part due to alterations in the gut microbiota. The results of these new studies suggest that modulation of the gut microbiota by dietary interventions could be a new preventive and therapeutic approach.

US researchers analyzed the microbiome data of 307 male participants in the Health Professionals Follow-up Study as well as their eating habits and biomarkers of blood glucose regulation, lipid metabolism and inflammation. The Mediterranean-style diet (consisting mainly of vegetables, legumes, fruits, nuts, olive oil, and some wine and red meat) was associated with a composition of the gut microbiota conducive to good cardiometabolic health. The positive association between the Mediterranean-style diet and a lower risk of cardiometabolic disease was particularly strong among participants whose microbiota contained little Prevotella copri bacteria. Researchers do not yet understand why the Mediterranean diet is less effective in people whose microbiota contains the bacterium Prevotella copri, however, they make several hypotheses that will need to be verified in future studies. In any case, it can be envisaged that prevention approaches may one day be personalized according to the intestinal microbial profile of each person.

Benefits of intermittent fasting for hypertension
Intermittent fasting involves compressing the time during which one eats over a short period (6-8 h) and “fasting” the rest of the day (16-18 h). Intermittent fasting has positive effects on weight and body fat loss, chronic inflammation, metabolism, and cardiovascular health (see our articles on the subject here and here). The main metabolic benefits of intermittent fasting are reduced blood LDL cholesterol levels, increased insulin sensitivity and better blood glucose control in diabetics, reduced oxidative stress and inflammation. On the one hand, we know that an imbalance in the intestinal microbiota (intestinal dysbiosis) contributes to the development of hypertension. On the other hand, studies in recent years have shown that fasting and caloric restriction significantly reduce blood pressure, both in animal models and in hypertensive patients.

A recent study shows that the beneficial effects of intermittent fasting on blood pressure are attributable, at least in part, to the modulation of the gut microbiota. The researchers used an animal model commonly used in hypertension research: spontaneously hypertensive stroke-prone (SHRSP) rats, a unique genetic model of severe hypertension and stroke. Hypertensive SHRSP rats and normotensive Wistar-Kyoto (WKY) rats were subjected for 8 weeks to one or the other of the following diets: 1) ad libitum throughout the study (control groups) or 2) a diet alternating a day with food at will and a day without access to food (intermittent fasting). Hypertensive (SHRSP) and normotensive (WKY) rats in the control groups ingested the same amount of food. In contrast, the rats subjected to intermittent fasting ate more on days with food at will than those in the control groups, presumably to compensate for the fasting day. Despite this, the total amount of food ingested during the study was significantly lower in hypertensive (-27%) and normotensive (-35%) rats subjected to intermittent fasting, compared to animals in the respective control groups that had access to food at will. Despite a similar food intake, the hypertensive rats in the control group gained significantly less weight than the normotensive rats.

As expected, the blood pressure of hypertensive rats measured weekly was significantly higher than that of normotensive rats. In contrast, intermittent fasting significantly reduced blood pressure in hypertensive rats by an average of about 40 mmHg by the end of the study, compared to hypertensive rats who had access to food at will. This significant decrease brought the blood pressure of hypertensive rats to levels comparable to those of normotensive rats.

Role of the gut microbiota in the regulation of blood pressure
Animal models allow experiments on the role of the gut microbiota that could not be done in humans. In order to find out whether the gut microbiota plays a role in the effect of intermittent fasting, the researchers continued their studies by “transplanting” the microbiota from hypertensive and normotensive rats into “germ-free” rats, i.e. rats reproduced under special conditions in such a way that they do not contain any microorganisms.

Germ-free rats that received microbiota from hypertensive rats had significantly higher blood pressure than those that received microbiota from normotensive rats when subjected to the control diet (ad libitum). In contrast, intermittent fasting reduced the blood pressure of germ-free rats that received microbiota from hypertensive rats to levels comparable to those of rats that received microbiota from normotensive rats. These results demonstrate that the alterations in the microbiota of hypertensive rats caused by intermittent fasting are sufficient to cause a reduction in blood pressure. Analysis of the microbiota by whole-genome shotgun sequencing has enabled researchers to identify bile acid metabolism as a potential mediator of blood pressure regulation. Subsequent analyses revealed that the blood levels of 11 bile acids (out of 18) in hypertensive SHRSP rats were significantly lower than those in normotensive rats. In support of the hypothesis, the addition of cholic acid (a precursor of bile acids) in the food or the activation of the bile acid receptor (TGR5) significantly reduced the blood pressure (by 18 mmHg) of hypertensive rats.

In summary, the quality of food and frequency with which we eat has a significant impact on the microorganisms in our microbiota, cardiometabolic risk factors and, ultimately, our overall health. By changing the diet and the frequency of meals, it may be possible to significantly improve the condition of people with chronic diseases.

Gradual return to physical activity after recovering from COVID-19

Gradual return to physical activity after recovering from COVID-19


  • People with persistent symptoms or who have had a severe form of COVID-19 or who may have a history of cardiopathy should consult a doctor before resuming physical activity.
  • People who have had a mild form of COVID-19 and want to resume physical activity should do so very gradually.
  • Do not resume exercise until at least seven days without symptoms and start with at least two weeks of minimal exercise.
  • Use daily self-monitoring to track your progress and determine when to seek additional medical help if needed.

Here we provide a summary of guidelines and advice from public health organizations for returning to exercise after COVID-19 (see hereherehere and here).

After a mild form of COVID-19, some people have a prolonged recovery, especially when trying to resume exercise. In addition, many affected people may have long-term complications from COVID-19, including chronic COVID syndrome (post-COVID syndrome or long COVID), cardiopulmonary disease, and, in some people, psychological sequelae (1234). This article presents a pragmatic approach to help people safely return to physical activity after symptomatic SARS-CoV-2 infection, focusing on those who have lost their physical condition or have had a prolonged period of inactivity but who do not have chronic COVID syndrome.

The health benefits of physical activity, for cardiovascular as well as mental health, are well established (56). Conversely, the harms of physical inactivity make it a major risk factor for noncommunicable diseases around the world, as are smoking and obesity (7). Before the COVID-19 pandemic, the majority of adult Canadians (82.5%) did not meet physical activity guidelines (at least 150 minutes of moderate-intensity physical activity per week at a rate of at least 10 minutes per session) and were sedentary for most of the day (9.6 hours) (8). There has been a further decline in physical activity since the start of the pandemic among people with chronic conditions like obesity and hypertension (9), conditions that are associated with severe forms of COVID-19 (10). Brief advice can help people engage in physical activity, with the associated positive health effects, and help those recovering from illness to return to previous levels of physical activity or beyond (11). Some people may not know how and when to resume physical activity after COVID-19, and if it is safe. Some may have tried returning to their baseline exercise and found that they were unable to do so.

You should consult a doctor before exercising after having COVID-19 when:

  • The illness required treatment in the hospital.
  • Myocarditis has been diagnosed.
  • You experienced heart symptoms during the illness (chest pain, palpitations, severe shortness of breath or syncope).
  • You experience persistent symptoms (respiratory, gastrointestinal, rheumatic or other).

If you had no complications during the illness and have had no symptoms for 7 days, you can gradually resume physical activity (Figure 1):

Resuming in four phases (minimum of 7 days for each phase):

Phase 1: Very low intensity physical activity, such as flexibility and breathing exercises.

Phase 2: Low-intensity physical activity such as slow walking, light yoga, light housework and gardening, gradually increasing the duration to 10–15 minutes per day, when the exercise is well tolerated.

At both phases 1 and 2, the person should be able to hold a normal conversation without difficulty while doing the exercises.

Phase 3: Aerobic and strength exercises of moderate intensity, such as brisk walking, jogging, swimming, cycling, going up and down stairs. You shouldn’t feel like the exercise is “hard”. It is recommended to do two 5-minute intervals of exercise separated by a recovery block. People should add one interval per day if exercise is well tolerated.

Phase 4: Aerobic and strength exercises of moderate intensity with control of coordination and functioning skills, such as running with changes of direction, side steps, but without it feeling too difficult. Two days of training followed by a day of recovery.

Phase 5: Return to regular exercise (pre-COVID).


Figure 1. Suggested return to physical activity after COVID-19. Adapted from Salman et al., BMJ, 2021.


It is proposed to devote a minimum of 7 days to each phase to avoid sudden increases in training load. However, people should stay at the stage they feel comfortable with for as long as necessary. Watch for any inability to recover 1 hour after exercise and the next day, for abnormal shortness of breath, abnormal heart rate, excessive fatigue or lethargy, and markers of poor mental health. If this happens or if you are not progressing as planned, you should return to a previous phase and seek medical attention if in doubt. Keeping a journal of exercise progress, as well as the intensity of exertion, any changes in mood and, for those who are used to measuring it, objective fitness data such as heart rate, can be useful in tracking progress.

Association between chronic stress and heart attacks

Association between chronic stress and heart attacks


  • Cortisol concentration in recent hair growth was measured in middle-aged people shortly after suffering a heart attack, and in people of the same age group who were in apparent good health.
  • The median concentration of cortisol in the hair of people with a myocardial infarction was 2.4 times higher than that measured in the control group.
  • The risk of myocardial infarction was approximately 5 times higher in people with high cortisol levels compared to those with normal cortisol levels.
  • These results indicate that chronic stress appears to be an important risk factor for myocardial infarction.

It is well established that acute physical and/or emotional stress (accident, anger, fear) is a risk factor for heart attack (see our article on the subject). However, it is not clear whether high levels of chronic stress also contribute to the risk of myocardial infarction. One of the reasons that little is known about this potential risk factor is that until recently, it was only possible to measure acute stress, not chronic stress. The stress response involves activation of the corticotropic axis (or hypothalamic-pituitary-adrenal axis) and the autonomic nervous system, including the secretion of cortisol, one of the main stress hormones. Chronic stress can now be objectively and conveniently assessed in people by measuring cortisol levels in hair. As the hair grows, an amount of cortisol proportional to the blood concentration is incorporated into the hair. A 1 cm hair cut at the base of the scalp will have taken 4 to 6 weeks to grow, and its cortisol content will reflect the level of chronic stress the person has experienced during that time. The last 5–10 days of hair growth is in and under the scalp.

In a retrospective study of women and men under the age of 65 in Sweden, the levels of cortisol in the hair of 174 people who had suffered a myocardial infarction were compared to those of 3156 people in apparent good health. The median concentration of cortisol in the hair of people with a myocardial infarction was 2.4 times higher (53.2 pg/mg) than that measured in the control group (22.2 pg/mg).

Analysis of the data shows a very clear dose-response relationship, i.e. that the higher the levels of cortisol detected in the participants’ hair, the greater the risk of a heart attack. This dose-effect relationship is not linear, as can be seen in Figure 1: the cortisol levels of the first 3 quintiles are not associated with a significantly higher risk of myocardial infarction, but this risk increases very significantly for cortisol levels in quintiles 4 and 5.

Figure 1. Relative risk of myocardial infarction as a function of the concentration of cortisol in the hair of the participants. *Very significant (p <0.001). From Faresjö et al., 2020.


This retrospective study shows an association between high cortisol levels and myocardial infarction, but this type of study does not establish a causal link. Results from other studies also suggest that cortisol may cause myocardial infarction. For example, the elevated cortisol levels seen in people with Cushing’s syndrome or in patients receiving glucocorticoid therapy are linked to an increased prevalence of cardiovascular risk factors and myocardial infarction. It is therefore plausible that increased cortisol levels cause metabolic disorders that lead to atherosclerosis and, in the long term, to coronary artery blockage and myocardial infarction. Increased blood cortisol levels also have direct effects on the cardiovascular system, including increased contractility of blood vessels, inhibition of angiogenesis, and increased platelet activation, which can lead to thrombosis.

Exposure to chronic stress is typical of our modern societies and can be the cause of many illnesses. We have to learn to manage this chronic stress, for example by practicing cardiac coherence or meditation. I encourage readers to learn more on this subject; there are many very accessible books: Christophe André: Looking at Mindfulness, Matthieu Ricard: The Art of Meditation, Jon Kabat-Zinn: Full Catastrophe Living, and Rick Hanson: Hardwiring Happiness.