The old debate over whether egg consumption is detrimental to cardiovascular health has been revived since the recent publication of a study that finds a significant, albeit modest, association between egg or dietary cholesterol consumption and the incidence of cardiovascular disease (CVD) and all-cause mortality. Eggs are an important food source of cholesterol: a large egg (≈50 g) contains approximately 186 mg of cholesterol. The effect of eggs and dietary cholesterol on health has been the subject of much research over the last five decades, but recently it has been assumed that this effect is less important than previously thought. For example, the guidelines of medical and public health organizations have in recent years minimized the association between dietary cholesterol and CVD (see the 2013 AHA/ACC Lifestyle Guidelines and the 2015–2020 Dietary Guidelines for Americans). In 2010, the American guidelines recommended consuming less than 300 mg of cholesterol per day; however, the most recent recommendations (2014–2015) do not specify a daily limit. This change stems from the fact that cholesterol intake from eggs or other foods has not been shown to increase blood levels of LDL-cholesterol or the risk of CVD, as opposed to the dietary intake of saturated fat that significantly increases LDL cholesterol levels, a significant risk of CVD.
Some studies have reported that dietary cholesterol increases the risk of CVD, while others reported a decrease in risk or no effect with high cholesterol consumption. In 2015, a systematic review and meta-analysis of prospective studies was unable to draw conclusions about the risk of CVD associated with dietary cholesterol, mainly because of heterogeneity and lack of methodological rigour in the studies. The authors suggested that new carefully adjusted and rigorously conducted cohort studies would be useful in assessing the relative effects of dietary cholesterol on the risk of CVD.
What distinguishes the study recently published in JAMA from those published previously is its great methodological rigour, in particular a more rigorous categorization of the components of the diet, which makes it possible to isolateindependent relationships between the consumption of eggs or cholesterol from other sources and the incidence of CVD. The cohorts were also carefully harmonized, and several fine analyses were performed. The data came from six U.S. cohorts with a total of 29,615 participants who were followed for an average of 17.5 years.
The main finding of the study is that greater consumption of eggs or dietary cholesterol (including eggs and meat) is significantly associated with a higher risk of CVD and premature mortality. This association has a dose-response relationship: for every additional 300 mg of cholesterol consumed daily, the risk of CVD increases by 17% and that of all-cause mortality increases by 18%. Each serving of ½ egg consumed daily is associated with an increased risk of CVD of 6% and an increased risk of all-cause mortality of 8%. On average, an American consumes 295 mg of cholesterol every day, including 3 to 4 eggs per week. The model used to achieve these results took into account the following factors: age, gender, race/ethnicity, educational attainment, daily energy intake, smoking, alcohol consumption, level of physical activity, use of hormone therapy. These adjustments are very important when you consider that egg consumption is commonly associated with unhealthy behaviours such as smoking, physical inactivity and unhealthy eating. These associations remain significant after additional adjustments to account for CVD risk factors (e.g. body mass index, diabetes, blood pressure, lipidemia), consumption of fat, animal protein, fibre and sodium.
A review of this study suggests that the association between cholesterol and the incidence of CVD and mortality may be due in part to residual confounding factors. The authors of this review believe that health-conscious people reported eating fewer eggs and cholesterol-containing foods than they actually did. Future studies should include “falsification tests” to determine whether a “health consciousness” factor is the cause of the apparent association between dietary cholesterol and CVD risk.
Eggs, TMAO and atherosclerosis
A few years ago, a metabolomic approach identified a compound in the blood, trimethylamine-N-oxide (TMAO), which is associated with increased cardiovascular risks. TMAO is formed from molecules from the diet: choline, phosphatidylcholine (lecithin) and carnitine. Bacteria present in the intestinal flora convert these molecules into trimethylamine (TMA), then the TMA is oxidized to TMAO by liver enzymes called flavin monooxygenases. The main dietary sources of choline and carnitine are red meat, poultry, fish, dairy products and eggs (yolks). Eggs are an important source of choline (147 mg/large egg), an essential nutrient for the liver, muscles and normal foetal development, among others.
A prospective study indicated that elevated plasma concentrations of TMAO were associated with a risk of major cardiac events (myocardial infarction, stroke, death), independent of traditional risk factors for cardiovascular disease, markers of inflammation, and renal function. It has been proposed that TMAO promotes atherosclerosis by increasing the number of macrophage scavenger receptors, which carry oxidized LDL (LDLox) to be degraded within the cell, and by stimulating macrophage foam cells (i.e. filled with LDLox fat droplets), which would lead to increased inflammation and oxidation of cholesterol that is deposited on the atheroma plaques. A randomized controlled study indicates that the consumption of 2 or more eggs significantly increases the TMAO in blood and urine, with a choline conversion rate to TMAO of approximately 14%. However, this study found no difference in the blood levels of two markers of inflammation, LDLox and C-reactive protein (hsCRP).
Not all experts are convinced that TMAO contributes to the development of CVD. A major criticism is focused on fish and seafood, foods that may contain significant amounts of TMAO, but are associated with better cardiovascular health. For example, muscle tissue in cod contains 45–50 mmol TMAO/kg. For comparison, the levels of choline, a precursor of TMAO, are 24 mmol/kg in eggs and 10 mmol/kg in red meat. The only sources of choline that are equivalent to that in TMAO in marine species are beef and chicken liver. TMAO contained in fish and seafood is therefore significantly more important quantitatively than TMAO that can be generated by the intestinal flora from choline and carnitine from red meat and eggs. This was also measured: plasma levels of TMAO are much higher in people who have a fish-based diet (> 5000 μmol / L) than in people who eat mostly meat and eggs (139 μmol / L). In their response to this criticism, the authors of the article point out that not all fish contain the same amounts of TMAO and that many (e.g. sea bass, trout, catfish, walleye) do not contain any. Fish that contain a lot of TMAO are mainly deep-sea varieties (cod, haddock, halibut). The TMAO content of other fish, including salmon, depends on the environment and when they are caught.
Other experts believe this could be a case of reverse causality: the reduction in renal function associated with atherosclerosis could lead to an accumulation of TMAO, which would mean that this metabolite is a marker and not the cause of atherosclerosis. To which the authors of the hypothesis counter that the high concentration of TMAO is associated with a higher risk of cardiovascular events even when people have completely normal kidney function.
Diabetes and insulin resistance
People who are overweight (BMI> 25) and obese (BMI> 50) are at higher risk of becoming insulin resistant and having type 2 diabetes and metabolic syndrome, conditions that can, independently or in combination, lead to the development of cardiovascular disease. There is evidence that dietary cholesterol may be more harmful to diabetics. Intestinal absorption of cholesterol is impaired in diabetics, i.e. it is increased. However, in a randomized controlled trial, when diabetic patients consumed 2 eggs per day, 6 times per week, their lipid profile was not altered when their diet contained mono- and polyunsaturated fatty acids. Other studies (mostly subsidized by the egg industry) suggest that eggs are safe for diabetics.
Dr. J. David Spence of the Stroke Prevention & Atherosclerosis Research Center believes that people at risk for CVD, including diabetics, should avoid eating eggs (see also this more detailed article). This expert in prevention argues that it is the effects of lipids after a meal that matter, not fasting lipid levels. Four hours after a meal high in fat and cholesterol, harmful phenomena such as endothelial dysfunction, vascular inflammation and oxidative stress are observed. While egg whites are unquestionably a source of high-quality protein, egg yolks should not be eaten by people with cardiovascular risks or genetic predispositions to heart disease.
The association between the consumption of eggs or foods containing cholesterol and the risk of CVD is modest. But since this risk increases with the amount consumed, people who eat a lot of eggs or foods containing cholesterol have a significant risk of harming their cardiovascular health. For example, according to the study published in JAMA, people who consume two eggs per day instead of 3 or 4 per week have a 27% higher risk of CVD and a 34% higher risk of premature mortality. It is therefore prudent to minimize the consumption of eggs (less than 3 or 4 eggs per week) and meat in order to limit the high intake of cholesterol and choline and avoid promoting atherosclerosis.
So-called “sugary drinks” generally refer to beverages containing added sugars (sucrose, corn syrup, juice concentrates or other sweeteners) such as soft drinks, fruit punches, energy drinks or even sports drinks. These beverages are the main source of simple sugar in the diet of North Americans and a significant proportion of calories consumed daily, especially among teenagers and young adults. In the United States, for example, sugary drinks account for an average of 9.3% of calories among young men and 8.2% among young women. This is huge, especially considering that the World Health Organization recommends limiting the total daily energy intake of added sugars to a maximum of 10% of calories, or 50 g of sugar.
This 10% limit is based on a large number of studies showing that a high intake of added sugars promotes overweight and increases the risk of type 2 diabetes, coronary heart disease and stroke. The negative impact on cardiovascular health is of particular concern, as a recent study has shown that regular consumption of soft drinks for several years is associated with an increased risk of premature mortality of around 20%, mainly as a result of cardiovascular disease.
Traditionally, 100% pure fruit juices are not included in the sugary drinks category as the sugar they contain is of natural origin and not artificially added. However, fruit juice sugar is identical to that of artificially sweetened drinks (glucose and fructose) and is present in quite comparable amounts (Figure 1). It is therefore possible that fruit juices, even when 100% pure, may cause the same adverse effects as other sugary drinks when consumed in large quantities.
Figure 1. Comparison of the sugar content of different fruit juices and beverages containing added sugars. Adapted from Gill and Sattar (2014).
This possibility has recently been explored by an analysis of the link between the consumption of sugary drinks and pure fruit juice and the risk of premature death. Looking at the eating habits of 13,440 participants, the researchers found that people who drank a lot of sugary drinks including pure fruit juice (10% or more of daily calories) were 44% more likely to die prematurely from coronary artery disease compared to people who limit the consumption of these drinks to less than 5% of daily calories. When the types of sugary drinks were analyzed separately, the increased risk of coronary death is 11% for each serving of 355 mL of sweetened beverages and 24% for each 355 mL of pure juice consumed. It should be noted, however, that the small number of deaths associated with coronary heart disease in the study does not support the conclusion that fruit juices are more harmful than other sugary drinks at these levels. Certainly, however, it seems that pure juices, when consumed in large quantities, can greatly contribute to the rise in premature death caused by sugary drinks. These results strengthen the case of the growing number of people (see here and here, for example) for whom fruit juices, even when 100% pure, are sugary drinks in the same category as the others and should therefore be totally eliminated from the diet.
A question of quantity
However, it should be noted that the negative effect of fruit juices on the risk of premature mortality is observed for fairly large quantities of juice, well above the quantities that are generally recommended (150 mL per day). At these more moderate amounts, the effect of fruit juice on health is much more nuanced: a review of the studies carried out to date shows that the consumption of reasonable quantities of fruit juice, i.e., a serving of 150–240 mL a day, has little effect on weight gain, both in adults (gain of about 0.2 kg over 3–4 years) and children (very slight increase in the BMI-z score, i.e., the body mass index of children adjusted for sex and age) (Table 1). These increases are significantly lower than those observed for sugary drinks such as soft drinks: for example, a study showed that each serving of soft drink consumed daily causes an increase in body weight of about 1 kg over a period of 4 years, three times more than the one associated with the consumption of a daily serving of pure fruit juice (0.3 kg).
Table 1. Health effects of consumption of pure fruit juices. Adapted from Auerbach et al. (2018).
* 240 mL serving; ** “BMI-z” (Body mass index z-score) is a relative measure of weight, adjusted for age and sex of the child.
|Outcome|| ||Population||Subjects||Amounts consumed||Results||Study
|Tooth decay||Children||1,919||≥1 serving*/d vs. ≤1 serving/week||20% increase in risk||Salas et al. (2015)
|Weight gain||Adults||108,708||Each additional serving/day||Gain of 0.22 kg over 4 years||Hebden et al. (2015)
|Children||20,639||Consumption vs. no consumption||No association||O’Neil and Nicklas (2008)
|Children||34,470||Each additional serving/day||BMI z score** change of 0.09 U over 1 year (0.03, 0.17 U) in children 1–6 y and no change in children 7–18 y||Auerbach et al. (2017)
|Adults||49,108||For each serving/day||Gain of 0.18 kg over 3 years||Auerbach et al. (2018)
|Cardiovascular diseases||Adults||114,279||Each additional serving/d of 100% citrus juice||28% decrease in risk of ischemic stroke||Joshipura et al. (2009)
|Adults||54,383||Highest vs. lowest consumers||15% decrease in the risk of acute coronary syndromes||Hansen et al. (2010)
|Adults||109,635||For each serving/day (citrus juice)||No significant effect||Hung et al. (2004)
|Adults||34,560||1–7 servings (150 mL)/week||17% decrease in risk of cardiovascular disease (24% risk of stroke)||Scheffers et al. (2019)
|Type 2 diabetes||Adults||137,663||Highest vs. lowest consumers||3% increase in risk||Xi et al. (2014)
|Adults||440,937||Each additional serving/day||7% increase in risk||Imamura et al. (2015)
|Adults||120,877||≥1 serving/day vs. ≤1 serving/month||No effect||Schulze et al. (2004)
A marked difference in the risk of developing type 2 diabetes has also been observed between artificially sweetened beverages and pure fruit juices. For example, one study found that daily consumption of soft drinks or fruit punches with added sugars caused an approximately two-fold increase in the risk of diabetes, while that of fruit juice had no impact (Figure 2). A meta-analysis of 4 studies reported similar results, i.e., fruit drinks containing added sugars increased the risk of diabetes while consumption of pure fruit juices had no effect. It should be noted, however, that other studies have reported a slight increase in the risk of diabetes in people consuming 240 mL and more per day of fruit juice (see Table 1).
Figure 2. Comparison of the increased risk of type 2 diabetes associated with the consumption of soft drinks, fruit juices containing added sugars, and 100% pure fruit juices. From Schulze et al. (2004).
The effect of moderate amounts of pure fruit juice is particularly interesting with regard to cardiovascular health. It has long been known that people who eat a lot of fruits are less likely to be affected by cardiovascular disease. These benefits are due, at least in part, to the high fruit content of polyphenols (including flavonoids) that prevent the oxidation of LDL cholesterol and prevent the development of atherosclerotic plaques. Since these polyphenols are extracted during fruit pressing and are therefore present in pure fruit juices, it is possible that these juices may also have positive effects on cardiovascular health. This has recently been highlighted by a study in the Netherlands among 34,560 participants aged 20 to 69 (EPIC-NL study). The researchers found that people who regularly consumed small amounts of pure fruit juice (150 mL daily, 7 days a week) were 17% less likely to be affected by cardiovascular disease, especially stroke (24% less risk). However, these protective effects disappeared at higher amounts of juice (> 8 glasses of pure juice per week), suggesting that the window of consumption associated with these preventive effects is relatively narrow. Decreases in the risk of ischemic stroke and acute coronary events following consumption of pure fruit juice have also been reported. It is also interesting to note that a study recently reported that people who consumed 150 mL of orange juice every day had half the risk of cognitive decline compared to those who rarely consumed it (once a month).
It is therefore possible that the different molecules present in fruit juices (vitamins, minerals, polyphenols) in some way counteract the negative effects of high amounts of sugar by reducing oxidative stress and chronic inflammation, two phenomena involved in the development of cardiovascular and neurodegenerative diseases. In any event, these observations suggest that it is clearly an exaggeration to say that pure fruit juices, in small quantities, are as harmful to health as beverages containing added sugars. It is only in high quantities that pure fruit juice becomes a sugary drink like any other and can cause the many health problems that are associated with excess sugar.
That being said, everyone agrees that the best way to consume fruits is in their whole form. In addition to the different bioactive compounds that are present in juices, whole fruits also contain fibres that increase the feeling of satiety (which reduces the amount of sugar ingested), prevent excessive fluctuations in blood sugar, and contribute to the maintenance of a diversified intestinal microbiome. Ideally, we should therefore favour the consumption of fresh fruits and drink water rather than juice to quench our thirst.
However, for people who may have difficult access to fresh fruit or prefer to consume it in a liquid form, the studies mentioned earlier suggest that pure fruit juice may be a valid alternative, but only when consumed in moderate amounts, around a small glass (150 mL) a day. At these amounts, juices significantly contribute to the daily intake of vitamins and minerals, and studies to date suggest a positive impact on the prevention of cardiovascular disease, especially stroke. It also appears that a moderate intake of pure juices does not have a major impact on the risk of overweight and diabetes, including in young children, confirming the validity of the recommendations of the American Academy of Pediatrics to limit the consumption of pure juice to 150 mL per day.
Red meat: An issue for human health and the health of the planet.
Consumption of red meat and processed meat is associated with an increase in all-cause mortality and mortality from cardiovascular diseases, diabetes, respiratory diseases, liver and kidney diseases, and certain cancers. On the contrary, consumption of white meat and fish has been associated with a decreased risk of premature death. Another troubling aspect with the production of red meat is that it is harmful to the global environment.
In traditional European agricultural societies, meat was consumed once or less than once a week, and annual meat consumption rarely exceeded 5 to 10 kg per person. In some rich countries (U.S.A., Australia, New Zealand), meat consumption now stands at 110–120 kg per person per year, > 10 times more than in traditional agricultural societies. Livestock farming occupies more than 30% of the world’s land area, and more than 33% of arable land is used to produce livestock feed. World consumption of red meat is rising sharply, especially in developing countries. This has adverse consequences for the environment and represents an unsustainable situation according to several experts.
The main harmful effects to our planet caused by meat production (Potter, BMJ 2017)
- Depletion of aquifers (producing 1 kg of meat requires more than 110,000 L of water).
- Groundwater pollution.
- Decrease of biodiversity.
- Destruction of rainforest for livestock and the production of greenhouse gases by livestock. Both combined contribute more to climate change than fossil fuels used for transport.
- Production of 37% of methane (CH4) from human activity (with 23 times the global warming
potential of CO2).
- Production of 65% of nitrous oxide (N2O) from human activity (almost 300 times the global
warming potential of CO2).
- Production of 64% of ammonia (NH3) from human activity, which contributes significantly to
acid rain and acidification of the ecosystem.
Other potential negative effects associated with red meat include accelerated sexual development, caused either by the consumption of meat and fat, or by the intake of growth hormones naturally present in meat or added to livestock feed; more extensive antibiotic resistance caused by their use to promote animal growth; a reduction in the food available for human consumption (for example, 97% of the world’s soybeans are used to feed livestock); and higher risks of infections (such as bovine spongiform encephalopathy or “mad cow disease”) due to faulty practices in intensive farming.
Experts agree that we will have to reduce our consumption of red and processed meat in order to live longer, healthier lives, but especially so that our planet is in better condition and can support human activity long term. Eating mostly cereals, fruits, vegetables, nuts, and legumes, and little or no meat is probably the ideal solution to this environmental problem, but for many, red meat is a delicious food that is hard to replace. To satisfy meat lovers who still want to reduce their consumption, companies have recently developed products made only from plants whose appearance, texture and taste are similar to meat, whereas others are trying to produce artificial meat from in vitro cell cultures.
New plant-based patties: Beyond Burger and Impossible Burger
Plant-based burgers have long been available in grocery stores, but these meatless products are intended for vegetarians and consumed mainly by them. New products made from plants, but designed to have the same appearance, texture, and taste as meat have appeared on the market recently. These meat alternatives target omnivorous consumers who want to reduce their meat consumption. Among the most popular products, there is the Beyond Burger, available at the fast food chain A&W and recently in most supermarkets in Quebec, as well as the Impossible Burger, which will soon be on the menu at fast food chain Burger King under the name “Impossible Whopper.”
The main ingredients of Beyond Burger are pea protein isolate, canola oil and refined coconut oil. This food also contains 2% or less of other ingredients used to create a meat-like texture, colour and flavour, as well as natural preservatives (see box). It is an ultra-processed food that does not contain cholesterol, but almost as much saturated fat (from coconut oil) and 5.5 times more sodium than a lean beef patty. Nutrition and public health experts have suggested avoiding coconut oil in order not to increase blood LDL cholesterol (“bad cholesterol”) and maintain good cardiovascular health (see “Saturated fats, coconut oil and cardiovascular disease”). Moreover, the nutritional contribution of these two products is similar (calories, proteins, total lipids).
Beyond Burger ingredients:
Water, pea protein isolate, canola oil, refined coconut oil, 2% or less of: cellulose from bamboo, methylcellulose, potato starch, natural flavour, maltodextrin, yeast extract, salt, sunflower oil, vegetable glycerine, dried yeast, gum arabic, citrus extract, ascorbic acid, beet juice extract, acetic acid, succinic acid, modified food starch, annatto.
Impossible Burger ingredients: Water, soy protein concentrate, coconut oil, sunflower oil, natural flavours, 2% or less of: potato protein, methylcellulose, yeast extract, dextrose, food starch modified, soy leghemoglobin, salt, soy protein isolate, mixed tocopherols (Vitamin E), zinc gluconate, thiamine hydrochloride (vitamin B1), sodium ascorbate (vitamin C), niacin (vitamin B3), pyridoxine hydrochloride (vitamin B6), riboflavin (vitamin B2), vitamin B12.
The Impossible Burger is made from soy protein, coconut oil and sunflower oil. It also contains ingredients that are used to create a meat-like texture, colour and flavour, as well as vitamins and natural preservatives. Among the ingredients added to mimic the colour and flavour of meat is soy leghemoglobin, a hemoprotein found in the nodules on the roots of legumes that has a similar structure to animal myoglobin. Rather than extracting this protein from the roots of soybean plants, the manufacturer uses leghemoglobin produced by yeast (Pichia pastoris) in which the DNA encoding for this protein has been introduced. The use of P. pastoris soybean leghemoglobin was approved by the US Food and Drug Administration in 2018. The fact that the leghemoglobin used is a product of biotechnology rather than from a natural source does not appear to pose a particular problem, but some researchers suspect that the heme it contains could have the same negative health effects as those associated with the consumption of red meat, i.e., an increased risk of cardiovascular disease and certain types of cancer. A causal link between heme and these diseases has not been established, but population studies (see here and here) indicate that there is a significant association between heme consumption and a rise (19%) in mortality risk from all causes. In contrast, non-heme iron from food (vegetables and dairy products) is not associated with an increased risk of mortality.
Beyond Burger and Impossible Whopper, served with mayonnaise and white bread, are not suitable for vegans (eggs in mayonnaise) or a particularly healthy option because of the saturated fat and salt they contain. However, the manufacture of these products requires much less energy and has a much smaller environmental footprint than real red meat, which is their strong selling point. According to one study, the production of a Beyond Burger patty generates 90% less greenhouse gas emissions and requires 46% less energy, 99% less water and 93% less arable land than a beef patty.
We believe that it is preferable, as much as possible, to obtain unprocessed fresh plant products and to do the cooking yourself, in order to control all the ingredients and thus avoid ingesting sodium or saturated fat in excessive amounts, as is the case with most ultra-processed products, including these new meatless patties. Fatty and salty foods taste good to a large majority of human beings, and the food industry takes this into account when designing the ultra-processed food products it offers on the market. If you want to eat a “burger” without meat, why not try to prepare it yourself with black beans (recipes here and here), oats, lentils or quinoa?
Production of “meat” in the laboratory
In vitro “meat” production involves culturing animal muscle cells (from undifferentiated cells or “stem cells”) in a controlled or laboratory environment. The first beef patty produced in a laboratory in 2013 cost 215,000 pounds (Can$363,000), but the price has dropped considerably since then. However, this product is not yet ready to be commercialized, as there are still several technological problems to solve before it can be produced on a large scale. Moreover, if the current experimental product can be used to successfully mimic ground meat, we are still far from being able to grow cells in a three-dimensional form that looks like a steak, for example.
The technology could be used to produce, for example, “Fugu” (puffer fish) meat, a delicacy prized by the Japanese, but which can be deadly if the chef or specialized companies do not prepare the fish properly. Indeed, tetradoxine contained in the liver, ovaries and skin of the fugu is a powerful paralyzing poison for which there is no antidote. Laboratory-made fugu meat would not contain any poison and would be safe for consumers.
Another example of an advantageous application would be the production of duck foie gras. A majority of the French (67%) are against the traditional method of production by gavage, which makes the animals suffer. One company (Supreme) is developing a method to obtain fatty liver from isolated duck egg cells.
Other companies are developing methods to produce egg white and milk proteins by fermentation rather than using animals. Although this “cellular agriculture” still seems a little “futuristic”, it could become increasingly important in the food industry and help reduce the production of meat that is harmful to our planet.
Updated May 30, 2019
Our eating habits have changed considerably in recent years. Sometimes for the better, for example by taking advantage of the availability of several foods, ingredients and spices from around the world to diversify our diet and broaden our culinary horizons. But also sometimes for the worse, especially because of a very significant increase in the consumption of ultra-processed industrial foods high in fat, sugar, and salt (see box for the definition of ultra-processed foods). The revolution generated by these “new” foods is particularly remarkable: even though these products did not even exist just a century ago, they currently account for about 50% of all calories consumed by the population.
Unfortunately, most of these ultra-processed products should be considered foods of poor nutritional quality. Not only does their high sugar and fat content give them a very high energy density that promotes the overconsumption of calories, but the use of inexpensive ingredients for their manufacture also ensures that they are deprived of several essential elements found in unprocessed foods (fibres, omega-3s, polyphenols, vitamins, minerals, etc.). For all these reasons, it is recommended that the consumption of these ultra-processed foods be limited as much as possible and that home-cooked meals should be preferred, as proposed in the latest version of Canada’s Food Guide.
The NOVA classification
Instead of the traditional classification of foods according to their content in certain nutrients (proteins, carbohydrates, vitamins), in 2009, Brazilian researchers proposed a new way of categorizing them according to their degree of transformation. This classification, called NOVA, includes four groups:
Group 1: Unprocessed or minimally processed foods
Unprocessed foods can be of plant origin (leaves, shoots, roots, tubers, fruits, nuts, seeds) or animal (meat, eggs, milk). These foods are perishable and must be consumed shortly after their production. These foods are said to be “minimally processed” when they are subjected to certain treatments that increase their shelf life (washing, freezing, pasteurization, etc.) or that modify their taste (yogurt fermentation, coffee roasting), but without altering their nutritional properties.
Examples: fruits and vegetables (fresh, frozen), cereals, mushrooms, meat and fish, seafood, poultry, eggs, pasteurized milk, plain yogurt, coffee, tea, spices, nuts and seeds.
Group 2: Processed culinary ingredients
These products are obtained from group 1 foods through various physical transformations (pressing, grinding, refining). These ingredients are not consumed as is, but rather used in combination with group 1 foods to prepare different dishes.
Examples: vegetable oils, flour, butter, sugar, salt, vinegar.
Group 3: Processed foods
Foods in this group are products made with group 1 foods, to which group 2 substances (salt, oil, sugar, etc.) are added to increase their shelf life, or by using different processes to make them more attractive and palatable. Although these products generally retain the attributes and constituents of the whole foods from which they are derived, their nutritional profile is mostly altered due to the addition of fat, sugar or salt.
Example: canned foods, smoked foods, cured meats, cheeses. It should be noted that alcoholic beverages, which are made by fermentation of foods from the first group, are also part of group 3.
Group 4: Ultra-processed foods
These products are pure industrial creations made from several isolated ingredients. Some of these ingredients are from group 2 (sugar, oil, flour, salt), while others are unknown in nature and manufactured industrially (hydrolyzed proteins, hydrogenated oils, modified starches). Ultra-processed products also contain a wide range of additives to improve their appearance, taste, texture and shelf life (emulsifiers, stabilizers, texturizers, colourants, artificial flavours, sweeteners). In short, ultra-processed products are not foods in the usual sense, but rather a combination of ingredients, designed to give the illusion of a food.
Examples: breakfast cereals, instant soups and noodles, pastries, cakes, breads, various sweet and savoury snacks (cereal bars, cookies, potato chips, crackers, etc.), soft drinks or energy drinks, margarine, candies, “ready-to-eat” food (chicken nuggets or fish, frozen pizza and pasta, etc.).
Ultra-processed foods and weight gain
One of the main arguments against ultra-processed foods is that it has been suspected for several years that their high caloric content could promote the development of obesity. For example, all countries, without exception, that have increased the proportion of ultra-processed industrial foods in their diets must deal with a greater proportion of obese individuals. This is particularly striking in countries in economic transition, where the high availability and low cost of ultra-processed foods mean that the incidence of obesity has skyrocketed, even among the poor.
A remarkable study has just confirmed the close link between ultra-processed food consumption and weight gain. In this randomized clinical trial by Dr. Kevin Hall’s team (National Institute of Health), researchers compared the effects of a diet consisting exclusively of ultra-processed foods to that of a diet based on minimally processed foods. They recruited 20 healthy young people (but who were slightly overweight with an average BMI of 27), and, for a financial compensation of $6,000, the volunteers agreed to be accommodated for 28 consecutive days in the center’s laboratories, with no possibility of going out and with the obligation to eat meals exclusively made from ultra-processed (group 1) or minimally processed (group 2) foods prepared by the research team. In all cases, meals were developed to be equivalent in terms of calories, energy density, fat, sugar and salt, but necessarily differed greatly in the types of sugars and fats present. For example, ultra-processed foods contained significantly more added sugars (54% of total sugars, compared to 1% for unprocessed foods), saturated fats (34% of total fat, compared with 19%), and four times less omega-3s. The subjects were instructed to eat their fill, without worrying about the quantities ingested.
For the first two weeks, each participant ate 3 meals per day from group 1 (ultra-processed foods such as cereals, muffins, white bread or flavoured yogurts for breakfast, deli sandwiches for lunch, and chicken nuggets for dinner) or group 2 (unprocessed foods such as fresh fruits and vegetables, eggs, fish, poultry, whole grains, nuts) (the difference in the types of meals consumed by participants can be viewed here). Snacks were available to volunteers all day long (potato chips, crackers and granola bars for group 1 or nuts, almonds and fruits for group 2). For the next two weeks, the volunteers switched to the other diet, that is, those who ate the ultra-processed foods were now fed the unprocessed foods and vice versa.
The most dramatic result of the study is that the mere fact of being exposed to ultra-processed foods causes a very large increase in the number of calories consumed throughout the duration of the study (Figure 1). Overall, this increase is about 510 kcal per day, the result of an increase in carbohydrate intake (280 kcal/day) and fat intake (230 kcal/day) (but not protein).
Figure 1. Comparison of calorie intake in people on diets of ultra-processed or unprocessed foods. From Hall et al. (2019).
Such a large increase in the calorie intake is obviously not without consequence: the daily weighing of participants shows a rapid increase in body weight which reached 1 kg at the end of the first week of the study (Figure 2). Conversely, people who had eaten the unprocessed diet had lost 1 kg over the course of the study, resulting in a net difference of 2 kg with those fed ultra-processed foods. This is huge, especially considering that these differences can be observed in just two weeks.
Figure 2. Variation in body weight associated with the consumption of ultra-processed or unprocessed foods. From Hall et al. (2019).
Why eat more?
Ultra-processed foods are designed first and foremost to create sensory pleasure (appearance, texture) and satisfy our natural inclination for fat, sugar and salt. It could thus have been expected that the increased intake of these foods by study participants was due to the fact that they preferred to eat these meals rather than those prepared with unprocessed foods. This is not the case, however, as the level of satisfaction of the participants with respect to both food classes was identical, both in terms of appetite and pleasure derived from their consumption. The main difference observed between the two groups is that people ate almost twice as fast when their meals consisted of ultra-processed rather than unprocessed foods (50 kcal/min versus 30 kcal/min). This is probably due to the fact that ultra-processed foods are generally easier to chew and swallow, allowing more food to be ingested in a shorter amount of time and thus excess calories. In this sense, it should be noted that researchers observed that blood levels of peptide YY (a hormone that reduces appetite) were increased in people who ate low-processed foods, while levels of ghrelin (a hormone that stimulates the appetite) were diminished. It is therefore possible that the consumption of ultra-processed food disrupts mechanisms involved in satiety, which promotes overconsumption of food.
These observations strongly suggest that consumption of ultra-processed foods plays a predominant role in the dramatic increase in the incidence of overweight people worldwide. This is truly a major breakthrough that has the potential to revolutionize our understanding of the mechanisms behind this obesity epidemic. For several years, excess weight has always been considered in terms of excessive fat or sugar intake and there are countless “miracle” diets that promise significant weight loss by cutting one or the other. Yet, as we mentioned in another article, there is really no clinically significant difference in the effectiveness of low-fat or low-carb diets in inducing long-term weight loss. Instead of being overly concerned about the amount of fat and/or sugar ingested, Dr. Hall’s study strongly suggests that it is the source of these nutrients that is the most important factor in controlling body weight. To stay slim, the key is to eat unprocessed foods as often as possible and minimize the consumption of ultra-processed industrial foods. Especially since several recent studies have shown that people who regularly consume such foods are at higher risk of cardiovascular disease and premature mortality.
According to recent studies, adopting a healthy lifestyle, i.e., eating well, exercising, managing stress, and not smoking or drinking too much alcohol, has beneficial effects on the aging of our cells. One of the well-documented phenomena that occur during cellular aging is the degradation of telomeres, unique structures found at the ends of each of our chromosomes; however, a healthy lifestyle can slow down this process
Telomeres and aging
Telomeres are repetitive DNA structures, shaped like a “hairpin”, found at both ends of chromosomes and that ensure the integrity of the genome during cell division. At each division, the telomeres shorten until they become too short to fulfill their protective function: the cell can no longer divide and enters senescence, then dies. Telomere shortening is countered by the action of telomerase, an enzyme that lengthens telomeres during each DNA replication. Telomere shortening in peripheral blood mononuclear cells (lymphocytes and monocytes) is associated with aging and aging-related diseases such as cancer, stroke, dementia, cardiovascular disease, obesity, osteoporosis and type 2 diabetes. Leukocyte telomere length is significantly, albeit weakly, associated with mortality, but cannot predict survival as well as other variables (age, mobility, cognition, smoking, daily life activities).
Physical training improves many aspects of human health, including exercise capacity, blood pressure regulation, insulin sensitivity, lipid profile, reduction of abdominal fat and inflammation. These beneficial effects contribute to increased endothelial function, delay the progression of atherosclerotic lesions, and improve collateralization of blood vessels in people with type 2 diabetes, coronary artery disease and heart failure. The underlying mechanisms are known in part, but details at the molecular level are less well known and are the subject of much research.
The process of cellular aging can be slowed down by sustained exercise. A study published in 2009 showed that sustained physical training in young and middle-aged athletes was associated with higher telomerase activity, increased expression of telomere-stabilizing proteins, and longer telomeres, compared to sedentary people.
The same research group recently conducted a randomized controlled trial to demonstrate that exercise is the cause of increased telomerase activity and telomere length. The results of the study were published in 2018 in the European Heart Journal. The researchers recruited 124 middle-aged men and women (≈50 years) who were in good health, but did not exercise. During the six-month study, participants were randomly divided into four groups: a control group and three groups that did different types of exercise 3 times a week; one group did endurance training (walking/running, 45 min/day); another group exercised at high intensity intervals (4 min at high intensity/4 min rest, repeated 4 times); and the third group did resistance exercises (various weight machines). Blood samples were taken before, during, and at the end of the study to measure telomere length and telomerase activity in leukocytes (white blood cells).
At the end of the study, those who exercised, regardless of the type, had better cardiorespiratory capacity than at the beginning of the study. Telomerase activity was 2–3 times higher in the leukocytes of those who did endurance or interval exercises, compared to the control group. However, this effect was not observed in people who did resistance exercises (weight training). Similarly, telomere length was greater in those who did endurance or interval exercises, but not in those who did resistance exercise.
These results suggest that endurance exercises such as running, brisk walking or swimming are more effective than resistance exercises to keep longer telomeres and delay cellular aging. It should not be concluded, however, that resistance exercises are useless for healthy aging. Resistance exercises increase overall fitness, which is one of the most important indicators of longevity. The researchers suggest further study on the effects of various combinations of endurance and resistance exercises on cellular aging. The lead author concludes that the central message of his study is that it is never too late to start exercising and that it will have beneficial effects on aging.
Proteomic approach to the effects of exercise
Researchers have studied the effects of endurance exercise on the expression of 1,129 proteins in the blood plasma (plasma proteome), classified into 10 modules or patterns according to their level of interconnection. Exercise altered protein expression of four modules in young men, and five modules in older men. Modules affected by the exercise included proteins related to signalling pathways involved in wound healing, apoptosis (cell death) regulation, glucose, insulin and cellular stress signalling, as well as immune and inflammatory responses. In addition, several exercise-affected modules could be correlated with physiological and clinical indicators of a healthy life, including diastolic blood pressure, insulin resistance, maximal aerobic capacity, and vascular endothelial function.
According to a systematic review of studies published on the subject, five studies indicate that fruit and vegetable consumption is associated with longer telomeres, while eight other studies have not identified a significant association. For foods other than fruits and vegetables, including grains and meats, the data are inconclusive as a whole. Some studies, however, indicate unfavourable associations between certain food groups and the length of telomeres: grains, processed meats, sugary drinks, fats and oils. With regard to eating habits, only the Mediterranean diet has been associated with longer telomeres, but not in all the studies published to date. Future larger-scale observational studies and more focused randomized controlled trials could help to better identify which elements of the diet are beneficial for telomere maintenance and help slow the process of cellular aging.
Effect of stress
Several cross-sectional studies have reported associations between telomere stability and stress exposure (review articles here, here and here). The association lasts throughout life and has been observed in children whose mothers had been under significant stress. It seems that even prenatal stress indirectly experienced by the fœtus is associated with shorter telomeres after birth. Prolonged or repeated exposure to stress is associated with a shortening of telomeres and the development of age-related diseases such as type 2 diabetes, heart disease, dementia and osteoarthritis. According to some studies, people with bipolar disorder, schizophrenia, major depression and post-traumatic stress disorder have shorter telomeres. Stress and mental illnesses therefore have direct effects on the aging of our cells, with consequences for health over the course of life.
For men diagnosed with low-grade prostate cancer, adopting a completely different and healthy lifestyle (plant-based, low-fat diet, exercise, stress management, social support) has been associated with a 10% increase in telomere length in their lymphocytes and monocytes, five years after the start of the intervention. Participants in the control group (active surveillance only), on the contrary, saw the average length of their telomeres decrease slightly (-3%). This intervention study included only a small group of people (n = 30), so larger-scale randomized controlled trials are needed to confirm these findings.
There is growing evidence that physical activity has a significant influence on health and quality of life as people age. For example, older people who exercise regularly are often in better shape, they are more muscular, and they are less likely to develop chronic illnesses or physical disabilities than sedentary seniors. Adopting a lifestyle that combines healthy eating, regular exercise and stress management is certainly one of the best things one can do to prevent or fight age-related diseases.
The role of dietary fat in the development of obesity, cardiovascular disease and type 2 diabetes has been the subject of vigorous scientific debate for several years. In an article recently published in the prestigious Science, four experts on dietary fat and carbohydrate with very different perspectives on the issue (David Ludwig, Jeff Volek, Walter Willett, and Marian Neuhouser) identified 5 basic principles widely accepted in the scientific community and that can be of great help for non-specialists trying to navigate this issue.
This summary is important as the public is constantly bombarded with contradictory claims about the benefits and harmful effects of dietary fat. Two great, but diametrically opposed currents have emerged over the last few decades:
- The classic low-fat position, i.e., reducing fat intake, adopted since the 1980s by most governments and medical organizations. This approach is based on the fact that fats are twice as caloric as carbohydrates (and therefore more obesigenic) and that saturated fats increase LDL cholesterol levels, a major risk factor for cardiovascular disease. As a result, the main goal of healthy eating should be to reduce the total fat intake (especially saturated fat) and replace it with carbohydrate sources (vegetables, bread, cereals, rice and pasta). An argument in favour of this type of diet is that many cultures that have a low-fat diet (Okinawa’s inhabitants, for example) have exceptional longevity.
- The low-carb position, currently very popular as evidenced by the ketogenic diet, advocates exactly the opposite, i.e., reducing carbohydrate intake and increasing fat intake. This approach is based on several observations showing that increased carbohydrate consumption in recent years coincides with a phenomenal increase in the incidence of obesity in North America, suggesting that it is sugars and not fats that are responsible for excess weight and the resulting chronic diseases (cardiovascular disease, type 2 diabetes, some cancers). One argument in favour of this position is that an increase in insulin in response to carbohydrate consumption can actually promote fat accumulation and that low-carb diets are generally more effective at promoting weight loss, at least in the short term.
Reaching a consensus from two such extreme positions is not easy! Nevertheless, when we look at different forms of carbohydrates and fat in our diet, the reality is much more nuanced, and it becomes possible to see that a number of points are common to both approaches. By critically analyzing the data currently available, the authors have managed to identify at least five major principles they all agree on:
1) Eating unprocessed foods of good nutritional quality helps to stay healthy without having to worry about the amount of fat or carbohydrate consumed.
A common point of the low-fat and low-carb approaches is that each one is convinced it represents the optimal diet for health. In fact, a simple observation of food traditions around the world shows that there are several food combinations that allow you to live longer and be healthy. For example, Japan, France and Israel are the industrialized countries with the two lowest mortality rates from cardiovascular disease (110, 126 and 132 deaths per 100,000, respectively) despite considerable differences in the proportion of carbohydrates and fat from their diet.
It is the massive influx of ultra-processed industrial foods high in fat, sugar and salt that is the major cause of the obesity epidemic currently affecting the world’s population. All countries, without exception, that have shifted their traditional consumption of natural foods to processed foods have seen the incidence of obesity, type 2 diabetes, and cardiovascular disease affecting their population increase dramatically. The first step in combating diet-related chronic diseases is therefore not so much to count the amount of carbohydrate or fat consumed, but rather to eat “real” unprocessed foods. The best way to do this is simply to focus on plant-based foods such as fruits, vegetables, legumes and whole-grain cereals, while reducing those of animal origin and minimizing processed industrial foods such as deli meats, sugary drinks, and other junk food products.
2) Replace saturated fat with unsaturated fat.
The Seven Countries Study showed that the incidence of cardiovascular disease was closely correlated with saturated fat intake (mainly found in foods of animal origin such as meats and dairy products). A large number of studies have shown that replacing these saturated fats with unsaturated fats (e.g., vegetable oils) is associated with a significant reduction in the risk of cardiovascular events and premature mortality. A reduction in saturated fat intake, combined with an increased intake of high quality unsaturated fat (particularly monounsaturated and omega-3 polyunsaturated), is the optimal combination to prevent cardiovascular disease and reduce the risk of premature mortality.
These benefits can be explained by the many negative effects of an excess of saturated fat on health. In addition to increasing LDL cholesterol levels, an important risk factor for cardiovascular disease, a high intake of saturated fat causes an increase in the production of inflammatory molecules, an alteration of the function of the mitochondria (the power plants of the cell), and a disturbance of the normal composition of the intestinal microbiome. Not to mention that the organoleptic properties of a diet rich in saturated fats reduce the feeling of satiety and encourage overconsumption of food and accumulation of excess fat, a major risk factor for cardiovascular disease, type 2 diabetes and some cancers.
3) Replace refined carbohydrates with complex carbohydrates.
The big mistake of the “anti-fat crusade” of the ’80s and ’90s was to believe that any carbohydrate source, even the sugars found in processed industrial foods (refined flours, added sugars), was preferable to saturated fats. This belief was unjustified, as subsequent studies have demonstrated beyond a doubt that these refined sugars promote atherosclerosis and can even triple the risk of cardiovascular mortality when consumed in large quantities. In other words, any benefit that can come from reducing saturated fat intake is immediately countered by the negative effect of refined sugars on the cardiovascular system. On the other hand, when saturated fats are replaced by complex carbohydrates (whole grains, for example), there is actually a significant decrease in the risk of cardiovascular events.
Another reason to avoid foods containing refined or added sugars is that they have low nutritional value and cause significant variations in blood glucose and insulin secretion. These metabolic disturbances promote excess weight and the development of insulin resistance and dyslipidemia, conditions that significantly increase the risk of cardiovascular events. Conversely, increased intake of complex carbohydrates in whole-grain cereals, legumes, and other vegetables helps keep blood glucose and insulin levels stable. In addition, unrefined plant foods represent an exceptional source of vitamins, minerals and antioxidant phytochemicals essential for maintaining health. Their high fibre content also allows the establishment of a diverse intestinal microbiome, whose fermentation activity generates short-chain fatty acids with anti-inflammatory and anticancer properties.
4) A high-fat low-carb diet may be beneficial for people who have disorders of carbohydrate metabolism.
In recent years, research has shown that people who have normal sugar metabolism may tolerate a higher proportion of carbohydrates, while those with glucose intolerance or insulin resistance may benefit from adopting a low-carb diet richer in fat. This seems particularly true for people with diabetes and prediabetes. For example, an Italian study of people with type 2 diabetes showed that a diet high in monounsaturated fat (42% of total calories) was more effective in reducing the accumulation of fat in the liver (a major contributor to the development of type 2 diabetes) than a diet low in fat (28% of total calories).
These benefits seem even more pronounced for the ketogenic diet, in which the consumption of carbohydrates is reduced to a minimum (<50 g per day). Studies show that in people with a metabolic syndrome, this type of diet can generate a fat loss (total and abdominal) greater than a hypocaloric diet low in fat, as well as a higher reduction of blood triglycerides and several markers of inflammation. In people with type 2 diabetes, a recent study shows that in the majority of patients, the ketogenic diet is able to reduce the levels of glycated haemoglobin (a marker of chronic hyperglycaemia) to a normal level, and this without drugs other than metformin. Even people with type 1 diabetes can benefit considerably from a ketogenic diet: a study of 316 children and adults with this disease shows that the adoption of a ketogenic diet allows an exceptional control of glycemia and the maintenance of excellent metabolic health over a 2-year period.
5) A low-carb or ketogenic diet does not require a high intake of proteins and fats of animal origin.
Several forms of low carbohydrate or ketogenic diets recommend a high intake of animal foods (butter, meat, charcuteries, etc.) high in saturated fats. As mentioned above, these saturated fats have several negative effects (increase of LDL, inflammation, etc.), and one can therefore question the long-term impact of this type of low-carb diet on the risk of cardiovascular disease. Moreover, a study recently published in The Lancet indicates that people who consume little carbohydrates (<40% of calories), but a lot of fat and protein of animal origin, have a significantly increased risk of premature death. For those wishing to adopt a ketogenic diet, it is therefore important to realize that it is quite possible to reduce the proportion of carbohydrates in the diet by substituting cereals and other carbohydrate sources with foods rich in unsaturated fats like vegetable oils, vegetables rich in fat (nuts, seeds, avocado, olives) as well as fatty fish.
In short, the current debate about the merits of low-fat and low-carb diets is not really relevant: for the vast majority of the population, several combinations of fat and carbohydrate make it possible to remain in good health and at low risk of chronic diseases, provided that these fats and carbohydrates come from foods of good nutritional quality. It is the overconsumption of ultra-processed foods, high in fat and refined sugars, which is responsible for the dramatic rise in food-related diseases, particularly obesity and type 2 diabetes. Restricting the consumption of these industrial foods and replacing them with “natural” foods, especially those of plant origin, remains the best way to reduce the risk of developing these diseases. On the other hand, for overweight individuals with metabolic syndrome or type 2 diabetes, currently available scientific evidence suggests that a reduction in carbohydrate intake by adopting low-carb and ketogenic diets could be beneficial.