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

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

OVERVIEW

  • 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

OVERVIEW

  • 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

OVERVIEW

  • 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.

The benefits of extra virgin olive oil on cardiovascular health

The benefits of extra virgin olive oil on cardiovascular health

OVERVIEW

  • In addition to being an excellent source of monounsaturated fat, olive oil is the only vegetable oil that contains a significant amount of phenolic compounds with antioxidant and anti-inflammatory properties.
  • These molecules are found in much larger quantities in extra virgin quality oils compared to refined olive oils.
  • Several studies indicate that the presence of these phenolic compounds contributes to the many positive effects of extra virgin olive oil on cardiovascular health.

The traditional Mediterranean diet has several positive effects on cardiovascular health by improving the lipid profile (cholesterol, triglycerides) and by reducing chronic inflammation, blood pressure, blood sugar and the risk of diabetes. Several studies have clearly established that these effects result in a significant reduction in the risk of cardiovascular disease.

The Mediterranean diet is characterized by the abundant consumption of plant-based foods (fruits, vegetables, whole-grain cereals, legumes, nuts, herbs), a moderate intake of fermented dairy products (yogurt, cheese), fish, seafood and red wine as well as a low consumption of red meat and added sugars. It is therefore an exemplary diet, in which complex plant sugars are the main sources of carbohydrates and where the proteins come mainly from fish and legumes instead of red meat.

Another important feature of the Mediterranean diet is the daily use of large amounts (60–80 mL) of olive oil as the main source of fat for cooking. Several studies have reported that countries that are heavy consumers of olive oil have a much lower incidence of cardiovascular disease than those that consume mainly animal fats, suggesting a positive role of olive oil in this protective effect. Traditionally, these beneficial properties of olive oil have been attributed to its very high content (around 80%) of oleic acid, a monounsaturated fatty acid that contributes to its antioxidant properties. However, and unlike most vegetable oils, olive oil also contains a host of minor compounds (1–3% of the oil) that also play very important roles in its positive effects on cardiovascular health (see below). This is particularly the case for several phenolic compounds found exclusively in olive oil, including phenolic alcohols such as hydroxytyrosol and tyrosol and polyphenols of the secoiridoid family such as oleuropein, ligstroside, oleacein and oleocanthal (Figure 1).

 

Figure 1. Molecular structures of the main phenolic compounds of olive oil.


One fruit, several types of oils
Most vegetable oils come from seeds that have been extracted with an organic solvent (e.g. hexane) and subsequently heated to a high temperature to evaporate this solvent and remove impurities that give them an undesirable smell and flavour. These drastic procedures are not necessary for olive oil as the olives are simply pressed and the oil in the pulp is extracted by mechanical pressure, without using chemical processes or excessive heat.

Olive oils are classified according to the quality of the oil that is obtained by the pressing procedure (Figure 2). Good quality oils, i.e. those with low acidity (<2% free oleic acid) and that meet certain taste, bitterness and spiciness criteria are called “virgin” olive oils or, if their acidity is less than 0.8%, “extra virgin” olive oils. These oils contain the majority of the polyphenols in the starting olives and, after centrifugation and filtration, can be consumed as is.

On the other hand, some olive varieties give an inferior quality oil due to too high acidity (> 2%) and/or an unpleasant smell and taste that does not meet the established criteria. These oils, which are unfit for consumption, are called “lampantes” (a name which comes from their ancient use as fuel in oil lamps) and must be refined as is done for other vegetable oils, i.e. using different physicochemical procedures (neutralization with soda, high temperature bleaching and deodorization, hexane extraction, etc.). These steps remove the compounds responsible for the excess acidity and the unpleasant taste of the oil and produce a “neutral” olive oil that has lost its acidity and its flaws, but that is now devoid of the smell, flavour, colour and most of the phenolic components of the starting virgin olive oil. To stabilize these oils and improve their taste, a certain proportion (15–20%) of virgin olive oil is subsequently added and the final product, which is a mixture of refined olive oil and virgin olive oil, is what is sold in grocery stores as “pure olive oil” or simply “olive oil”.

In short, there are three main types of olive oil on the market: virgin olive oil (VOO), extra virgin olive oil (EVOO), and regular olive oil (OO).

Figure 2. The different types of olive oil. From Gorzynik-Debicka et al. (2018).

 

These manufacturing differences obviously have a huge impact on the amount of polyphenols present in virgin, extra virgin, and refined oils (Table 1). For OO-type olive oils (which contain refined oils), the polyphenols come exclusively from virgin olive oil that has been added to restore a minimum of taste and colour (from yellow to greenish) to the chemically treated oil. The amount of these polyphenols is therefore necessarily less than in VOO and EVOO and, as a general rule, does not exceed 25–30% of the content of these two oils. This difference is particularly striking for certain polyphenols of the secoiridoid family (oleuropein, oleocanthal, oleacein and ligstroside) whose concentrations are 3 to 6 times greater in EVOO than in OO (Table 1). It should be noted, however, that these values ​​can vary greatly depending on the origin and cultivar of the olives; for example, some extra virgin olive oils have been found to contain up to 10 times more hydroxytyrosol and tyrosol than regular olive oils. The same goes for other polyphenols like oleocanthal: an analysis of 175 distinct extra virgin olive oils from Greece and California revealed dramatic variations between the different oils, with concentrations of the molecule ranging from 0 to 355 mg/kg.

It should also be mentioned that even if the quantities of phenolic compounds in regular olive oil are lower than those found in virgin and extra virgin oils, they nevertheless largely exceed those present in other vegetable oils (sunflower, peanut, canola, soy), which contain very little or none at all.

FamilyMoleculesOO (mg/kg)VOO (mg/kg)EVOO (mg/kg)
Secoiridoidsoleocanthal38.95 ± 9.2971.47 ± 61.85142.77 ± 73.17
oleacein57.37 ± 27.0477.83 ± 256.09251.60 ± 263.24
oleuropein (aglycone)10.90 ± 0.0095.00 ± 116.0172.20 ± 64.00
ligstroside (aglycone)15.20 ± 0.0069.00 ± 69.0038.04 ± 17.23
Phenolic alcoholshydroxytyrosol6.77 ± 8.263.53 ± 10.197.72 ± 8.81
tyrosol4.11 ± 2.245.34 ± 6.9811.32 ± 8.53
Flavonoidsluteolin1.17 ± 0.721.29 ± 1.933.60 ± 2.32
apigenin0.30 ± 0.170.97 ± 0.7111.68 ± 12.78
Phenolic acidsp-coumaric -0.24 ± 0.810.92 ± 1.03
ferulic -0.19 ± 0.500.19 ± 0.19
cinnamic - -0.17 ± 0.14
caffeic -0.21 ± 0.630.19 ± 0.45
protocatechuic -1.47 ± 0.56 -
Table 1. Comparison of the content of phenolic compounds in olive oil (OO), virgin olive oil (VOO) and extra virgin olive oil (EVOO). Please note that the large standard deviations of the mean values reflect the huge variations in polyphenol content depending on the region, cultivar, degree of fruit ripeness, and olive oil manufacturing process. Adapted from Lopes de Souza et al. (2017).

 

Anti-inflammatory spiciness
The amounts of polyphenols contained in a bottle of olive oil are not indicated on its label, but it is possible to detect their presence simply by tasting the oil. The polyphenols in olive oil are indeed essential to the organoleptic sensations so characteristic of this oil, in particular the sensation of tickling or stinging in the throat caused by good quality extra virgin oils, what connoisseurs call “ardour”. Far from being a defect, this ardour is considered by experts as a sign of a superior quality oil and, in tasting competitions, the “spiciest” oils are often those that receive the highest honours.

It is interesting to note that it is by tasting different olive oils that a scientist succeeded, by coincidence, in identifying the molecule responsible for the sensation of spiciness caused by extra virgin olive oil (see box).

Plant ibuprofen

Chance often plays a role in scientific discoveries, and this is especially true when it comes to the discovery of the molecule responsible for the typical irritation caused by olive oil. On a trip to Sicily (Italy) to attend a conference on the organoleptic properties of different foods, Dr. Gary Beauchamp and his colleagues were invited by the organizers of the event to a meal where guests were encouraged to taste extra virgin olive oil from olive trees cultivated on their estate. Even though it was the first time he had tasted this type of olive oil, Dr. Beauchamp was immediately struck by the tingling sensation in his throat, which was similar in every way to that caused by ibuprofen, and that he had experienced multiple times as part of his work to replace acetaminophen (paracetamol) with ibuprofen in cough syrups. Suspecting that olive oil contained a similar anti-inflammatory drug, Dr. Beauchamp and his team subsequently managed to isolate the molecule responsible for this irritation, a polyphenol they called “oleocanthal”. They subsequently discovered that oleocanthal had, like ibuprofen, a powerful anti-inflammatory action and that regular consumption of extra virgin olive oil, rich in oleocanthal, provided an intake equivalent to about 10 mg of ibuprofen and therefore may contribute to the well-documented anti-inflammatory effects of the Mediterranean diet. 

But why is the stinging sensation of olive oil only felt in the throat? According to work carried out by the same group, this exclusive localization is due to a specific interaction of oleocanthal (and ibuprofen, for that matter) with a subtype of heat-sensitive receptor (TRPA1). Unlike other types of heat receptors, which are evenly distributed throughout the oral cavity (the TRPV1 receptor activated by the capsaicin of chili peppers, for example, and which causes the burning sensation of some particularly hot dishes), the TRPA1 receptor is located only in the pharynx and its activation by oleocanthal causes a nerve impulse signalling the presence of an irritant only in this region. In short, the more an olive oil stings in the back of the throat, the more oleocanthal it contains and the more anti-inflammatory properties it has. As a general rule, extra virgin olive oils contain more oleocanthal (and polyphenols in general) than virgin olive oils (see Table 1) and are therefore considered superior, both in terms of taste and their positive effects on health.

The superiority of extra virgin olive oil
Several studies have shown that the higher polyphenol content in extra virgin olive oil is correlated with a greater positive effect on several parameters of cardiovascular health than that observed for regular olive oil (see Table 2). For example, epidemiological studies carried out in Spain have reported a decrease of about 10–14% in the risk of cardiovascular disease among regular consumers of extra virgin olive oil, while regular consumption of olive oil had no significant effect. A role of phenolic compounds is also suggested by the EUROLIVE study where the effect of daily ingestion, over a period of 3 weeks, of 25 mL of olive oils containing small (2.7 mg/kg), medium (164 mg/kg), or high (366 mg/kg) amounts of polyphenols was compared. The results show that an increased intake of polyphenols is associated with an improvement in two important risk factors for cardiovascular disease: an increase in the concentration of HDL cholesterol and a decrease in oxidized LDL cholesterol levels. Collectively, the data gathered from the intervention studies indicate that the polyphenols found in extra virgin olive oil play an extremely important role in olive oil’s positive effects on cardiovascular health.

Measured parameterResultsSources
Incidence of cardiovascular disease10% reduction in risk for every 10 g/day of EVOO. No effect of regular OO.Guasch-Ferré et al. (2014)
14% reduction in risk for each 10 g/day of EVOO. No effect of regular OO.Buckland et al. (2012)
Lipid profileLinear increase in HDL cholesterol as a function of the amount of polyphenols.Covas et al. (2006)
Increase in HDL cholesterol only observed with EVOO.Estruch et al. (2006)
Blood glucoseEVOO improves postprandial glycemic profile (decrease in glucose levels and increased insulin).Violo et al. (2015)
Polyphenol-rich EVOO reduces fasting blood glucose and glycated hemoglobin (HbA1c) levels in diabetic patients.Santagelo et al. (2016)
InflammationEVOO, but not OO, induces a decrease in inflammatory markers (TXB(2) and LTB(4)).Bogani et al. (2017)
EVOO, but not OO, induces a decrease in IL-6 and CRP.Fitó et al. (2007)
EVOO, but not OO, decreases the expression of several inflammatory genes.Camargo et al. (2010)
EVOO, but not OO, decreases levels of inflammatory markers sICAM-1 and sVCAM-1.Pacheco et al. (2007)
Oxidative stressStrong in vitro antioxidant activity of phenolic compounds of olive oil.Owen et al. (2000)
Linear decrease in oxidized LDL levels as a function of the amount of polyphenols.Covas et al. (2006)
Lower levels of oxidized LDL after ingestion of EVOO compared to OO.Ramirez-Tortosa et al. (1999)
EVOO phenolic compounds bind to LDL particles and protect them from oxidation.de la Torre-Carbot et al. (2010)
EVOO induces the production of neutralizing antibodies against oxidized LDL.Castañer et al. (2011)
EVOO decreases urinary levels of 8-isoprostane, a marker of oxidative stress.Visioli et al. (2000)
EVOO positively influences the oxidative/antioxidant status of blood plasma.Weinbrenner et al. (2004)
Blood pressureEVOO causes a decrease in systolic and diastolic pressures in hypertensive women.Ruíz-Gutiérrez et al. (1996)
EVOO, but not OO, causes a decrease in systolic pressure in hypertensive coronary patients.Fitó et al. (2005)
EVOO improves postprandial endothelial dilation.Ruano et al. (2005)
EVOO increases the NO vasodilator and decreases systolic and diastolic pressures.Medina-Remón et al. (2015)
EVOO, but not OO, improves vessel dilation in pre-diabetic patients.Njike et al. (2021)
EVOO, but not OO, decreases systolic pressure by 2.5 mmHg in healthy volunteers.Sarapis et al. (2020)
Table 2. Examples of studies comparing the effect of EVOO and OO on several cardiovascular health parameters.

 

In addition to its multiple direct actions on the heart and vessels, it should also be noted that extra virgin olive oil could also exert an indirect beneficial effect, by blocking the formation of the metabolite trimethylamine N-oxide (TMAO) by intestinal bacteria. Several studies have shown that TMAO accelerates the development of atherosclerosis in animal models and is associated with an increased risk of cardiovascular events in clinical studies. Extra virgin olive oils (but not regular olive oils) contain 3,3-dimethyl-1-butanol (DMB), a molecule that blocks a key enzyme involved in TMAO production and prevents development of atherosclerosis in animal models fed a diet rich in animal protein. Taken together, these observations show that there are only advantages to favouring the use of extra virgin olive oil, both for its superior taste and its positive effects on cardiovascular health.

Some people may dislike the slightly peppery taste that extra virgin olive oil leaves in the back of the throat, but interestingly, this irritation is greatly reduced when the oil is mixed with other foods. According to a recent study, this attenuation of the pungent taste is due to the interaction of the polyphenols in the oil with the proteins in food, which blocks the activation of the heat receptors that are normally activated by these polyphenols. People who hesitate to use extra virgin olive oil because of its irritant side can therefore get around this problem and still enjoy the benefits of these oils simply by using it as the main fat when preparing a meal.

Why do the Japanese have the highest life expectancy in the world?

Why do the Japanese have the highest life expectancy in the world?

OVERVIEW

  • The Japanese have the highest life expectancy at birth among the G7 countries.
  • The higher life expectancy of the Japanese is mainly due to fewer deaths from ischemic heart disease, including myocardial infarction, and cancer (especially breast and prostate).
  • This exceptional longevity is explained by a low rate of obesity and a unique diet, characterized by a low consumption of red meat and a high consumption of fish and plant foods such as soybeans and tea.

Several diets are conducive to the maintenance of good health and to the prevention of cardiovascular disease, for example, the Mediterranean diet, the DASH diet (Dietary Approaches to Stop Hypertension), the vegetarian diet, and the Japanese diet. We often refer to the Mediterranean Diet in these pages, because it is well established scientifically that this diet is particularly beneficial for cardiovascular health. Knowing that the Japanese have the highest life expectancy among the G7 countries, the special diet in Japan has also captured the attention of experts and an informed public in recent years.

Japanese life expectancy
Among the G7 countries, Japan has the highest life expectancy at birth according to 2016 OECD data, particularly for women. Japanese men have a slightly higher life expectancy (81.1 years) than that of Canadian men (80.9 years), while the life expectancy of Japanese women (87.1 years) is significantly higher (2.4 years) than that of Canadian women (84.7 years). The healthy life expectancy of the Japanese, 74.8 years, is also higher than in Canada (73.2 years).

The higher life expectancy of Japanese people is mainly due to fewer deaths from ischemic heart disease and cancers, particularly breast and prostate cancer. This low mortality is mainly attributable to a low rate of obesity, low consumption of red meat, and high consumption of fish and plant foods such as soybeans and tea. In Japan, the obesity rate is low (4.8% for men and 3.7% for women). By comparison, in Canada 24.6% of adult men and 26.2% of adult women were obese (BMI ≥ 30) in 2016. Obesity is an important risk factor for both ischemic heart disease and several types of cancers.

Yet in the early 1960s, Japanese life expectancy was the lowest of any G7 country, mainly due to high mortality from cerebrovascular disease and stomach cancer. The decrease in salt and salty food intake is partly responsible for the decrease in mortality from cerebrovascular disease and stomach cancer. The Japanese consumed an average of 14.5 g of salt/day in 1973 and probably more before that. They eat less salt these days (9.5 g/day in 2017), but it’s still too much. Canadians now consume on average about 7 g of salt/day (2.76 g of sodium/day), almost double the intake recommended by Health Canada.

The Japanese diet
Compared to Canadians, the French, Italians and Americans, the Japanese consume much less meat (especially beef), dairy products, sugar and sweeteners, fruits and potatoes, but much more fish and seafood, rice, soybeans and tea (Table 1). In 2017, the Japanese consumed an average of 2,697 kilocalories per day according to the FAO, significantly less than in Canada (3492 kcal per day), France (3558 kcal per day), Italy (3522 kcal per day), and the United States (3766 kcal per day).

Table 1. Food supply quantity (kg/capita/year) in selected countries in 2013a.

              aAdapted from Tsugane, 2020. FAO data: FAOSTAT (Food and agriculture data) (http://www.fao.org/).

Less red meat, more fish and seafood
The Japanese eat on average almost half as much meat as Canadians (46% less), but twice as much fish and seafood. This considerable difference translates into a reduced dietary intake of saturated fatty acids, which is associated with a lower risk of ischemic heart disease, but an increased risk of stroke. On the contrary, dietary intake of omega-3 fatty acids found in fish and seafood is associated with a reduced risk of ischemic heart disease. The lower consumption of red meat and higher consumption of fish and seafood by the Japanese could therefore explain the lower mortality from ischemic heart disease and the higher mortality from cerebrovascular disease in Japan. Experts believe that the decline in death from cerebrovascular disease is associated with changes in the Japanese diet, specifically increased consumption of animal products and dairy products, and consequently of saturated fat and calcium (a consumption which remains moderate), combined with a decrease in salt consumption. Indeed, contrary to what is observed in the West, the consumption of saturated fat in Japan is associated with a reduction in the risk of hemorrhagic stroke and to a lesser extent of ischemic stroke, according to a meta-analysis of prospective studies. The cause of this difference is not known, but it could be attributable to genetic susceptibility or confounding factors according to the authors of the meta-analysis.

Soybeans
Soy is a food mainly consumed in Asia, including Japan where it is consumed as is after cooking (edamame) and especially in processed form, by fermentation (soy sauce, miso paste, nattō) or by coagulation of soy milk (tofu). It is an important source of isoflavones, molecules that have anticancer properties and are beneficial for good cardiovascular health. Consumption of isoflavones by Asians has been linked to a lower risk of breast and prostate cancer (see our article on the subject).

Sugar
The Japanese consume relatively few sugars and starches, which partly explains the low prevalence of obesity-associated diseases such as ischemic heart disease and breast cancer.

Green tea
The Japanese generally consume green tea with no added sugar. Prospective studies from Japan show that green tea consumption is associated with a lower risk of all-cause mortality and cardiac death.

Westernization of Japanese eating habits
The westernization of the Japanese diet after World War II allowed the inhabitants of this country to be healthier and to reduce mortality caused by infectious diseases, pneumonia and cerebrovascular diseases, thereby considerably increasing their life expectancy. A survey of the eating habits of 88,527 Japanese from 2003 to 2015 indicates that this westernization continues. Based on the daily consumption of 31 food groups, the researchers identified three main types of eating habits:

1- Plant foods and fish
High intakes of vegetables, fruits, legumes, potatoes, mushrooms, seaweed, pickled vegetables, rice, fish, sugar, salt-based seasonings and tea.

2- Bread and dairy
High intakes of bread, dairy products, fruits and sugar. Low intake of rice.

3- Animal foods and oils
High intakes of red and processed meat, eggs, vegetable oils.

A downward trend in the “plant foods and fish” group (the staple of the traditional Japanese diet or washoku) was observed in all age groups. An increase in the “bread and dairy” group was observed in the 50–64 and ≥65 years age groups, but not among the youngest. For the “animal foods and oils” group, an increasing trend was observed during the thirteen years of the study in all age groups except the youngest (20–34 years). The Japanese are eating more and more like Westerners. Will this have an adverse effect on their health and life expectancy? It is too early to know, only the next few decades will tell.

Contribution of genes and lifestyle to the health of the Japanese
Some risk factors for cardiovascular disease and cancer are hereditary, while others are associated with lifestyle (diet, smoking, exercise, etc.). At the turn of the 20th century, there was significant Japanese immigration to the United States (especially California and Hawaii) and South America (Brazil, Peru). After a few generations, the descendants of Japanese migrants adopted the way of life of the host countries. While Japan has one of the lowest incidences of cardiovascular disease in the world, this incidence doubled among the Japanese who migrated to Hawaii and quadrupled among those who chose to live in California according to a 1975 study. What is surprising is that this increase has been observed regardless of blood pressure or cholesterol levels, and seems rather directly related to the abandonment of the traditional Japanese way of life by migrants.

Since the 1970s, the average cholesterol level of the Japanese has nonetheless increased, but despite this and the high rate of smoking in this country, the incidence of coronary heart disease remains substantially lower in Japan than in the West. To better understand these differences, a 2003 study compared the risk factors and diets of Japanese living in Japan with third- and fourth-generation Japanese migrants living in Hawaii in the United States. Men’s blood pressure was significantly higher among Japanese than among Japanese-Americans, while there was no significant difference for women. Far fewer Japanese were treated for hypertension than in Hawaii. More Japanese people (especially men) smoked than Japanese-Americans. Body mass index, blood levels of LDL cholesterol, total cholesterol, glycated hemoglobin (an indicator for diabetes), and fibrinogen (a marker of inflammation) were significantly lower in Japan than in Hawaii. HDL cholesterol (the “good” cholesterol) was higher in the Japanese than in the Japanese-Americans. The dietary intake of total fat and saturated fatty acids (harmful to cardiovascular health) was lower in Japan than in Hawaii. In contrast, the intake of polyunsaturated fatty acids and omega-3 fatty acids (beneficial for good cardiovascular health) was higher in Japan than in Hawaii. These differences may partly explain the lower incidence of coronary heart disease in Japan than in Western industrialized countries.

In other words, even if these migrants have the same basic risk as their compatriots who have remained in the country of origin (age, sex and heredity), the simple fact of adopting the lifestyle of their host country is enough to significantly increase their risk of cardiovascular disease.

Although the Japanese diet is different from those of Western countries, it has similar characteristics to the Mediterranean diet. Why not prepare delicious Japanese soy dishes from time to time (for example, tofu, edamame, miso soup), drink green tea, eat less meat, sugar and starch and more fish? Not only will your meals be more varied, but you could enjoy the health benefits of the Japanese diet.