Dr Louis Bherer, Ph. D., NeuropsychologueProfesseur titulaire au Département de Médecine de l’Université de Montréal. Directeur du Centre ÉPIC de l’Institut de cardiologie de Montréal.4 January 2023
- Participants in a study who had a high dietary intake of flavonols had slower cognitive decline than those who had a lower intake.
- Higher total flavonol intake was associated with a significantly slower decline in episodic memory, semantic memory, perceptual speed and working memory.
- Among the flavonols, kaempferol and quercetin were associated with slower cognitive decline, but not myricetin and isorhamnetin.
Flavonoids are polyphenolic compounds found in plants and in large quantities in fruits and vegetables in particular. These compounds are best known for their anti-inflammatory and antioxidant properties. Flavonoids have been associated in several previous studies with slowing age-related cognitive decline and dementia. However, few studies have attempted to identify which flavonoid subclasses and individual molecules are most active in protecting brain health. A recently published American study provides some answers by evaluating the effect of the intake of total flavonols and individual flavonols (kaempferol, quercetin, myricetin, isorhamnetin) on the cognitive performance of the elderly.
The study was conducted among 961 participants from the city of Chicago in the United States, aged 60 to 100, who were part of the Rush Memory and Aging Project cohort, and who were followed for 6.9 years on average. The participants, whose average age was 81 at the start of the study, were mostly female (75%), Caucasian (98%), and had an average of 15 years of schooling. Participants’ diet was assessed using a validated semi-quantitative questionnaire, and dietary flavonol intake was inferred from the collected data. The participants’ cognitive performance was assessed annually with a battery of 19 standardized tests.
A higher dietary intake of total flavonols and individual flavonols was associated with a lower rate of overall cognitive decline and several cognitive domains. A higher intake of total flavonols was associated with a slower decline in episodic memory (memories of personal events), semantic memory (memory of facts and concepts), perceptual speed, and working memory (short-term memory), but had no effect on visuospatial construction ability (understanding and representation of space in 2 and 3 dimensions).
Analysis of individual flavonols indicates that higher intakes of kaempferol and quercetin are associated with slower cognitive decline. In contrast, myricetin and isorhamnetin were not associated with an effect on global cognitive decline. Kale, beans, tea, spinach and broccoli were the foods highest in kaempferol among those consumed in this study. Tomatoes, kale, apples and tea were the foods highest in quercetin in this study.
The mechanisms underlying this favourable association are not yet well understood. The study authors suggest that the anti-inflammatory properties of flavonols may decrease the amplitude or duration of neuroinflammation. In addition, the antioxidant properties of flavonols could reduce or even prevent cell damage caused by oxidative stress, which generates reactive oxygen derivatives (free radicals, oxygenated ions, peroxides).
An earlier study by the same group of researchers reported that green leafy vegetables (spinach, kale, collard greens, lettuce) and certain constituents including kaempferol were associated with slowing overall cognitive decline. The authors concluded that “eating about one serving per day of green leafy vegetables and foods high in phylloquinone, lutein, nitrate, folate, α-tocopherol, and kaempferol may help slow cognitive decline with age.”
The protective role of certain flavonols on cognition has been demonstrated in animal models. Thus, quercetin supplementation improves memory and learning in transgenic mice used as an animal model of Alzheimer’s disease. In another study, kaempferol and myricetin improved memory and learning and reduced oxidative stress in mice used as a model of Alzheimer’s disease.
The prospective design of the American study does not make it possible to establish a causal link between dietary flavonol intake and cognition. Randomized clinical trials would confirm the role of flavonols on cognitive performance and, in the longer term, the prevention of cognitive decline associated with age. This type of study would also make it possible to clarify the dose-response relationship for optimal brain health. In any case, the study also has several strong points: a large number of participants, duration of the study, robust measurement of cognition by the 19 cognitive tests, validated questionnaires. The results were adjusted to minimize residual confounders, since it is possible that a higher dietary intake of flavonols is an indirect effect of a healthier diet. Among the limitations of this study are: self-reported food intake is subject to recall bias; because of their advanced age, participants are at risk of mild cognitive impairment that could cause errors when answering food questionnaires; there remains a possibility of reverse causation (cognitive decline may have altered participants’ eating habits). According to the authors, additional analyses (sensitivity analyses), however, indicate that reverse causation is unlikely.
The results of this study suggest that the consumption of fruits and vegetables (especially green leafy vegetables) in the elderly may not only help them maintain good health in general, but also delay or prevent cognitive decline. However, more studies are needed to confirm and better understand how flavonols slow cognitive and memory decline.
Dr Louis Bherer, Ph. D., NeuropsychologueProfesseur titulaire au Département de Médecine de l’Université de Montréal. Directeur du Centre ÉPIC de l’Institut de cardiologie de Montréal.7 October 2022
- Participants in a prospective study who walked more had a significantly reduced risk of dementia, premature mortality (all causes), mortality from cardiovascular disease, and cancer incidence.
- The optimal beneficial effect of walking is obtained at almost 10,000 steps/day for the risks of dementia, premature death and cancer.
- As little as 3,800 steps/day is associated with a 25% reduced risk of dementia, half the maximum effect (50%) obtained at 9,800 steps/day.
- Higher intensity (steps/minute) of walking was associated with favourable effects on premature death and the incidence of cardiovascular disease and cancer.
Several studies published to date suggest that increasing the number of daily steps is important to prevent the development of chronic diseases and premature death. We often hear in the news or on social media that 10,000 steps/day is the target to reach to enjoy the maximum health benefits. However, some studies indicate that at 6,000 to 8,000 steps/day, the maximum protective effect is achieved and that taking more steps does not significantly reduce the risk of death from all causes, for example. However, there is relatively little data on the subject, and the studies published to date do not distinguish between the different types of walking (daily life vs. exercise) and have paid little attention to the relative importance of walking intensity or cadence.
A prospective study recently examined the dose-response association between the amount (number of steps/day) and intensity (cadence) of walking and the incidence of dementia. The study, which lasted an average of 6.9 years, was carried out among 78,430 people aged 40 to 79 who were part of the UK Biobank cohort. Participants wore an accelerometer around their dominant wrist 24 hours a day, 7 days a week for at least 3 consecutive days and had no diagnosed cardiovascular disease, cancer or dementia at the start of the study. From the data collected by the accelerometer, it was possible to determine:
- the total number of steps/day;
- the number of steps related to activities of daily living (e.g., walking from one room to another), defined as less than 40 steps/minute;
- the number of steps taken during intentional physical activity, defined as 40 or more steps per minute (e.g., walking for exercise);
- the maximum 30-minute cadence (i.e., the average number of steps per minute recorded for the 30 minutes, not necessarily consecutive, when the cadence was maximal).
By the end of the study, 6.9 years after its start, 866 participants had developed dementia. The results show a nonlinear association between the number of total steps/day and the risk of dementia. The risk of dementia decreases with the number of total steps/day up to a 51% decrease at 9,826 steps/day. A number of steps/day of 3,826 is associated with a reduction in the risk of dementia by 25%, or half of the maximum effect.
Figure 1. Dose-response association between total daily steps taken and incidence of dementia. Adapted from del Pozo Cruz et al., 2022.
For the number of steps related to daily life, the optimal dose was 3,677 steps/day, with a 42% reduction in the risk of dementia. Regarding the number of purposeful steps, the optimal dose was 6,315 steps, with a decrease in the risk of dementia by 57%. For the maximum cadence over 30 minutes, the optimal dose was 112 steps/minute, with a reduction in the risk of dementia of 62%.
Associations with risk of mortality, cardiovascular disease and cancer
In a second publication by the same researchers and with the same UK Biobank cohort mentioned above, the dose-effect association between the amount and intensity of walking and premature mortality, mortality due to cardiovascular diseases, and cancer incidence was examined. During the seven years of the study, 1,325 participants died from cancer and 664 participants died from cardiovascular disease.
The risk of premature mortality decreases with increasing number of total steps/day, up to approximately 10,000 steps/day. For every additional 2,000 steps, the risk of premature death decreases by 8%, 10% and 11%
Figure 2. Dose-response association between total steps walked/day and all-cause mortality (panel A), cardiovascular disease mortality (panel B), and incidence of 13 cancers known to be associated with a low level of physical activity (panel C). Adapted from del Pozo Cruz et al., 2022.
The strengths of this study are the very large cohort size and the use of accelerometry and algorithms that helped distinguish walking steps from other ambulatory activities (a problem in some previous studies). Among the limitations, there is firstly that this type of study, of an observational nature, does not make it possible to establish a causal link. Second, the accelerometry data at the start of the study was collected only once and therefore may not fully reflect participants’ walking habits. However, multiple measurements carried out 4 years after the start of the study indicates that there is little variation between the data obtained during the different measurements. In addition, there remains a risk of reverse causation, i.e. that the disease (dementia, cardiovascular, cancer) could be the cause of a low number of steps, despite certain precautions taken by the researchers to minimize this risk.
The researchers are of the opinion that the right part of the dose-response curves does not reflect a real reduction in the favourable effect of walking after 10,000 steps, but rather reflects the scarcity of walking data or events (diagnoses of dementia, cardiovascular disease, death) for these few great walkers. In addition, some particularly health-conscious participants may have set a target (popularized in the media) of 10,000 steps/day, which could explain why the optimal effect is observed at this amount of walking.
Walking more and walking faster are associated with health and longevity benefits. Although the optimal health effect seems to be achieved around 10,000 steps/day, it is important to note that walking between 5,000 and 8,000 steps/day allows us to greatly benefit from the positive effects associated with walking. Moreover, there is no minimum threshold for the beneficial association between the number of total daily steps walked and mortality and morbidity. For example, as few as 3,800 steps/day are associated with a reduction in the risk of dementia equivalent to half of the maximum effect obtained at approx. 10,000 steps/day. Future recommendations for the prevention of dementia, cardiovascular disease and cancer could take this new evidence into account and encourage the population to walk more and at a faster pace, in order to optimally benefit from the health benefits of walking.
Dr Louis Bherer, Ph. D., NeuropsychologueProfesseur titulaire au Département de Médecine de l’Université de Montréal. Directeur du Centre ÉPIC de l’Institut de cardiologie de Montréal.25 August 2022
- Among participants in an observational study in the UK, those who ate the most ultra-processed foods had a significantly higher risk of developing dementia.
- By one estimate, substituting as little as 10% of ultra-processed foods with minimally or unprocessed foods in the daily diet is associated with a 19% decreased risk of dementia.
What is ultra-processed food?
Ultra-processed foods are usually prepared from 5 or more ingredients, often using complex industrial processes. These foods are inexpensive to make, appetizing, high in added sugars, salt and fat, but low in protein, polyunsaturated fat and fibre. Some examples of ultra-processed foods include ready meals, chicken or fish nuggets, sausages, cookies, sweetened fruit yogurts, breakfast cereals, energy bars, soft drinks, sweets. Consumption of these energy-dense but nutritionally poor foods has increased considerably in recent decades, to the point that they now constitute more than 50% of the total dietary intake in some countries, such as the United States (58%).
Ultra-processed foods have been linked to adverse health effects such as cardiovascular disease, diabetes, cancer, depression, and all-cause mortality. Researchers from China and Sweden wondered if there was also an unfavourable association between the consumption of ultra-processed foods and the risk of dementia.
The researchers used data from the UK Biobank, a prospective study of 72,083 participants aged 55 or older who were followed for an average of 10 years. All participants showed no signs of dementia at the start of the study. After 10 years, 518 participants (0.72%) were diagnosed with dementia, including 287 participants (0.4%) who developed Alzheimer’s disease and 119 participants (0.17%) who developed vascular dementia. During the study, participants completed at least two detailed questionnaires about their diet, which allowed the researchers to estimate what percentage of the foods they consumed were ultra-processed. The researchers then divided the participants into four groups (quartiles) based on their level of consumption of ultra-processed foods.
Participants in the first quartile consumed an average of 225 g of ultra-processed foods (9% of daily food intake), while those in the top quartile consumed 814 g (28% of the daily intake). In order, soft drinks, sweets and ultra-processed dairy products were the most consumed ultra-processed foods. One hundred and five of the 18,021 participants in the first group who consumed the least ultra-processed foods developed dementia, compared to 150 of the 18,021 participants in the group (quartile) who consumed the most ultra-processed foods. After adjusting the data for age, gender, family history of dementia and heart disease, and other factors, it was estimated that for every 10% increase in daily intake of ultra-processed foods, participants had a 25% higher risk of dementia. The link was even stronger for vascular dementia (28%) compared to Alzheimer-type dementia (14%).
According to the same study, it was estimated that substituting 10% of ultra-processed foods with minimally or unprocessed foods (fruits, vegetables, legumes, milk and meat) is associated with a reduced risk of dementia by 19%. More concretely, an increase of 50 g/day of unprocessed food, equivalent to half an apple for example, replacing 50 g/day of ultra-processed food (equivalent to a chocolate bar or a slice of bacon) could reduce the risk of dementia by 3%. Thus, small changes in diet, requiring little effort, could make a big difference in a person’s risk of dementia.
Dr Louis Bherer, Ph. D., NeuropsychologueProfesseur titulaire au Département de Médecine de l’Université de Montréal. Directeur du Centre ÉPIC de l’Institut de cardiologie de Montréal.23 December 2021
- In a study on aging and diet conducted in Greece, 1,059 older people reported in detail what they ate for three years.
- At the end of the study, people with the most inflammatory diet had a 3-fold higher risk of developing dementia compared to those whose diet had a low-inflammatory index.
- The main anti-inflammatory foods are vegetables, fruits, whole grains, tea, and coffee. The main pro-inflammatory foods that should be avoided or eaten infrequently and in small amounts are red meat, deli meats, refined flours, added sugars, and ultra-processed foods.
Dietary Inflammatory Index
Several studies suggest that the nature of the foods we eat can greatly influence the degree of chronic inflammation and, in turn, the risk of chronic disease, including cardiovascular disease. For example, a pro-inflammatory diet has been associated with an increased risk of cardiovascular disease, with a 40% increase in risk in people with the highest index (see our article on the subject).
Pro-inflammatory diet and risk of dementia
In order to see if there is an association between a diet that promotes systemic inflammation and the risk of developing dementia, 1,059 elderly people residing in Greece were recruited as part of the study Hellenic Longitudinal Investigation of Aging and Diet (HELIAD). Only people without a diagnosis of dementia at the start of the study were included in the cohort. The inflammatory potential of the participants’ diet was estimated using the Dietary Inflammatory Index (DII) based on the known effect of various foods on the blood levels of inflammatory markers . The main pro-inflammatory foods are red meat, deli meats, refined flour, added sugars, and ultra-processed foods. Some of the main anti-inflammatory foods are vegetables, fruits, whole grains, tea, coffee, and red wine.
After a follow-up of 3 years on average, 62 people were diagnosed with dementia. Participants who had the diet with the highest inflammatory index had a three-fold higher risk of developing dementia at the end of the study, compared to those with the least inflammatory index. In addition, there appears to be a dose-response relationship, with an increased risk of dementia that increases by 21% for each unit of the inflammatory index.
Inflammation, interleukin-6, and cognitive decline
The study in Greece is not the first to be conducted on the impact of a pro-inflammatory diet on the incidence of dementia. In a Polish study of 222 postmenopausal women, those with cognitive deficits had significantly higher blood levels of interleukin-6 (IL-6; a marker of inflammation), were less educated, and were less physically active, compared to women with normal cognitive functions. Postmenopausal women who had a pro-inflammatory diet were much more likely to have cognitive impairment compared to those who had an anti-inflammatory diet, even after adjusting for age, height, body mass index, level of education, and levels of physical activity. Each one-point increase in the dietary inflammatory index was associated with a 1.55-fold increase in the risk of cognitive impairment.
In addition to these studies, it is interesting to see that a meta-analysis of 7 prospective studies including 15,828 participants showed that there is an association between the concentration of IL-6 in the blood and the overall cognitive decline in the elderly. Participants who had the most circulating IL-6 had a 42% higher risk of suffering cognitive decline than those with low blood IL-6 levels.
Several studies have suggested that systemic inflammation (i.e., outside the central nervous system) may play a role in neurodegeneration, Alzheimer’s disease, and cognitive decline in older adults. People with Alzheimer’s disease and mild cognitive impairment tend to have high blood levels of markers of inflammation (IL-6, TNF-α, CRP). In addition, a study indicates that people who have elevated levels of markers of inflammation during midlife have an increased risk of cognitive decline in subsequent decades.
Since the studies described above are observational, they do not establish a causal link between inflammatory diet and dementia. They only show that there is an association. Further studies are needed in the future to establish a cause and effect relationship and identify the underlying molecular mechanisms.
Evidence from recent studies should encourage experts to more often recommend diets high in flavonoids that decrease systemic inflammation and are conducive to the maintenance of good cognitive health. Mediterranean-type diets or the hybrid MIND diet (Mediterranean-DASH Intervention for Neurodegenerative Delay) with an abundance of plants are particularly effective in reducing or delaying cognitive decline.
Dr Martin Juneau, M.D., FRCPCardiologue et Directeur de la prévention, Institut de Cardiologie de Montréal. Professeur titulaire de clinique, Faculté de médecine de l'Université de Montréal. / Cardiologist and Director of Prevention, Montreal Heart Institute. Clinical Professor, Faculty of Medicine, University of Montreal.26 October 2020
- Hypertension is the main risk factor for cardiovascular disease and is responsible for 20% of deaths worldwide.
- Early hypertension, before the age of 45, is associated with an increased risk of cardiovascular disease, cognitive decline and premature mortality.
- Adopting an overall healthy lifestyle (normal weight, not smoking, regular physical activity, moderate alcohol consumption, and a good diet including sodium reduction) remains the best way to maintain adequate blood pressure.
According to the latest data from the Global Burden of Disease Study 2019, excessively high blood pressure was responsible for 10.8 million deaths worldwide in 2019, or 19.2% of all deaths recorded. This devastating impact is a direct consequence of the enormous damage caused by hypertension on the cardiovascular system. Indeed, a very large number of studies have clearly shown that excessive blood pressure, above 130/80 mm Hg (see box for a better understanding of blood pressure values), is closely linked to a significant increased risk of coronary heart disease and stroke.
Systolic and diastolic
It is important to remember that blood pressure is always expressed in the form of two values, namely systolic pressure and diastolic pressure. Systolic pressure is the pressure of the blood ejected by the left ventricle during the contraction of the heart (systole), while diastolic pressure is that measured between two beats, during the filling of the heart (diastole). To measure both pressures, the arterial circulation in the arm is completely blocked using an inflatable cuff, then the cuff pressure is allowed to gradually decrease until blood begins to flow back into the artery. This is the systolic pressure. By continuing to decrease the swelling of the cuff, we then arrive at a pressure from which there is no longer any obstacle to the passage of blood in the artery, even when the heart is filling. This is the diastolic pressure. A blood pressure value of 120/80 mm Hg, for example, therefore represents the ratio of systolic (120 mm Hg) and diastolic (80 mm Hg) pressures.
As shown in Figure 1, this risk of dying prematurely from coronary heart disease is moderate up to a systolic pressure of 130 mm Hg or a diastolic pressure of 90 mm Hg, but increases rapidly thereafter to almost 4 times for pressures equal to or greater than 150/98 mm Hg. This impact of hypertension is even more pronounced for stroke, with an 8 times higher risk of mortality for people with systolic pressure above 150 mm Hg and 4 times higher for a diastolic pressure greater than 98 mm Hg (Figure 1, bottom graph). Consequently, high blood pressure is by far the main risk factor for stroke, being responsible for about half of the mortality associated with this disease.
Figure 1. Association between blood pressure levels and the risk of death from coronary heart disease or stroke. From Stamler et al. (1993).
Blood pressure tends to increase with aging as blood vessels become thicker and less elastic over time (blood circulates less easily and creates greater mechanical stress on the vessel wall). On the other hand, age is not the only risk factor for high blood pressure: sedentary lifestyle, poor diet (too much sodium intake, in particular), and excess body weight are all lifestyle factors that promote the development of hypertension, including in younger people.
In industrialized countries, these poor lifestyle habits are very common and contribute to a fairly high prevalence of hypertensive people, even among young adults. In Canada, for example, as many as 15% of adults aged 20–39 and 39% of those aged 40–59 have blood pressure above 130/80 mm Hg (Figure 2).
Figure 2. Prevalence of hypertension in the Canadian population. Hypertension is defined as systolic pressure ≥ 130 mm Hg or diastolic pressure ≥ 80 mm Hg, according to the 2017 criteria of the American College of Cardiology and the American Heart Association. The data are from Statistics Canada.
This proportion of young adults with hypertension is lower than that observed in older people (three in four people aged 70 and over have hypertension), but it can nevertheless have major repercussions on the health of these people in the longer term. Several recent studies indicate that it is not only hypertension per se that represents a risk factor for cardiovascular disease, but also the length of time a person is exposed to these high blood pressures. For example, a recent study reported that onset of hypertension before the age of 45 doubles the risk of cardiovascular disease and premature death, while onset of hypertension later in life (55 years and older) has a much less pronounced impact (Figure 3). These findings are consistent with studies showing that early hypertension is associated with an increased risk of cardiovascular mortality and damage to target organs (heart, kidneys, brain). In the case of the brain, high blood pressure in young adults has been reported to be associated with an increased risk of cognitive decline at older ages. Conversely, a recent meta-analysis suggests that a reduction in blood pressure with the help of antihypertensive drugs is associated with a lower risk of dementia or reduced cognitive function.
Figure 3. Change in risk of cardiovascular disease (red) or death from all causes (blue) depending on the age at which hypertension begins. Adapted from Wang et al. (2020).
Early hypertension should therefore be considered an important risk factor, and young adults can benefit from managingtheir blood pressure as early as possible, before this excessively high blood pressure causes irreparable damage.
The study of barbershops
In African-American culture, barbershops are gathering places that play a very important role in community cohesion. For health professionals, frequent attendance at these barbershops also represents a golden opportunity to regularly meet Black men to raise their awareness of certain health problems that disproportionately affect them. This is particularly the case with hypertension: African American men 20 years and older have one of the highest prevalence of high blood pressure in the world, with as many as 59% of them being hypertensive. Also, compared to whites, Black men develop high blood pressure earlier in their lives and this pressure is on average much higher.
A recent study indicates that barbershops may raise awareness among African Americans about the importance of controlling their blood pressure and promoting the treatment of hypertension. In this study, researchers recruited 319 African Americans aged 35 to 79 who were hypertensive (average blood pressure approximately 153 mm Hg) and who were regular barbershop customers. Participants were randomly assigned to two groups: 1) an intervention group, in which clients were encouraged to see, in the barbershops, pharmacists specially trained to diagnose and treat hypertension and 2) a control group, in which barbers suggested that clients make lifestyle changes and seek medical attention. In the intervention group, pharmacists met regularly with clients during their barbershop visits, prescribed antihypertensive drugs, and monitored their blood pressure.
After only 6 months, the results obtained were nothing short of spectacular: the blood pressure of the intervention group fell by 27 mm Hg (to reach 125.8 mm Hg on average), compared to only 9.3 mm Hg (to reach 145 mm Hg on average) for the control group. Normal blood pressure (less than 130/80 mm Hg) was achieved in 64% of participants in the intervention group, while only 12% of those in the control group were successful. A recent update of the study showed that the beneficial effects of the intervention were long-lasting, with continued pressure reductions still observed one year after the start of the study.
These reductions in blood pressure obtained in the intervention group are of great importance, as several studies have clearly shown that pharmacological treatment of hypertension causes a significant reduction in the risk of cardiovascular diseases, including coronary heart disease and stroke, as well as kidney failure. This study therefore shows how important it is to know your blood pressure and, if it is above normal, to normalize it with medication or through lifestyle changes.
The importance of lifestyle
This last point is particularly important for the many people who have blood pressure slightly above normal, but without reaching values as high as those of the participants of the study mentioned above (150/90 mm Hg and above). In these people, an increase in the level of physical activity, a reduction in sodium intake, and body weight loss can lower blood pressure enough to allow it to reach normal levels. For example, obesity is a major risk factor for hypertension and a weight loss of 10 kg is associated with a reduction in systolic pressure from 5 mm to 10 mm Hg. This positive influence of lifestyle is observed even in people who have certain genetic variants that predispose them to high blood pressure. For example, adopting an overall healthy lifestyle (normal weight, not smoking, regular physical activity, moderate alcohol consumption, and a good diet including sodium reduction) has been shown to be associated with blood pressure approximately 3 mm Hg lower and a 30% reduction in the risk of cardiovascular disease, regardless of the genetic risk. Conversely, an unhealthy lifestyle increases blood pressure and the risk of cardiovascular disease, even in those who are genetically less at risk of hypertension.
In short, taking your blood pressure regularly, even at a young age, can literally save your life. The easiest way to regularly check your blood pressure is to purchase one of the many models of blood pressure monitors available in pharmacies or specialty stores. Take the measurement in a seated position, legs uncrossed and with the arm resting on a table so that the middle of the arm is at the level of the heart. Two measurements in the morning before having breakfast and drinking coffee and two more measurements in the evening before bedtime (wait at least 2 hours after the end of the meal) generally give an accurate picture of blood pressure, which should be below 135/85 mm Hg on average according to Hypertension Canada.
Dr Martin Juneau, M.D., FRCPCardiologue et Directeur de la prévention, Institut de Cardiologie de Montréal. Professeur titulaire de clinique, Faculté de médecine de l'Université de Montréal. / Cardiologist and Director of Prevention, Montreal Heart Institute. Clinical Professor, Faculty of Medicine, University of Montreal.1 August 2018
Berries are becoming increasingly popular in our diet, whether consumed fresh, frozen, dried or canned, and in related products such as jams, jellies, yogurts, juices and wines. Berries provide significant health benefits because of their high content of phenolic compounds, antioxidants, vitamins, minerals and fibres. Recognizing these health benefits has recently led to a 21% increase in world berry production.
The generic term “berries” is sometimes used to refer to small fruits, but from a botanical point of view, if some berries are genuineberries (blueberries, bilberries, cranberries, currants, lingonberries, elderberries), others are polydrupes (raspberries, blackberries), and the strawberry is a “false fruit” since the achenes (the small seeds on the outer surface of the strawberry) are the actual fruits of the strawberry. Berry fruits are rich in phenolic compounds such as phenolic acids, stilbenes, flavonoids, lignans and tannins (see the classification and structure of these compounds in Figure 1). Berries are particularly rich in anthocyanidins, pigments that give the skin and flesh of these fruits their distinctive red, blue or purple colour (Table 1).
Figure 1. Classification and chemical structure of phenolic compounds contained in berries. Adapted from Parades-López et al., 2010 and Nile & Park, 2014.
Like most flavonoids, anthocyanidins are found in nature as glycosides (compounds made of a sugar and another molecule) called anthocyanins. These anthocyanins can be absorbed in their whole form (linked to different sugars) both in the stomach and in the intestine. Anthocyanins that reach the large intestine can be metabolized by the microbiota (intestinal flora). The maximum concentration of anthocyanins in the bloodstream is reached from 30 minutes to 2 hours after eating berries. However, the maximum plasma concentration (1–100 nmol/L) of anthocyanins is much lower than what is measured in intestinal tissues, indicating that these compounds are metabolized extensively before entering the systemic circulation as metabolites. After administering a radiolabelled anthocyanin to humans, 35 metabolites were identified, 17 in blood, 31 in urine and 28 in feces. Thus, it is likely that these metabolites, rather than the intact molecule, are responsible for the health benefits associated with anthocyanins.
Table 1. Content of phenolic compounds, flavonoids, and anthocyanins of different berries. Adapted from Parades-López et al., 2010 and Nile & Park, 2014.
|Berries (genus and species)||Phenolic compounds||Flavonoids||Anthocyanins
|(mg/100 g fresh fruit)||(mg/100 g fresh fruit)||(mg/100 g fresh fruit)
|Raspberry (Rubus ideaous)||121||6||99
|Blackberry (Rubus fruticosus)||486||276||82–326
|Strawberry (Fragaria x. ananassa)||313||–||54
|Blueberry (Vaccinium corymbosum)||261–585||50||25–495
|Bilberry (Vaccinium myrtillus )||525||44||300
|Cranberry (Vaccinium macrocarpon)||315||157||67–140
|Redcurrant (Ribes rubrum)||1400||9||22
|Blackcurrant (Ribes nigrum)||29-60||46||44
|Elderberry (Sambucus nigra)||104||42||45-791
|Red cranberry (Vitis vitis-idea)||652||74||77
Biological activities of berries
Data from in vitro and animal experimental models indicate that the phenolic compounds in berries may produce their beneficial effects through their antioxidant, anti-inflammatory, antihypertensive, and lipid-lowering activities, which could prevent or mitigate atherosclerosis. Perhaps the best-known of the biological activities of phenolic compounds is their antioxidant activity, which helps protect the body’s cells from damage caused by free radicals and counteract certain chronic diseases associated with aging. According to several studies using in vitro and animal models, berries also have anti-cancer properties involving several complementary mechanisms such as induction of metabolic enzymes, modulation of the expression of specific genes and their effects on cell proliferation, apoptosis (programmed cell death, an unsettled process in cancer cells), and signalling pathways inside the cell.
In a prospective study conducted in China with 512,891 participants, daily consumption of fruit (all types of fruit) was associated with an average decrease in systolic blood pressure of 4.0 mmHg on average, a decrease of 0.5 mmol/L of blood glucose concentration, a 34% reduction in the risk of major coronary events and a 40% reduction in the risk of cardiovascular mortality. These results were obtained by comparing participants who ate fruits daily to those who did not consume them at all or very rarely. In this study, there was a strong dose-response correlation between the incidence of cardiovascular events or cardiovascular mortality and the amount of fruit consumed. Studies suggest that among the constituents of fruit, it is the flavonoids, and especially the anthocyanins, that are responsible for these protective effects.
A number of prospective and cross-sectional studies have examined the association between the consumption of anthocyanins and cardiovascular risk factors (see this review). In four out of five studies that examined the risks of coronary heart disease or nonfatal myocardial infarction, anthocyanin consumption was associatedwith a reduction in coronary artery disease risk from 12% to 32%. The impact of anthocyanins on the risk of stroke was investigated in 5 studies, but no evidence of a protective effect was found in this case.
With respect to cardiovascular risk factors, studies indicate that higher consumption of anthocyanins is associated with decreased arterial stiffness, arterial pressure, and insulinemia. The decrease in blood pressure associated with the consumption of anthocyanins, -4 mmHg, is similar to that seen in a person after quitting smoking. The effect of anthocyanins on insulin concentration, an average reduction of 0.7 mIU/L, is similar to the effects of a low-fat diet or a one-hour walk per day. A decrease in inflammation has been associated with the consumption of anthocyanins and flavonols, a mechanism that may underlie the reduction of cardiovascular risk and other chronic diseases.
Randomized controlled trials
A systematic review and meta-analysis of 22 randomized controlled trials, representing 1,251 people, report that berry consumption significantly reduces several cardiovascular risk factors, such as blood LDL cholesterol , systolic blood pressure , fasting glucose concentration , body mass index , glycated haemoglobin , and tumour necrosis factor alpha , a cytokine involved in systemic inflammation. In contrast, no significant changes were observed for the other markers of cardiovascular disease that were tested: total cholesterol, HDL cholesterol, triglycerides, diastolic blood pressure, ApoAI, ApoB, Ox-LDL, IL-6, CRP, sICAM-1,and sICAM-2.
Another systematic review published in 2018 evaluated randomized controlled trials on the effects of berry consumption on cardiovascular health. Among the 17 high-quality RCTs, 12 reported a beneficial effect of berry consumption on cardiovascular and metabolic health markers. Four out of eleven RCTs reported a reduction in systolic and/or diastolic blood pressure; 3/7 studies reported a favourable effect on endothelial function; 2/3 studies reported an improvement in arterial stiffness; 7/17 studies reported beneficial effects for the lipid balance; and 3/6 studies reported an improvement in the glycemic profile.
Berries and cognitive decline
Greater consumption of blueberries and strawberries was associated with a slowdown in cognitive decline in a prospective study of 16,010 participants in the Nurses’ Health Study aged 70 or older. Consumption of berries was associated with delayed cognitive decline of approximately 2.5 years. In addition, nurses who had consumed more anthocyanidins and total flavonoids had a slower cognitive decline than participants who consumed less.
The exceptional content of phenolic compounds in berries and their positive effects on health remind us that the quality of food is not just about nutrients: proteins, carbohydrates, lipids, vitamins and minerals; a wide variety of other molecules found in plants are absorbed from the intestines and routed through the bloodstream to all cells in the body. While not essential nutrients, phytochemicals such as flavonoids can contribute to better cardiovascular health and healthier aging.