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.
Updated on February 11, 2019
Not only are plants important sources of vitamins, fibres and minerals but they also contain phytochemicals such as polyphenols that play a very important role in the positive effects of these foods on cardiovascular health. Among the thousands of distinct polyphenols found in nature, the family of flavonoids has received special attention in recent years because of its presence in a large number of plants (fruits, vegetables, nuts, legumes) and beverages (tea, coffee, red wine) that are part of our daily diet. The impact of these molecules on health appears to be particularly important, as population studies indicate that people with the highest flavonoid intake have a lower risk of stroke or coronary artery disease, effects that are accompanied by a decrease in cardiovascular mortality and overall mortality.
Cocoa and its by-products, especially dark chocolate, are exceptional sources of polyphenols (Table 1), in particular flavonoids, suggesting that regular consumption of cocoa products could be very positive for cardiovascular health.
Table 1. Polyphenol content of some foods and beverages. Adapted from Pérez-Jiménez et al. (2010).
(mg/100 g or 100 mL)
The first clue to this positive effect comes from Marjorie McCullough’s observations on the Kuna Indians of the San Blass Islands, an archipelago off Panama. These people are very large consumers of cocoa, which they use to prepare a beverage according to the traditional method of pre-Colombian civilizations. The Kuna drink about five cups of cocoa a day, which translates into a polyphenol intake of around 1800 mg per day, almost 10 times more than North Americans. These people are also distinguished for their very low blood pressure (110/70 mmHg even at over 60 years old), despite a very high salt diet, and their low incidence of myocardial infarction and stroke. These characteristics are not of genetic origin, because the individuals who have left the island to live on the mainland see their blood pressure quickly increase. Among the lifestyle factors that may explain this difference, the most plausible is the drastic decrease in continental cocoa consumption, which is 10 times lower than among islanders. Therefore, it seems that cocoa polyphenols can have a real impact on cardiovascular health by lowering blood pressure and, at the same time, the risk of ischemic events such as heart attack or stroke that result from hypertension.
Several epidemiological studies have confirmed that high cocoa intake is indeed associated with a decrease in blood pressure and a reduction in the risk of cardiovascular disease and premature mortality. For example, a 15-year Dutch study of 500 people over the age of 65 found that those who consumed the most cocoa-based products had an average systolic pressure of 3.7 mm Hg and a marked reduction (50%) in the risk of cardiovascular mortality. These results have been confirmed by several randomized clinical trials where the consumption of dark chocolate, cocoa or cocoa-derived polyphenols is associated with a decrease in blood pressure and an improvement in endothelial function and insulin sensitivity. These vascular effects are largely due to an increase in the formation of nitric oxide (NO), a powerful vasodilator, by some cocoa flavonoids. A beneficial effect of cocoa consumption on the lipid profile (triglycerides, LDL and HDL cholesterol) and on the reduction of chronic inflammation has also been reported and could contribute to the benefits of dark chocolate for cardiovascular health.
These beneficial effects are also suggested by the results of a meta-analysis of 14 prospective studies conducted with a total of 508,705 participants, followed for a period of 5 to 16 years. The authors observed that people who consumed the most cocoa had a lower risk of coronary heart disease (10% decrease), stroke (16% decrease), and diabetes (18% decrease).
The most recent meta-analysis, which included 23 prospective studies with 405,304 participants, indicates that chocolate consumption is associated with a reduced risk of cardiovascular disease (CVD), if consumption is limited to less than 100 g/week. Those who consumed more chocolate had a 12% lower risk of CVD in general (stroke: -16.3%, myocardial infarction: -16.2%) than those who consumed little. However, the dose-response analysis (Figure 1) shows that at more than 100 g/week there is no longer any protective effect and that the risk of CVD increases at higher doses, which could be attributable to the harmful effect of consuming too much sugar. According to the authors of this meta-analysis, the best dose of chocolate to reduce the risk of CVD is 45 g/week (about half of a 100 g chocolate bar, a common size sold in grocery stores).
Figure 1. Dose-effect association between the consumption of chocolate and the risks of cardiovascular events. From Ren et al., Heart, 2019.
It is now clearly established that several risk factors for cardiovascular disease (hypertension, inflammation, insulin resistance, metabolic syndrome) also increase the risk of cognitive decline and dementia. Conversely, recognized factors to protect cardiovascular health, such as physical exercise or the Mediterranean diet, are associated with a significant decrease in the risk of cognitive disorders. In other words, what is good for the heart is also good for the brain, which raises the interesting possibility that the regular consumption of cocoa-based products can also result in benefits for cognitive function. Studies conducted to date support this, as a high intake of flavonoid-rich foods such as tea, red wine and chocolate is associated with reduced risk of cognitive decline and improved brain performance. In a study of people aged 65 to 82 who showed clinical signs of early cognitive decline, daily consumption of a beverage made with chocolate high in polyphenols was associated with significant improvement of cognitive functions.
More recently, a randomized clinical study showed that dark chocolate consumption was associated with a significant improvement in visual acuity and contrast sensitivity a few hours after intake, a positive impact possibly related to an improvement in blood circulation in the richly vascularized retina. Milk chocolate, which contains less polyphenols, has no effect, suggesting that flavonoids in cocoa are responsible for this improvement in vision.