An estimated 18 million people died of heart disease in 2017, making up 31% of all global deaths. Of these deaths, 85% are due to heart attack and stroke. Most cardiovascular disease can be prevented by addressing behavioral risk factors such as tobacco use, unhealthy diet and obesity, physical inactivity, and prolonged alcohol consumption using population-wide approaches. WHO estimates shows that more than 75% of early cardiovascular disease is preventable and that improving associated risk factors can help reduce the growing burden of cardiovascular disease for both individuals and healthcare professionals. Diet and lifestyle have an eminent effect on LDL cholesterol levels and the risk of cardiovascular disease. Patients with cardiovascular disease should be educated about lifestyle modifications to reduce cigarette smoking, ingestion of fat, cholesterol, and too many calories.
They should likewise ensure adequate physical activity in order to maintain a healthy BMI. In the prevailing years, it has been reported that in most heart disease there is a concurrent imbalance of the redox systems that generates oxidative stress. It has been well established from previous reports that sugars are involved in the development of atherosclerosis, hypertension, peripheral vascular disease, coronary artery disease, heart failure and cardiac arrhythmias and that these effects of added sugars are mediated by free radicals. According to epidemiological evidence, a diet low in saturated fat and rich in fruits, vegetables and essential fatty acids, as well as moderate consumption of wine, appears to protect against cardiovascular disease. Saturated and trans fatty acids are associated with a high cardiovascular risk; monounsaturated (omega-9) and polyunsaturated (omega-3, omega-6) fatty acids reduce the risk of coronary heart disease.
Polyphenols and their biological actions
Despite many previous published reports on flavonoids (including dietary flavonoids) and their health benefits in various human diseases such as cancer, neurodegenerative and cardiovascular diseases, etc., there are no clear reports available in the current literature indicating safe modes of flavonoids. food associated with cardioprotective effects. An exception could be resveratrol, the red grape polyphenol that has been extensively studied. Despite its very low quantities in wine (a few mg per 100ml), it activates biological signals that have visible effects, but this is not the case for most polyphenols. Flavonoids, such as quercetin, kaempferol and myricetin, found in fruits and vegetables, including apples, grapes, berries, tomatoes, onions, lettuce, etc., need many milligrams (25-100) to exert visible biological effects.
On the other hand, the best known compounds in the flavanone group are hesperidin, naringenin and eriodicthiol, which are regularly found in the white part of the citrus peel (albedo) such as lemon, orange and grapefruit. Isoflavonoids are less distributed in plants and are usually found in lentils, beans, soy and other legumes. Anthocyanins are a widely studied class of flavonoids. The anthocyanins best known to experts are cyanidin, delphinidin, malvidin, pelargonidin and peonidin. These compounds are found in strawberries, raspberries, blueberries, blackberries, blue corn, black beans, among others. In Asian countries, soy is the main source of flavonoids (isoflavones) as well as tea, coffee and legumes. In the West, the main food sources of flavonoids are tea, chocolate, cocoa, vegetables, fruit, red wine and legumes.
In a meta-analysis of prospective cohort studies, regular diets containing flavonoids were accompanied by a lower risk of mortality from cardiovascular disease. Furthermore, consumption of 200 mg / day of total flavonoids is associated with a reduced risk of all-cause mortality. Overall, in vitro and in vivo studies suggest that flavonoids exhibit a long range of activities such as the antihypertensive effect by inhibiting ACE, potentiating the effects of bradykinin, decreasing endothelin levels and increasing vasodilation. They can protect the heart muscle from ischemia and cell death in the event of a heart attack; they also have antithrombotic activity and prevent LDL oxidation, thus inhibiting the progression of atherosclerosis.
The problem of bioavailability
Although flavonoids have shown countless health benefits, their low oral bioavailability has been a major concern in drug development. The most important factors associated with the absorption and bioavailability of food flavonoids are the type, number and location of sugar binding, metabolism via metabolic enzymes, and the gut microbiota. In foods, flavonoids are often present in their glycosylated form; but once ingested, the sugar fraction is removed before the absorption phase. This mechanism is implemented in the brush border of the small intestine by the enzyme lactase-phlorizin hydrolase (GPL) which produces the hydrolysis of the structure and the sugar is removed to release the aglycone, to enter the epithelial cells by passive diffusion.
The food matrix and the location of flavonoids in food sources play an important role in the absorption and bioavailability of various flavonoids. Evidently, the ethanol present in red wine increases the absorption of anthocyanins from the intestine. Co-administration of flavonoids with carbohydrate-containing foods showed increased gut absorption and bioavailability. A fatty matrix can increase the absorption of flavonoids and slow down their elimination. On the other hand, the oral bioavailability of many flavonoids is reduced when taken in a protein meal. Another important mechanism of non-absorbed flavonoids in the small intestine consists in their passage into the distal colon, where the intestinal microbiota makes some changes and produces aromatic compounds different from the original ones.
Polyphenols and intestinal microbiota
Given the above, it does not mean that it becomes useless to take foods rich in polyphenols with the diet, since there are many factors that can determine their bioavailability. In any case, the food associations listed above to facilitate their absorption are fully exploitable. If alcoholic beverages can promote the absorption of polyphenols, you can take advantage of the consumption of moderate doses of red or black wine after the end of a meal rich in vegetable and / or raw foods. Consuming controlled quantities of red wine is allowed by the scientific community, both for the presence of polyphenols and for the fluidifying action of alcohol on blood platelets. Finally, there is more and more evidence that part of the protective actions of polyphenols on our health depend on the fact that they are taken up by the bacteria of the intestinal microbiota.
It is the metabolic fate that they undergo from bacteria that seems to partly affect our general health. Polyphenols are particularly desired by Gram-positive bacteria such as Lactobacillus and Bifidobacteria and the like, all species that keep both the intestine and general metabolism healthy. These are known to suffer from the consumption of plant fibers (pre-biotics), which bacteria also ferment for their nutritional needs. Therefore, the consumption of fresh fruit and vegetables (rich in vegetable fibers and polyphenols) is a health directive that the scientific community has fully achieved. As with any other part of the body, therefore, polyphenols can protect our heart health both directly and indirectly by maintaining a healthy intestinal microbiota.
- Edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
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Dott. Gianfrancesco Cormaci
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