Bioavailability of Dietary Polyphenols and the Cardiovascular Diseases

Abstract

Epidemiological studies indicate that the higher intake of fruits and vegetables may reduce the risks of many degenrative diseases like cancer, cardiovascular disease, cataract etc. This is attributed mainly to the intake of dietary polyphenols as seen in Mediterranean diets. However, the bioavailability of polyphenols is reported to be low due to poor absorption in the gut, intestine and colon and depends on the type of compounds, chemical structure, food matrix, extent of conjugation and individual colon microflora. In general, flavonoids, aglycones and pure compounds are absorbed more when compared to the glycosides. Diversity in intestinal mocroflora also contributes to a great extent for the variation in absorption of polyphenols as seen in a few studies for the absorption of isoflavones. Among the polyphenols, isoflavones are known to be more bioavailable followed by phenolic acids, flavanols, flavanones, flavonols and lowest bioavailability was seen for anthocyanins and proanthocyanidins. Many human and animal studies have shown that dietary polyphenols reduce the cardiovascular diseases by inhibiting LDL oxidation, promoting vasodilation and by antiplatelet properties. However, the relationship between the level of polyphenols in plasma and their in vivo cardioprotective effects are poor. It is clear that more studies with improved methods are needed to understand the involvement of polyphenols in reducing the risks of degenerative diseases. In order to translate the in vitro results to in vivo, bioavailability of dietary polyphenols have to be increased significantly. One way to achieve this would be to study food preparation methods that can increase the bioavailability of these compounds through the use of different additives, cooking methods, enzymes and microorganisms. Microorganisms appear to play an important role in increasing the bioavailability of polyphenols by removing the conjugation and by breaking polyphenols into simpler absorbable phenols. We feel more bacteria and fungi should be used in food preparations such as yeasts for bread and wine making; lactic acid bacteria for fermenting idlies, dosas, curds; and Bacillus strains for soy fermentation products to increase bioavalability of polyphenols. Enzyme treated or microbial digested food may become the future of food industry. This article was written with a view to supplement Dr. R. B. Singh's life long ambition to prevent cardio- vascular diseases through the use of diet and discuss the above points in greater detail.