Polyphenols: food sources and bioavailability

Abstract

Polyphenols are abundant micronutrients in our diet, and evidence for their role in the prevention of degenerative diseases such as cancer and cardiovascular diseases is emerging. The health effects of polyphenols depend on the amount consumed and on their bioavailability. In this article, the nature and contents of the various polyphenols present in food sources and the influence of agricultural practices and industrial processes are reviewed. Estimates of dietary intakes are given for each class of polyphenols. The bioavailability of polyphenols is also reviewed, with particular focus on intestinal absorption and the influence of chemical structure (eg, glycosylation, esterification, and polymerization), food matrix, and excretion back into the intestinal lumen. Information on the role of microflora in the catabolism of polyphenols and the production of some active metabolites is presented. Mechanisms of intestinal and hepatic conjugation (methylation, glucuronidation, sulfation), plasma transport, and elimination in bile and urine are also described. Pharmacokinetic data for the various polyphenols are compared. Studies on the identification of circulating metabolites, cellular uptake, intracellular metabolism with possible deconjugation, biological properties of the conjugated metabolites, and specific accumulation in some target tissues are discussed. Finally, bioavailability appears to differ greatly between the various polyphenols, and the most abundant polyphenols in our diet are not necessarily those that have the best bioavailability profile. A thorough knowledge of the bioavailability of the hundreds of dietary polyphenols will help us to identify those that are most likely to exert protective health effects.

Associations between dietary flavonoid intakes and bone health in a scottish population

“…The validity study did not use biomarkers because correlations between these and dietary records of flavonoid intakes are not good (r ¼ 0.35) (33) owing to their bioavailability and metabolism in the gut. (34)(35)(36) Limitations of this study include those associated with using an FFQ because FFQs are known to overestimate the true overall frequency of consumption of fruit and vegetables. (37,38) There are issues that affect the flavonoid content of foods, namely, analytical and environmental factors, processing, storage, and species differences, and these cannot be detected using a FFQ because it is a crude measure of diet.…”

Fermentation and germination improve nutritional value of cereals and legumes through activation of endogenous enzymes

“…Soyabeans are rich sources of isoflavones such as genistein, daidzein, and glycitein which are potent antioxidants. Fermentation was reported to reduce isoflavones significantly due to hydrolysis of glucosides into aglycone (Manach, Scalbert, Morand, Remesy, & Jimenez, 2004). …”

Antioxidants and polyunsaturated fatty acids in multiple sclerosis

“…Flavonoids belong to a group of at least 4000 naturally occurring compounds found in fruit, vegetables, grains, tea and wine (Manach et al, 2004). Flavonoids share a common polyphenolic structure consisting of two aromatic rings that are bound together by three carbon atoms that form an oxygenated heterocycle.…”

“…The health effects of polyphenols depend on intake and bioavailability (Manach et al, 2004). By using the data of the Dutch National Food Consumption Survey 1987Survey -1988, the daily human intake of a subset of five anticarcinogenic flavonoids was estimated to be around 23 mg/day (Hertog et al, 1993).…”

“…But data on the bioavailability of flavonoids in the brain and other tissues are very scarce (Manach et al, 2004). Two studies demonstrated the presence of flavonoids in the brain tissue of mice (Abd El Mohsen et al, 2002) and rats (Datla et al, 2001) after oral administration.…”