Bioavailability of plant phenols

Enrichment of processed food with plant material or plant extracts rich in polyphenols has two aspects in relation to human nutrition and human health. Food protected against oxidation has better keeping quality and will stay healthy longer since formation of toxic oxidation products, like cholesterol oxides, is being prevented (Britt et al., 1998). The other aspect is the beneficial effects of the intake of polyphenols on human health. Both of these aspects are, however, related to the availability of the phenolic substances. 

Polyphenols are ubiquitous in all plant organs where they are found as monomers or in polymerised forms (Schofield et al, 2001). In addition to the beneficial effect of poljq)henols, they also bind minerals and precipitate proteins and carbohydrates, in effect reducing the nutritive value of foods. Polyphenols have been classified for nutritional purposes into extractable and non-extractable types (Bravo, 1998). Extractable polyphenols are low-and intermediate-weight phenolics while non-extractable polyphenols have high molecular weight and are insoluble in normal solvents. 

Plants modified to have higher content of polyphenols for use by the food industry or for production of dietary supplements will become available together with polyphenol mixtures produced by cell cultures. However, in order to benefit from such production of optimised mixtures for food use, a 

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