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Digestive Health Summit – March 2005: Abstracts
Polyphenols in Fruits and Vegetables: The Impact on Digestive Health
Andrew L. Waterhouse, PhD
University of California, Davis
Polyphenols are well known food constituents, occurring at high levels in fruits, some vegetables, chocolate, tea and coffee. These substances are similar in some respects, but very diverse in other respects, there being over 5000 individual substances reported in the literature. All polyphenols have an antioxidant effect, though the magnitude of the effect can vary quite a bit. Recent studies have focused on more specific effects of polyphenols, specific effects on enzyme systems, receptor sites and cell signaling. While polyphenols appear to be poorly absorbed, their concentration in gut can be conversely very high. One study a few years ago showed that red wine polyphenols greatly inhibited the oxidative damage to rat colon DNA. This result was thought to suggest that dietary polyphenols would have a protective and therapeutic effect in diseases with oxidative pathologies. Subsequent studies have shown that hydroxycinnamates specifically reduce the formation of oxidized DNA as well as affect the expression of glutathione-related enzymes, and a similar study showed a protective effect by reducing chemically induced intestinal inflammation. And finally, hydroxycinnates as well as other polyphenolic extracts reduce the induction of colon cancer in animal studies. In conclusion, it is clear that polyphenolic substances can mitigate much of the intestinal oxidative damage caused by environmental insults, and as others have concluded, provide a protective effect on the chronic diseases caused by oxidation.
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