Polyphenols are found in many plants and give some flowers, fruits, and vegetables their color and taste properties.
Polyphenols are the most abundant antioxidants in the diet. Their main dietary sources are fruits and plant-derived beverages such as fruit juices, tea, coffee, and red wine. Vegetables, cereals, chocolate, and dry legumes also contribute to the total polyphenol intake.
Current evidence strongly supports a contribution of polyphenols to the prevention of cardiovascular diseases, cancers, and osteoporosis and suggests a role in the prevention of neurodegenerative diseases and diabetes mellitus.
Epidemiologic studies tend to confirm the protective effects of polyphenol consumption against cardiovascular diseases. Evidence for protective effects of polyphenols against cancers, neurodegenerative diseases, and brain function deterioration is still largely derived from animal experiments and in vitro studies; we await the discovery of predictive biomarkers for such diseases or large intervention studies.
A considerable body of literature supports a role for oxidative stress in the pathogenesis of age-related human diseases and a contribution of dietary polyphenols to their prevention.
The current evidence for protective effects of polyphenols against diseases has generated new expectations for improvements in health, with great interest from the food and nutritional supplement industry regarding promotion and development of polyphenol-rich products.
Wu et al (2) studied the total phenolic content, antioxidant activity and antiproliferative activity of Dragon fruit or red pitaya on melanoma cells and to determine if it is a valuable source of antioxidants and an anticancer agent. Their work indicated that the flesh and peel were both rich in polyphenols and were good sources of antioxidants. The red pitaya peel fulfilled its promise to inhibit the growth of melanoma cells.
1. Scalbert A, Johnson IT, Saltmarsh M. Polyphenols: antioxidants and beyond. Am J Clin Nutr. 2005 Jan;81(1 Suppl):215S-217S.
2. Wu, L.C., Hsu, H.W., Chen, Y.C., Chiu, C.C., Lin, Y.I. and Annie Ho, J.A. 2006. Antioxidant and antiproliferative activities of red pitaya. Food Chemistry 95: 319-327
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3. Photo: Dawn at a Dragon Fruit farm, courtesy of COMEN Resort Farm, Melaka