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Health promotion by flavonoids, tocopherols, tocotrienols, and other phenols: direct or indirect effects? Antioxidant or not?
Am J Clin Nutr 2005; 81(1 Suppl):268S-276SAJ

Abstract

Foods and beverages rich in phenolic compounds, especially flavonoids, have often been associated with decreased risk of developing several diseases. However, it remains unclear whether this protective effect is attributable to the phenols or to other agents in the diet. Alleged health-promoting effects of flavonoids are usually attributed to their powerful antioxidant activities, but evidence for in vivo antioxidant effects of flavonoids is confusing and equivocal. This may be because maximal plasma concentrations, even after extensive flavonoid intake, may be low (insufficient to exert significant systemic antioxidant effects) and because flavonoid metabolites tend to have decreased antioxidant activity. Reports of substantial increases in plasma total antioxidant activity after flavonoid intake must be interpreted with caution; findings may be attributable to changes in urate concentrations. However, phenols might exert direct effects within the gastrointestinal tract, because of the high concentrations present. These effects could include binding of prooxidant iron, scavenging of reactive nitrogen, chlorine, and oxygen species, and perhaps inhibition of cyclooxygenases and lipoxygenases. Our measurements of flavonoids and other phenols in human fecal water are consistent with this concept. We argue that tocopherols and tocotrienols may also exert direct beneficial effects in the gastrointestinal tract and that their return to the gastrointestinal tract by the liver through the bile may be physiologically advantageous.

Authors+Show Affiliations

Department of Biochemistry, Faculty of Medicine, Singapore. bchbh@nus.edu.sgNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Review

Language

eng

PubMed ID

15640490

Citation

Halliwell, Barry, et al. "Health Promotion By Flavonoids, Tocopherols, Tocotrienols, and Other Phenols: Direct or Indirect Effects? Antioxidant or Not?" The American Journal of Clinical Nutrition, vol. 81, no. 1 Suppl, 2005, 268S-276S.
Halliwell B, Rafter J, Jenner A. Health promotion by flavonoids, tocopherols, tocotrienols, and other phenols: direct or indirect effects? Antioxidant or not? Am J Clin Nutr. 2005;81(1 Suppl):268S-276S.
Halliwell, B., Rafter, J., & Jenner, A. (2005). Health promotion by flavonoids, tocopherols, tocotrienols, and other phenols: direct or indirect effects? Antioxidant or not? The American Journal of Clinical Nutrition, 81(1 Suppl), 268S-276S. doi:10.1093/ajcn/81.1.268S.
Halliwell B, Rafter J, Jenner A. Health Promotion By Flavonoids, Tocopherols, Tocotrienols, and Other Phenols: Direct or Indirect Effects? Antioxidant or Not. Am J Clin Nutr. 2005;81(1 Suppl):268S-276S. PubMed PMID: 15640490.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Health promotion by flavonoids, tocopherols, tocotrienols, and other phenols: direct or indirect effects? Antioxidant or not? AU - Halliwell,Barry, AU - Rafter,Joseph, AU - Jenner,Andrew, PY - 2005/1/11/pubmed PY - 2005/2/19/medline PY - 2005/1/11/entrez SP - 268S EP - 276S JF - The American journal of clinical nutrition JO - Am. J. Clin. Nutr. VL - 81 IS - 1 Suppl N2 - Foods and beverages rich in phenolic compounds, especially flavonoids, have often been associated with decreased risk of developing several diseases. However, it remains unclear whether this protective effect is attributable to the phenols or to other agents in the diet. Alleged health-promoting effects of flavonoids are usually attributed to their powerful antioxidant activities, but evidence for in vivo antioxidant effects of flavonoids is confusing and equivocal. This may be because maximal plasma concentrations, even after extensive flavonoid intake, may be low (insufficient to exert significant systemic antioxidant effects) and because flavonoid metabolites tend to have decreased antioxidant activity. Reports of substantial increases in plasma total antioxidant activity after flavonoid intake must be interpreted with caution; findings may be attributable to changes in urate concentrations. However, phenols might exert direct effects within the gastrointestinal tract, because of the high concentrations present. These effects could include binding of prooxidant iron, scavenging of reactive nitrogen, chlorine, and oxygen species, and perhaps inhibition of cyclooxygenases and lipoxygenases. Our measurements of flavonoids and other phenols in human fecal water are consistent with this concept. We argue that tocopherols and tocotrienols may also exert direct beneficial effects in the gastrointestinal tract and that their return to the gastrointestinal tract by the liver through the bile may be physiologically advantageous. SN - 0002-9165 UR - https://www.unboundmedicine.com/medline/citation/15640490/full_citation L2 - https://academic.oup.com/ajcn/article-lookup/doi/10.1093/ajcn/81.1.268S DB - PRIME DP - Unbound Medicine ER -