Health effects of natural phenols and polyphenols
Because of the large structural diversity and extensive metabolism of dietary polyphenols, it is difficult to determine their fate in vivo and assert specific health effects. Although many are speculated to be part of the health-promoting effects of consuming fruits and vegetables, no evidence exists to date that dietary polyphenols actually provide health benefits. To what extent effects would apply to entire organisms, and clinical outcomes in human disease in particular, remains an undefined topic in nutrition science and disease prevention.
Polyphenols have poor bioavailability, indicating that most of what are consumed are extensively metabolized and excreted. Gallic acid and isoflavones may show absorption of about 5%, with amounts of catechins (flavan-3-ols), flavanones, and quercetin glucosides even less. The least well-absorbed phenols are the proanthocyanidins, galloylated tea catechins, and anthocyanins.
A review published in 2012 found insufficient consensus for the hypothesis that the specific intake of food and drink containing flavonoids may play a meaningful role in reducing the risk of cardiovascular disease. The reviewers stated that research to date had been of poor quality and the large and rigorous trials are needed better to study the science, and to investigate possible adverse effects associated with excessive polyphenol intake. Currently, lack of knowledge about safety suggests that polyphenol levels should not exceed that which occurs in a normal diet.
As interpreted by the Linus Pauling Institute and the European Food Safety Authority (EFSA), dietary flavonoids have little or no direct antioxidant food value following digestion. Unlike controlled test tube conditions, the fate of natural phenols in vivo shows they are poorly conserved (less than 5%), with most of what is absorbed existing as chemically-modified metabolites destined for rapid excretion.
||This section needs more medical references for verification or relies too heavily on primary sources. (October 2014)|
Maternal high flavonoid content diet is suspected to increase risk of particularly acute myeloid leukemia in neonates. High intake of flavonoid compounds during pregnancy is suspected to increase risk of neonatal leukemia. Therefore "bioflavonoid" supplements should be not used by pregnant women.
Some polyphenols, particularly from the flavan-3-ol (catechin-type), have both anticarcinogenic-proapoptotic and mutagenic effects. The DNA changes were increased by treatment with flavonoids in cultured blood stem cells. Some natural polyphenols share the properties of some anticancer drugs such as etoposide and doxorubicin while other polyphenols may induce DNA mutations in the MLL gene, which are common findings in neonatal acute leukemia.
- "Flavonoids". Linus Pauling Institute, Micronutrient Information Center, Oregon State University. 2015. Retrieved 8 June 2015.
- EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA)2, 3 European Food Safety Authority (EFSA), Parma, Italy (2010). "Scientific Opinion on the substantiation of health claims related to various food(s)/food constituent(s) and protection of cells from premature aging, antioxidant activity, antioxidant content and antioxidant properties, and protection of DNA, proteins and lipids from oxidative damage pursuant to Article 13(1) of Regulation (EC) No 1924/20061" (PDF). EFSA Journal 8 (2): 1489. doi:10.2903/j.efsa.2010.1489 (inactive 2015-02-01).
- Halliwell B (2007). "Dietary polyphenols: Good, bad, or indifferent for your health?". Cardiovasc Res 73 (2): 341–347. doi:10.1016/j.cardiores.2006.10.004. PMID 17141749.
- Manach, C; Williamson, G; Morand, C; Scalbert, A; Rémésy, C (2005). "Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies". American Journal of Clinical Nutrition 81 (1 Suppl): 230S–242S. PMID 15640486.
- Habauzit, V.; Morand, C. (2011). "Evidence for a protective effect of polyphenols-containing foods on cardiovascular health: An update for clinicians". Therapeutic Advances in Chronic Disease 3 (2): 87–106. doi:10.1177/2040622311430006. PMC 3513903. PMID 23251771.
- Williams, Robert J; Spencer, Jeremy P.E; Rice-Evans, Catherine (2004). "Flavonoids: Antioxidants or signalling molecules?". Free Radical Biology and Medicine 36 (7): 838–49. doi:10.1016/j.freeradbiomed.2004.01.001. PMID 15019969.
- Ross, JA (1998). "Maternal diet and infant leukemia: a role for DNA topoisomerase II inhibitors?". International journal of cancer. Supplement 11 (S11): 26–8. doi:10.1002/(SICI)1097-0215(1998)78:11+<26::AID-IJC8>3.0.CO;2-M. PMID 9876473.
- Ross, J. A. (2000). "Dietary flavonoids and the MLL gene: A pathway to infant leukemia?". Proceedings of the National Academy of Sciences 97 (9): 4411–3. Bibcode:2000PNAS...97.4411R. doi:10.1073/pnas.97.9.4411. PMC 34309. PMID 10781030.
- Spector, L. G.; Xie, Y; Robison, LL; Heerema, NA; Hilden, JM; Lange, B; Felix, CA; Davies, SM; et al. (2005). "Maternal Diet and Infant Leukemia: The DNA Topoisomerase II Inhibitor Hypothesis: A Report from the Children's Oncology Group". Cancer Epidemiology Biomarkers & Prevention 14 (3): 651–5. doi:10.1158/1055-9965.EPI-04-0602. PMID 15767345.
- Strick R, Strissel PL, Borgers S, Smith SL, Rowley JD; Strissel; Borgers; Smith; Rowley (2000). "Dietary bioflavonoids induce cleavage in the MLL gene and may contribute to infant leukemia". Proc Natl Acad Sci U S A 97 (9): 4790–5. Bibcode:2000PNAS...97.4790S. doi:10.1073/pnas.070061297. PMC 18311. PMID 10758153.
- Paolini, M; Sapone, Andrea; Valgimigli, Luca (2003). "Avoidance of bioflavonoid supplements during pregnancy: a pathway to infant leukemia?". Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 527 (1–2): 99–101. doi:10.1016/S0027-5107(03)00057-5. PMID 12787918.
- Thirman MJ, Gill HJ, Burnett RC, Mbangkollo D, McCabe NR, Kobayashi H, et al. (1993). "Rearrangement of the MLL gene in acute lymphoblastic and acute myeloid leukemias with 11q23 chromosomal translocations". N Engl J Med 329 (13): 909–14. doi:10.1056/NEJM199309233291302. PMID 8361504.
- Barjesteh van Waalwijk van Doorn-Khosrovani S, Janssen J, Maas LM, Godschalk RW, Nijhuis JG, van Schooten FJ (2007). "Dietary flavonoids induce MLL translocations in primary human CD34+ cells". Carcinogenesis 28 (8): 1703–9. doi:10.1093/carcin/bgm102. PMID 17468513.
- van der Linden MH et al (2012) Diagnosis and management of neonatal leukaemia. Semin Fetal Neonatal Med 17(4):192-5
- Fraga, Cesar G. (editor) Plant Phenolics and Human Health: Biochemistry, Nutrition and Pharmacology. 2010. Wiley. ISBN 9780470287217