Green Tea Extracts Lower Serum Folates in Rats at Very High Dietary Concentrations Only and Do Not Affect Plasma Folates in a Human Pilot Study

Augustin, K., Frank, J., Augustin, S., Langguth, P., Ohrvik, V., Witthoft, C. M., Rimbach, Gerald and Wolffram, S. (2009) Green Tea Extracts Lower Serum Folates in Rats at Very High Dietary Concentrations Only and Do Not Affect Plasma Folates in a Human Pilot Study Journal of Physiology and Pharmacology, 60 (3). pp. 103-108.

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Abstract

Green tea catechins (GTC) have been shown to inhibit the activities of enzymes involved in folate uptake. Hence, regular green tea drinkers may be at risk of impaired folate status. The present experiments aimed at studying the impact of dietary GTC on folate concentrations and metabolism. In a human pilot study (parallel design) healthy men consumed for 3 weeks 6 capsules (similar to 670 mg GTC) per day (2 capsules with each principal meal) containing aqueous extracts of the leaves of Camellia sinensis (n=17) or placebo (n=16). No differences in plasma folate concentrations were observed between treatments. We further fed groups of 10 male rats diets fortified with 0, 0.05, 0.5, 1, or 5 g GTC/kg for 6 weeks. Only at the highest intake, GTC significantly decreased serum 5-methyl-tetrahydrofolate concentrations in rats, while mRNA concentrations of reduced folate carrier, proton-coupled folate transporter/heme carrier protein 1, and dihydrofolate reductase (DHFR) remained unchanged in intestinal mucosa. Using an in vitro enzyme activity assay, we observed a time- and dose-dependent inhibition of DHFR activity by epigallocatechin gallate and a green tea extract. Our data suggest that regular green tea consumption is unlikely to impair folate status in healthy males, despite the DHFR inhibitory activity of GTC.

Document Type: Article
Keywords: folatescatechins bioavailability human rat folic-acid dihydrofolate-reductase intestinal-absorption antifolate activity caco-2 cells catechins inhibition homocysteine vitamins carrier
Research affiliation: Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
ISSN: 0867-5910
Projects: Future Ocean
Date Deposited: 11 Feb 2011 12:14
Last Modified: 05 Oct 2017 09:37
URI: http://eprints.uni-kiel.de/id/eprint/9275

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