Green Tea Is a Poor Contributor to Tissue Folate in a Folate Depletion-Repletion Rat Model

Kaori Endoh,Keizo Umegaki,Michael Fenech

doi:10.4236/fns.2013.42019

Abstract

Green tea contains folate and epigallocatechin gallate (EGCg), which is suggested to be an antifolate. In this study, we examined whether green tea was a good source of folate in a folate depletion/repletion rat model. Rats fed a folate deficient diet for 4 weeks were supplied with folate for 7 days, and then folate repletion effects were evaluated in terms of increase in total folate level in plasma, liver, and bone marrow and decrease in plasma homocysteine level. In this model, the folic acid treatment effect was observed to be dose-dependent and an appropriate dose of folic acid was 40 μg/kg/day or greater. Based on this finding, green tea as well as spinach, chicken liver, and folic acid as a reference were applied to this model. Increase in tissue folate level in response to the food samples varied among tissues, with bone marrow showing the smallest response. Increase in tissue folate level was in the order of spinach > chicken liver > green tea, which produced only a slight increase in tissue folate level and further diminished bone marrow folate level. EGCg administered by intragastric gavage at an approximate dose of 8 mg/kg did not attenuate the increase in tissue folate level when repletion was performed with folic acid. These results suggested that green tea is a poor source of food folate, but EGCg in green tea at a low dose has little effect on folic acid absorption.

Highlights

Folate has a role in the transfer and utilization of onecarbon groups and is involved in the de novo synthesis of nucleic acid bases and amino acids
We showed that natural folate from green tea was less bioavailable than folate from other sources in a folate depletion/repletion rat model
Food folate bioavailability estimated based on the increase in plasma and liver folate concentration would be only 17% 21% for green tea folate, 27% - 42% for chicken liver folate, and 57% - 88% for spinach folate, when compared to folic acid as a reference

Summary

Introduction

Folate has a role in the transfer and utilization of onecarbon groups and is involved in the de novo synthesis of nucleic acid bases and amino acids. Low folate status leads to an increase in plasma homocysteine level, which is a risk factor for atherosclerosis, and impairs DNA synthesis and repair, resulting in increased DNA damage and cancer initiation [3,4]. Folate naturally occurring in food (“natural folate”) mainly occurs in the polyglutamated form, but is converted to the monoglutamate form before absorption by deconjugation in the intestine. Synthetic folic acid (pteroylmonoglutamic acid), which is used for dietary supplementation and in fortified food, is the most oxidized and stable form, and is highly bioavailable. The bioavailability of folic acid is estimated to be, on average, about 2 times that of natural folate, but this varies de-

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