Influence of green and black tea on folic acid pharmacokinetics in healthy volunteers: potential risk of diminished folic acid bioavailability

Abstract

Previous in vitro studies using Caco-2 cell monolayers suggested a possible interaction between green and black tea and folic acid at the level of intestinal absorption. The main purpose of the present study was to investigate a possible pharmacokinetic interaction between tea and folic acid in healthy volunteers. In an open-labeled randomized cross-over study, the pharmacokinetic interaction between tea and folic acid (0.4 mg and 5 mg) was investigated in healthy volunteers. Water was used as the reference drink. Subjects ingested 0.4 mg folic acid tablets with water, green or black tea (0.3 g extract/250 ml) or 5 mg folic acid tablets with water or green tea (0.3 g extract/250 ml). Blood samples were collected over a period of 8 h. Serum folate analysis was carried out by a competitive immunoassay which uses direct chemiluminescent technology. At the 0.4 mg folic acid dose, green and black tea reduced the mean C(max) of serum folate by 39.2% and 38.6%, and the mean AUC(0 --> infinity) by 26.6% and 17.9%, respectively. At the 5 mg folic acid dose, the mean C(max) of serum folate was reduced by 27.4% and the mean AUC(0 --> infinity) was decreased significantly by 39.9% by the co-application of green tea. The present results suggest an in vivo interaction between tea and folic acid with even low concentrations of green and black tea extracts yielding decreased bioavailabilities of folic acid.

Zein nanoparticles for oral folic acid delivery

“…The highest serum concentration of folic acid occurred 1 h after the administration, and values returned to baseline after 24 h. These results are in line with previous data reported in the literature by other research groups [39,40]. On the other hand, zein nanoparticles provided higher folic acid levels than the aqueous solution.…”

Which Sources of Flavonoids: Complex Diets or Dietary Supplements?

“…In our studies in rats, green tea extract significantly decreased serum 5-methyl-tetrahydrofolate concentrations (47). In agreement with the cell culture studies, a study in humans suggests a potential risk of diminished folic acid bioavailability by both green and black tea extracts (49). However, in our human pilot study, no differences in plasma folate concentrations in response to dietary GTC supplementation were observed (47).…”

Interactions between Herbs and Conventional Drugs: Overview of the Clinical Data

“…Possibly due to its vitamin K content, green tea might reduce the anticoagulant effect of warfarin [109]. Furthermore, green tea has been shown to reduce acid folic and the plasma level of statins through a mechanism that remains to be clarified [110,111]. Lastly, green tea has minor effects on human CYP3A4 [112,113].…”