Bioavailability of Green Tea and Coffee Polyphenols

Summary

There is little information on the dietary intake, absorption, metabolism and bioavailability (degree to which a substance becomes available to the target tissues upon administration) of polyphenols (natural substances present in a variety of foods) in human participants.

This study assessed the bioavailability in healthy participants of polyphenols from 2 supplements containing green tea and green coffee extracts.

Eleven participants were recruited and their habitual diet was assessed to estimate polyphenol intake. After completing a 24-hour urine collection, participants were given six green tea extract and three green coffee extract tablets, which they took daily for a period of 8 weeks. No tablets were taken during the last 4 weeks of the study. Further 24-hour urines were collected at 2, 4, 8 and 12 weeks.

Participants were required to attend HNR (medical laboratory) the day after each 24hour urine collection. At these visits, they were asked to bring along their urine collections, completed documents (urine collection sheet, checklist for tablet intake/side effects) and any remaining supplements, which were used to assess tablet compliance.

The investigators identified and quantified the amount of polyphenols in the supplement tablets as well as the amount of polyphenols and their metabolites in urine. The investigators then evaluated polyphenol bioavailability from the relationship between their dietary intake and urinary output.

Evidence from this research could inform future intervention studies by providing data on the bioavailability of green tea and coffee polyphenols, and on the individual differences related to phenolic intake.

Conditions

• Diet, Food, and Nutrition
• Dietary Supplements

Interventions

DIETARY_SUPPLEMENT

Green tea and green coffee extract tablets

1. Tablets: participants were required to take 6 green tea and 3 green coffee extract tablets daily for a period of 8 weeks. No tablets were taken during the last 4 weeks of the study. Randomly chosen tablets were analysed to quantify their polyphenol content. 2. Urine collections: Several urine collections were required during the supplementation period in order have sufficient time points to estimate the plateau of the concentration of green tea and coffee polyphenols excreted in the urine to then be able to determine their bioavailability. There was a total of five 24-hour urine collections (at week 0 -before supplementation-, 2, 4, 8, and 12 -4 weeks after finishing the supplementation period). 3. Completion of study documents: Participants were provided with urine collection sheets, polyphenol questionnaires, checklists to record polyphenol tablet intake, and detailed instructions.

Sponsors & Collaborators

• MRC Human Nutrition Research

  lead OTHER_GOV

Principal Investigators

• Virginia Tomatis, PhD · MRC HNR

Study Design

Allocation

NA

Purpose

BASIC_SCIENCE

Masking

NONE

Model

SINGLE_GROUP

Eligibility

Min Age

18 Years

Max Age

45 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2013-04-10

Primary Completion

2013-10-18

Completion

2013-10-18

Countries

• United Kingdom

Study Locations