Multiple Daily Condensed Tannin Supplementation and Iron Bioavailability: The Tannin Dose Response Trial
Public ClinicalTrials.gov record NCT03030716. Field values are reproduced from the official study page; the official ClinicalTrials.gov record remains the source of truth for eligibility, enrollment, and contact information.
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Official title
Long-term, Multiple Daily Condensed Tannin Supplementation in Increasing Concentrations Does Not Affect Iron Status or Bioavailability: Results From the Tannin-dose Response Trial.
Brief summary
Reproduced verbatim from the official ClinicalTrials.gov record. Not medical advice.
Tannins are known to inhibit iron absorption through formation of insoluble tannin-mineral complexes, and have thus been termed 'antinutritional.' Despite this, there is evidence that adaptation to similar antinutritional factors is possible when consumed over time. Limitations in current studies include short (single meal) duration, and use of incongruent tannin types from the condensed tannins that are commonly consumed. If adaptation to tannins does happen, it may be due to salivary proline-rich proteins, which have been found to be protective of iron status in animal models. The primary objectives of this study are: 1) To determine whether condensed tannins impact iron bioavailability or status when consumed in multi-dose, multiple daily supplements and 2) to test whether salivary protein production may impact iron bioavailability with tannin supplementation. Secondary objectives included assessment of the reliability of astringency as a measure of salivary protein production and iron absorption. The study has been conducted in an iron absorption study of 11 women, aged 18-35 years old, to determine iron bioavailability with supplementation of 0.03, 0.25, and 1.5 g 95% proanthocyanidin rich grape seed extract before and after regular, three times daily supplementation for four weeks. Each participant consumed all three concentrations of supplement over the 26-week study, with a two-week washout between interventions. Direct iron absorption was measured using area under the curve. Iron status was measured by changes in hemoglobin and ferritin, and was adjusted by participant c-reactive protein levels. Salivary samples were collected before and after supplement consumption during meal challenges, and analyzed on HPLC. Astringency testing was conducted at the end of each meal challenge. Iron absorption and status markers were analyzed by ANOVA, and mixed-modeling followed by pairwise comparison by least significant differences. Pearson's correlations were used to correlated salivary proteins and astringency with iron bioavailability. The present study will provide important information regarding the approximate influence of condensed tannin consumption on iron bioavailability and storage over time, at different doses. Data will also help to delineate possible physiological mechanisms underlying tannin adaptation and possible ways to detect individuals who better adapt than others.
Study identification
- NCT ID
- NCT03030716
- Recruitment status
- Completed
- Study type
- Interventional
- Phase
- Not applicable
- Enrollment
- 11 participants
Conditions and interventions
Conditions
Interventions
- 95% condensed proanthocyanidins from grape seed extract Dietary Supplement
Dietary Supplement
Eligibility (public fields only)
- Age range
- 18 Years to 35 Years
- Sex
- Female
- Healthy volunteers
- Accepts healthy volunteers
This page does not interpret eligibility. Detailed inclusion and exclusion criteria are on the official ClinicalTrials.gov record.
Study timeline
- Start date
- Jun 24, 2016
- Primary completion
- Dec 9, 2016
- Completion
- Dec 9, 2016
- Last update posted
- Jan 24, 2017
2016
United States locations
- U.S. sites
- 1
- U.S. states
- 1
- U.S. cities
- 1
| Facility | City | State | ZIP | Site status |
|---|---|---|---|---|
| Physical Activity and Nutrition Research Consortium | Manhattan | Kansas | 66502 | — |
Site contact phone numbers, emails, and investigator names are intentionally not displayed here. Open the official ClinicalTrials.gov record for site contact information.
About this trial record page
- What this page shows
- Public field values for ClinicalTrials.gov record NCT03030716, including study identification, conditions, interventions, eligibility (age, sex, healthy volunteer), timeline, and U.S. site list.
- What this page does not do
- No medical advice, eligibility judgments, treatment recommendations, study quality scoring, or AI-generated medical summaries. No site contact phone numbers, emails, or investigator names.
- Where the data comes from
- Sourced from the official ClinicalTrials.gov public API. The official record is the source of truth.
- Last refresh
- Last update posted Jan 24, 2017 · Synced Sep 6, 2026
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Open the official record
The complete protocol, eligibility criteria, and contact information for NCT03030716 live on ClinicalTrials.gov.