Multiple Daily Condensed Tannin Supplementation and Iron Bioavailability: The Tannin Dose Response Trial
Condition: Iron Deficiency Anemia; Iron-deficiency
MeSH terms: Anemia, Iron-Deficiency; Iron Deficiencies
Study type: Interventional

Summary: 
      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.
    


Intervention name(s): 95% condensed proanthocyanidins from grape seed extract
Intervention type(s): Dietary Supplement
Intervention description(s): 0.03, 0.25, and 1.5 g 95% condensed proanthocyanidins from grape seed extract consumed three times daily for 4 weeks each
Intervention MeSH terms: Proanthocyanidin; Grape Seed Extract; Procyanidin
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Prevention
Keywords: antinutrients; tannins; proanthocyanidins; salivary proline-rich proteins