Polyphenols present in tea are known to inhibit the absorption of non heme iron. The inhibiting effect of tea on non-heme iron absorption is attributed to the flavonoids present in tea. It is well known that Ferrous sulfate is not absorbed well in the presence of polyphenols. We would like to evaluate the effect of polyphenols on the newly developed compound, sodium iron chlorophyllin (SIC), which mimics the heme iron structure. Comparisons of fractional absorption of SIC and Ferrous Sulfate in the presence of polyphenols can help identify the performance of the compounds as vehicles for iron delivery in the presence of iron absorption inhibitors.

In a single-blind randomized cross-over study using stable iron isotope technique, iron bioavailability from SIC delivered with an inhibitory matrix can therefore be determined when given along with black tea

New approaches to treat iron deficiency include developing novel iron compounds with possible iron absorption routes that increase iron bioavailability and reduce gastrointestinal side effects.

Sodium iron chlorophyllin (SIC) is a water-soluble semisynthetic chlorophyll derivative where the magnesium in the porphyrin ring has been substituted by iron. Given the porphyrin ring heme-like structure of SIC, it may be an alternative delivery route for iron, suitable also for vegetarians and vegans. Yet, there are few studies investigating the use of SIC for this purpose.

We recently completed the study entitled "Evaluation of iron bioavailability from iron chlorophyllin in young women using the iron stable isotopic method" based on previous in vitro and in vivo studies.. The study showed a 7% fractional iron absorption (FIA) from SIC when compared to the control compound, ferrous sulfate, which had a FIA of 30%, indicating a Relative Bioavailability of SIC of 20%. The study showed an inverse relationship between ferritin status and iron absorption from SIC in the study participants and an increase in the FIA in the presence of ascorbic acid. Both these findings lean towards the possibility that that the iron contributing to the FIA from SIC may be iron that was dissociated from the porphyrin ring of the chlorophyllin and entering the common non heme iron pool. This inverse relationship in ferritin and FIA is well known for ferrous sulfate. However, one cannot confirm the pathway taken up by SIC to deliver iron based on the previous study alone.

Polyphenols present in tea are known to inhibit the absorption of non heme iron.The inhibiting effect of tea on non-heme iron absorption is attributed to the flavonoids present in tea. There are several types of tea flavonoids: monomers (catechin), dimers (theaflavin), and polymers (thearubigin). Black tea contains 10% flavanols, 25% catechins, 20% theaflavins and 45% thearubigins. The mechanism of iron absorption inhibition by tea is by formation of a complex of the flavonoids with iron. It is mainly the galloyl group in these phenolic compounds that specifically binds iron. A cup of black tea, brewed with 2.5 g tea leaves contains about 200 mg tea flavonoids . Heme iron absorption has also been shown to be inhibited by the presence of polyphenols but unclear to what extent. Thus, comparisons of fractional absorption of SIC and Ferrous Sulfate in the presence of polyphenols can help identify the performance of the compounds as vehicles for iron delivery in the presence of iron absorption inhibitors.

In a single-blind randomized cross-over study using stable iron isotope technique, iron bioavailability from SIC delivered with an inhibitory matrix can therefore be determined when given along with black tea.

SIC has been produced at the HNL with a 50% incorporation of iron into the chlorophyll. Our protocol is based on a Unilever patent that is no longer active, with in-house adaptation. The SIC has a neutral taste and will be presented as a dark green liquid, being the solution of SIC in water.

If SIC, as hypothesized, behaves in a similar way to heme, then iron absorption inhibitors, such as the polyphenols, will not have an effect on the absorption of iron from SIC.

Inclusion Criteria:

• female aged between 18-45 y old;
• SF <80 µg/L;
• BMI 18.5-24.9 kg/m2;
• weight <70 kg;
• signed informed consent;
• able to communicate and comprehend English language.

Exclusion Criteria:

• anemia (Hb <12 g/dL);
• Inflammation (CRP > 5 mg/L);
• chronic digestive, renal and/or metabolic disease;
• chronic medications (except for oral contraceptives);
• use of vitamin, mineral and pre- and/or probiotic supplements in the previous 2 weeks before study initiation and during the course of the study;
• blood transfusion, blood donation or significant blood loss over the past 4 months;
• difficulties with blood sampling;
• antibiotic treatment in the 4 weeks before study initiation;
• pregnancy (tested in serum at screening) or intention to become pregnant;
• lactation up to 6 weeks before study initiation;
• earlier participation in a study using stable isotopes or participation in any clinical study within the last 30 days;
• unable to comply with study protocol (e.g. not available on certain study appointment days or difficulties with blood withdrawal);
• inability to understand the information sheet and the informed consent form due to cognitive or language reasons;
• smoking;
• unwilling to use an effective method of contraception.

Only females

There will be no masking as the ferrous sulfate solutions will be colourless compared to the green color solution of SIC