Effect of folic acid on heme iron absorption

Recently, for the first time an intestinal heme transporter (HCP1) was
identified. In a later study, the same transporter was identified to be a
proton-coupled folate transporter (PCFT) with a higher affinity for folates
than for heme iron. Therefore, use of folic acid supplements may inhibit the
absorption of heme iron.

To measure the effect of folic acid supplementation on heme iron absorption in
vivo.

The study is designed as a placebo controlled cross-over experiment.

On two consecutive days, 4 mg of iron will be administered either as 32.4 mg of
57Fe protoporhyrin chloride or 32 mg of 58Fe protoporphyrin chloride with a
spread on a bread roll. In addition, 1 mg of folic acid or placebo will be
administered.

Participants are asked to visit the research site once for screening and four
times after inclusion. At each occasion, 5-20 mL whole blood will be collected
by venapuncture. Venapunctures occasionally lead to painful bruises which
usually disappear within one week. Participants will be asked to fill out a
questionnaire on relevant general and medical issues, and basic anthropometrics
(weight, height) will be taken. During the study, 4 mg of iron labelled with
stable isotopes (57Fe and 58Fe) will be administered orally as hemin at two
consecutive days. Stable isotopes are non-hazardous to humans. The administered
compounds will be subdued to standard toxicity procedures (purity, presence of
heavy metals). All subjects will have a check-up of their iron status. Since
included subjects will be marginally iron deficienct, participants will receive
dietary advice in order to improve their iron status after the study and will
be referred to their general practitioner on a voluntary basis.