A new study suggests it may be difficult for the body to absorb iron in the necessary or desired quantities when iron supplements are administered in 24-hour intervals.
Investigators believe this is due to hepcidin. They found that giving subjects iron supplements at doses of 60 mg or higher increased hepcidin levels for up to 24 hours and was associated with lower iron absorption on the following day.
The team postulated that administering low-dose iron on alternate days may overcome this problem, but they said more research is needed to confirm this.
The investigators reported their findings in Blood.
Diego Moretti, PhD, of the Swiss Federal Institute of Technology Zürich, and his colleagues conducted this study in 54 young women.
The women had depleted iron reserves but were not yet anemic (plasma ferritin ≤20 mcg/L). They received a daily dose of at least 40 mg of iron, as is commonly prescribed in cases of iron deficiency.
Afterward, the investigators measured how the hepcidin concentration developed and quantified its effect on the absorption of subsequent doses of iron.
To analyze iron reabsorption, the team used stable iron isotopes as indicator substances. These substances have a modified ratio of stable iron isotopes. Iron-56 is the most frequent naturally occurring stable iron isotope (91.7%), followed by iron-54 (5.8%), and iron-57 (2.1%). Iron-58 occurs only in trace amounts.
The investigators used tablets with increased quantities of iron-57, iron-54, and iron-58. And they were able to measure endogenous iron absorption by observing isotope ratio changes within the body.
The team found that hepcidin reached its peak concentration after 6 to 8 hours, but even 24 hours after the first dose of iron, it was still present in high enough quantities to markedly reduce absorption of the second dose.
The body was only partly able to absorb a second dose of iron, which was given either on the same day or 24 hours after the first dose.
“To improve the percentage of iron absorbed, it would likely be more efficient to wait longer between doses,” Dr Moretti said.
However, he noted that more research is needed to confirm this, particularly because this study had 2 limitations. The first is that participants were all healthy young women without anemia, and the second is that iron absorption was observed over 2 days only.
The investigators are now preparing to conduct a follow-up study to analyze hepcidin concentration over the course of an iron supplementation regimen lasting several weeks.
