Wisdom Wednesday: Iron Absorption from Oral Iron Supplements

Current guidelines to treat iron deficiency recommend daily provisions of serous iron divided through the day to increase absorption. However, daily dosing and split dosing might increase serum hepcidin and decrease iron absorption from subsequent doses. Our study aim was to compare iron absorption from oral iron supplements given on consecutive versus alternate days and given as single morning doses versus twice-daily split dosing.

Methods – Two prospective, open-label, randomized controlled trials were performed assessing iron absorption using (Fe)-labelled ferrous sulfate in iron-depleted (serum ferritin < 25 ug/L) women aged 18-40 years. In study 1, one group was given 60 mg iron on consecutive days for 14 day, and the other group was given the same doses on alternate days for 28 days. In study 2, the women were stratified by serum ferritin so that two groups with similar iron statuses could be formed. One group was given 120 mg iron and the other was given the dose split into two divided doses of 60 mg. The groups were crossed over to the other regimen after two weeks. The co-primary outcomes in both studies were iron bioavailability and serum hepcidin. Findings – In iron-depleted women, providing iron supplements daily as divided dosses increases serum hepcidin and reduces iron absorption. Providing iron supplements on alternate days and in single doses optimizes iron absorption and might be a preferable dosing regimen. My Take:
I dumbed this study down but left enough data to show just how a good randomized controlled study should be structured.

Despite an excellent format, I have some concerns with the study. First, the dosage was so high that absorption was probably reduced in all groups. I typically use 10 mg of iron taken once daily. Second, ferrous sulfate is a very poorly absorbed form of iron. I much prefer a food source product where the iron is organically bound. Of course, you can’t radioactively label organic iron, so it could never be tracked through the body like (Fe) labelled ferrous sulfate.

When iron in the diet fails to be absorbed, it ends up in the large intestine where it creates severe constipation. I can’t imagine that any of these women pooped during the trials!

Prior to the onset of constipation, the stool generally turns black from the presence of small amounts of iron. Clinically, I use constipation and a dark stool to titrate iron supplementation for maximum absorption.

As a side note, detecting iron is the stool is the basis of the occult blood test used to find GI bleeds. Iron intake is restricted for five days (no red meat, supplementation, etc.) then the fecal smear is performed on days 3, 4, and 5. It’s an inexpensive way to test the bowel in the presence of anemia of unknown cause.

The Bottom Line:
If you suffer from iron deficiency anemia (microcytic anemia) start with very low doses of iron and use a food source in lieu of ferrous sulfate. Based on this study, I will try supplementing alternate days to see if it improves the results of low dose iron supplementation.

Source: October 9, 2017 The Lancet