Clinical question: Is oral iron supplementation absorption influenced by the timing and/or nutritional elements concurrently consumed in healthy iron-deficient women?
Background: Current guidelines advise consumption of iron supplements in the morning, accompanied by ascorbic acid (AA) to enhance iron uptake, separate from mealtimes. There is, however, scant evidence to support the timing of intake, the influence of alternate dietary options, and how these factors may influence the absorption in otherwise healthy, non-anemic, iron-deficient women. This study measured the impact of timing and dietary intake and its effect on iron absorption levels.
Study design: Randomized, open-label, controlled, crossover trial
Setting: The trial was conducted within the ETH Zurich system, recruiting women from public research universities in Zurich, Switzerland between June 2021 and December 2022.
Synopsis: This study monitored 34 iron-depleted women aged 18 to 45 years, over 43 days. Participants received 100 mg elemental iron in the form of ferrous fumarate, following six distinct nutritional accompaniments:
Morning following overnight fasting:
- water
- 80 mg AA
- 500 mg AA
- coffee
- breakfast
Afternoon following four-hour fasting:
- water
Primary outcomes measured fractional iron and total iron absorption levels. Results showed both doses of AA similarly increased iron absorption by 30%, drinking coffee decreased absorption by 54%, and eating breakfast decreased absorption by 66%.
When taken in the afternoon, absorption was 37% lower than morning absorption. It was also noted that serum hepcidin levels were higher in the afternoon regardless of fasting. Limitations included: an additional three-hour fasting period following doses and breakfast with untested individual components. These results confirm that every-other-morning doses of iron supplementation with AA as an enhancer contribute to higher absorption rates. The additional three-hour fasting period following the consumption of supplements may pose an impractical hindrance to long-term adherence.
Bottom line: Recommendation for practical optimized strategies for iron supplementation timing to every other day in the mornings, in conjunction with AA or orange juice, best taken before a meal, to improve iron status in iron-deficient women.
Citation: von Siebenthal HK, Moretti D, et al. Effect of dietary factors and time of day on iron absorption from oral iron supplements in iron deficient women. Am J Hematol. 2023;98(9):1356-63.
Ms. Oro
Ms. Oro is a nurse practitioner in the department of heart transplant and mechanical circulatory support at Stanford Health Care in Palo Alto, Calif.