Title

The impact of morning versus afternoon exercise on iron absorption in athletes

Document Type

Journal Article

Publication Title

Medicine and Science in Sports and Exercise

ISSN

1530-0315

Volume

51

Issue

10

First Page

2147

Last Page

2155

PubMed ID

31058762

Publisher

Lippincott Williams and Wilkins

School

School of Medical and Health Sciences

RAS ID

28570

Funders

Australian Institute of Sport High Performance Sport Research Fund

Federation University Australia Seed Funding Grant

Comments

Originally published as: McCormick, R., Moretti, D., McKay, A. K., Laarakkers, C. M., Vanswelm, R., Trinder, D., ... Peeling, P. (2019). The impact of morning versus afternoon exercise on iron absorption in athletes. Medicine and Science in Sports and Exercise, 51(10), 2147-2155. Original publication available here

Abstract

PURPOSE: This study examined postexercise inflammatory, hepcidin, and iron absorption responses to endurance exercise performed in the morning versus the afternoon.

METHODS: Sixteen endurance-trained runners (10 male, 6 female) with serum ferritin (sFer) < 50 μg·L completed a 90-min running protocol (65% vV˙O2max) in the morning (AM), or the afternoon (PM), in a crossover design. An iron-fortified fluid labeled with stable iron isotopes (Fe or Fe) was administered with a standardized meal 30 min following the exercise and control conditions during each trial, serving as a breakfast and dinner meal. Venous blood samples were collected before, immediately after, and 3 h after the exercise and control conditions to measure sFer, serum interleukin-6 (IL-6), and serum hepcidin-25. A final venous blood sample was collected 14 d after each trial to determine the erythrocyte iron incorporation, which was used to calculate iron absorption. Linear mixed-modeling was used to analyze the data.

RESULTS: Overall, exercise significantly increased the concentrations of IL-6 (4.938 pg·mL; P = 0.006), and hepcidin-25 concentrations significantly increased 3 h after exercise by 0.380 nM (P < 0.001). During the PM trial, hepcidin concentrations exhibited diurnal tendency, increasing 0.55 nM at rest (P = 0.007), before further increasing 0.68 nM (P < 0.001) from prerun to 3 h postrun. Fractional iron absorption was significantly greater at breakfast after the AM run, compared with both the rested condition (0.778%; P = 0.020) and dinner in the AM run trial (0.672%; P = 0.011).

CONCLUSIONS: Although exercise resulted in increased concentrations of IL-6 and hepcidin, iron was best absorbed in the morning after exercise, indicating there may be a transient mechanism during the acute postexercise window to promote iron absorption opposing the homeostatic regulation by serum hepcidin elevations.

DOI

10.1249/MSS.0000000000002026

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