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1.
Refining Treatment Strategies for Iron Deficient Athletes.
McCormick, R, Sim, M, Dawson, B, Peeling, P
Sports medicine (Auckland, N.Z.). 2020;(12):2111-2123
Abstract
Iron deficiency (ID) is a prevailing nutritional concern amongst the athletic population due to the increased iron demands of this group. Athletes' ability to replenish taxed iron stores is challenging due to the low bioavailability of dietary sources, and the interaction between exercise and hepcidin, the primary iron-regulatory hormone. To date, copious research has explored the link between exercise and iron regulation, with a more recent focus on optimising iron treatment applications. Currently, oral iron supplementation is typically the first avenue of iron replacement therapy beyond nutritional intervention, for treatment of ID athletes. However, many athletes encounter associated gastrointestinal side-effects which can deter them from fulfilling a full-term oral iron treatment plan, generally resulting in sub-optimal treatment efficacy. Consequently, various strategies (e.g. dosage, composition, timing) of oral iron supplementation have been investigated with the goal of increasing fractional iron absorption, reducing gastric irritation, and ultimately improving the efficacy of oral iron therapy. This review explores the various treatment strategies pertinent to athletes and concludes a contemporary strategy of oral iron therapy entailing morning supplementation, ideally within the 30 min following morning exercise, and in athletes experiencing gut sensitivity, consumed on alternate days or at lower doses.
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2.
Iron considerations for the athlete: a narrative review.
Sim, M, Garvican-Lewis, LA, Cox, GR, Govus, A, McKay, AKA, Stellingwerff, T, Peeling, P
European journal of applied physiology. 2019;(7):1463-1478
Abstract
Iron plays a significant role in the body, and is specifically important to athletes, since it is a dominant feature in processes such as oxygen transport and energy metabolism. Despite its importance, athlete populations, especially females and endurance athletes, are commonly diagnosed with iron deficiency, suggesting an association between sport performance and iron regulation. Although iron deficiency is most common in female athletes (~ 15-35% athlete cohorts deficient), approximately 5-11% of male athlete cohorts also present with this issue. Furthermore, interest has grown in the mechanisms that influence iron absorption in athletes over the last decade, with the link between iron regulation and exercise becoming a research focus. Specifically, exercise-induced increases in the master iron regulatory hormone, hepcidin, has been highlighted as a contributing factor towards altered iron metabolism in athletes. To date, a plethora of research has been conducted, including investigation into the impact that sex hormones, diet (e.g. macronutrient manipulation), training and environmental stress (e.g. hypoxia due to altitude training) have on an athlete's iron status, with numerous recommendations proposed for consideration. This review summarises the current state of research with respect to the aforementioned factors, drawing conclusions and recommendations for future work.
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3.
The Impact of Morning versus Afternoon Exercise on Iron Absorption in Athletes.
McCormick, R, Moretti, D, McKay, AKA, Laarakkers, CM, Vanswelm, R, Trinder, D, Cox, GR, Zimmerman, MB, Sim, M, Goodman, C, et al
Medicine and science in sports and exercise. 2019;(10):2147-2155
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.
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4.
The effects of carbohydrate ingestion during endurance running on post-exercise inflammation and hepcidin levels.
Sim, M, Dawson, B, Landers, G, Wiegerinck, ET, Swinkels, DW, Townsend, MA, Trinder, D, Peeling, P
European journal of applied physiology. 2012;(5):1889-98
Abstract
The effect of carbohydrate (CHO) consumption during prolonged endurance running on post-exercise inflammation and hepcidin levels was investigated. Eleven well-trained male endurance athletes completed a graded exercise test, followed by two experimental running trials in a randomized order. The two experimental trials consisted of a 90 min run at 75% of the peak oxygen uptake velocity (vVO(2peak)), while consuming a solution with either 6% CHO or a placebo (PLA) equivalent at 3 ml kg(-1) every 20 min. Serum interleukin-6 (IL-6), free hemoglobin (Hb), haptoglobin (Hp), hepcidin and iron parameters were assessed throughout the post-run recovery period. Serum iron and IL-6 were significantly elevated immediately post-run in both CHO and PLA (p ≤ 0.05), with no differences between trials. Serum-free Hb increased and Hp decreased significantly immediately post-run in both conditions (p ≤ 0.05). Serum soluble transferrin receptor levels were significantly below the baseline at 3 and 24 h post-run in both conditions (p ≤ 0.05). Serum hepcidin concentration recorded 3 h post-run in both conditions was significantly elevated (p ≤ 0.05), and had returned to the baseline by 24 h post-run (p ≤ 0.05). The use of a 6% CHO solution at 3 ml kg(-1) 20 min(-1) during endurance running did not attenuate the inflammatory response and subsequent increase in serum hepcidin levels during the post-run recovery period.