The Effectiveness of Transdermal Iron Patches in Athletes With Suboptimal Iron Status (Part 1)

Methodological Considerations for Investigating Iron Status and Regulation in Exercise and Sport Science Studies

Iron deficiency is a common health issue in active and athlete populations. Accordingly, research into iron status, regulation, absorption, and iron deficiency treatment strategies is increasing at a rapid rate. However, despite the increase in the quantity of research, various methodological issues need to be addressed as we progress our knowledge in this area. The purpose of this review is to highlight specific considerations for conducting iron-related research in active and athlete populations. First, we discuss the methodological importance of assessment and interpretation of iron status, with reference to blood collection protocols, participant screening procedures, and biomarker selection. Next, we consider numerous variables that should be accounted for in the design of iron-related research studies, such as the iron regulatory hormone hepcidin and its interaction with exercise, in addition to an examination of female physiology and its impact on iron metabolism. Subsequently, we explore dietary iron and nutrient interactions that impact iron regulation and absorption, with recommendations made for optimal methodological control. Consideration is then given to key features of long-term study designs, such as the monitoring of training load, oral iron supplementation, dietary analysis, and general lifestyle factors. Finally, we conclude our recommendations with an exploration of stable iron isotope tracers as a methodology to measure iron absorption. Ultimately, it is our intention that this review can be used as a guide to improve study design, biomarker analysis, and reporting of findings, to maximize the quality of future research outputs in iron-related research focused on active and athlete populations.

Peeking into the future: Transdermal patches for the delivery of micronutrient supplements

Adhesive transdermal delivery devices (patches) are the latest advancement in the delivery of micronutrients. A common challenge in this mode of delivery includes surpassing the physical barrier of the skin, while the use of microneedle (MN) arrays, or pretreatment of the skin with MNs can be used for a more successful outcome. Limited evidence from human non-randomized trials point to a sub-optimal delivery of iron through skin patches, although no MNs were used in those trials. Moreover, the use of patches proved inefficient in reducing the prevalence of micronutrient deficiencies in post-bariatric surgery patients. The delivery of minerals was tested in animals using reservoir-type patches, gel/foam patches, MNs and iontophoresis. Results from these studies indicate a possible interplay between the dietary manipulation of mineral intake and the trandermal delivery through patches, as reduced, or regular dietary intake seems to increase absorption of the delivered mineral. Moreover, intervention duration could be an additional factor affecting absorption. Possible adverse events from animal studies include redness or decolorization of skin. In vitro and ex vivo studies revealed an increase in vitamin K, vitamin D and iron delivery, however a variety of methodological discrepancies are apparent in these studies, including the models used, the length of the MNs, the duration of application, temperature control and total micronutrient load in the patches. Data indicate that pre-treating the skin with MNs might enhance delivery; however, a source of variability in the observed effectiveness might include the different molecular weights of the nutrients used, skin factors, the ideal tip radius and MN wall thickness. Non-human studies indicate a potential benefit in combining MN with iontophoresis. Presently, the transdermal delivery seems promising with regard to nutritional supplementation, however limited evidence exists for its efficacy in humans. Future research should aim to control for both intervention duration, possible deficiency status and for the dietary intake of participants.

Refining Treatment Strategies for Iron Deficient Athletes

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.