Influence of iron supplementation on fatigue, mood states and sweating profiles of healthy non-anemic athletes during a training exercise: A double-blind, randomized, placebo-controlled, parallel-group study

Iron is specifically important to athletes, and attention has grown to the association between sports performance and iron regulation in the daily diets of athletes. The study presents new insights into stress, mood states, fatigue, and sweating behavior among the non-anemic athletes with sweating exercise habits who consumed a routine low dose (3.6 mg/day) of iron supplementation. In this double-blind, randomized, placebo-controlled, parallel-group study, both non-anemic male (N = 51) and female (N = 42) athletes were supplemented either with a known highly bioavailable iron formulation (SunActive® Fe) or placebo during the follow-up training exercise period over four weeks at their respective designated clinical sites. The effect of oral iron consumption was examined on fatigue, stress profiles, as well as the quality of life using the profile of mood state (POMS) test or a visual analog scale (VAS) questionnaire, followed by an exercise and well-being related fatigue-sweat. Also, their monotonic association with stress biomarkers (salivary α-amylase, salivary cortisol, and salivary immunoglobulin A) were determined using spearman's rank correlation coefficient test. Repeated measure multivariate analysis of variance (group by time) revealed that the total mood disturbance (TMD) score was significantly lower (P = 0.016; F = 6.26) between placebo and iron supplementation groups over the four weeks study period among female athletes. Also, a significant reduction in tired feeling/exhaustion after the exercise (P = 0.05; F = 4.07) between the placebo and iron intake groups was noticed. A significant within-group reduction (P ≤ 0.05) was noticed in the degree of sweat among both male and female athletes after 2 and 4 weeks of iron supplementation, while athletes of the placebo intake group experienced a non-significant within-group reduction in the degree of sweat. Overall, the result indicates routine use of low dose (3.6 mg/day) iron supplementation is beneficial for non-anemic endurance athletes to improve stress, mood states, subjective fatigue, and sweating conditions.