Low dose, high impact: Daily iron intake improves fatigue and stress among athletes – Taiyo study

Between the placebo and iron intake group, the latter saw a significant reduction in feelings of exhaustion (P = 0.05; F = 4.07) after exercise, and degree of sweat (P ≤ 0.05) for both male and female athletes after two and four weeks of consuming a low dose (3.6 mg/day) of iron.

This was not only reflected in the self-reported assessments of the athletes, but also in their biomarkers. The iron status and salivary cortisol of athletes, which would supposedly drop with physical activity, were also maintained in the current results.

“The biomarkers salivary cortisol, salivary immunoglobulin A, and salivary α-amylase are considered reliable and convenient indicators of the stress response to exercise and change due to the intensity levels of physical exercise and recovery. Salivary cortisol levels can be modulated by the intensity and duration of exercise. ​

“Salivary cortisol levels reported in the present study are within the reported normal range for healthy adults. We observed that even a low dose of iron supplement helps to maintain normal levels of salivary cortisol which indicates the reduction of exercise-associated stress during the training period since the low levels of cortisol are reported to cause weakness, fatigue, and low blood pressure,” ​the researchers explained.

Interestingly, only female athletes experienced significantly lower (P = 0.016; F = 6.26) negative moods between placebo and iron intake groups.

Sponsored by Taiyo Kagaku Co. Ltd., Japan, the researchers come from Otsuma Women’s University and Nippon Sport Science University in Japan, and paper was published in Contemporary Clinical Trials Communications ​journal.

Study​

The researchers conducted a double-blind, randomised, placebo-controlled, parallel-group study in non-anaemic endurance athletes, investigating the influence of iron intake on fatigue, mood states, and sweating profiles during the training exercise periods.

This involved 51 male athletes and 42 female athletes divided into two groups, either receiving iron intake or the placebo. Participants were directed to consume the treatment once a day, either before or after meals for four weeks

The iron intake group was prescribed with a known highly bioavailable iron formulation (SunActive® Fe). A high iron bioavailability implies the extent to which iron is absorbed from the diet for bodily functions.

Male and female athletes were prescribed respective exercise regimens to follow, and had to record their exercise to ensure identical physical energy balance during the training. They were also instructed to maintain their daily lifestyle during the study period, and to keep a food dairy to record their energy input.

Three times during the study period, the researchers took self-reported questionnaires and biochemical assessments such as biomarkers on the participants’ mood, stress, and sweat behaviours.

Explained​

Iron deficiency is commonly experienced by athletes compared to sedentary individuals.

Past literature elicited that iron is responsible for “oxygen transport and energy metabolism among endurance athletes to maintain their exercise capacity​”, and the lack of iron in the body can lead to symptoms such as fatigue, weakness, and lethargy.

“The mechanisms that cause iron loss during exercise are haemolysis due to mechanical forces and oxidative stress, gastrointestinal and urinary tract bleeding due to microscopic lesions, and extreme sweating, which can result in iron deficiency. Sweat excretion from eccrine sweat glands is primarily a mechanism of thermoregulation but is also a way the body loses iron. ​

“For instance, the daily sweat-related iron loss is estimated to be 1–2 mg per 2h of exercise, equivalent to 1% and 3% of recommended daily intake of iron for women and men respectively,​” the researchers explained.

In terms of research implications, the paper emphasised that for athletes to maintain their iron levels, they should look at a diet focusing on increasing total dietary iron, or improve iron bioavailability in commercial formulations. In this instance, the researchers had optimised the Sunactive Fe® product which is known for its enhanced iron absorption.

“The take-home message is that even a low dose daily iron supplementation can help maintain and may be useful to improve the overall wellness of non-anaemic athletes engaged in endurance exercise, as well as individuals with marked sweat losses due to heavy physical work,” ​the researchers concluded.

Source: Contemporary Clinical Trials Communications​

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

https://doi.org/10.1016/j.conctc.2023.101084​

Authors: Kapoor, M.P., et al.​