Regular aerobic exercise reduces efficacy of iron supplementation
Aerobic training on a regular basis lessens the apparent effectiveness of iron supplementation in improving serum ferritin (sFer), leaving doubts on whether conventional measures of iron status accurately reflect iron metabolism in physically active, nonanaemic women, suggests a study.
Individuals in both the iron-supplemented trained and untrained groups, compared with either of the placebo groups, had significantly improved sFer, soluble transferrin receptor (sTfR) and body iron values following treatment. Trained participants also had significantly greater aerobic fitness measures than untrained participants.
The sFer response to supplementation changed with training (p=0.07), with the iron-supplemented trained group showing significantly lower sFer than the iron-supplemented untrained group at week 8 (mean, 31.8 and 47.6 μg/L, respectively; p=0.042). However, no significant difference was observed between the placebo trained and untrained groups (mean, 21.3 and 20.3 μg/L, respectively; p=1.00).
The authors enrolled 72 iron-depleted, nonanaemic Chinese women (sFer <25 μg/L and haemoglobin >110 g/L) in an 8-week, partially blinded, randomized controlled trial with a 2x2 factorial design including iron supplements (42 mg elemental Fe/day) or placebo and aerobic training (five 25-min sessions/week at 75‒85 percent of maximum heart rate) or no training.
They examined the association between supplement type, training and changes in iron over time (measured by sFer, haemoglobin, sTfR and estimated total body iron) using linear mixed models.
“Despite its known detrimental effects, iron deficiency remains the most common micronutrient deficiency in the world. Many interventions that aim to improve iron status involve physically active populations. Intense aerobic exercise training negatively affects iron status,” the authors said.