TFRC and nutritional disorder: The following cut‐off points were applied: iron deficiency [ferritin < 12 μg/L or soluble transferrin receptor (sTfR) > 8.3 mg/L], vitamin A deficiency (retinol‐binding protein < 0.69 μmol/L) and zinc deficiency (serum zinc < 65 μg/dl for morning sample and <57 μg/dl for afternoon sample).