Endurance performers are susceptible to iron-deficiency because the absorption of iron cannot balance the losses incurred through training. Therefore, a preventive daily dose of 105 mg of ferrous sulphate is necessary, especially for young women. The symptoms of iron-deficiency often remain undiscovered. The haematological parameters of training iron-deficient and anaemic women improve when a daily 210mg ferrous sulphate dose is applied. In endurance performers the effects of iron-deficiency on the synthesis of neurotransmitters, cognitive function, mitochondrial function and protein metabolism remain topics for future research studies.