Diet for Female Marathon Runners

Female athletes may be at risk of sports amenorrhoea and osteopenia.

Sports amenorrhoea is described as menstrual dysfunction occurring among female athletes. Menstrual dysfunction includes a delay in menarche (first menstrual occurrence), no menstrual cycle for three months or greater, or a menstrual cycle that occurs only at intervals of three months or more.

When a women has sports amenorrhoea, she will have reduced levels of oestrogen and progesterone. Many factors may contribute to sports amenorrhoea, including the type of sport, training programme, body weight and composition, and dietary factors.

Dietary factors include low energy, fat and calcium intake, a vegetarian diet (especially avoidance of red meat), and excessive intake of fibre.

Amenorrhoea could also be caused by medical conditions and other causes, and should always be investigated. Sports amenorrhoea is a concern because it means women are at greater risk of bone loss and sports osteopenia.

Sports osteopenia means reduced bone mass, and can be the cause of stress fractures and premature osteoporosis in sportswomen. There may be several causes of sports osteopenia, the most important being reduced oestrogen and progesterone levels and dietary factors. Other factors include race, slender build, cigarette smoking and family history.

Bones are always changing, constantly losing and gaining calcium due to a combination of factors. There are two types of bone: cortical bone, which forms the dense outer portion of the bone (that is, the shaft of long bones like arms and legs); and trabecular bone, which is the lattice-like bone found in the vertebrae, pelvis, flat bones and ends of long bones. Trabecular bone changes the most.

When oestrogen and progesterone levels are reduced in amenorrhoeic athletes, more bone is lost and less replaced, leading to lower bone mass, weakness in the trabecular bone and increased risk of cracks and breaks in the bone. Dietary factors that contribute to osteopenia include a low-calcium intake – if you do not eat enough foods containing calcium, there is not enough calcium to add to the bones to achieve and maintain optimal bone mass. Peak bone mass is usually achieved when people are in their twenties.

High intake of salt, protein, phosphorus, caffeine, alcohol, and possibly soft drinks, may reduce calcium balance.

Menstrual irregularities can lead to sports osteopenia, fractures and premature osteoporosis. So, if menstruation has stopped or become irregular, you should talk to your doctor and dietician and work with them to ensure your return to peak health.
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