Low levels of iron may contribute to the high incidence of colds and flu in endurance athletes, according to a University of Queensland study.
Human Movement Studies Department researchers have studied the effect of iron supplements on athletes' performance, iron levels and immune function.
Associate Professor Laurel Mackinnon conducted the project in collaboration with Dr Mike Flynn of the University of Toledo, a recipient of a University of Queensland travel grant.
Dr Mackinnon said results showed it was important for female endurance athletes with heavy training schedules to have their iron levels checked and get dietary advice.
"Athletes have a high incidence of minor viral infections such as colds and flu, so we have been trying to find out why that happens," Dr Mackinnon said.
"Data suggest that if they are low in iron they have lower cellular immunity function. They are not immune deficient, but may be more susceptible to colds and flu - something which for most people is a minor thing, but which can have a major impact on an athlete's training and ability to be in top form for major competiton.'
The study, funded by the Australian Sports Commission, involved 22 female endurance athletes, 13 of whom were iron deficient - as determined by low blood ferritin levels - at the start of the project.
"Women athletes are at greater risk than men because they already lose blood every month through menstruation, many are vegetarian so their intake of iron through diet is fairly low, and they also lose iron through sweating," Dr Mackinnon said.
"We knew that iron supplements can raise levels of ferritin - the protein which stores iron in the body - in non-athletes, but no research had been done on iron levels and immune function."
Athletes taking part in the study increased their normal levels of training for two weeks before returning to normal training schedules and taking either iron supplements or a placebo. The double-blind study, in which neither the researchers nor the athletes knew the results of the initial blood tests or who were taking the iron supplements, ran for eight weeks.
At the end of the program, the researchers looked at the levels of natural killer (NK) cells, which are active in the early stages of infection, to see if their levels were initially lower and if supplements altered NK activity.
"We found that women with low ferritin levels to start with also had lower NK activity. However, iron supplements did nothing to alter NK cell numbers or immune function.
'So the supplements increased their iron stores but did not change their immune function," Dr Mackinnon said.
"It is still unclear if there is a relationship between iron levels and NK activity or whether a longer period of improved ferritin level is needed to improve NK cell function.
"It is interesting that at the end of the study we asked the athletes whether they thought they were taking iron supplements or the placebo, and all but one of the women on supplements guessed correctly.
"They said that within a week of starting on the supplements they had more energy, and were less tired at night."
Dr Mackinnon said female endurance athletes needed to have their iron levels checked and get dietary advice if they were feeling tired and run down, had heavy training schedules and didn't eat a lot of meat.
For more information, please contact Associate Professor Mackinnon on (07) 3365 6379.
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