Intense exercise lowers blood count

Exercise is good for you, but watch it: A new study found that young men engaging in strenuous physical activity are "an often overlooked" group that's at risk for low blood counts and iron deficiency.

Dr Drorit Merkel from the Chaim Sheba Medical Centre, Tel-Hashomer and colleagues studied 153 males, all 18 years old, who were training to join an elite combat unit in the Israel Defence Force.

In the Journal of Adolescent Health, the investigators report that before the start of training, about 18% of the recruits had low blood count, or anaemia. That rate almost tripled after six months of intensive military training, to just over 50%.

The rate of iron deficiency nearly doubled, from about 15% to 27%. The researchers do not report whether the recruits had any symptoms of anaemia.

’Sports anaemia’ common
The researchers point out that the males in the study had a higher-than-average rate of anaemia to begin with, which could explain some of the results. That's because recruits who intend to compete for membership in elite units often participate in intense pre-recruitment preparatory training.

"Iron deficiency and anaemia," the investigators point out, "are generally uncommon findings in healthy male adolescents. However, athletes who engage in strenuous physical activity are known to be at increased risk for so-called 'sports anaemia.'"

So why the higher risk? Potential reasons include drinking lots of water, which temporarily dilutes the blood and damage to blood cells that can result from high levels of physical activity.

"The prevalence of iron deficiency in new recruits indicates a military public health issue, and the preventive and therapeutic implications of these findings require further evaluation," Merkel and colleagues conclude. – (Reuters Health, September 2009)

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