Male blood donors seem to have a lower risk of heart attacks than those who do not donate blood, Finnish researchers said Friday.
The report in the British Medical Journal said this could be because donating blood lowers the iron level, which is linked to heart attack risk.
Jukka Salonen and colleagues at the University of Kuopio in Finland checked 2,600 men who were taking part in a heart disease study.
They found that 153 of the participants gave blood in the two years before their first examination. Of them, only one, or fewer than 1%, had a heart attack, compared to 226, or 9.8%, of the non-donors.
Filtering out other possible factors such as medical history and health barely changed the percentages, the researchers said.
"This is the first study to report a reduced risk of coronary events in male blood donors," they wrote.
"The mechanism through which donating blood reduces the risk of coronary events could be the depletion of body iron stores," they added. Some studies indicate that blood loss through menstruation could be one reason why women have fewer heart attacks than men.
High iron levels also seem to affect the process during which fats oxidize and harden on the walls of arteries, which can lead to heart attacks and heart disease.
"However, voluntary blood donors seem to be generally more health-conscious and more healthy than those who do not donate blood," the researchers added, saying this could affect those who took part in the study.