Frequent blood donation doesn't boost cancer risk

Frequent blood donation is not harmful to your health, a new study confirms.

"No one should worry that giving blood causes cancer," Dr. Gustaf Edgren of the Karolinska Institutet in Stockholm, the study's lead author, told Reuters Health. "If anything, blood donation may actually be good for you."

People who donate blood show lower cancer and mortality rates than their non-donating peers, Edgren and his colleagues note in their report, published in the Journal of the National Cancer Association, but the fact that blood donors tend to be healthier overall could mask any ill effects of frequent donation.

There are also several mechanisms by which frequent blood donation could theoretically affect health, Edgren noted in an interview. For one, drawing blood causes the body to ramp up production of blood cells in the bone marrow. This accelerated cell division, or "mitotic stress," could increase the likelihood of malignancy in blood-forming tissues.

Giving blood has also been shown to result in immune system changes, and some have suggested these immunologic effects could be associated with cancer.

On the positive side, excess iron stores have been tied to heart disease and certain types of cancer, so people who have their blood drawn regularly may be depleting these stores and thus improving their health.

To better understand how repeated blood donations affect health, Edgren and his team looked at data from Swedish and Danish blood banks and transfusion clinics containing records of individuals who donated blood at least once between 1968 and 2002, a total of 1,110,212 people.

The investigators found no relationship between how frequently a person gave blood and their risk of cancer. However, among male donors, the risk of liver, lung, colon, stomach and throat cancer declined as the frequency of donations increased, which suggests that iron depletion may reduce cancer risk.

The researchers also found an increased risk of non-Hodgkin lymphoma among frequent plasma donors, but this was only seen among people who donated plasma before 1986. This finding "must be interpreted cautiously," Edgren and colleagues write. Additional research may produce new insights about the cause of this malignancy.

Even a small excess risk of cancer associated with blood donation would be "a very serious matter," Edgren noted, because so many people donate blood.

However, he added, "we've more or less made very clear that there is no excess risk of cancer associated with frequent blood donation."