Blood donation lowering risk of cancer and stroke.

Blood donation helps lower risk of heart attack and stroke due to reduced blood viscosity via iron removal.

The iron removal reduces damage caused from oxidative stress which helps lower your risk of cancer.

Original published study on the American Journal of Epidemiology here.
Reference: 1998;148:445-51., Vol. 148, No. 5

Original published study on the Journal of the National Cancer Institute here.
Reference: JNCI J Natl Cancer Inst (2008) 100 (14): 996-1002. doi: 10.1093/jnci/djn209 First published online July 8, 2008