Donating blood is an act of generosity that saves lives, yet few donors think about how it affects their own health. Each donation triggers a surge in blood cell production, a process that could subtly shape the long-term health of blood-forming stem cells. A recent study found that frequent blood donation promotes the expansion of specific blood stem cell mutations that support healthy red blood cell production.

Researchers analyzed blood samples from 217 older men who had donated more than 100 times and compared them to 212 men who had donated fewer than 10 times. They looked for clonal hematopoiesis, a condition where blood stem cells acquire genetic changes that allow specific cell populations to expand. They also used gene-editing techniques to study how particular mutations behaved when exposed to erythropoietin, a hormone that increases after blood loss.

They found that the overall rate of clonal hematopoiesis was similar between frequent and infrequent donors. However, mutations in the DNMT3A gene showed distinct patterns in frequent donors. Some of these mutations responded to erythropoietin by expanding, while others, known to be associated with leukemia, were more likely to grow in response to interferon-gamma, a protein involved in the immune response. Further analysis revealed that the erythropoietin-responsive mutations tended to push blood stem cells toward making more red blood cells rather than leading to abnormal or harmful changes.

These findings suggest that repeated blood donation encourages the expansion of specific blood stem cell mutations, but the effects support normal blood cell production rather than increase disease risk. Blood donation also lowers levels of iron—a key nutrient that, in excess, harms the brain. Learn more in this episode featuring Dr. Gordon Lithgow.