Donating blood is one of the most important and life-saving things everyday people can do. Yet, while it’s often seen as purely altruistic, new research suggests that frequent donors may be gaining something in return: a potential boost to their blood cell health and a reduced risk of blood cancer.

The new study shows how the bodily stress of frequent donations can subtly reshape the genetic makeup of our blood cells.

Blood and Clones

Our blood is home to billions of cells that are constantly replenished by a small army of hematopoietic stem cells (HSCs). These stem cells are the body’s blood factories, churning out red blood cells, white blood cells, and platelets. But as we age, these stem cells can accumulate mutations during cellular division.

Sometimes, a single mutated stem cell gains a competitive edge, outgrowing its peers and dominating the blood system. This phenomenon, known as clonal hematopoiesis (CH), is a natural part of aging. Most of the time, these clones are harmless. But in some cases, they can pave the way for blood cancers or other diseases.

In their new study, the researchers at Francis Crick Institute in London set out to explore whether frequent blood donation — a form of repeated, significant blood loss — could influence this process. 

Researchers analyzed blood samples from 429 men in Germany collected with the help of the German Red Cross, who were divided into two groups. One group had donated blood more than 100 times over their lifetimes, while the other had donated fewer than 10 times. The researchers discovered that frequent donors were more likely to carry specific mutations in two genes called DNMT3A and TET2. These mutations were largely low-risk, meaning they were unlikely to lead to cancer or other serious health problems. In fact, quite the opposite — the mutations appear to give their blood cells a competitive edge.

Advantages of Altruism

One of the most intriguing findings of the study was the role of erythropoietin (EPO), a hormone that stimulates red blood cell production. After a blood donation, EPO levels rise to help the body replenish its lost blood. The researchers discovered that certain mutations in the DNMT3A gene, found more often in frequent donors, made cells more responsive to EPO. This suggests that the repeated cycles of blood loss and recovery may give these mutations a fitness advantage, allowing them to thrive in the EPO-rich environment created by frequent donations.

“It suggests that, every blood donation, you’re going to have a burst of EPO in your system, and this is going to favor the growth of cells with these DNMT3A mutations,” co-author Hector Huerga Encabo explained for New Scientist.

To test their findings, the team genetically engineered human blood stem cells — the precursors to all blood cells — with the DNMT3A mutations and observed their behavior in lab dishes. When exposed to EPO, the mutated cells grew 50% faster than their unmodified counterparts. Without EPO, both types grew at the same rate.

The researchers then mixed these cells with others carrying mutations linked to leukemia. In the presence of EPO, the DNMT3A-mutated cells outcompeted the leukemia-prone cells, producing healthier red blood cells. This suggests that the mutations might suppress the growth of cancerous cells, offering a potential protective effect.

“It’s like the donation of blood is providing a selection pressure to enhance the fitness of your stem cells and their ability to replenish,” said Ash Toye, a researcher at the University of Bristol who was not involved in the study. “Not only could you save someone’s life, but maybe you are enhancing the fitness of your blood system.”

What This Means for Donors

For the millions of people who donate blood regularly across the world, this study offers both insight and reassurance. Frequent donations do leave a mark on the genetic makeup of blood cells, but the changes are unlikely to pose a health risk. In fact, the act of donating blood frequently could actually protect the donor from cancer.

For donors like the 57-year-old man described in the study, who had given blood 116 times over 35 years, this kind of monitoring can provide peace of mind.

Could other forms of stress, like intense exercise or chronic illness, have similar effects on our blood cells? And what about platelet donors, who undergo a different kind of blood donation that stimulates the production of platelets rather than red blood cells? These are questions that future research will need to explore.

For now, the message is clear: blood donation is safe, and the benefits far outweigh any potential risks.

The findings appeared in the journal Blood.