Reference News, January 16 report: According to a recent report from the US website "Popular Science", as people age, they grow white hair, which may be a signal that the body is reducing the risk of cancer. New research shows that white hair may be an indication that the body effectively protects itself from cancer.
The study found that cancer-inducing factors such as ultraviolet light or certain chemicals activate the body's natural defense pathway, leading to premature graying of hair, but at the same time also reduces the incidence of cancer.
Researchers tracked the stem cells responsible for producing hair pigment. In mouse experiments, they found that these cells have two responses when facing DNA damage: either stop growing and dividing, leading to white hair; or replicate uncontrollably, eventually forming tumors.
The authors of the study said that the results of this research, published in the journal "Nature - Cell Biology" in October 2025, highlight the importance of these protective mechanisms that appear with age, which can defend against DNA damage and disease.
Healthy hair growth depends on a constantly self-renewing population of stem cells within the hair follicles. A small pocket inside the follicle stores melanocyte stem cells, which are precursors to the cells that produce melanin, the pigment that gives hair its color.
Dot Bennett, a cell biologist at City University London's St George's, who did not participate in this study, said: "During each hair cycle, these melanocyte stem cells divide and produce some mature, differentiated cells. They migrate downward to the bottom of the hair follicle and begin to produce pigment to color the hair."
When these cells cannot produce enough pigment to color each strand of hair, the hair turns white.
"This is a form of cellular aging," Bennett explained. "It is a limit on the total number of divisions a cell undergoes, and it seems to be an anti-cancer mechanism that prevents uncontrolled proliferation of random genetic errors that occur due to aging of the organism."
When melanocyte stem cells reach this "stemness checkpoint," they stop dividing, meaning the hair follicle no longer has a source of pigment to color the hair. Normally, as people age, stem cells naturally reach this limit.
Professor Eimi Nishimura from the University of Tokyo's Department of Stem Cell Age-Related Medicine and her colleagues were interested in how the same mechanism works when there is DNA damage. DNA damage is a key trigger for cancer.
In the mouse study, the team used various techniques to expose individual melanocyte stem cells to different harmful environments (including ionizing radiation and carcinogenic compounds), and tracked their development during the hair cycle. Interestingly, they found that the type of damage affects the cell's response.
Ionizing radiation caused the stem cells to differentiate and ultimately activated the biochemical pathways that lead to cellular aging. As a result, the melanocyte stem cell reserves rapidly depleted during the hair cycle, thereby stopping the production of fully developed melanocytes, leading to white hair.
At the same time, by essentially shutting down cell division, this aging pathway prevents mutated DNA from being passed on to new cells, thus reducing the likelihood of these cells forming malignant tumors.
Stem cells exposed to chemical carcinogens seemed to bypass this protective mechanism and switch to a competitive cell pathway.
In the team's mouse study, this alternative chemical sequence prevented cellular aging, allowing the hair follicles to retain their stem cell reserves and ability to produce pigment even after DNA damage. The research team stated in a statement that this means the hair can maintain its original color, but in the long term, uncontrolled replication of damaged DNA leads to tumors and cancer.
The main author of the study, Nishimura, said in a statement: "This redefines the relationship between white hair and melanoma (skin cancer), which are not 'unrelated events,' but rather different outcomes of the stem cell stress response." (Translated by Wenyi)
Original: toutiao.com/article/7595861151213240882/
Statement: This article represents the views of the author(s) only.