Researchers say children who are breastfed for at least six months as infants have a lower risk of developing childhood leukemia later than children who were breastfed for less time or not at all.
Children and teenagers who were breastfed for six months were 19 percent less likely to be diagnosed with leukemia, a review of numerous studies indicates. The work was published on June 1 in the journal JAMA Pediatrics.
The most common childhood cancer, leukemia — which affects the production of blood cells in a child's bone marrow — accounts for around 30 percent of all cancers striking children.
"We still don't know what causes childhood leukemia," says Efrat Amitay of the University of Haifa's School of Public Health in Israel, who conducted the review along with colleague Lital Keinan-Boker. "There have been all kinds of hypotheses about it, and one of the things that emerged in the research is breastfeeding."
One such hypothesis on the cancer's cause is that a prenatal genetic mutation leaves children susceptible to leukemia, with exposure to an "infective agent" after birth or later in life triggering the start of the cancer's growth.
Scientists have long theorized breastfeeding may offer protection against such an occurrence by providing antibodies and compounds that can strengthen a child's immune system.
The study review suggests an association but not a direct cause and effect, the researchers acknowledge, saying more research is needed to confirm the breastfeeding link and perhaps uncover the biological processes involved.
"There is so much research supporting the health benefits of breast milk," says Amitay. "It contains antibodies, natural killer cells and all kinds of active, live substances that can't be produced in a factory."
Breastfeeding of infants for at least six months to optimize health, development and growth has long been the recommendation given to mothers by the American Academy of Pediatrics.
For their review, Amitay and Keinan-Boker analyzed 18 existing studies on the relationship between breastfeeding and childhood leukemia, studies that examined more than 10,000 children and teenagers diagnosed with leukemia and compared them with more than 17,000 control cases who weren't disagnosed.
Health care professionals should be informed of the recognized benefits of breastfeeding, the researchers suggest, and provided with the tools to assist new mothers.
As a form of cancer protection, breastfeeding is "highly accessible and low-cost," they note.
"The many potential preventive health benefits of breastfeeding should also be communicated openly to the general public, not only to mothers, so breastfeeding can be more socially accepted and facilitated," the study authors write.