Breast-feeding -- even for a short time -- may lower a baby's later risk of childhood leukemia, a new study suggests.
The researchers found that babies breast-fed for at least six months appear to have a 19 percent lower risk of childhood leukemia compared to children who were never breast-fed or were breast-fed for fewer months.
"Breast-feeding is a highly accessible and low-cost preventive public health measure that has been found in numerous studies to be associated not only with lower risk for childhood leukemia but also with lower risk for Sudden Infant Death Syndrome (SIDS), gastrointestinal infection, ear infection, type 2 diabetes and obesity later in life," said the study's lead author, Efrat Amitay, of the School of Public Health at the University of Haifa in Israel.
"There is, therefore, a distinct public benefit in breast-feeding and it should be encouraged and facilitated widely," Amitay added.
Although breast-feeding has been shown to have a number of benefits for both mother and baby, the new study found only an association between breast-feeding and a possibly lower risk of childhood leukemia. Because of the study design, it could not prove that breast-feeding caused the lower cancer risk.
Approximately 175,000 cases of childhood cancer occur worldwide every year, according to background information in the study, which was published June 1 online in JAMA Pediatrics. Leukemia, a cancer of blood cells, accounts for about 30 percent of all childhood cancers, making it the most common of childhood cancers, the study noted.
To see if there was any connection between breast-feeding and a lower risk of leukemia, the study authors reviewed 18 studies that included more than 10,000 children with leukemia, and more than 17,500 healthy children.
The researchers also performed a separate analysis of 15 studies to see if having been breast-fed led to a benefit over never having been breast-fed. This second analysis didn't include three of the studies from the original group because they didn't have data on infants who had never been breast-fed.
The researchers also noted that the definition of "never breast-fed" varied among the studies. Some considered never having been breast-fed as no breast-feeding at all, while others defined it as having been breast-fed for less than one month.
This analysis found an 11 percent reduced risk of childhood leukemia for the breast-fed babies.
The study authors were not entirely sure how breast-feeding might protect children from leukemia, but they said that breast milk may influence the development of the infant's immune system.
"Breast milk is a total food, intended by nature to exclusively supply all of the infant's nutritional needs for the first few months of life. Breast milk is a live substance, containing antibodies manufactured by the mother and other unique qualities that promote a healthy flora in the intestines of the infant and influence the development of the child's immune system," Amitay said.
Breast milk is especially beneficial because the mother's body makes antibodies tailored to the harmful substances that the mother and baby are exposed to, Amitay added.
"There are multiple health benefits to breast-feeding," said Dr. Jennifer Wu, an obstetrician and gynecologist at Lenox Hill Hospital in New York City. "The newest study, which reviews the collected data from previous studies, shows a reduction in leukemia in children who are breast-fed for at least six months. When doctors are encouraging new moms to try breast-feeding, they may want to add this information to the list of benefits."