By To-wen Tsneg. Originally posted on San Diego County Breastfeeding Coalition's Blog.
Leukemia, a cancer of the blood and bone marrow, is the most common childhood malignancy in western countries. It accounts for one third of all cancers occurring in children under the age of 15, and strikes about 3,500 young people under the age of 20 in the United States each year. About three quarters of leukemia diagnoses are Acute Lymphoblastic Leukemia (ALL). The other form of leukemia in children is Acute Myelogenous Leukemia (AML).
The causes of leukemia are not well understood. The biggest risk factors include having Down Syndrome, having a sibling with leukemia, and having a history of radiation treatment for another cancer. It has been hypothesized that leukemia in some people may be the result of exposure to a specific bacterial or viral source. In theory, passive immunity given by breast milk could have a preventive effect. For this reason, a possible association between breastfeeding and a lower risk of diagnosis of childhood leukemia continues to be explored.
One of the earliest study on breastfeeding and risk of childhood acute leukemia was a 1999 study done by the Department of Pediatrics at University of South California School of Medicine. In the study researchers tested the hypothesis that breastfeeding decreases the risk of childhood acute leukemia, and found that breastfeeding was associated with a reduced risk of the disease.
In its 2012 Breastfeeding and the Use of Human Milk policy statement, the American Academy of Pediatrics (AAP) said, “There is a reduction in leukemia that is correlated with the duration of breastfeeding.” Their conclusion was based on several earlier studies showing that infants who were breastfed six months or longer had 20 percent reduction in the risk of ALL, and those who were breastfed less than six months had a 12 percent reduction in risk.
The results of a recent study presented at the International Conference on Frontiers in Cancer Prevention Research sponsored by the American Association for Cancer Research (AACR) lend further support to the AAP premise that infant feeding plays a role in the development of childhood leukemia.
How infant nutrition influences leukemia risk is unclear, but earlier studies suggest a link between infant feeding practices, including breastfeeding, formula-feeding, and introduction of solid foods, and immune system development and levels of insulin-like growth factor.
In an effort further examine “the association between infant feeding practices and age at introduction of solids on risk of ALL,” a team of researchers at the University of Texas Austin recruited 426 children from the Texas Children’s Cancer Center and the National Children’s Study. Participants included 142 children between ages 1 to 7 years who had been diagnosed with ALL and were receiving treatment and 284 healthy children of the same age group. Mothers of the children completed a questionnaire that provided information about their child’s breastfeeding and formula-feeding history, as well as their age at the introduction of solid foods.
It turned out that children who had been diagnosed with ALL had a longer duration of formula-feeding. Further analysis showed that each month of formula-feeding raised the child’s risk of ALL by 16 percent.
Jeremy Schraw, a member of the research team, explained that “if a baby is fed only formula, he or she will not be getting any immune factors from the mother, which could be leading to this greater risk.”