The paper, to be published November in the journal Public Health Reports, found that breastfeeding was linked to lower risks of both acute lymphoblastic leukemia (ALL), the most common of the childhood cancers, and acute myeloblastic leukemia (AML).
"Our paper is the first to systematically review the epidemiologic evidence of the link between maternal breastfeeding and the risk of childhood leukemia," said Marilyn Kwan, UC Berkeley post-doctoral researcher in epidemiology at the School of Public Health and lead author of the study. "We conducted this meta-analysis because the studies that had been conducted previously have been inconclusive and contradictory. Our review of the scientific literature shows that the evidence is definitely pointing towards the benefits of breastfeeding when it comes to the risk for two kinds of childhood leukemia, ALL and AML."
The 14 case-control studies, taken from around the world, were published between 1988 and 2003. They included 6,835 cases of ALL and 1,216 cases of AML.
While the causes of childhood leukemia are not completely understood, it is believed that the disease begins with a genetic change that occurs while the fetus is in the womb. This theory is supported by researchers, led by Mel Greaves of London's Institute of Cancer Research, who studied blood samples taken at birth and found the presence of an abnormal fusion of two genes, TEL and AML1.
The cause of the gene fusion is not certain, said Kwan, but it has been shown to interfere with the normal formation and development of blood cells in animals and is found in 25 percent of children with leukemia.
The genetic abnormality does not guarantee that a child will go on to develop leukemia, said the researchers. Studies indicate
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Contact: Sarah Yang
scy@pa.urel.berkeley.edu
510-643-7741
University of California - Berkeley
27-Oct-2004