Got Milk? How Breast Milk May Cut Risk for Leukemia

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Researchers from the Israel Center for Disease Control and the University of Haifa have discovered that breast-fed babies have a reduced risk for childhood leukemia, the most common form of childhood cancer. The study, published this week in the Journal of the American Medical Association (JAMA) Pediatrics, shows that breast-fed children and teens-who were breast-fed for at least six months-are 19 percent less likely to develop childhood leukemia than their counterparts breast-fed for less than six months.

30 percent of childhood cancers are made up of patients with leukemia. Cancer is the second most common cause of death for children under 15 years of age. Leukemia rates have also been rising in the US-about 0.7 percent per year between 1975 and 2011.

The team posited that leukemia has both genetic and immunological roots. The Greaves hypothesis, which formed the basis for this research, states that children susceptible to leukemia possess a prenatal genetic mutation and are then exposed to an "infective agent" after they are born. This is what triggers the growth of cancer.

Breast milk nourishes the baby's gut microbiome and contains "immunologically active components," both of which help fight infections. Therefore, the researchers believed that if the Greaves hypothesis is correct, breast milk should protect against leukemia.

The team tested the hypothesis by analyzing data from previous reports on leukemia and breast-feeding, which described results with about 10,292 children and teens with leukemia and 17,517 control subjects.

The study authors found that "14 percent to 19 percent of all childhood leukemia cases may be prevented by breastfeeding for 6 months or more."

The data showed that regardless of the parameters of analysis, there was always an inverse relationship between leukemia and breast-feeding. Even when only the nine studies with the best data, the risk was still 14 percent lower, and these protective indications were seen even in children diagnosed before age one. Finally, even among children who breast-fed for one month there was a higher protective factor against leukemia than for children who nursed for a shorter time or not at all.

The team emphasized the importance of breastfeeding: "Because the primary goal of public health is prevention of morbidity, health care professionals should be taught the potential health benefits of breastfeeding and given tools to assist mothers with breastfeeding, whether themselves or with referrals to others who can help. 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. In addition, more high-quality studies are needed to clarify the biological mechanisms underlying this association between breastfeeding and lower childhood leukemia morbidity."