Breastfeeding and Colorectal Cancer

I, like every pediatrician I know, believe that breast milk is the best nutrition for human newborns. Its balance of nutritive elements and its role in preventing of a wide range of illnesses are so great that we are still learning the extent of their magnitude. It just makes sense that a mother’s milk is most well suited for her baby.

I am a bit less unambiguous about breastfeeding. By that I mean the process of providing breast milk to an infant directly from its mother’s breast. Before you yank my AAP membership card, let me make it clear that I think every woman should consider breastfeeding her infant. But we must accept that in a few situations, even with help from caring and enlightened health care providers and family members, breastfeeding doesn’t work as well as we would have hoped. Fortunately, there are alternatives.

William G. Wilkoff, MD

My reservations about the process are few, and until recently I have had an unwaveringly positive attitude toward the safety of breast milk. The cause of my little bit of uncertainty arrived in a recent study by two researchers at the Dana Farber Institute in Boston, in which the investigators examining the health histories of more than 150,000 women found that those who were breastfed incurred a 23% greater risk of developing colorectal cancer when they reached adulthood. A younger cohort within that larger group had a dramatic 40% increased risk of developing high-risk cancer before reaching age 55.

The population the investigators studied came from the large Nurses’ Health Study II, a well-known repository of longitudinal health data. The researchers reported that they included biometric data and a large collection of lifestyle factors including smoking, alcohol intake, and diet in their calculations. However, breastfeeding continued to register the highest association. Interestingly, the investigators found that women who were breastfed for 9 months or longer had twice the risk of colorectal cancer as those who breastfed for from 4 to 8 months.

The study population was all women and predominantly white. However, in the general population it is the non-Hispanic white population that is experiencing the greatest increase in incidence. Of course, the study could not answer whether this association with breastfeeding also existed in minority populations.

The researchers suspect that what they are seeing is a reflection of the Westernization of the American lifestyle. One of the researchers is interested in the gut biome of infants and plans to further the investigation in that direction. Could some substance from the environment be concentrating in breast milk? Or is something missing in breast milk? She points out that, while formulas are generally fortified with vitamin D, breast milk is not.

As concerning as the results of this study may sound, the authors are very careful to urge mothers to continue to breastfeed and choose it as their first choice for feeding their babies. I have been pleasantly surprised that this study has not gotten widespread media attention because bad news travels fast. I have chosen to share it with you because at some point you may begin getting questions from concerned parents.

While apparently well done, this study is just the beginning. Like any good research, it poses more questions than it answers. For us as pediatricians it means we should continue to recommend breast milk as the first food. But, we must stay alert as further research looks deeper into this association.

We should also take advantage of our special access to young parents, a demographic that less frequently sees a physician for preventive care. For whatever reason colorectal cancer is occurring at younger ages. When we have the opportunity we should be reminding 40-year-olds not to wait until age 50 to screen for colorectal cancer, particularly if they have a family history of the disease.

Dr. Wilkoff practiced primary care pediatrics in Brunswick, Maine, for nearly 40 years. He has authored several books on behavioral pediatrics, including “How to Say No to Your Toddler.” Other than a Littman stethoscope he accepted as a first-year medical student in 1966, Dr. Wilkoff reports having nothing to disclose. Email him at pdnews@mdedge.com.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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Cite this: Breastfeeding and Colorectal Cancer - Medscape - Nov 14, 2023.