White Coat, Black Art·DR. BRIAN'S BLOG

Long-term exclusive breastfeeding may have a downside

A new study suggests that the duration of breastfeeding and when solid foods are introduced could have an impact on the development of food allergies.

Study suggests need to balance breastfeeding with solid food introduction in food allergy prevention

A new study found that infants with suspected food allergies or intolerances were breastfed significantly longer than other babies. The health benefits of breastfeeding are important, but the latest research says it's also important to introduce potential food allergens early. (Nikolas Giakoumidis/Associated Press)

The Public Health Agency of Canada says breastfeeding gives newborns the best possible start in life, with established health benefits for both baby and mother.  

new study suggests that the duration of breastfeeding — and knowing when to introduce solid foods — could have an impact on the development of food allergies.  

In a study presented at the 2019 Annual Meeting of the American Academy of Allergy, Asthma & Immunology on Monday, researchers at Children's National Health System in Washington D.C., analyzed data from the Infant Feeding Practices Study II, which tracked what more than 2,000 women ate during pregnancy and what they fed their babies during the first year of life. 

Breastfeeding mothers in the study were surveyed when their babies were four, nine and 12 months old and asked whether the infants had experienced allergic reactions, sensitivities or intolerance to food.

The mothers reported that about 11 per cent of the babies had a suspected food allergy or were intolerant to at least one food in their diets.

(A food intolerance occurs when someone had trouble digesting a type of food. Celiac disease is a serious example of food intolerance. A food allergy causes someone's immune system to respond with an allergic reaction that can be life-threatening, such as anaphylaxis. Someone with a food allergy needs to carry an epinephrine auto-injector, such as an EpiPen, in case they are exposed to the food.) 

The researchers compared those babies with food allergies or intolerances to those without. Infants who had no food issues were breastfed for an average of 32 weeks. Those with food intolerances were breastfed an average of 40 weeks. Those with suspected food allergies were breastfed for nearly 46 weeks.

The current study is one of the first to look at the association between the duration of breastfeeding and suspected food allergies, intolerances or food sensitivities among babies eating their first bites of solid food. 

Breastfeeding important, researchers emphasize

No one is saying breastfeeding triggers food allergies. The researchers are saying that it's the duration of breastfeeding that might have a detrimental effect on the risk of food allergies. That's because it's plausible that the longer a child is breastfed, the more likely it is that the parents delay introducing solid food — including common allergy-causing staples — into the baby's diet. 

The World Health Organization recommends that babies be breastfed exclusively until six months of age. That recommendation predates research on the benefits of introducing allergenic food early in life. It was not made with food allergies in mind.

That's important given the fact that studies have shown that food allergies are on the rise. According to the U.S. Centers for Disease Control and Prevention, the rate of children with food allergies in the U.S. rose from 3.4 per cent in 1997 to just over five per cent in 2011.

The numbers suggest a growing public health problem that has led led doctors to shift their attention from treatment of food allergies to preventing them. 

Recent studies have suggested it might be possible to prevent egg and peanut allergies in kids by introducing them to either or both foods early in their lives. For example, researchers intrigued by the low prevalence of peanut allergies in Israel conducted a study that found peanuts are introduced as a staple early in that country.

Researchers need to learn more about the interplay between food allergies and what infants eat to aid prevention efforts. 

Any new recommendation to introduce solid foods earlier in infancy may conflict with current recommendations for exclusive breastfeeding during the first six months of life. Breastfeeding for a long duration has been associated with reduced gastrointestinal and respiratory infections in infants.

For the mother, breastfeeding exclusively for the first six months is associated with more rapid loss of weight gained during pregnancy and a delay in resuming menstruation. The early introduction of formula to the baby's diet reduces the total duration of breastfeeding. However, the introduction of solid foods does not appear to have the same effect.

Last month, the Canadian Paediatric Society published revised recommendations on when to introduce allergy-causing solid foods into an infant's diet. The guidelines state that there is emerging evidence that early food introduction (between four and six months of age) may play a role in preventing egg and peanut food allergies in high-risk infants.

For infants at high risk for allergic disease, the society now recommends that commonly allergenic solids be introduced at around six months of age, but not before four months of age. The introduction of these foods should be guided by the infant's developmental readiness for food.

The pediatric guidelines emphasize that continued breastfeeding should be encouraged and supported because of its many health benefits. But at the same time, parents should also consider when they add solid foods to their baby's diet.  The research on food allergies — and how to potentially prevent them — is constantly evolving, so parents shouldn't hesitate to ask their health-care provider any questions they may have.  

About the Author

Dr. Brian Goldman

Dr. Brian Goldman is a veteran ER physician and an award-winning medical reporter. As host of CBC Radio’s White Coat, Black Art, he uses his proven knack for making sense of medical bafflegab to show listeners what really goes on at hospitals and clinics. He is the author of The Night Shift and The Power of Kindness: Why Empathy is Essential in Everyday Life.

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