Currently, mothers are recommended to exclusively nurse their children for the first six months, and begin introducing solid foods thereafter. The reason for this delayed schedule is to slow the introduction of potential allergy triggers until the gastrointestinal tract matures.
A study published this month in the journal Pediatrics challenges this food introduction strategy. In fact, the authors of this study found that the longer the delay in adding several categories of foods, the more risk of allergy and asthma by the age of five.
This new study followed 1000 Finnish children from birth to age five. In addition to tracking food introduction data, the authors measured blood levels of IgE, a class of antibodies associated with allergy.
After correcting for key variables in the data, including maternal age and smoking habits, income, and household pets, the authors found that the longer the duration of exlusive nursing, the higher the risk of developing both food and inhalant allergies.
The level of evidence for the exclusive six month nursing recommendation has always been a little slight. Largely, it was based on a theoretical understanding of the maturation process of the intestinal barrier. Previously published clinical trials have been inconsistent, although they have not challenged current regulations in the way this newest study does.
There is one potential issue that makes this study hard to extrapolate to the whole population, however. The children enrolled all were considered to have high risk of diabetes due to specific mutations in HLA, an important gene that helps to control immune system function.
Because of this particular irregularity, I think it is probably premature to change guidelines around nursing. Still, I think this piece of information makes it hard to support a belief that early introduction of solid foods significantly increases the risk of allergy down the road.
I’d be interested to see a follow-up further down the road. I thought exclusive bfing for longer also decreased the risk of diabetes later in life, which apparently this study does not address.