Infants who are introduced to their first solid foods before 17 weeks of age have a higher likelihood of developing food allergies by 2 years, a U.K. team of researchers found.
Additionally, the researchers discovered that infants who receive their first cow’s milk products while still being breastfed were less likely to develop allergies than were those introduced to cow’s milk after breastfeeding had stopped.
The research, led by Kate E.C. Grimshaw, Ph.D., of the University of Southampton, England, and published online Nov. 18 in Pediatrics (2013 [doi:10.1542/peds.2012-3692]), supports current recommendations by the American Academy of Pediatrics that solid food be introduced at between 4 and 6 months*, concurrent with breastfeeding, to prevent allergies (Pediatrics 2008;121:183-91; Pediatrics 2012;129:e827-41).
Dr. Grimshaw and her colleagues’ study identified the 17-week mark as the "crucial time point," with solid food introduced before this time appearing to promote food allergies, while solid food introduced after this time apparently not doing so.
For their research, Dr. Grimshaw and her colleagues used a large prospective cohort study (n = 1,140) to identify mothers of 41 infants diagnosed with food allergies by age 2 years. These infants were matched with 82 controls born on close to the same date. All mothers of infants in the cohort study kept detailed daily food diaries describing their feeding practices through the first year after birth.
Dr. Grimshaw and her colleagues found that solid foods were introduced significantly earlier among the infants with allergies, with 35% of the former receiving their first solids before and including 16 weeks, compared with 14% of control infants (P = .011).
Of the infants who received cow’s milk concurrently with breast milk, the duration of concurrent feeding was longer – 9 weeks – in the control group, compared with 5.5 weeks in the allergy group (P = 0.47), suggesting that the duration of overlap was important and that longer overlap was helpful. However, there was no significant difference between the two groups in terms of the age at when the cow’s milk was introduced into the diet, they said.
Dr. Grimshaw and her colleagues listed as strengths of their study its prospective design that allowed for data collection from birth onward, and before any signs of allergy could become evident; only three infants in the study had evidence of allergy before 24 months. Also, they noted, a thorough diagnostic standard was used to identify allergies.
Although the optimum duration of exclusive breastfeeding has yet to be established, "Health professionals can provide advice that is consistent by encouraging exclusive breastfeeding for as long as possible followed by continued breastfeeding alongside the introduction of complementary foods to maximize the duration of concurrent breastfeeding and solid food introduction," Dr. Grimshaw and her colleagues wrote in their analysis.
The study was funded by the U.K. Food Standards Agency. Dr. Grimshaw declared an advisory relationship with Nutricia, while her coauthor Dr. Graham Roberts disclosed a relationship with Danone Baby Nutrition. Another coauthor on the study, Clare Mills, Ph.D., disclosed associations with Novartis, PepsiCo International, and DBV Technologies.
*Correction, 11/25/13: A previous version of this story misstated the AAP's recommendation for when solid foods should be introduced.