The Risks of Early Introduction of Solids for Breastfed and Formula Fed Infants
by Anne Eglash MD, IBCLC, FABM
Despite the general health professional recommendation to avoid giving complementary foods (solids) under 6 months of age, the practice of feeding solids before 6 months is still very common in the USA. Many physicians and other providers don’t seem to be aware of, or perhaps not concerned about, risks regarding solid food introduction before 6 months of age.
The authors of today’s article sought to further explore infant health risks of early introduction of solids by analyzing data from the USA Infant Feeding Practices Study II for the years 2005-2007. The study sent out questionnaires to mothers at the end of their pregnancy, and then approximately monthly postpartum for the first year. The researchers focused on questions having to do with infant illness within the recent few weeks of receiving the survey, such as fever, cough/wheeze, diarrhea, recent hospitalization, hard stools, and correlated the information with the timing of solids introduction, and whether the infants were breastfed, formula fed, or mixed fed.
The authors found that among 2794 infants, feeding complementary foods before 6 months of age was associated with statistically increased risk of hard stools, diarrhea, fever, cough/wheeze, runny nose, cold symptoms, receiving medication, and hospitalization, after controlling for breastfeeding status, birthweight, time spent in the NICU, household size and income, mother’s age, and geographic region.
- Formula-fed infants are more likely to receive complementary foods before 4 months of age as compared to breastfed infants.
- Among infants fed solids at 2 months of age, those who were formula fed were more likely to wheeze as compared with those who were breastfed.
- Formula fed infants who were introduced to solids after 6 months were less likely to have diarrhea, fever, cough/wheeze as compared to breastfed infants who were fed solids before 6 mo.
- For exclusively breastfed infants, introduction of complementary food before 6 months is associated with a higher risk of infant illness than introduction of formula.
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Global health agencies agree that infants should not be fed complementary foods before 4 to 6 months of age. However, given the World Health Organization (WHO) definition of complementary food as "anything other than breast milk," little is known about the relative risks of formula compared with other complementary foods on infant health. This article aims to fill this gap in the literature, by assessing how differences in the timing of the introduction of nonformula complementary food between breastfed and formula-fed infants impacts infant health.
Eight health outcomes by complementary food introduction, breast-feeding, formula feeding, and mixed feeding (breastfed and formula-fed) were predicted using logistic regression with generalized estimating equations on the newborn through 6-month waves of the Infant Feeding Practices Study II (IFPS-II).
Complementary foods increased the likelihood for all health risks measured. Given greater prevalence of early complementary food introduction among formula-fed infants, most health differences between breast-feeding groups shift to nonsignificance in full models, with the exception of higher rates of hard stool and cough/wheeze among formula-fed and mixed-fed infants but lower rates of diarrhea (LO = -0.577; 95% confidence interval [CI] = -1.074 to 0.080) and runny nose or cold (LO = -3.19; 95% CI = -0.552 to -0.086) for mixed-fed than breastfed infants.
Our results confirm health benefits of exclusive breast-feeding and that the introduction of complementary foods before 4 to 6 months poses a greater risk to infant health than does formula. Greater attention to the early introduction of complementary foods is needed in research and clinical practice.
According to this 2005-2007 study, complementary feeding before 6 months was very common. By 2 months of age, 46% of formula-fed, 30% of mixed fed, but only 1% of breastfed infants were fed complementary foods. Although the diagnosis of infant illness was based on parent reportal rather than medical records, this is the largest study to show the relationship between complementary feeding before 6 months of age and infant illness.
When to introduce solids is one of the most common questions I encounter in my practice. It is reassuring to have more data to support the recommendation of waiting until 6 months. Parents should be made aware that earlier introduction of solids may increase health risks for their infant(s).