What are the risks associated with formula feeding? A re-analysis and review.

Background: Most infant feeding studies present infant formula use as 'standard' practice, supporting perceptions of formula feeding as normative and hindering translation of current research into counseling messages supportive of exclusive breastfeeding. To promote optimal counseling, and to challenge researchers to use exclusive breastfeeding as the standard, we have reviewed the scientific literature on exclusive breastfeeding and converted reported odds ratios to allow discussion of the 'risks' of any formula use.

Methods: Studies indexed in PubMed that investigated the association between exclusive breastfeeding and otitis media, asthma, types 1 and 2 diabetes, atopic dermatitis, and infant hospitalization secondary to lower respiratory tract diseases were reviewed. Findings were reconstructed with exclusive breastfeeding as the standard, and levels of signidicance calculated.

Results: When exclusive breastfeeding is set as the normative standard, the re-calculated odds ratios communicate the risks of any formula use. For example, any formula use in the first 6 months is significantly associated with increased incidence of otitis media (OR: 178, 95% CI: 1.19, 2.70 and OR: 4.55, 95% CI: 1.64, 12.50 in the available studies; pooled OR for any formula in the first 3 mo: 2.00, 95% CI: 140, 2.78). Only shorter durations of exclusive breastfeeding are available to use as standards for calculating the effect of 'any formula use' for type 1 diabetes, asthma, atopic dermatitis, and hospitalization secondary to lower respiratory tract infections.

Conclusions: Exclusive breastfeeding is an optimal practice, compared with which other infant feeding practices carry risks. Further studies on the influence of presenting exclusive breastfeeding as the standard in research studies and counseling messages are recommended.