Lancet asthma study refuted

The study by Sears and colleagues in the Lancet (20 September 2002) finds no protective effect of breastfeeding against asthma and other allergic diseases. This contradicts the findings of other studies, notably research published in July by Oddy and colleagues.

The difference in the findings is likely to be explained by the different approaches in relation to exclusive breastfeeding.

Sears compares babies who were breastfed for more than 4 weeks with those who were not. Just 15% of babies are classed as 'exclusively' breastfed, and the author accepts that many of these "received a nightly formula feed while in hospital". This differs from the internationally accepted definition of exclusive breastfeeding, which is that babies receive no food or drink other than breastmilk. Furthermore, using a cut-off point of 4 weeks of 'exclusive breastfeeding' means that the breastfeeding group would in fact have included babies whose mothers stopped breastfeeding or moved to mixed bottle- and breastfeeding shortly after 4 weeks.

Oddy, on the other hand, found that children who had been exclusively breastfed for their first 4 months were less likely to suffer from asthma at age 6 years.

It is believed that a single feed of artificial infant formula to a susceptible baby can trigger an allergic response. The findings of Sears and colleagues should therefore be treated with great caution.

Oddy WH et al (2002). Maternal asthma, infant feeding, and the risk of asthma in childhood. J Allergy Clin Immunol 110: 65-7
Sears MR et al (2002). Long-term relation between breastfeeding and development of atopy and asthma in children and young adults: a longitudinal study. Lancet 360: 901-07.

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