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The benefits of breastfeeding or the harm of formula feeding?

As an epidemiologist engaged, among other activities, in programmes, projects and research on infant and young child feeding, I am often asked to say or write something on the benefits of breastfeeding. Many years ago, I used to respond enthusiastically to these requests and to spend nights searching the literature to provide my often very small audience and readership with the most up-to-date science. The turning point was 1989 when I read a paper that Michael Kramer had published the year before on breastfeeding and atopic disease. “To avoid another 50 years of unresolved controversy,” wrote Kramer, “future studies should improve both the biological and methodological aspects of their design and analysis” (see panel). Should I wait 50 years, I asked myself, before I act to protect, promote and support breastfeeding? Encouraged by the joint statement published that same year by WHO and UNICEF, my answer was no. From then on, my response to requests for talks and papers on the benefits of breastfeeding became progressively colder and I started to build a rationale to defend my cold acceptance and, with time, refusal: • Did my mother breastfeed to protect me from atopic disease? Do human beings breastfeed their offspring because they are aware of the benefits of breast milk or because they are mammals? • Are the advocates of breastfeeding responsible for the evidence on its benefits, or should those who propose (and market with huge profits) alternative ways of feeding be required to show that their option is superior or at least equivalent? • Given our limited resources, should we invest time and money for research on the benefits of breastfeeding, to the detriment of research on effective interventions to protect, promote and support it? Yet I continue to get requests. Why? Probably because the overemphasis on the benefits of breastfeeding has become a paradigm. Probably because we are used to labelling breastfeeding as “best”, “optimal” and “ideal”, thus regarding formula feeding as “good” and “normal”. Does it mean that all research on the benefits of breastfeeding is useless? As long as we invest more on research on effective interventions, having more evidence on the benefits of breastfeeding is useful, but we should perhaps start using that evidence in a different way. If breastfeeding is the biological norm, we should not say that breastfed babies are healthier; we should say that formula-fed babies are less healthy. We should change our paradigm to the harm, or risks, of not breastfeeding. In this sense, the article by Ortega-García and collaborators published in this issue of the journal is welcome. But can we use it with confidence to state that non-breastfed babies have a higher risk of paediatric cancer? In other words, does the study comply with the standards set by Kramer? The authors tried to gather as accurate as possible data on exposure and outcome, and used accepted statistical methods. Their data would have probably qualified for inclusion in recent systematic reviews. Yet the study was not perfect, especially as far as assessment of exposure is concerned: despite the explanations given in the discussion, there is still the possibility of a differential recall bias associated with the different age distribution of cases and controls. Moreover, cases and controls were overmatched (i.e. matched for variables related to the exposure of interest), and this may have reduced the efficiency of the study as the same odds ratio might have been estimated with a smaller sample. Cases and controls were matched also for variables that may be related to outcome, and this may affect the validity of the results, despite the inclusion of the matching variables in the regression analysis. Also, one should remember that associations derived from case control studies, as most studies on risk factors for childhood cancer are, may have a non-causal explanation. Finally, the estimated odds ratios, especially at the lower end of the confidence limits, are small and may have little public health importance in the prevention of paediatric cancer, especially in populations where the prevalence, exclusivity and duration of breastfeeding are high and unlikely to increase dramatically. To conclude, if I accepted again to talk or write on the benefits of breastfeeding, or if I had to advise a pregnant woman to breastfeed, I would not hesitate to use strong arguments such as, for example, the higher risk of hospitalization for diarrhoea and lower respiratory tract infection associated with formula feeding. But I would not use as main argument the possible reduction of the risk of paediatric cancer or the beneficial effect on intelligence and school performance. Many health professionals would avoid using these arguments for fear of making mothers feel guilty. I do not agree. We tell obese patients to diet and exercise, and we write papers on driving safely. We are not afraid of making patients and drivers feel guilty because we consider some physical activity, a good diet and driving at low speed as normal. In a society where breast is best and formula feeding is normal, the guilt for not breastfeeding falls on policies, health systems and health workers, not on women. In a society where breast is normal and formula feeding is just a surrogate, as a dental plate is for teeth, women will not feel guilty if we tell them to breastfeed and provide adequate support. We do not need to use weak and shaky arguments to convince mammals to breastfeed. Unit for Health Services Research and International Health, Institute for Child Health “Burlo Garofolo”, Trieste, Italy (cattaneo@burlo.trieste.it) doi:10.1111/j.1440-1754.2007.01263.x