A number of newspaper articles have today reported on a Norwegian study which has found an association between higher levels of male hormones in pregnancy and the ability to breastfeed after birth. The authors are reported to have extrapolated from their findings that mothers’ ability to breastfeed is entirely down to these hormone levels. They are also reported to have claimed that exposure to high levels of testosterone before birth account for the differences in health outcomes between breast and bottle fed babies. The findings of this small study are of interest and may warrant further investigation. However, the claims made in relation to these findings do not account for the large differences in breastfeeding rates between countries, with some having 99% of mothers successfully breastfeeding. They are also contradicted by the large body of evidence which shows that levels of successful breastfeeding can be increased by a range of improved support interventions.
The claims made relating to the health outcomes of breastfeeding do not account for the dose response found in many studies, which show that babies breastfed exclusively or for longer periods have the best overall outcomes.
The study does not account for or tally with the known mechanisms for how breastmilk protects against illness. For example, breastmilk contains a range of anti-infective properties including immunoglobulins, white cells, anti-inflammatory components, enzymes and non-antibody factors such as lactoferrin and the bifidus factor.
The body of evidence for the benefits of breastfeeding is very large and comes from a wide range of studies into many different illnesses, carried out by numerous researchers in many different universities. Systematic reviews of the literature have also been carried out and are especially useful, as they are able to eliminate weak studies and combine the findings of all the high-quality papers in order to demonstrate with the greatest reliability whether a protective effect truly exists. It is important to note that there is variability in the quality and depth of evidence in relation to some illnesses which is why the authors of these reviews tend to call for further research to clarify the finding. It remains the case, however, that the evidence for the advantages of breastfeeding is strong.
The two most recent and influential reviews were carried out by the Agency for Health and Research Quality and the World Health Organization and are summarised below:( Read more...Collapse )