Not all journalists have been as sensationalist as the Daily Mail, amongst others. The BBC website ran with the headline: Hormones 'govern ability to breastfeed'.
The BBC report opens: "Mothers who find breastfeeding so hard that they give up should not blame themselves, researchers say. A Norwegian study concludes that difficulty feeding a newborn may be down to higher levels of the male hormone testosterone during pregnancy."
I've written in the past on the subject of guilt. My view is that it is a woman's decision on how she feeds her baby and no-one should try to make her feel guilty.
However, as UNICEF points out, there are some countries where 99% of mothers breastfeed, so the theory that excess male hormones prevent mothers from breastfeeding seems dubious.
Other doubts are being cast over this conclusion. The sample size was small - 180 pregnant women - and mothers with higher levels of male hormone are associated with lower birth weight babies. Whether medical interventions were made during birth also needs to be explored.
The research was looking at the hormone impact on pregnancy and breastfeeding, not on health outcomes from breastfeeding compared to formula feeding - Professor Carlsen's comments on this come from his interpretation of a selection of existing research and he agreed this finds health benefits, while disagreeing this was down to breastfeeding having intrinsic benefits.
His interpretation of the research on breastfeeding is not widely held. Journalists wrote similar sensationalist stories last year regarding Professor Kramer, who complained he had been misrepresented, but the damaging false information had gone around the world and few journalists published corrections to their stories. See:
UNICEF Baby Friendly Initiative in the UK has released a statement responding to the research, which is available at:
I include the full text below:
---UNICEF UK Baby Friendly Initiative statement on new breastfeeding research
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:
Ip S, et al (2007) Breastfeeding and Maternal Health Outcomes in Developed Countries. AHRQ Publication No. 07-E007.Rockville, MD: Agency for Healthcare Research and Quality.
This review carried out in the USA screened over 9,000 papers and used evidence from 400. It refers only to health outcomes in developed countries. The review found that breastfeeding is associated with a significant reduction in the incidence of: acute otitis media, non-specific gastroenteritis, severe lower respiratory tract infections, atopic dermatitis, obesity, type 1 diabetes, type 2 diabetes, childhood leukaemia, sudden infant death syndrome, necrotizing enterocolitis, maternal breast cancer and ovarian cancer. Link.
Horta B et al (2007) Evidence on the long-term effects of breastfeeding. WHO.
This paper reports on a series of systematic reviews to assess the effects of breastfeeding on blood pressure, diabetes and related indicators, serum cholesterol, overweight and obesity, and intellectual performance. It found a significant reduction in the incidence of obesity and overweight and type 2 diabetes. It also found that breastfed babies had lower systolic blood pressure, lower cholesterol and better performance in intelligence tests. Link.
Although the protective effects of breastfeeding on gastroenteritis and respiratory infections have not been questioned, attempts have been made to dismiss these in developed countries as mere ‘tummy upsets’ or ‘coughs and colds’, whereas in reality a reduction in severe infection resulting in hospitalisation has been found. The Millennium Cohort Study is a nationally representative longitudinal study of 18,819 infants who were born in the UK in 2000-2002. Data on infant feeding, infant health, and a range of confounding factors were available for 15,890 healthy, singleton, term infants who were born during this period. This study found that 53 per cent of diarrheal hospitalisations each month could have been prevented by exclusive breastfeeding and 31 per cent by partial breastfeeding. A total of 27 per cent of lower respiratory tract infections could have been prevented each month by exclusive breastfeeding and 25 per cent by partial breastfeeding. Quigley M et al (2007) Breastfeeding and Hospitalization for diarrheal and respiratory infection in the United Kingdom Millennium Cohort Study. The full paper can be found here.
It is important to be aware that the protective effect of breastfeeding is stronger in relation to some illness, notably gastroenteritis, than it is for other illnesses such as allergies. This does not mean that there is no protective effect against those other illnesses, rather that the risk to the bottle-fed baby is greater for some illnesses than for others. Importantly, where the evidence shows a slight protective effect of breastfeeding, this can still be the result of well performed research. Therefore, to describe the evidence as weak because of a lower degree of protection is inaccurate and misleading. It is important to note that a small protective effect of breastfeeding against a significant illness will have a dramatic effect across a population.
The role of the Baby Friendly Initiative and of health professionals is to give pregnant women and new parents the full facts about infant feeding based on the best available evidence in an objective and non-judgemental manner in order to allow informed decision making. We then need to help mothers to make decisions appropriate to their circumstances and to support them in their decision whatever that may be.