Friday January 14 2011
The researchers stated that their study is not anti-breastfeeding
“Babies 'need solid food as well as breast milk' in first six months,” reported the Daily Mirror. The BBC said: “Weaning before six months 'may help breastfed babies'.”
These and many similar stories in today’s press are based on a study published in the British Medical Journal. The authors of this informal review of recent scientific research suggest that babies in developed countries, including Britain, may benefit from being fed solids before the currently recommended age of six months so that they receive a full range of nutrients. They say that existing government advice – that British women should exclusively breastfeed for six months – should be reassessed. According to the report, only in developing countries, where water quality is poor (and the risk of infection higher), is there a clear rationale for exclusive breastfeeding for six months.
It is important to note that the study is in no sense against breastfeeding. The study confirms the sentiment of the slogan “breast is best”, but also points out that there is good scientific evidence that solids should be introduced to an infant’s diet earlier than previously advised. "I really want to emphasise we are not in any way anti-breastfeeding, particularly in the long term," said Mary Fewtrell, one of the authors. "We're extremely pro-breastfeeding. We would go along with recommendations to breastfeed exclusively for four months."
The study suggests that by introducing solids earlier, the possibility of infants developing iron-deficiency anaemia may be reduced. The authors add that it is unlikely that current government advice will have harmed any children because so few mothers breastfeed exclusively for six months anyway.
The Department of Health said: "Breast milk provides all the nutrients a baby needs up to six months of age and we recommend exclusive breastfeeding for this time. Mothers who wish to introduce solids before six months should always talk to health professionals first.
"The Department of Health will review this research alongside all emerging evidence on infant feeding. In September 2010, we asked the Scientific Advisory Committee on Nutrition to undertake a review of infant feeding."
Where did the story come from?
The study was carried out by researchers from the Institute of Child Health in London, the University of Edinburgh and the Institute of Child Health at the University of Birmingham. The authors report that no external funding was received for this research. The study was published in the peer-reviewed British Medical Journal.
This story was covered by numerous media sources, some of which overstated the strength of the research or misinterpreted it. Claims that breast is no longer best are unfounded, and the claim that exclusive breastfeeding for six months causes anaemia or allergies is not proven. This narrative review by child health experts points out that the original review conducted by the World Health Organization (WHO), on which recommendations for exclusive breastfeeding for six months are based, may now be out of date and could be revisited.
What kind of research was this?
This was a non-systematic or narrative review. The authors are all child health researchers, specialising in child health and nutrition and paediatric gastroenterology. They say that the recommendation that UK mothers exclusively breastfeed for six months should be discussed again because it is “a controversial area in infant nutrition”. The researchers do not provide any methods for their review such as how they found the studies, the total number published and how they selected those they discuss.
In 2003, the Department of Health issued a recommendation that incorporated guidance from the WHO that newborns should be exclusively breastfed for the first six months. The original WHO recommendation was based on a systematic review of the evidence in 2001 by Kramer and Kakuma. This review concluded that weaning at six months after exclusive breastfeeding was better than weaning at three to four months, and led to no apparent growth deficits and had no apparent relationship to allergies, poorer iron status and delayed return to menstruation for the mother. The research included in the 2001 review mainly consisted of observational studies, which can show associations between things but cannot prove cause and effect. Seven of the 16 studies that were included were conducted in developing countries. This original systematic review was well conducted and the researchers were explicit about their methods, citing the research sources and how they selected the studies they discussed.
What were the basic results?
The authors discuss several new studies that have been published since 2001 researching the following health outcomes for newborns. All of the studies are observational (there have been no randomised controlled trials comparing weaning from exclusive breastfeeding at six months versus weaning between three and four months). Observational studies often cannot prove causation and the authors say that the results should be interpreted cautiously. Below is a summary of the authors' discussion of the evidence.
Four new studies have been published on infection in newborns since 2001. Overall, the findings suggest that exclusive breastfeeding for six months reduces the risk of pneumonia, recurrent otitis media, gastroenteritis and chest infection.
Research from 2007 suggests that US infants exclusively breastfed for six months had lower iron levels and a greater risk of anaemia.
Allergy and coeliac disease
The authors say the evidence here is complicated. Studies apparently suggest that there is an increased risk of allergy if solids are introduced before babies reach three to four months of age. However, the evidence that this is the case after this period is weak. Paradoxically, allergy to certain substances may be increased by a delayed exposure to them. For example, the incidence of coeliac disease appeared to rise in a Swedish sample when women were advised to delay their baby’s exposure to gluten until they were six months old. Another study suggested that gluten may be best introduced between three and six months. The authors say there are currently two randomised controlled trials underway that will provide a decent quality of evidence that can inform this question further.
A long-term follow-up of an observational study in Belarus, which was discussed by WHO when it made its recommendation in 2001, reported no difference between babies exclusively breastfed for three months and those breastfed for six months in blood pressure, cognition, allergies and dental health. However, those exclusively breastfed to six months were more overweight when they were 6.5 years old than children in the other group. This contradicts findings from a Danish study that earlier introduction of solids was associated with greater risk of being overweight at the age of 42 years.
How did the authors interpret their findings?
The authors say that policies for exclusive breastfeeding are defensible in developing countries, but that the recommendation could be reviewed specifically for the UK. They acknowledge that it is associated with a reduced risk of infection, but that it may also increase the risk of iron-deficiency anaemia and that there are concerns it may affect allergy risk and the risk of coeliac disease.
The authors acknowledge that the new evidence they discuss is observational, so caution is needed in interpreting the results. They call for a more vigorous evidence-based system of policy-making in this area. Until then, they cannot say whether the current policy should be changed or not. They suggest that it is time to revisit the evidence again and report that a survey suggests that less than 1% of British women breastfeed exclusively to six months anyway.
The keys points of the review are:
- The original WHO policy was based on a systematic review of evidence conducted in 2001, which included 16 studies, seven of which were conducted in developing countries. However, when studies from developed countries were analysed separately, there wasn’t any evidence that there should be different recommendations for these populations.
- The authors discuss some recent research that has been published since WHO made its recommendations. They say the fact that there is new evidence, even if it is observational evidence, suggests that a new systematic review should be carried out and the findings taken into account in policy.
- This narrative review gave no description of how the authors found the research they discuss. It provides a good discussion of some studies, but a systematic review to identify all recent research on this topic would be better.
- Kramer and Kakuma, the authors of the original review on which WHO based its recommendations in 2001, updated their review in 2006 (it is a published Cochrane review). The review now includes a total of 22 studies, 11 from developing countries and 11 from developed countries. They continue to conclude that, on the basis of these studies (all of which are observational), there is evidence that children exclusively breastfed for six months are not adversely effected in terms of growth, have a reduced infection risk, and that there is no difference in allergy or asthma risk. They say that, in their opinion, there is no risk in continuing to recommend this policy.
- The newer evidence discussed by these researchers is also of poor quality and, like the older studies in the original review, cannot prove causation. These studies suggest that six months of exclusive breastfeeding reduces the risk of infection compared with weaning at three to four months, although there may be an increased risk of anaemia and lower iron in the blood. There is contradictory evidence about allergies.
- A recent review by the European Food Safety Authority’s panel on dietetic products, nutrition and allergies, concluded that “complementary foods may be introduced safely between four and six months, and six months of exclusive breastfeeding may not always provide sufficient nutrition for optimal growth and development.”
This review raises an important issue that is highly relevant to many people in the UK. It must not be interpreted out of context, and the conclusions of the reviewers should not be overstated. New research is published all the time and old policies are updated where they can be on the basis of this. The study findings highlight just how difficult it is to formulate a policy when the evidence is not strong.