Babies fed only on breast milk up to the age of six months have a lower risk of developing asthma-related symptoms in early childhood, and this appears to be independent of infectious and allergic diseases, according to a study by researchers at the Erasmus Medical Center in Rotterdam in The Netherlands that was published early online recently in the European Respiratory Journal. The researchers said their findings add support to the idea that babies in industrialized countries should be given only breast milk up to the age of six months.

The research is part of the Generation R Study, which is following thousands of multi-ethnic urban children from before birth until early adulthood, to identify early environmental and genetic causes of normal and abnormal growth, development and health.

Although other studies have already linked breastfeeding to asthma risk, the researchers said their findings are the first to show a link between duration of breastfeeding and number of wheezing periods. They also found that asthma-related symptoms appear earlier in children who are breastfed for fewer months or who are also given other milk or solids earlier (in the first four months).

The researchers used questionnaire-gathered data to look at the effect of breastfeeding duration and the introduction of other liquid and solid food on 5,368 children. The data told them whether the children had been breastfed in their first 12 months of life, when they stopped having breast milk, and whether they were given any other milk or solids, and if so, when.

Another set of data came from questionnaires filled in later, when the children reached 1, 2, 3 and 4 years of age. This told them about diseases and illnesses, including asthma-related symptoms such as wheezing, shortness of breath, dry cough and persistent phlegm.

The results showed that:

  • Compared to children who were breastfed for 6 months or more, children who had never received breast milk had an increased risk of wheezing, shortness of breath, dry cough and persistent phlegm in their first 4 years.
  • The strongest associations were with persistent phlegm (children who were never breastfed had 1.5 times higher risk of this symptom), and wheezing (1.4 times higher risk if never breastfed).
  • Being fed solids or other milk as well as breast milk during the first four months were linked to higher risk of wheezing, shortness of breath, dry cough and persistent phlegm in preschool years compared to having only breast milk in the first four months.
  • Adjusting for potential influencers, the links between breastfeeding and asthma-related symptoms could not be explained by eczema, but partly by lower respiratory tract infections.

The researchers concluded that:

“Shorter duration and non-exclusivity of breastfeeding were associated with increased risks of asthma-related symptoms in preschool children. These associations seemed at least partly explained by infectious but not by atopic mechanisms.”

Lead author Dr Agnes Sonnenschein-van der Voort, who also works in the Department of Paediatrics in the Division of Respiratory Medicine at the Erasmus Center, told the press that although more studies should be done to look at whether breastfeeding protects against asthma later in life:

“These results support current health policy strategies that promote exclusive breastfeeding for 6 months in industrialised countries.”

“Duration and exclusiveness of breastfeeding and childhood asthma-related symptoms.”
A.M.M. Sonnenschein-van der Voort, V.V.W. Jaddoe, R.J.P. van der Valk, S.P. Willemsen, A. Hofman, H.A. Moll, J.C. de Jongste, and L. Duijts
Eur Respir J erj01781-2010; published ahead of print 20 July 2011: doi:10.1183/09031936.00178110
Link to Abstract.

Additional source: European Lung Foundation.

Written by: Catharine Paddock, PhD