“Exclusive breastfeeding for six months wards off baby infections,” reported the BBC. “Regardless of other factors, such as good healthcare and vaccination programmes, breastfeeding still gives babies a boost,” explained the website.
The story is based on a study which found that babies who were breastfed exclusively for six months had fewer infections during the first year of life. They were also less likely to be admitted to hospital with an infection than babies who were partially breastfed or not breastfed at all.
The findings of this large study support previous research, which showed that breastfed babies are less prone to a variety of infections. The study also suggests that partial breastfeeding (giving the baby a mix of breast and formula milk, other fluids or solids) does not provide the same protection.
However, certain aspects of this study could make its result less reliable. First, instead of relying on medical records, researchers asked mothers to remember in detail how many infections their babies had had and how severe the infections were. Second, only 91 of the 926 babies whose mothers took part were exclusively breastfed. This is a small number of babies on which to base the results.
Also, when the researchers considered other factors which might influence the results, such as parental health and education, breastfeeding was only associated with a reduction in respiratory infections, such as coughs and colds. It did not significantly reduce other types of infection.
The Department of Health advises mothers to exclusively breastfeed babies for the first six months of life.
Where did the story come from?
The study was carried out by researchers from the University of Crete. No external sources of funding were reported. It was published in the peer-reviewed medical journal Archives of Diseases in Childhood.
The study was covered accurately in the BBC’s report, which also included advice on the benefits of breastfeeding from independent experts.
What kind of research was this?
The researchers point out that although research already suggests that breastfed infants are less prone to a variety of infections, it has been argued that this may be because of other differences (called confounding factors) between breastfeeding and bottle-feeding mothers. Alternatively, the protection provided by breastfeeding may be less marked in societies with high healthcare standards. The researchers also say that many studies have focussed only on particular infections, the effect of breastfeeding during the first few months after birth or how often, but not how severe, the infections were.
This prospective cohort study looked at the effect of breastfeeding on both the frequency and severity of infections during the first year of life in a group of babies born in Crete. Prospective studies, in which groups of people are identified at the start of the research and followed for a period of time, are considered more reliable than retrospective studies, which look backwards in time.
What did the research involve?
The study took place on the island of Crete, where researchers initially recruited 1,049 mothers and their children, who were born between October and December 2004, and April and July 2005. During the study, all the infants were routinely immunised with standard vaccines. The mothers were interviewed while on maternity wards and filled in detailed questionnaires about their families, health, smoking habits, breastfeeding experience and whether they intended to breastfeed. The mothers were subsequently contacted by telephone by the same investigator at one, two, six, nine and 12 months after birth. In follow-up questionnaires, they were asked about breastfeeding, visits to the doctor and admissions to hospital, and all episodes of illness in their children.
Researchers then classified the reported episodes of ear infection (acute otitis media), acute respiratory infections, stomach upset (gastroenteritis), urinary tract infections, conjunctivitis and oral thrush using standardised definitions. All of these are common infections of infancy. The researchers defined exclusive breastfeeding as an infant receiving only breast milk and no other liquids or solids, and partial breastfeeding as receiving breast milk in combination with infant formula or other liquids or solids.
The researchers used standard statistical methods to look at the possible association between the feeding method and the frequency and severity of infections. Frequency of infection was estimated by the total number of episodes recalled, and severity was estimated by the number of visits to the doctor and admissions to hospital.
What were the basic results?
Of the initial sample of mothers, 926 were successfully followed up for the whole study period. While nearly 61% of mothers were breastfeeding (either exclusively or in combination with other feeding) during the first month, at six months this figure was nearly 17%, with just over 10% exclusively breastfeeding.
The study found that, after the figures were adjusted for the influence of potential confounders, babies who were exclusively breastfed for six months had fewer episodes of acute respiratory infection (coughs, colds or chest infections) during the first six months of life than partially or non-breastfed babies (42% risk reduction, odds ratio 0.58, 95% confidence interval 0.36 to 0.92). There was also a trend for reduced risk of acute otitis media, gastroenteritis, conjunctivitis and oral thrush, but none of these risk reductions were statistically significant.
They also found that overall, babies who were exclusively breastfed for six months had fewer infectious episodes in the first 12 months and were less likely to be admitted to hospital for infection.
Partial breastfeeding was not associated with any protective effect against infection.
The researchers also found that several other factors had an effect on the frequency of infections during pregnancy. These included parental age and education, ethnicity, tobacco smoke exposure and season of birth.
How did the researchers interpret the results?
The researchers suggest that exclusive breastfeeding protects against common infections in infancy and lessens the frequency and severity of infectious episodes, even in countries with high healthcare standards. The maximum protection is provided by exclusively breastfeeding for the first six months of life. The researchers suggest this protective factor might be explained by the presence in maternal milk of maternal antibodies and other factors that may affect the immune system, and also by the effect of maternal milk on infantile bacteria in the gastrointestinal tract.
This large and reasonably well-conducted study supports previous findings on the protective nature of breast milk. It also suggests that only breastfeeding exclusively confers protection against infection and that partial breastfeeding seems to have no protective effect. However, as the researchers note, their study has limitations, in particular its reliance on mothers recalling precise information about the severity and frequency of their children’s infections. Also, it should be noted that although there was a trend for reduced risk of all of the common infections examined, exclusive breastfeeding during the first six months significantly reduced the risk of chest infection only. Although the researchers adjusted their results for confounding factors, it is possible that other unmeasured confounders could have influenced the results. The relatively small number of babies who were exclusively breastfed (91 out of 926) is a further limitation.
Current Department of Health advice to mothers is to exclusively breastfeed babies for the first six months of life. Alongside the various other benefits of breastfeeding, this study lends support to its protective effect against common infections during the first six months of life.