Babies that are exclusively breastfed for six months are less likely to catch an infection, and when they do it is not as severe, a new report claims.
The study, published online in the Archives of Disease in Childhood, tracked around 1,000 infants for the first 12 months of their lives.
Any common infections they had at one, three, six, nine and 12 months were recorded, including ear infections (otitis media), stomach upsets (gastroenteritis), conjunctivitis, thrush, and respiratory and urinary infections.
The infants were drawn from a total of 6,878 births in 2004 in Crete. All were routinely vaccinated and had access to a high standard of healthcare.
The 91 infants that were exclusively breastfed for six months, with no substitute formula feeds, had significantly fewer common infections than their peers who were either partially breastfed or not breastfed at all during their first year of life. The infections they picked up were also less severe.
Partial breastfeeding did not exert the same protective effects. The findings held true for respiratory infections, otitis media, and thrush, even after adjusting for other potentially influential factors.
Factors such as parental age and education, exposure to environmental tobacco smoke, ethnicity and number of siblings influenced the frequency of infections, the findings showed.
Antibodies passed on through the mother's milk, as well as nutritional and immunological factors, may account for the differences between infants who are exclusively breastfed and those given formula feed or a mix, say the authors.
They conclude: "Exclusive breastfeeding helps protect infants against common infections, and lessens the frequency and severity of infectious episodes, not only in developing countries but also in communities with adequate vaccination coverage and healthcare standards."
Other research has suggested that breastfed infants are less prone to infections, but studies have not made clear whether other factors play a part, including high standards of healthcare provision such as vaccination programmes.