Breastfeeding may protect children against the gluten intolerance known as coeliac disease, research suggests.
People with coeliac disease are intolerant of wheat-based foods
The Archives of Disease in Childhood study was a review of over 900 children with coeliac disease and almost 3,500 healthy children.
The longer a child was breastfed, the lower their risk of the condition was.
However, it is not clear whether this apparent protection is permanent or how breastfeeding might protect a child. Other studies show conflicting results.
An estimated 1% of the UK population has coeliac disease.
People with this condition develop a permanent sensitivity or intolerance to gluten - a protein found in cereals such as wheat, rye, and barley.
A number of studies have suggested that early infant feeding practices, as well as genetic factors, may be important in coeliac disease.
A team at Manchester University, the UK, looked at recent research on the effect of breastfeeding on the risk of gluten intolerance.
They found six studies all showing a link between breastfeeding and reduced risk of coeliac disease.
Those infants who were being regularly breastfed when they were first introduced to foods containing gluten cut their risk of developing coeliac disease by 52% compared with those who were not being breastfed.
The researchers said there were a number of possible explanations for the findings.
More research is needed
It might be that a child is simply exposed to less gluten during weaning if he or she is being breastfed.
Alternatively, breastfeeding might protect against coeliac disease by preventing gastrointestinal infections in an infant which can weaken the lining of the bowel and allow gluten to pass deeper into the gut than normal.
Breast milk also contains certain immune cells from the mother that might confer protection against gluten intolerance, they said.
A spokeswoman from the British Nutrition Foundation said: "The review provides encouraging evidence for a protective effect of breastfeeding at the time of gluten introduction - which is not recommended before 6 months - on the risk of developing coeliac disease."
But she added: "While the findings of this review are encouraging, there is a need for longer-term studies to investigate further the relation between breast feeding and coeliac disease, and for research to elucidate the mechanism whereby breastfeeding may protect against coeliac disease."
Professor Paul Ciclitira, a coeliac disease expert at King's College London, said there was no consensus as to whether breastfeeding did protect against coeliac disease or not and that more research was still needed.
A spokesman from Coeliac UK said: "We welcome this review as it provides strong evidence of the protection conferred by breastfeeding where infants are at risk of coeliac disease.
"However, it is still not clear whether breastfeeding delays the onset of the disease, temporarily or provides permanent protection."
The World Health Organization recommends exclusive breastfeeding for the first six months of life.
Thereafter, to meet their evolving nutritional requirements, infants should receive nutritionally adequate and safe complementary foods while breastfeeding continues for up to two years of age or beyond, it says.