PARIS, Sept 12, 2007 (AFP) - Long-term breast feeding, while famously rich in nutrients for baby, does nothing to reduce the risk of developing childhood asthma and allergies, a new study suggests.

Canadian and Belarusian doctors recruited 17,046 breastfeeding women who were attending maternity clinics in Belarus in the late 1990s.

The volunteers were split into two groups.

In one group, the women (and the healthworkers at the maternity clinics) carried out their normal practices and policies of breastfeeding.

In the other, breastfeeding was promoted and supported, with the result that more infants of women in this group were breastfed exclusively for their first three months of life, and for longer periods, at up to 12 months.

When the children reached the age of six and a half, they were tested for any symptoms of asthma and their parents were asked to detail any symptoms of wheezing, chest tightness, hay fever and eczema.

In addition, the children were given allergy pricks to test for any response to house dust mites, cats, birch pollen, mould and grass pollen.

A total of 13,889 youngsters were followed up this way.

There was no difference between the groups on the questions of asthma, hay fever or eczema -- and the results from the allergy pricks showed that in the "pro-breastfeeding" group, the youngsters were more sensitive to dust mites and grass pollen than their counterparts.

"These results do not support a protective effect of prolonged and exclusive breastfeeding on asthma or allergy," say the investigators, led by Michael Kramer of The Montreal Children's Hospital, Canada.

They note that asthma and allergies have surged in incidence in the past few decades while breastfeeding has enjoyed a renaissance.

This "strong suggests that breast feeding does not have a potent protective effect .125against these disease.375 at population level."

In 2002, a smaller study, conducted among 1,037 New Zealand infants, found that babies who had been breastfed for more than four weeks rank almost double the risk of contracting asthma and allergies in their childhood compared with counterparts who had been fed on infant formula.

The paper was published online Wednesday by the British Medical Journal (BMJ).