A New Zealand study contradicts beliefs that breastfeeding reduces the likelihood of children developing asthma and other allergies.

One of the authors of the study, Professor Robin Taylor of Otago University, said his university and McMaster University in Canada had shown that children who were breastfed for four weeks or more were twice as likely to develop asthma.

"Contrary to expectations, the children who were breastfed for four weeks or longer had a higher risk of allergy in mid-childhood and early adulthood, compared with those not breastfed," Professor Taylor said.

The researchers looked at 1037 Dunedin children born in 1972 and 1973, 49 per cent of whom had been breastfed.

The results of the study appear to contradict information from the World Health Organisation during world breastfeeding week in August.

It claimed that breastfeeding cut the mother's risk of breast cancer and the benefits to the child included stronger immune systems and decreased incidence and severity of food allergies, asthma, colic and eczema.

The co-author of the new research, Professor Malcolm Sears of McMaster University, said that although the findings showed the link to asthma, mothers should continue breastfeeding their children.

The study will be published tomorrow in the British medical journal the Lancet.

- NZPA