The benefits of breast-feeding have been greatly exaggerated, a leading Canadian pediatrician says.

Professor Michael Kramer, from Montreal's McGill University, claimed much of the information used to persuade mothers to breast-feed was either wrong or out of date.

He has spent more than 20 years studying the subject and believes a significant amount of evidence behind the claims is flawed, The Advertiser reports.

Those promoting the "breast is best" message say a mother's milk wards off a host of ills including protecting against obesity, allergies, asthma and diabetes.

But Kramer's work has failed to show breast-feeding provides such protection. He claims many of the supposed advantages can be explained by differences in lifestyle.

"I don't favor overselling the evidence -- we should not be conveying false information," he said.

But Kramers says studies showing breast milk wards off ear infections and stomach bugs stand up to scrutiny. He also believes it may be good for the developing brain, leading to a slight increase in IQ.

Click here for more on this study from news.com.au.