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A leading New Zealand academic who endorsed a book linking milk with a range of illnesses says milk is "perfectly safe" to drink.
Sir John Scott, emeritus professor of medicine at the University of Auckland, said Devil in the Milk - by Professor Keith Woodford from Lincoln University - should not dissuade people from drinking milk.
But he also said the scientific evidence deserved closer scrutiny.
"It needs a lot more money and investment because this idea will not go away," Professor Scott said.
The book argues the dairy industry is not doing enough about a tiny protein fragment in milk that is linked to heart disease, diabetes and schizophrenia.
The industry and the Food Standards Authority yesterday urged people to keep drinking milk as a "nutritious food".
The scientific argument points to what Professor Woodford calls the "milk devil" - beta-casomomorphin7, a derivative of A1 beta-casein, a gene found in cows' milk.
About half of New Zealand cows carry the gene. The alternative, A2, is carried by the other half of the herd, but the milk products are often mixed.
Professor Woodward wants the industry to switch completely to A2, which he estimates would take 10 years.
A study in the early 1980s revealed a link between A1 milk and diabetes.
But in Professor Woodford's book - to be published on Monday - he argues the dairy industry and the Food Standards Authority have denigrated or ignored the risks.
Director of Food Standards Carole Inkster said yesterday a review in 2004 concluded there was "insufficient overall evidence that either milk has benefits over the other".
She said the review also suggested further work was needed to determine links between types of milk and any diseases.
"We are not aware of any new research from anywhere in the world, and can only conclude that the world's medical researchers have not seen the A2 hypothesis as a high priority for investigation."
The authority was concerned that "unsubstantiated claims do nothing more than scare some people away from a safe, nutritious and beneficial food".
Federated Farmers president Charlie Pedersen rejected the claims that some ordinary milk may be hazardous to health. He said the issue had been around for about 10 years and debate had reignited because some people stood to gain financially by "denigrating something that had been consumed for hundreds, if not thousands, of years".
A spokeswoman from Fonterra declined to comment.
