Severe food-poisoning outbreaks linked to consumption of raw-milk products have struck Manawatu and Waikato, affecting children and prompting a leading health expert to advise caution.

Ministry of Health data released under the Official Information Act show 19 people were hospitalised this year after consuming raw-milk products.

Records show four people were hospitalised in Waikato on March 5, receiving treatment for potentially deadly e.coli infection - the youngest victim aged two. The next day, five more people including a 4-year-old also fell ill. A month later, six more were struck down with tummy bug campylobacter in a short period of time, at least three of them young children. Scientists determined that consumption of raw-milk products was a common factor.

A total 55 cases of hospitalisations linked to raw-milk consumption have been recorded nationwide in the past two years.

In 2011, nine Manawatu people fell ill on one occasion, and Massey University EpiLab director and food safety Professor Nigel French, who has been studying the outbreaks as part of a government review of the industry, has tracked their cases back to one raw-milk source.

When those patients were interviewed, it was noted they had little knowledge of the risks associated with raw milk.

Policy-makers are faced with the task of deciding how best to balance consumer choice and public health responsibilities as New Zealand's burgeoning raw-milk consumer industry comes under the microscope.

The pasteurisation process is used to prevent milk contaminated with potentially deadly bugs from entering the milk supply.

Prof French said consumers should be free to eat and drink what they wanted, but parents should think carefully about what they fed their kids.

"We're not wanting to wrap people in cotton wool," he said. "I feel strongly that people should have the choice to eat raw food if they want to - but they should do it in full knowledge of the potential risks to their health."

Claims that Kiwi farm-kids raised on raw milk never got sick did not wash with the scientist, who himself grew up drinking it.

"If you have been brought up in an environment where you have been exposed to some bugs then you are going to develop an immunity to them.

"If you challenge your immune system and drink a glass of milk that has come into contact with this bacteria that you've been exposed to all your life you might be fine. But if you live in an urban environment and have had no exposure to this bacteria there's a chance you will get very sick."

Raw-milk products are illegal in many countries around the world including Australia and Canada, and in England they must carry health-risk warning labels.

In New Zealand, it is growing in popularity with advocates claiming health benefits, including protein and vitamins not diluted by the pasteurisation process, as well as a better taste.

Current rules allow producers to sell up to five litres of milk daily at the farmgate to buyers who purchase it for themselves or their family.

MPI general director of general food safety standards Carol Barnao said rules to manage hazards associated with drinking raw milk were difficult to interpret, apply, and enforce.

Last year, then Food Safety minister Kate Wilkinson agreed to support the continuation of sales.

MPI has proposed to put limits on the amount sold, and testing requirements for animal health and hygiene has gone out for consultation.