Why Justin Trudeau is fighting over milk

Milk cartons in a grocery store in Toronto

A change to Canada's national food guide has become a surprise issue in the run-up to the October elections.

In January, Health Canada released an updated food guide that eliminated a daily dose of dairy as a requirement for a healthy diet.

Most dieticians heralded the move, but it was slammed by the dairy lobby.

Conservatives have accused Justin Trudeau's Liberals of kowtowing to "ideologically driven" philosophies like veganism.

Last week, Conservative leader Andrew Scheer promised to overhaul the food guide to restore dairy's supremacy. The new guide said water should be everyone's beverage of choice, and got rid of food groups (including dairy) altogether.

• Canada drops milk in healthy-eating guide

• Is Canada's food guide past sell-by date?

• Why cheese is no longer my friend

Instead, it said people should eat a variety of minimally processed food, including daily servings of protein like dairy.

The guide also specifically called out chocolate milk for contributing to the childhood obesity processes.

Andrew Scheer (right), leader of the Conservative Party of Canada

"I truly do believe that chocolate milk saved my son's life," Mr Scheer joked after taking a question from a dairy producer.

"The idea that these types of products that we've been drinking as human beings and eating as human beings for millennia - that now all of a sudden they're unhealthy - it's ridiculous," he added.

Mr Trudeau wasted no time in calling Mr Scheer out, accusing him of "declaring war on Canada's food guide".