Protesters gathered in cities across the globe this weekend to rally against the American biotechnology giant Monsanto.

The third-annual March Against Monsanto was held in several major Canadian cities, including Toronto, Winnipeg, Calgary and Vancouver. In total, organizers said that events were being held in 428 cities in 38 countries.

The Montreal event was held, unusually, on Sunday at Dorchester Square. About 150 took part in the event.

In Toronto, protesters rallied outside of Queen's Park, before making their way across the city to a GMO-free festival and farmers market.

The group said that the event provides an opportunity for people to educate themselves about the "environmental and health effects" associated with GMOs.

Monsanto is one of the world's foremost producers of genetically engineered seeds.

"(The protest) raises the issues of corporate control over seeds and also environmental issues and issues around our democracy," Lucy Sharratt, a co-ordinator for the Canadian Biotechnology Action Network, told CTV Toronto.

"Can consumers and farmers have something to say about the future of our food system?" she added.

March Against Monsanto's website says that studies show genetically-modified foods "can lead to health conditions, such as the development of cancer tumours, infertility and birth defects."

However, a study conducted by Pew Research in January, found that 88 per cent of U.S. scientists connected with the American Association for the Advancement of Science believe genetically modified foods are "generally safe" for consumption.

The report also showed that the public doesn't share their confidence in genetically modified foods, as more than 57 per cent of those polled believe they are "generally unsafe" to eat.

Despite concerns, Monsanto insists its products are safe.

"Plants and crops with GM traits have been tested more than any other crops – with no credible evidence of harm to humans or animals," says the company's website.

The World Health Organization also says that genetically modified foods currently available on the international market "are not likely to present risks for human health."

This year's protest is being held partly in response to California's failed bid to require labels on genetically modified foods – it’s a provision that some Canadians also hope to see introduced at home.

"You should know everything that's being put inside your body and we don't have that choice because it's not being labelled," Ashley Watsko, one of the 100 protesters who attended a rally outside the Manitoba Legislative Building in Winnipeg, told CTV News.

Protester Shannon McGimpsey also called for increased regulation on GMO crops.

"I think it would be good for the government to show that they're putting people first as opposed to these multi-million dollar companies," said McGimpsey, who attended the demonstration in Winnipeg.

Monsanto is also behind the hugely popular herbicide glyphosate, more commonly known as Roundup.

Protesters say the weed-killer is also harmful to the health of humans.

"Roundup is the most widely used herbicide in the world, even though it has been linked to cancer, kidney and liver disease, infertility, chronic digestive disorders and other illness," said a statement from rally organizers.

A report from WHO released in March classified Roundup as "probably carcinogenic to humans."

And in the face of fears about Monsanto's products, many farmers continue to stand by the company.

Farmer Charles Fossey told CTV Winnipeg that his genetically modified canola fields, which are resistant to certain pesticides, allows him to protect his crop when he sprays to kill weeds and insects.

Fossey said that thanks to this innovation, he harvests 50 bushels per acre, twice as many as unmodified canola seeds.

"There are a lot of benefits to consumers: It provides them with healthier, better crops (and) it gives farmers more choices to control pests," Fossey told CTV News.

With a report from CTV News' Genevieve Beauchemin and CTV Toronto