Organizers say more than 400 demonstrations took place around the world on Saturday, in an effort to call attention to what the protesters claim are dangers posed by genetically modified food and the food giants that produce it.

The "Occupy Monsanto" group focused their efforts on one corporation — Monsanto, a leading producer of genetically engineered seed.

Rallies were held across Canada and the United States, in Europe, Australia, Brazil, Colombia and South Africa, among others.

Genetically modified plants or organisms, commonly called GMOs, are often created to resist disease and eliminate the need for pesticides.

In Vancouver, where about 400 people marched through downtown streets, organizer Lili Dion called on the public to educate themselves.

"I want people to ask questions," she said. "A lot of people, it's surprising, don't know what GMOs are, or the lack of testing and how much it is in our food. So I just want people to ask questions... do your own research."

Rachel Parent, 14, called for labelling on all GMO products during Saturday's rally in Toronto.

"That way people have the freedom of choice and that way they can choose for themselves," she told CBC News. "If they don't have GMO labelling maybe they have something to hide."

The GMO debate

The term "genetically modified" refers to the alteration of genetic material. Specifically, it means the genes of one organism have been "cut out" and then "pasted" into another organism.

Desired characteristics, such as a hardier texture, higher nutritional value or faster growth, are chosen to produce a kind of "super food."

However, GMOs have been the source of much public debate regarding their necessity and safety.

Most processed foods in Canada contain at least some genetically modified ingredients. Companies are not required to label products that contain GMOs, but in the European Union there have been regulations requiring such labels for more than a decade.

Monsanto Co., based in St. Louis, Mo., has said that, while it respects people's rights to express their opinion on the topic, it maintains that its seeds improve agriculture by helping farmers produce more from their land while conserving resources such as water and energy.

GMOs safe: Health Canada

On Saturday, former Health Canada scientist Shiv Chopra spoke at a rally in Toronto accusing the agency of not assessing the risks associated with GMOs.

"Any product must be proven to be safe in advance of sale, in advance of distribution," he said. "Health Canada has never received any such results."

CBC News contacted Health Canada for comment, but did not receive a response.

On its website, Health Canada says it requires genetically modified food manufacturers to submit data for safety assessments and that the agency considers GMOs to be safe.