Protesters marched and waved signs in hundreds of cities around the world Saturday as part of a global demonstration against genetically modified foods.

In 436 cities in 52 countries, protesters took to the streets to "March Against Monsanto," one of the preeminent corporations in the industry. Monsanto, based in St. Louis, and its competitors engineer genetically modified seeds that are designed to resist pesticides, among other desirable traits including bigger crop yields and value-added nutritional benefits.

Most corn, soybean, and cotton grown in the United States now comes from genetically modified seed, which opponents say may harm human health and the environment. Health advocates who oppose genetically modified foods have been pushing the federal government to require food producers to label genetically modified foods, although government officials and many scientists say the technology is safe.

Tami Canal, a political activist who organized the protest, told reporters she was impressed by the turnout. "It was empowering and inspiring to see so many people, from different walks of life, put aside their differences and come together today," Canal said. "We will continue until Monsanto complies with consumer demand. They are poisoning our children, poisoning our planet," she said. "If we don't act, who's going to?"

The US Food and Drug Administration does not require food producers to label products as genetically modified or not, though many producers of "organic" foods have been lobbying for more regulation.

The Anonymous "hactivist" group also issued a statement criticizing Monsanto as a beneficiary of corporate subsidies from the federal government. Monsanto had no comment on the protests but emphasizes on its website that billions of people around the world depend upon mass-produced food -- and that during the next few decades humans will grow more food than was produced since the dawn of the agricultural revolution, 10,000 years ago.