The battle over GMOs (Genetically Modified Organisms): are GMOs the answer to feeding a hungry world, or Frankenfoods that put the environment--and us--at risk?

• Author: Potenza, Alessandra
• Position: SCIENCE

Thousands of people recently took to the streets in 400 cities worldwide. The cause of their anger? Not oppressive governments, unemployment, or income inequality, but apples that don't brown when sliced and corn that's bred to fight off insects. In short, GMOs--genetically modified organisms.

In Los Angeles, protesters chanted, "Hell no GMO!" In Strasbourg, France, demonstrators held a minute of silence in front of the European Parliament. And in Rio de Janeiro, Brazil, people accused GMO producers of "bioterrorism."

GMOs are organisms whose DNA has been combined with a gene from an unrelated species to produce a desired trait. Some crops are genetically modified to survive herbicide sprays that kill weeds. Others are engineered to be more nutritious: A pink pineapple awaiting U.S. government approval has the same antioxidant that makes tomatoes red and may help prevent cancer. In November, the U.S. Food and Drug Administration approved the first genetically modified animal: a salmon engineered to grow to market size in about half the time as a regular salmon.

But GMOs haven't been very popular lately. Only 37 percent of Americans think they're safe to eat, according to the Pew Research Center. McDonald's recently refused to use a new genetically modified potato that produces less of a cancer-causing chemical when fried. Chipotle dropped GMOs from its U.S. offerings. And General Mills stopped using GMOs in original Cheerios after a yearlong campaign by environmentalists.

'I Don't Think We Know Enough'

While some see GMOs as Frankenfoods that hurt the environment, and us, others see them as the most promising solution to feeding the world's population, which is expected to skyrocket from 7 billion today to 10 billion by 2050. The government agencies regulating GMOs in the U.S. say they're safe. But some scientists and consumers argue that GMOs haven't been around long enough for us to know their long-term health effects.

"We're putting genes into crops that have never been in the food supply before," says Doug Gurian-Sherman, a scientist at the Center for Food Safety, a nonprofit organization opposing GMOs. "I don't think we know enough."

The first GMO, a tomato that ripened without softening, was sold in the U.S. in 1994. (It was later taken off the market.) In 1996, soybeans and corn that resist herbicides and kill pests were introduced. Both crops proved extremely popular with farmers. Today, 94 percent of soybeans and 93 percent of corn...