As the debate rages in Europe on what are often branded there as "Frankenstein" foods, the United Nations' health agency said there was no evidence to suggest that any foods currently on the market posed health risks. In a 58-page report, the WHO said genetically-modified organisms (GMO) can increase crop yields and food quality, thereby improving health and levels of nutrition, as well as boost profits for farmers and industry.
But since some of the genes used in GMO crops have not been in the food chain before, the potential effects on health and society must always be assessed before they are grown and sold.
"We have no data suggesting that GMO foods on the market are not safe, but that is not the same as saying GMO foods in the future are automatically safe," said Jorgen Schlundt, director of the WHO's food safety department.
"Current GMO foods can bring benefits, but safety assessments must continue. That is one of the main conclusions of the report," he added.
No absolute guarantees could be given about any foods, whether scientifically modified or not, he said, noting that even in the United States 5,000 people died each year from microbiological infections such as salmonella poisoning.
Furthermore, the argument over GMOs was complex and involved questions ranging from the impact on the environment, which could vary from one country or region to another, to issues of intellectual property rights, Schlundt said.
The subject is sensitive in Europe, where consumers are generally suspicious of GMOs, and the European Union is locked in a trade row with the United States, Canada and Argentina over Brussels' reluctance to authorise new imports.
An initial ruling by the World Trade Organisation (WTO) is due in early October.
The WHO said some 800 million people in developing countries were undernourished, despite a 50 percent decline in world food prices over the past two decades, and the global population was expected to reach eight billion in 2025 compared to six at the moment.
Although they were not a panacea, GMOs could play a role in helping to meet future food needs. They could also help to remedy vitamin and iron deficiencies in some poorer populations.
"Producing nutritionally enhanced properties in staple crops eaten by the poor could reduce the burden of disease in many developing countries," the WHO said in the report.
By cutting down on the use of often health-threatening pesticides, GMO crops could also bring other benefits to farmers in poorer countries, it added.
But so far all this remained little more than a hope because most of the effort put into developing GMOs had focused on crops grown in the richer countries.