Before a GM crop can be grown or eaten, it must be assessed for risks to human health and the environment. In the UK this is overseen by government regulators, and each crop is assessed case by case.Human health
• Allergens: a new protein could trigger allergies. Each new protein is compared with known allergens and tested, which is how the allergenic Brazil nut gene soya was detected.
• Toxins: the crop is checked for harmful substances and for unexpected changes in its composition.
• Antibiotic resistance: there was concern that antibiotic resistance marker genes could pass from GM food to gut bacteria. Transfer of genes between unrelated organisms is called horizontal gene transfer. The risk is thought to be very low, but marker genes are now often removed or replaced.Environment
• Genes may spread by pollen to wild relatives. Weeds that gain herbicide tolerance are sometimes called superweeds.
• Toxins such as Bt protein could harm non-target insects, such as pollinators.
• Pests and weeds may evolve resistance.
To study these risks, crops are grown in controlled field trials before approval, often with buffer zones around them.Evaluating the evidence
Major scientific bodies have concluded that approved GM foods are as safe to eat as conventional foods. When judging a study, consider whether it was peer-reviewed, repeated by others, had a control group and used a large enough sample size. A single small study claiming harm is much less reliable than many large studies showing none. Long-term effects are harder to rule out, which is why monitoring continues after approval.
• Allergens: a new protein could trigger allergies. Each new protein is compared with known allergens and tested, which is how the allergenic Brazil nut gene soya was detected.
• Toxins: the crop is checked for harmful substances and for unexpected changes in its composition.
• Antibiotic resistance: there was concern that antibiotic resistance marker genes could pass from GM food to gut bacteria. Transfer of genes between unrelated organisms is called horizontal gene transfer. The risk is thought to be very low, but marker genes are now often removed or replaced.Environment
• Genes may spread by pollen to wild relatives. Weeds that gain herbicide tolerance are sometimes called superweeds.
• Toxins such as Bt protein could harm non-target insects, such as pollinators.
• Pests and weeds may evolve resistance.
To study these risks, crops are grown in controlled field trials before approval, often with buffer zones around them.Evaluating the evidence
Major scientific bodies have concluded that approved GM foods are as safe to eat as conventional foods. When judging a study, consider whether it was peer-reviewed, repeated by others, had a control group and used a large enough sample size. A single small study claiming harm is much less reliable than many large studies showing none. Long-term effects are harder to rule out, which is why monitoring continues after approval.