A debate has raged around the potential risks and benefits of genetically modified (GM) foods for the last 20 years.

But opponents of GM foods like the Soil Association and Friends of the Earth fear GM foods may have the potential to harm both human health and the environment.

What are GM foods?

GM foods are foods derived from organisms whose genetic material (DNA) has been modified in a way that doesn't occur naturally, e.g. through the introduction of a gene from a different organism. Currently available GM foods stem mostly from plants, and microorganisms, but, in the future, foods derived from GM animals are likely to be introduced.

Friends of the Earth says that although food from 12 GM crops has been approved for sale in the EU, most UK supermarkets and food manufacturers have removed GM ingredients from their produce.

The arguments for GM

Most existing genetically modified crops have been developed to improve yield through resistance to plant pests or increased tolerance of herbicides. In the future, genetic modification could improve the nutrient content of food, reduce its allergenic potential or improve the efficiency of crop production.

Genes which enhance tolerance to drought, low temperatures or salt in the soil and which make plants grow faster can also be engineered into crops, opening up new areas for food production.

Professor Jonathan Jones, a senior scientist at The Sainsbury Laboratory and an expert on how plants resist disease, was featured on the Panorama programme.

“Producing enough food is hard, and currently there's a lot of control of disease and pests by spraying agrichemicals,” he said.

“We want to come up with crops that don't need to be sprayed because they're resistant, and also have some additional consumer benefits.”

As for the cons of GM foods, he says that most are without basis in fact.

“I can hardly bear to repeat them because they're all without foundation,” he said.

“GM opponents have this idealistic notion that we can have a perfect, utterly clean way of doing things, but this idealism isn't helpful because farming is a very pragmatic business. You've got to control weeds, so you need herbicides, and there are a lot of objections to them, but the question is, what's the least bad way to do it?

“The idealists suggest things could be done another way, without telling you what that other way is. They suggest there are unknown unknowns with regards to GM plants, but that's not true – we know what the unknowns are and can check for them.

“Anything that gets regulatory approval is completely safe, or at least as safe as its non-GM counterpart.”

The arguments against GM

GM opponents have a variety of concerns about genetically modified foods, particularly with regards to human health and the environment.

The World Health Organisation says the main fears for human health and GM foods are:

Allergic reactions - The potential to provoke allergic reaction by genes being transferred from commonly allergenic organisms to non-allergic organisms, No allergic effects have been found so far, says the WHO.

Gene transfer - The possibility of genes transferring from GM foods to body cells or to bacteria in the gut and adversely affecting human health. There's a particular concern that antibiotic resistance genes used when creating genetically modified organisms (GMOs), could be transferred. The WHO says the probability of such transfer is low.

Outcrossing - Concerns that the migration of genes from GM plants into conventional crops or related species in the wild ('outcrossing'), may have an indirect effect on food safety. Cases have been reported where GM crops approved for animal feed or industrial use were detected at low levels in products intended for human consumption.

Several countries have adopted strategies to reduce mixing, including clear separation of GM crop fields and conventional crops. However, the WHO stresses that GM foods currently available on the international market have passed safety assessments and aren't likely to present risks for human health.

Environmental fears - Issues of concern for the environment include the GM organism escaping and potentially introducing engineered genes into wild populations, the susceptibility of insects which aren't pests to the gene product, the loss of biodiversity, and increased use of chemicals in agriculture.

Helen Browning, chief executive of the Soil Association, says GM crops engineered to be resistant to weedkiller are leading to the use of “damaging” chemicals to control so-called ‘superweeds’ which are impervious to normal weedkiller.

“We still have millions of acres of GM crops that are harming the environment, sprayed with a chemical that is now thought be to be carcinogenic, and have not made any progress on maintaining consumer choice, labelling and liability for contamination of organic or non-GM crops,” she said.

“This just feels like propaganda to gain public acceptance of a technology that is doing such damage, and for which there is no recall button.”