The genetically modified food controversy is a dispute over the advantages and disadvantages of genetically modified (GM) food crops.

Laws regarding GM-food Safety is a major point of controversy. As of 2004 no adverse health effects in humans had been documentedrp: 8 and feeding trials had not observed toxic effects, but adverse health effects need to be screened for, because health effects are dependent upon the modifications made.NRC. (2004). Safety of Genetically Engineered Foods: Approaches to Assessing Unintended Health Effects. National Academies Press. Free full-text.rp: 8 The need for screening and testing increases as more changes are made, and as of 2005 scientists forecasted that "second-generation" GMs will require more testing.

Safety disputes

The only requirement for approval of genetically engineered food products is that it should be grossly similar to its natural counterpart. This is called the principle of "substantial equivalence". To decide if a modified product is substantially equivalent, only a limited set of characteristics selected and tested by the manufacturer are compared. If this procedure reveals no significant difference between the genetically engineered product and its natural counterpart, then no further food safety testing is required.

Critics argue that regulators should use independent studies, not industry studies for substantial equivalence, to prevent manipulation of data. An independently funded researcher, Professor Bela Darvas of Debrecen University was refused more Mon 810 corn to use in his studies after informing Monsanto that the variety was lethal to two Hungarian protected insect species and an insect classified as a rare. A cited example of what they considered an inadequate industry study was the approval of Novartis E 176 corn after being tested for only two weeks with three cows.

In 1989, Showa Denko genetically engineered a diet supplement to produce tryptophan at high levels which unexpectantly also produced trace amounts of a toxic dimerisation tryptophan product which caused Eosinophilia-myalgia syndrome. In the first months of use 37 people died and 1500 became permanently disabled. It is believed several hundred more have since died. The GE product was a purified single chemical which had passed the required substantial equivalence testing. Some scientists arguing for extreme caution in dealing with genetically engineered foods point out that if the substance had caused delayed harm, such as cancer 20 years later there would have been no way to attribute the harm to the cause.

A media firestorm erupted in 1998 when scientist Árpád Pusztai, who works on plant lectins, found that rats fed potatoes genetically modified to contain lectin developed immune system damage and other serious health problems. Even though the lectin itself caused no adverse effects his conclusion was that the GM process had somehow made the potatoes less nutritious. He felt he had a duty to speak out, "'just to inject some caution into this business". Rowett Institute's director, Philip James who had initially supported Pusztai, suspended him and used misconduct procedures to seize the data. His annual contract was not renewed and both Pusztai and his wife were banned from speaking publicly. After it was revealed that James had received two phone calls from the Prime Minister's office prior to implementing the ban, his supporters claimed that James had come under pressure from Downing Street to "put the lid on" Pusztai. Later a senior Rowett manager claimed Bill Clinton had telephoned Tony Blair and told him to sort out the problem. Although James denied the calls ever took place, Professor Robert Orskov OBE claims he was told that the phone calls went from Monsanto to Clinton to Blair.