Most genetically engineered foods are essentially foods with added substances - usually proteins. This is because genes code for proteins, and when genetic engineers add a new gene to a crop plant they are in most cases adding a new protein to foods derived from the crop. In most cases these added proteins will likely prove safe for human consumption, although, just as with conventional food additives, substances added to foods via genetic engineering may in some instances prove hazardous.
Adding proteins to foods via genetic engineering may cause susceptible individuals to become allergic to foods they previously could safely consume. Allergic reactions cause discomforts and in some cases can cause life-threatening anaphylactic shock. Since known food allergens are proteins, foods with new proteins added via genetic engineering could sometimes become newly allergenic. For example, one company has already dropped plans to commercialize soybeans with a Brazil nut gene after testing revealed the soybeans were likely to cause allergic reactions in Brazil nut allergic individuals.
The European Union (EU) has banned since 1998 any genetically modified foods from the USA, an action that it says is based on the "precautionary principle" but which the USA says has no scientific basis. For example, the European Commission has frozen the approval process for a genetically modified type of corn following publication of a study that found bioengineered corn may harm butterflies (May 1999). The bacterium used to make Bt corn, Bacillus thuringiensis, is used by some farmers as an organic pesticide. Some studies have shown that continuous exposure to Bt creates resistant insects. The use of Bt corn, potatoes and cotton could destroy the effectiveness of a safe, natural pesticide that is of great value to many small farmers and all organic farmers.
Since 1997, the EU has effectively barred US corn imports over the possibility that genetically engineered varieties unapproved in the EU have mixed with sanctioned crops. That has cost American farmers access to a $200 million-a-year market. More losses are likely as other countries restrict new biotech crops approved in the United States.
The Five-Year Freeze Coalition, an 86-member body representing 2.5 million people, has called for a moratorium on the growing and importing of all genetically modified foods in England.
In 2002, Zambia rejected 26,000 tonnes of US food aid, despite its famine, on the grounds that it contained GM crops which would pollute its seed stock and hurt exports.