Detractors cite several reasons for concern. Perhaps proteins made from the foreign genes will be directly toxic to humans. Maybe the genes will alter the functioning of a plant in ways that make its food component less nutritious or more prone to carrying elevated levels of the natural poisons that many plants contain in small amounts. Or perhaps the modified plant will synthesize proteins able to elicit allergic reactions. They are examining claims of allergic reactions to foods harboring that corn, but a scientific advisory committee has determined that the amounts in consumer products were quite low and thus unlikely to provoke allergic reactions.
Proponents offer a number of defenses for genetically engineered foods.
Inserting carefully selected genes into a plant is safer than introducing thousands of genes at once, as commonly occurs when plants are crossbred in the standard way. GM crops designed to limit the need for toxic pesticides can potentially benefit health indirectly, by reducing human exposure to those chemicals. More directly, foods under study are being designed to be more nutritious than their standard counterparts. Further, GM crops that produced extra nutrients or that grew well in poor conditions could provide critical help to people in developing nations who suffer from malnutrition. Advocates note, too, that every genetically engineered food crop has been thoroughly tested for possible health effects.