Hidden risks and benefits for human health

        The primary concern many people have about genetically engineered (GE) crops is the safety of food made from them. Although there continues to be quite a bit of controversy over this issue, no evidence has been found that foods made with the genetically engineered crops now on the market are any less safe to eat than foods made with the same kinds of conventional crops. Genetically engineered crop varieties are being subjected to far greater scientific scrutiny than that ordinarily given to conventional varieties, even though many scientists have argued that there is no strict distinction between the food safety risks posed by genetically engineered plants and those developed using conventional breeding practices.

        Safety assessments of foods developed using genetic engineering include the following considerations:
• evaluation of the methods used to develop the crop, including the molecular biological data which characterizes the genetic change
• the evaluation for the expected phenotype
• the general chemical composition of the novel food compared to conventional counterparts
• the nutritional content compared to conventional counterparts
• the potential for introducing new toxins
• the potential for causing allergic reactions.

        The goal is not to establish an absolute level of safety, but rather the relative safety of the new product so that there is a reasonable certainty that no harm will result from intended uses under the anticipated conditions of production, processing and consumption. Since conventional crops have known histories of safe use given certain identifiable risk factors, genetically engineered crops are considered to have the same relative safety as their conventional counterparts if they do not differ significantly from conventional crops for these risk factors.

        Some critics of GE crops point out that a lack of evidence for harmful effects does not mean they do not exist, but just as likely could mean that we have not done the proper studies to document them.

        Some reject the idea that we face the same kinds of risks from GE crops as from conventionally developed crops, believing the genetic engineering process itself introduces unique risks. A major concern often expressed about GE food safety is the risk for unintentional, potentially harmful changes that may escape detection in the evaluation process. It is true that the number of factors that are examined for change is small compared to the total number of components produced by plants. Also, more extensive comparisons of plant chemical compositions would be difficult because complete data describing the composition of conventional crop plants, including knowledge of variability among different cultivars or that due to environmental influences, is lacking. The random nature of transgene insertion when making GE plants, it is argued, may cause disruption of important genes, causing significant effects but little obvious change to the plant's phenotype.

        Some people are allergic to proteins that occur naturally in soybeans, and they could have a reaction if they are exposed to either conventional or transgenic soybeans or soy products. Soybeans are one of the eight most common sources of food allergies. Although less common, some people have food allergies associated with corn and they could be affected by either conventional or transgenic corn. No allergic reactions attributable to the proteins present as a result of genetic engineering have been reported in the transgenic soybeans being grown commercially at this time. Reports of an allergenic protein made as a result of genetic engineering in one particular type of transgenic corn could not be confirmed by subsequent testing.

        While there isn't any evidence that allergens have been introduced into food crops by genetic engineering, two incidents have received quite a bit of publicity and caused public concern about food allergies resulting from transgenic crops.

        The first incident involved soybean plants being developed by Pioneer Hi-Bred in the early 1990's. Pioneer used a gene from Brazil nuts to make soybeans that contained higher levels of the amino acid methionine. They wanted to make a more nutritious chicken feed that would eliminate the need for expensive feed supplements. While these transgenic soybeans were being tested, research funded by Pioneer discovered that the protein made by the Brazil nut gene could cause allergic reactions in humans. Pioneer stopped development of these soybeans in 1993, and they were never sold or grown for market.

        The second incident involved reports of allergic reactions in people who may have eaten food containing the insecticidal protein called Cry9C, one of several forms of the Bt insecticide. The gene for this protein had been genetically engineered into Starlink corn by Aventis CropScience. Starlink corn had only been approved for use as animal feed or for industrial purposes, but not for human consumption, because tests made when Starlink was being developed showed the Cry9C protein had certain characteristics in common with other proteins known to be allergenic. When food from grocery shelves tested positive for Cry9C, demonstrating that Starlink had accidentally made its way into the food supply, a massive screening and recall effort was put into effect. During this time, the reports surfaced of allergic reactions in people who had eaten corn products that may have been contaminated by Cry9C. The Food and Drug Administration and Centers for Disease Control investigations that followed found 28 cases where people had apparently suffered allergic reactions to something, but the special test developed by the FDA (an enzyme-linked immunosorbent assay, or ELISA test, to detect people's antibodies to the Cry9C protein) did not find any evidence that the reactions in the affected people were associated with hypersensitivity to the Cry9C protein. The test isn't 100% conclusive, though, partly because food allergies may sometimes occur without detectable levels of antibodies to allergens. The EPA ruled on July 27, 2001, to keep a zero tolerance policy for Cry9C in food, based on the original suspicions of potential allergenicity. A more detailed discussion of concerns about food allergies resulting from transgenic crops is available in our discussion of allergies.