Were Foods Made From Bt Corn Removed from the Market Because of Allergenicity Concerns?Response:
An example of a commercialized GE crop that was recalled owing to concerns about allergenicity is StarlinkTM corn, a variety engineered to express the Bt Cry9C protein (see “Is the Bt Protein Safe for Human Consumption?”). The EPA did not approve use of StarLinkTM corn for for human consumption; animal consumption was approved because farm animals do not have food allergies. The concern was that the Cry9c protein shared several molecular properties with proteins that are known food allergens (1)— namely, increased heat stability and slower digestibility characteristics. While additional testing was being conducted to determine human safety, StarlinkTM entered the human food supply because of problems encountered with segregating feed and food corn. As a result, the FDA issued a recall of numerous food products containing StarlinkTM corn.
In October 2000 the FDA asked the Centers for Disease Control and Prevention (CDCP) to investigate 51 reports of human illness that individuals claimed were related to consumption of products containing StarlinkTM corn. Of the 51 reports, 28 described symptoms consistent with a possible allergic reaction to corn products. Blood serum samples from 17 patients were tested using an enzyme-linked immunosorbent assay (ELISA) to detect antibodies to the Bt protein. The CDCP study (1) concluded that StarlinkTM-specific antibodies were not detected in those human sera; however, the study was not conclusive for two reasons. First, food allergies can occur in individuals even if they have no detectable allergy-specific antibodies that bind to the allergen (2). Second, the source of the protein to make antibodies was of bacterial origin, not plant, and this could have changed the conformational shape of the protein, compromising the ability of the antibodies to recognize the plant-made protein. However, researchers analyzed the corn-containing foods consumed by 10 of the 17 test subjects who reported allergic reactions. Detection of Bt protein was negative in 9 of 10 samples; the tenth was inconclusive (3)
Taken together, these results suggest that the Bt protein in StarlinkTM was not involved in the allergic reactions of the 17 individuals tested. But uncertainty still exists because blood and food samples were not received from all 28 individuals who experienced a true allergic reaction. In separate studies, an EPA scientific advisory panel concluded that the Bt in StarlinkTM had a moderate chance to cause allergies, on the basis of its biochemical nature. But the level of its presence in food at that time was low; Starlink corn represented between 0.4–0.5% of U.S. corn production (4) and levels of protein also influence its potential for allergenicity (5). StarlinkTM corn was removed from the market in 2000 and, on the basis of USDA monitoring, the food supply is now 99.99% Starlink free (6) and StarlinkTM corn therefore is not currently likely to cause allergy-related problems.
1. Cent. Dis. Control Prev. 2001. CDC report to FDA: Investigation of human health effects associated with potential exposure to genetically modified corn. June 11. http://www.cdc.gov/nceh/ehhe/Cry9cReport/pdfs/cry9creport.pdf. Last accessed 2011-12-8. PDF
2. Ogura Y, Ogura H, Zushi N, Morita H, Kurashige T. 1993. The usefulness and the limitations of the radioallerosorbent test in diagnosing food allergy in atopic dermatitis. Arerugi—Jpn. J. Allergol. 46:748–56
3. Environmental Protection Agency. 2001. White Paper on the Possible Presence of Cry9C Protein in Processed Human Foods Made from Food Fractions Produced through the Wet Milling of Corn. http://www.epa.gov/scipoly/sap/meetings/2001/july/wetmilling.pdf. Last accessed 2011-11-28. PDF
4. Segarra AE, Rawson JM. 2000. StarLink Corn Controversy: Background , CRS Report RS20732, November 17, 2000. http://www.cnie.org/nle/crsreports/agriculture/ag-51.pdf. Last accessed 2011-11-28. PDF
6. US EPA Off. Pesticide Programs. 2007. (Draft White Pap.) Concerning Dietary Exposure To Cry9c Protein Produced By Starlink® Corn And The Potential Risks Associated With Such Exposure, Oct. 16