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There are No Fish Genes in Tomatoes

“If genetically modified foods were properly labeled, I could still eat tomatoes,” was the angry remark. I was puzzled by this, but the gentleman went on to clarify. “I have a fish allergy,” he said, “and I have no way of knowing which tomatoes have been modified with fish genes, so I just don’t eat any tomato products.” He need not have worried. There are no fish genes in tomatoes, and if there were, the tomatoes would have to be so labeled according to existing regulations. What we have here is fear generated by misinformation.

During a public lecture on genetic modification I described an experiment that involved enriching soybeans with the amino acid methionine. Soybeans are widely used to raise animals but are low in this essential amino acid often necessitating the use of methionine supplements. Brazil nuts produce a protein that is particularly rich in methionine so the idea was to isolate and clone the gene that codes for the production of the methionine-rich protein and insert it into the genome of the soybean.

This raised an obvious concern. Although the modified soybeans were to be used mostly for poultry, the possibility that they could somehow end up in human food had to be considered. What if a person allergic to Brazil nuts happened to consume these soybeans, possibly triggering a life threatening reaction? Testing of blood drawn from people allergic to Brazil nuts revealed that the antibodies they had produced in response to ingesting Brazil nut proteins also latched on to proteins in the engineered soybeans, indicating the potential for an allergic reaction. As a result the research was abandoned and the modified soybeans were never produced.

The first comment after my talk picked up on the allergen issue. “If genetically modified foods were properly labeled, I could still eat tomatoes,” was the angry remark. I was puzzled by this, but the gentleman went on to clarify. “I have a fish allergy,” he said, “and I have no way of knowing which tomatoes have been modified with fish genes, so I just don’t eat any tomato products.” He need not have worried. There are no fish genes in tomatoes, and if there were, the tomatoes would have to be so labeled according to existing regulations. What we have here is fear generated by misinformation.

The Arctic flounder lives happily in the ice cold waters of the Arctic Ocean, its blood prevented from freezing by an “antifreeze protein.” Since tomato growers live under the threat of a sudden freeze destroying their crop, researchers wondered about the possibility of inserting the flounder gene that codes for the antifreeze protein into the genome of the tomato. Preliminary experiments showed that in plants this protein was not effective in preventing ice crystal formation and the project was dropped. But on the Internet, no story ever dies. The “fish genes in tomatoes” myth lives on, often illustrated with syringes plunged into tomatoes, or drawings of tomatoes shaped like fish. Had the technology proved promising, it would have required extensive testing of the specific fish protein used to determine if it was involved in producing an allergic reaction.

Such testing is not required when novel conventionally produced foods are introduced into the market place. Kiwis are an interesting example. Allergy to the fruit did not exist in North America until some thirty years ago for the simple reason that kiwis were not eaten. With the expansion of global marketing kiwis are now found in every supermarket and correspondingly, allergies have increased. Introducing a novel fruit, like the kiwi, introduces hundreds of novel proteins, many with allergenic potential. On the other hand, genetic modification commonly introduces only one specific protein, meaning a reduced chance of an allergic reaction. This suggests that as far as allergies go, it is more important to focus on new foods, not on genetically modified ones. As people eat a wider variety of foods they will develop a wider variety of allergies, but this problem doesn’t get nearly as much attention as the potential reaction to a single protein in genetically modified food.