Many a word has been spilled in connection with the scientific investigation of crops variously referred to as "transgenic," "bioengineered," "genetically engineered" or "genetically modified." In every case, what's being referred to is an otherwise ordinary fruit, vegetable, or fiber source into which genetic material from a foreign species has been inserted for the purpose of making that crop, say, sturdier or more drought- or herbicide- or pest-resistant.
Derided as "Frankenfoods" by critics, these crops have been accused of everything from being responsible for a very real global uptick in allergic diseases to causing cancer and autoimmune disease. But (flying in the face of the first accusation) allergic disorders are also rising in Europe, where genetically modified, or GM, crops' usage is far less widespread than in North America. It's the same story with autoimmune disease. And claims of a link between genetically modified crops and tumor formation have been backed by scant if any evidence; one paper making such a claim got all the way through peer review and received a fair amount of Internet buzz before it was ignominiously retracted last year.
But a huge natural experiment to test GM crops' safety has been underway for some time. Globally, between 70 and 90 percent of all GM foods are consumed by domesticated animals grown by farmers and ranchers. More than 95 percent of such animals - close to 10 billion of them - in the United States alone consume feed containing GM components.
This was, of course, not the case before the advent of commercially available GM feeds in the 1990s. And U.S. law has long required scrupulous record-keeping concerning the health of animals grown for food production. This makes possible a before-and-after comparison.
In a just-published article in the Journal of Animal Science, University of California-Davis scientists performed a massive review of data available on performance and health of animals consuming feed containing GM ingredients and products derived from them. The researchers conclude that there's no evidence of GM products exerting negative health effects on livestock. From the study's abstract:
Numerous experimental studies have consistently revealed that the performance and health of GE-fed animals are comparable with those fed [otherwise identical] non-[GM] crop lines. Data on livestock productivity and health were collated from publicly available sources from 1983, before the introduction of [GM] crops in 1996, and subsequently through 2011, a period with high levels of predominately [GM] animal feed. These field data sets representing over 100 billion animals following the introduction of [GM]crops did not reveal unfavorable or perturbed trends in livestock health and productivity. No study has revealed any differences in the nutritional profile of animal products derived from[GM]-fed animals.
In other words, the 100 billion GM-fed animals didn't get sick any more frequently, or in different ways. No noticeable difference at all.
Should that surprise us? We humans are, in fact, pretty transgenic ourselves. About 5 percent of our own DNA can be traced to viruses who deposited their genes in our genomes, leaving them behind as reminders of the viral visitations. I suppose that's a great case against cannibalism if you fear GM foods. But I can think of other far more valid arguments to be made along those lines.
Previously: Ask Stanford Medicine: Pediatric immunologist answers your questions about food allergy research, Research shows little evidence that organic foods are more nutritional than conventional ones and Stanford study on the health benefits of organic food: What people are saying
Photo by David B. Gleason