A new toxicology study states that rats eating genetically modified food and the weedkiller Roundup develop huge tumors and die. But many scientists beg to differ, and a close look at the study shows why.
Genetically modified organisms (GMOs) have always been a controversial topic. On the one hand are the many benefits: the higher crop yields from pesticide- and insect-resistant crops, and the nutritional modifications that can make such a difference in malnourished populations. On the other side is the question that concerns many people: We are modifying the genes of our food, and what does that mean for our health? These are important question, but the new study claiming to answer them misses the mark. It has many horrifying pictures of rats with tumors, but without knowledge about the control rats, what do those tumors mean? Possibly, nothing at all.
The recent study, from the Journal of Food and Chemical Toxicology has fueled the worst fears of the GMO debate. The study, by Italian and French groups, evaluated groups of rats fed different concentrations of maize (corn) tolerant to Roundup or Roundup alone, over a two year period, the longest type of toxicology study. (For an example of one performed in the U.S., see here.) The group looked at the mortality rates in the aging rats, as well as the causes of death, and took multiple samples to assess kidney, liver, and hormonal function.
The presented results look like a toxicologist’s nightmare. The authors reported high rates of tumor development in the rats fed Roundup and the Roundup-tolerant maize. There are figures of rats with visible tumors, and graphs showing death rates that appear to begin early in the rats’ lifespan. The media of course picked up on it, and one site in particular has spawned some reports that sound like mass hysteria. It was the first study showing that genetically modified foods could produce tumors at all, let alone the incredibly drastic ones shown in the paper.
Christina Agapakis is a synthetic biologist and postdoctoral research fellow at UCLA who blogs about about biology, engineering, biological engineering, and biologically inspired engineering at Oscillator.
When you factor in the fertilizer needed to grow animal feed and the sheer volume of methane expelled by cows (mostly, though not entirely, from their mouths), a carnivore driving a Prius can contribute more to global warming than a vegan in a Hummer. Given the environmental toll of factory farming it’s easy to see why people get excited about the idea of meat grown in a lab, without fertilizer, feed corn, or burps.
In this vision of the future, our steaks are grown in vats rather than in cows, with layers of cow cells nurtured on complex machinery to create a cruelty-free, sustainable meat alternative. The technology involved is today used mainly to grow cells for pharmaceutical development, but that hasn’t stopped several groups from experimenting with “in vitro meat,” as it’s called, over the last decade. In fact, a team of tissue engineers led by professor Mark Post at Maastricht University in the Netherlands recently announced their goal to make the world’s first in vitro hamburger by October 2012. The price tag is expected to be €250,000 (over $330,000), but we’re assured that as the technology scales up to industrial levels over the next ten years, the cost will scale down to mass-market prices.
Whenever I hear about industrial scaling as a cure-all, my skeptic alarms start going off, because scaling is the deus ex machina of so many scientific proposals, often minimized by scientists (myself included) as simply an “engineering problem.” But when we’re talking about food and sustainability, that scaling is exactly what feeds a large and growing population. Scaling isn’t just an afterthought, it’s often the key factor that determines if a laboratory-proven technology becomes an environmentally and economically sustainable reality. Looking beyond the hype of “sustainable” and “cruelty-free” meat to the details of how cell culture works exposes just how difficult this scaling would be.
Earlier this week, food columnist Ari LeVaux set off a storm of media reaction with a piece with this premise: tiny plant RNAs, recently discovered to survive digestion and alter host gene expression, are a major reason why genetically modified foods should be considered dangerous. For anyone familiar with the paper he referred to, or with molecular biology in general, the article was full of conflation and sloppy logic, and even as it became the most-emailed story on TheAtlantic.com, where it was published, biology bloggers and science writers were pointing out its significant flaws. To his credit, LeVaux revised the article to fix many (though not all) of the errors concerning genetics; the new version appeared yesterday at AlterNet and today replaced his original piece at The Atlantic.
So what did LeVaux get so wrong, and, once all of the wheat was sorted from the chaff, was there anything to what he was trying to say?
At the heart of the fracas is LeVaux’s claim that a class of molecules called miRNA is a reason to fear GMOs specifically, more than any other food plant or animal. miRNA, which is short for microRNA, is a class of molecules that perform various tasks in plants and animals. They were first discovered about twenty years ago, in nematode worms, and they regulate gene expression by binding the messenger RNA involved in translating a gene into a protein. The messenger RNA carries the “message” of the DNA’s sequence to a group of enzymes that translate it into the amino acid sequence of a protein. But if a miRNA binds to a messenger RNA, the message is destroyed, and the protein is never made. Thus, miRNA can be a powerful tool for preventing the expression of genes. In fact, that is what’s made it such an important lab tool in recent years: it allows researchers to knock down the expression of genes without physically removing them from an organism’s genome.
In the paper that LeVaux pegged his article on, Nanjing University researchers found that miRNAs usually seen in rice were circulating in the blood of humans, and that mice fed rice had the miRNA in their blood as well. That particular miRNA, in its native context, regulates plant development. When the researchers added it to human cells, it appeared to bind to the messenger RNA of a gene involved in removing cholesterol from the blood. Previous papers had found that plants have plenty of miRNA floating around in them [pdf] (as does just about everything we eat, since plants and animals make them by the thousands), but having them show up whole and unmolested in blood, apparently after digestion, was a new and very intriguing discovery.