Natural RNA, Transgenic DNA, and What They Actually Mean for Our Food

By Veronique Greenwood | January 13, 2012 2:33 pm

rice

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.

Here is where the trouble starts. LeVaux leapt immediately from “miRNA from plants can affect gene expression in humans” to “Genetically modified organisms will have miRNAs that could be dangerous to us” (paraphrasing here). It is reasonable to wonder whether miRNA that survives digestion might represent a new way that plants can have an effect on our health, a way that may not be accounted for in current safety regulation. In fact, that’s not a bad topic for a thoughtful essay. But in his (original) Atlantic article, LeVaux skipped a number of logical steps, and did not present this as an interesting possibility that could relate to any kinds of plants and animals we eat. Instead, he leaped to pin GMOs, and in so doing, missed the point that we don’t know right now whether the miRNA of any food affects human health. We have just one interesting finding at the moment, and other scientists and science writers are curious as to whether the miRNA really does come directly from food, since, as biologists can attest, RNA is pretty fragile stuff that can be destroyed by marauding enzymes even in tidy labs. How the heck it makes it through digestion will be hugely fascinating, if it indeed does. For more information on how LeVaux’s description of genetic modification is flawed, check out this post from Christie Wilcox at Scientific American.

As it turns out, what LeVaux was actually hoping to write about, judging from the updated piece, is the idea of “substantial equivalence,” which allows companies producing genetically modified foods to have their products considered by the FDA to be basically the same as unmodified versions. Ah, now that’s a topic with some meat on it.

Substantial equivalence is a concept developed in 1991 by the OECD, a group of nations that deals with international economic issues. It states that if a genetically modified food has biochemistry that falls within the range of the normal version of the food—same amount of certain proteins, same amount of nutrients, same basic nutritional profile—it shouldn’t require any safety testing before being deployed. (The principle also applies to new medical devices, if they are substantially equivalent to what already exists.) In the two decades since this approach was devised, millions of people have been eating genetically modified foods (primarily corn, soy, and canola), and there have been no credible reports of it causing health problems.

But it wouldn’t hurt to examine the way we regulate genetically modified foods with an eye toward making it more transparent. There is great interest on the part of the companies involved to make the regulatory process quicker, and the FDA, unfortunately, is notoriously overworked. Moreover, it’s surprisingly difficult for the interested consumer to find clear, recent information about how substantial equivalence is applied in practice. The FDA has an easy-to-find, thorough primer on how drugs are regulated; it would be nice if they provided similar information on what are still, at this point, relatively new foods.

Image courtesy of  AMagill / flickr

  • http://www.scienzeascuola.it Dr. Lombardo

    This kind of news demonstrates that is like we were little children playing with fire. It’s necessary more and more a prudential approach when one handles cells and their nuclei.

  • http://www.flashinthepan.net Ari LeVaux

    Thank you for understanding that my column was about substantial equivalence. The adequacy, or lack thereof, of this concept is a discussion worth having. Unfortunately, the holes in my science in the first draft distracted from my point.

    And thank you for acknowledging the new version of my piece. I’m sorry to see that, other than patting me on the back for doing it, you chose to ignore it.

    Oddly, you chose to paraphrase me here, as arguing:

    “‘Genetically modified organisms will have miRNAs that could be dangerous to us’ (paraphrasing here).”

    I’m curious why you did not use an actual quote to support that assertion. Could you not find one?

    You also wrote:

    “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”

    You claim to have read the rewrite, which clearly states:

    “This study had nothing to do with genetically modified (GM) food, but it could have implications on that front. The work shows a pathway by which new food products, such as GM foods, could influence human health in previously unanticipated ways.”

    I would like to ask, what is the point of rewriting a piece, other than a pat on the back, if I’m still held to my original, inferior argument?

    Please address my new argument. Shoot holes in it then, I’m sure you could. And paraphrase responsibly.

  • Diana

    So this is one way rice increases risks of cardiac failure in humans?

  • Pingback: Discover Magazine disses and discusses my column | Flash in the Pan

  • Christian

    The USDA, particularly APHIS, is the agency in charge of making the decision to deregulate GMOs. The FDA would only have a hand in the matter if the plant/animal were modified to produce pharmaceuticals. The real issue is that none of the GMO producers have long-term studies on the health effects of their products. I’m talking about generational/multi-generational studies in something other than mice. Humans thrived on a food supply developed naturally over the course of billions of years, and more recently (within the last 10,000) on a food supply selected by desirable traits. Introducing genes from foreign organisms, that could never have bred in nature, and subsequently releasing these organisms into nature–well, that is a cause for alarm given the lack of long-term knowledge concerning these organisms in nature.

  • http://appliedmythology.blogspot.com Steve Savage

    There is no logical connection to existing GMO foods on this topic. You did pretty well on the science up to that

  • David

    No thanks to the organic, heirloom wheat I grow in my own field and hello GMO wheat from the perennial winner of ‘The Most Responsible Company On The Planet’ award Monsanto!!!

    While I’m at it I’ll skip the truly free range, organic chickens I raise in my yard and have a double helping tonight of some wonderful factory farmed Tyson-brand chicken fed some of these wonderful GMO grains that are going to allow us to save the world by adding a few more billion to the planet’s population.

  • Pingback: Genetically Modified Shitstorm | Flash in the Pan

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