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Science and Repeatability: A Case in Point

Featured Article

By Jay Petrick, Ph.D., DABT*
Senior Toxiciologist

The laws of nature are pretty consistent. If I heat a pot of water to 212 degrees over and over and over again, it starts to boil every single time. That makes me confident in saying water boils at 212 degrees.

But what if one of my neighbors says he got water to boil at 180 degrees, and no one else in the neighborhood can recreate the result in their own kitchen? It’s more likely his thermometer is broken than he’s discovered something new about the boiling point of water.

That’s why repeatability is so important to good science. If an experiment in one lab gets a certain result, and scientists in other labs obtain the same result, then we can be pretty confident that the experiment’s findings are reliable, which helps us understand the world a little better.

The reality is that sometimes experimental results cannot be repeated because they aren’t reliable, often because some unknown or unseen aspect of the experiment influenced the results.  Scientists are required to publish their methods so that other scientists can repeat their work and confirm their findings.  Knowledge is based on evidence and is built on data that is testable and confirmable.  So when data cannot be validated, they should be treated with healthy skepticism until confirmed.

You might be familiar with some examples of this. A 1998 study claimed a link between vaccines and autism but subsequent critical analysis discredited the findings.  Some scientists challenge the fact that human activities are contributing to climate change, although the overwhelming number of scientists is convinced.  Certainly, there always will be differing views in science based on uncertainty, but to deny the weight of evidence can have consequences.

Confusion Created

A more recent example is a study published in 2012 that got some attention because its findings seemed to conflict with a lot of what we know about food – specifically with our understanding about what happens to the ribonucleic acid (RNA) in the foods we eat.

Sure enough, in the time since the paper was published, other scientists haven’t been able to reproduce the original results. This really isn’t that surprising, given the extraordinary claims and their implications for human health. But since the original study is sometimes touted as evidence that the foods we eat could have unexpected and troubling impacts on our bodies, it’s worth taking a closer look.

Mice, Rice, and RNA

Every living thing – from apples, to chickens, to you and me – uses RNA to carry information and regulate various biological functions. That means most foods you’ve ever eaten naturally contain a large variety of RNA molecules.

Certain RNAs, called microRNAs (miRNAs), regulate biological processes through a process called RNA interference (RNAi).  Plants, animals, humans and other higher organisms utilize RNAi.  It’s a critical part of your body and your biology.

The 2012 study suggested that the miRNA in rice might be able to interact with the RNA in mice. The authors of that study also reported finding plant miRNA in human blood samples (L. Zhang et al., 2012). That one study led some to jump to unsupported conclusions. Some even used it to assert that RNA in your food could actually impact your own biological processes.  If this were true, it could mean – for instance – that eating a carrot or an egg could potentially result in RNA from that carrot or egg directing the function of your own genes.

The Facts

So, can RNAs in your food create changes inside of you? The short answer is no, and many scientific studies suggest that this kind of impact does not happen. Let’s take a look at the facts.

Recent scientific studies have shown that miRNA occasionally seen in animal data sets resulted from contamination in the laboratory procedures (Y. Zhang et al., 2012). They’ve included feeding trials of monkeys (Witwer et al., 2013), humans and mice (Snow et al., 2013) that failed to demonstrate any biologically relevant uptake. And the pharmaceutical industry has spent significant sums of money over the years trying to find a way to make RNA-based drugs that could be given orally. But despite all that effort, they haven’t found any way to prevent RNA drugs from being digested and inactivated when administered orally.

But the most compelling fact is that when other scientists have run L. Zhang’s experiment, they’ve gotten a different result. This is described in a new publication by Dickinson and colleagues in the November 2013 issue of Nature Biotechnology, which was the subject of commentary by the journal. This paper essentially duplicated the study of L. Zhang et al, however, Dickinson and colleagues ensured that the feeding study was appropriately controlled. Using two very sensitive detection methods, Dickinson found no apparent uptake of the same miRNA measured by Zhang and colleagues. Instead, the study provided strong evidence that nutritional differences and experimental variation, rather than ingested miRNAs, were responsible for the observed changes reported in the earlier mouse feeding studies.

In a follow-up rebuttal to the most recent Nature Biotechnology study, Chen et al. (2013), try to assert that all methodology used by Dickinson and colleagues is flawed, while ignoring comparable supporting studies in the literature (e.g. Witwer & Snow publications). In addition, they ignore the key finding that a nutritionally equivalent diet with higher levels of miRNAs than reported in the initial study did not produce the reported biological response.  This clearly demonstrates that the observed changes in serum composition of the mice were due to dietary influences rather than the miRNA in question.

To put things simply, the bulk of available evidence supports what has long been believed – that eating plants does not pose any risk that food borne RNA will interfere with our bodies’ normal processes. Remember, RNA is found in all of the foods we safely consume on a daily basis, from apples to dairy to fish.

*DABT is Diplomate of the American Board of Toxicology.


Jon Entine at Forbes on Metastasizing Misinformation on  GMOs and RNA.

Gene Silencing News: Monsanto, miRAgen Data Further Contradicts Findings of Dietary microRNA Uptake.

Corante/In the Pipeline: It Doesn’t Repeat? Who’s Interested?

GMO Pundit: Controversial plant dietary RNA silencing results questioned again.

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