Several of our customers recently brought our attention to somewhat alarming news in the blogosphere that glyphosate (commonly known as Roundup) is sprayed on 97% of U.S. wheat crops right before harvest. To make matters worse, it seems like these glyphosate residues on wheat are what is causing celiac disease in so many Americans.
If this were true, it would be a good reason for Americans to insist on organic wheat, a notion that we whole-heartedly support. And some parts of this story do in fact ring true. One trip to the grocery store is all you need to realize that gluten intolerance seems to be much more common than it was even five years ago. It seems logical that we should be able to trace this strong increase back to some change in our environment. It is also not hard to believe that consuming the herbicide glyphosate is bad for you, or that somehow the combination of glyphosate and wheat, which is the main source of gluten in our diet, could somehow produce a toxic synergy that results in celiac disease.
But as much as one might want to believe that there is such an easy explanation for why so many Americans are allergic to gluten, other parts of the story sounded a little too suspect. Glyphosate is one of the most widely available herbicides on the market. You don’t need a license to buy it at any home improvement store, so your neighbors could be spraying it in their yards and gardens. Commercially, it is approved for use on most crops that we eat. The two crops that we Americans eat a lot of, corn and soy, have even been genetically-engineered to be “Roundup-Ready”–ready, that is, to be sprayed with glyphosate and not killed. Wheat is not necessarily the number one source of glyphosate in our environment.
So we wanted to get to the bottom this story. It seems like the original source is a paper published in the December 2013 issue of Interdisciplinary Toxicology entitled “Glyphosate, pathways to modern diseases II: Celiac sprue and gluten intolerance,” written by Anthony Samsel, an independant consultant, and Stephanie Seneff, a computer scientist. It struck us as strange that such a paper would be written by someone other than an epidemiologist, medical professional or public health official. But, no matter, the authors could have analyzed someone else’s data in a creative way, so we had a look inside.
The main thing we noticed is that most of the evidence that Samsel and Seneff gather to support their conclusion that glyphosate causes celiac disease is conjectural. For example, glyphosate has been shown to disrupt the mucosal lining of fish intestines, which is “highly reminiscent” of human celiac disease (p. 160). In another example, they argue that since glyphosate chelates iron in plants, that it is “conceivable” that it does the same in humans, implying that the chelation would lead to anemia, which happens to be one of many symptoms of celiac disease (p. 166). Logical, perhaps, but certainly not conclusive. In good science, these sorts of compelling correlations are what motivate researchers to formulate hypotheses about the action of glyphosate that are then specifically tested in controlled experiments. But bypassing the experiment and jumping from correlation to conclusion, as the authors do here, is more the stuff of pseudo-science.
Samsel and Saneff go on to correlate eleven other actions that glyphosate is known for in plants and non-human animals with symptoms of celiac disease. However compelling the correlations may be, they are still correlations. And mistaking correlation for causation is one of easiest logical fallacies to fall victim to. The widely reproduced first figure of this paper (above) shows celiac incidence rising in step with glyphosate application on wheat. The implication is that glyphosate on wheat is the cause of the increase in celiac disease. But it is equally possible to imagine this graph with any number of phrases substituted for “glyphosate on wheat.” Try, for example: “awareness of celiac disease symptoms among doctors,” “proportion of corn and soy in the American diet,” “per capita incidence of Type II diabetes,” or “proportion of Americans owning an iPod.” They could all be correlated with the increase in celiac disease, which is to say that there may–or may not–be a causal link between the two.
So while we aren’t convinced that glyphosate causes celiac disease, we still don’t want to eat it. We are still concerned about the statistic that 97% of spring wheat (the main bread wheat) that is grown in the US is sprayed with glyphosate right before harvest. This would mean that most conventional flour would be laced with glyphosate residues. We try to buy wheat that is both local and organic, but our reality is that we often have to choose between local, but conventionally-grown wheat and distantly-grown organic wheat. We believe in supporting our local economy, but this kind of information could change our minds.
When you first look at this figure and its accompanying table, you might come to the same conclusion that Sarah, The Healthy Home Economist arrived at in her blog post: that 97% of spring wheat is sprayed with glyphosate prior to harvest. But if you look closer, it actually says that herbicides (and not just glyphosate) were used on 97% of the acres on which spring wheat is grown at some point in the crop year. This does not mean that the herbicide was used on the wheat crop itself, it could have been used to clear the fields before the wheat was planted. In any case, according to the above table, glyphosate is not even one of the top three herbicides used by spring wheat farmers, so it’s unclear why it should get all the blame. So where did Samsel and Seneff get the idea that farmers are spraying glyphosate before they harvest wheat? This Monsanto publication, which discusses glyphosate use in Europe (not the U.S.). It seems likely that this non-peer-reviewed publication could possibly be biased to make it look like glyphosate is more widely used than it is so that more farmers buy it.
Let’s be clear: we are certainly not fans of glyphosate here at Little Hat Creek Farm. We avoid using any chemicals on our crops, and we buy as much organic flour as we can. But we found the Samsel and Seneff article (and the accompanying news items) to be more provocative and misleading than grounded in good science. Hopefully, their article will be the inspiration for clinical trials that could establish a causal link between glyphosate use and celiac disease. But in the meantime, we do not think there is as much cause for alarm as it may at first seem.