Wednesday, March 12, 2014

Has the Gluten Content of Wheat Increased Over Time?

As you might imagine from my recent posts about wheat as a scapegoat (highlighting the utter lack of correlation between wheat consumption and obesity rates) and the seven questions the gluten-free community should be asking, one of my big pet peeves is unsubstantiated claims, or worse, claims that are blatantly contradicted by the evidence (i.e., data). Today I'm diving into a related topic—the persistent (and false) notion that the gluten content of wheat has dramatically increased over the course of the past half century.

You don't have to look far—or far back—to find this claim mentioned in prominent outlets. Consider these examples from just one year ago: From the New York Times: "Blame for the increase of celiac disease sometimes falls on gluten-rich, modern wheat varietals..." From "50–60 years ago wheat containing only five percent gluten has become 50 percent gluten today... leading to the 10-fold increase of wheat's gluten." (Ha!) And from Mother Jones: "...the hybrid varieties [of wheat] we eat today contain more gluten..." Many other examples abound, but I call these three out specifically because they are recent, all published in early 2013. More recently, at least two readers wrote to me following my "Wheat, the Scapegoat" post espousing wheat's supposedly higher gluten content today compared to the wheat of our parents and grandparents.

Around the same time that the New York Times and Mother Jones articles came out last year, the Journal of Agricultural and Food Chemistry published a study by Don Kasarda, a respected cereals researcher with the USDA's Agricultural Research Service, asking—and answering—the fundamental question, "Can an increase in celiac disease be attributed to an increase in the gluten content of wheat as a consequence of wheat breeding?" The results of his research were a resounding "no." Kasarda wrote, "I found no evidence of any obvious trend toward higher protein content for either winter or spring wheats since the early part of the 20th century when the key ancestral varieties of bread wheats ... were introduced to the United States."

Kasarda's work should have been the definitive nail in the coffin of the "wheat's gluten content has been increasing" myth. And indeed, early and mid 2013 abounded with articles—from the mainstream media to the gluten-free community to the wheat industry—disabusing the public of the notion that today's wheat has more gluten than the wheat of the mid-20th century. Of the dozen or so that I read researching this post, nearly every one cited and/or linked to Kasarda's study. Yet myths die hard.

And so I took a page out of the book of the think tank where I'm editorial director. The unofficial slogan within the halls of our office is W. Edwards Deming's famous quote, "In God we trust; all others bring data." Here, then, is some good, hard data:

I focused on bread wheat, which accounts for some 95% of all wheat planted on Earth. It's higher in gluten content than other varieties of wheat, so if we're going to point the finger anywhere, it's at bread wheat—it's both abundant and high in gluten. Bread wheat is the colloquial term for the higher-gluten hard wheats (there are also lower-gluten soft wheats). Hard wheat comes in both winter and spring varieties. Hard spring wheat is better suited to northern climes, which is why you'll find it in places such as Montana and Minnesota in the United States. Hard winter wheat, on the other hand, can be found in great quantities farther south in the Great Plains.

For the graph above, I targeted hard winter wheat in Kansas specifically. I had a strong rationale for focusing on Kansas. For one, the state has a long history of wheat agriculture dating back to the 19th century. It also has a long and detailed record of wheat crops over that period of time, often including percent protein of each year's wheat crop. (And since gluten comprises 80% of the protein in wheat, a crop's percent protein is a reliable proxy for wheat's gluten content over time as well.)

In addition, Kansas grows more wheat than any other state in the nation, virtually all of it hard winter wheat, and of all the wheat varieties planted in the U.S. each year, hard winter wheat alone makes up more than half. Of the 56.5 million acres planted in the country in 2013, 9.4 million of those acres were in Kansas, 50% greater than the next closest state. When we describe the Great Plains as the nation's breadbasket, that moniker is closer to being literally true in Kansas than anywhere else. (I remember driving through western Kansas on assignment for a magazine, and passing a giant billboard of Jesus with his arms outstretched, standing armpit-high in a field of wheat...)

I pulled most of my data from two primary sources: 1) a historical document published in January 1940 by Kansas State University looking at the state's wheat crops from the early 1900s through 1939 and 2) the USDA's National Agricultural Statistics Service's Kansas wheat history, last updated November 2013 and which includes percent protein for each year's wheat crop starting in the late 1940s. Between the two documents, I could piece together a more or less continuous history of the state's wheat crop gluten content over the course of the last century. It offers one heck of a view.

Go ahead and click on the graph at the top of this post to get the full-screen view. The blue and red bars show the low and high range of the percent protein for Kansas's wheat crop in each of the reporting periods. You're looking at 100 years of wheat crops, and if one thing is abundantly clear it is this: the amount of protein (and thus, gluten) in the wheat has remained unchanged. There is no upward trend.

This conclusion holds true when you look beyond Kansas's hard winter wheat-filled borders to other wheat varieties, other states, and even other countries. For example, the graph at the bottom of this page from the Canadian Grain Commission shows that the protein (gluten) content of Canada Western Red Spring wheat has fluctuated plus or minus around a stable average for the last 90 years, similarly with no upward trend.

As previously promised, I'll soon be circling around to what has changed—about wheat, environmental influences, and science's understanding of our own gut ecosystem—in coming blog posts. But in the meantime, remember that wheat's percent gluten content over the years has been remarkably steady. Other factors are clearly to blame for the rising rates of celiac disease and other forms of gluten intolerance.



Lisa said...

Maybe the difference in yeast and the shorter rise times? Some products have added gluten too.

Jen H. said...

I am really happy you are doing the research for me! I can't believe the number of people who point to a popular media article for proof that a claim is true without looking for any reliable research to support the claim. Once people have an idea in their head as fact it is nearly impossible to get them to move on, despite overwhelming research. One only has to look as far as vaccines causing autism for proof of that.

Jamie said...

Great article. I posted it on my Facebook page - I get tired of all of the unsubstantiated rumors as well. I think this one started with the book Wheat Belly. Jamie at

Laura said...

It is not that wheat has more gluten than it used to have that causes problems. It is the increase in the genes (from 2 to 14) that causes the problem. More genes, more characteristics. The wheat with these new characteristics has been never tested to see what their effect would be on the human body.

I am not an ignorant person. I have a degree in Chemistry and attended medical school and later became a Physician Assistant. I have a very good scientific background.

I do not think the obesity problem can be fully lain at wheat's doorstep, but it is part of the lousy food we have nowadays that is causing this terrible epidemic.

peterbronski said...

Lisa, In a future blog post I'll be looking at some recent research about long-rise-time sourdoughs!

Jen and Jamie, Thanks for your compliments. Three cheers for data-based information rather than fear-mongering hearsay!

Laura, You're right that the nature of gluten has changed over time (a subject of a forthcoming blog post), even though gluten's percent content of wheat hasn't increased. However, other claims you state are factually wrong. Ancient varieties of wheat were either diploid (2 sets of 7 chromosomes from the A genome) or tetraploid (2 sets of 7 chromosomes from each of the A and B genomes). Modern bread wheat has a third genome, D, so it has 42 chromosomes (2 sets x 7 chromosomes per genome x 3 genomes) compared to the 14 or 28 chromosomes of ancient varieties.

Cheers, Pete