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Dr William Davis claims that the protein gliadin in wheat (at least, strains grown since the '60s or so) stimulates appetite, leading to obesity. He has released a book on the topic, called Wheat Belly: Lose the Wheat, Lose the Weight, and Find Your Path Back to Health. His claims (including a video) are described in a CBS report:

This thing has many new features nobody told you about, such as there's a new protein in this thing called gliadin. It's not gluten. I'm not addressing people with gluten sensitivities and celiac disease. I'm talking about everybody else because everybody else is susceptible to the gliadin protein that is an opiate. This thing binds into the opiate receptors in your brain and in most people stimulates appetite, such that we consume 440 more calories per day, 365 days per year

In an article on BlissTree, Elizabeth Nolan Brown disputes Dr Davis's claims:

Lie #1: Gliadin is a ”new protein” being engineered into wheat. Actually, gliadin has always been in wheat.

[...]

Lie #2: Gliadin is an appetite-expanding opiate. Giadin[sic] is not actually an opiate. Gliadin polypeptides can bind to opiate receptors in the brain, but there’s no evidence that this stimulates appetite

Her claims about the origins of gliadin are not well referenced, and she doesn't consider the quantity.

The Grain Foods Foundation have also disputed the risks of gliadin:

Cutting out one specific food is not only unrealistic, it’s dangerous. Omitting wheat entirely removes the essential (and disease-fighting!) nutrients it provides including fiber, antioxidants, iron and B vitamins.

Besides this, the advice dished out by Dr. Davis is completely counter to the Dietary Guidelines for Americans, the gold standard of scientifically-sound nutrition advice. The Guidelines call for the average healthy American to consume six one-ounce servings of grain foods daily, half of which should come from whole grains and the other half from enriched grains. Wheat is the basis for a number of healthful whole and enriched grain foods including breads, cereal, pasta and wheat berries that provide valuable nutrients to the American diet and have been shown to help with weight maintenance.

Has wheat been modified to introduce gliadins? Do they act as opiates to increase appetite?

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I originally intended to watch something on effects of eating wheat on the current affairs show "60 Minutes", but I missed the episode. I think it's reasonably likely its the same video that may have been shown though. I consider that notable, in addition to the various articles on the web discussing the claims. –  Highly Irregular Oct 14 '12 at 23:15
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The comments from the GFF sound typical of a trade organization protecting its turf. 1) If removing a specific food was inherently dangerous, then they would be advising we eat a diet rich in every food*. They don't do that. Also, what evidence is there that those who avoid wheat due to gluten or other allergies suffer from nutrition deficiencies or other problems they imply? 2) Dr. Davis' advice is obviously contrary to "main stream" health advice; else it wouldn't be interesting. Neither of the points maid by the GFF hold any water. But that doesn't say Davis' claims do either. –  Flimzy Oct 16 '12 at 18:47
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I have seen a video (Part 1 and 2) by Dr. Davis on wheat. Quite interesting, and compelling; but only one side. I am quite interested in hearing the whole wheat story! (Yeah, yeah, pun intended) –  Flimzy Oct 16 '12 at 18:48
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Related, on gluten fad: skeptics.stackexchange.com/questions/4724/… –  Sklivvz Oct 17 '12 at 6:23
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As a matter of interest, I read The Wheat Belly and found it was reasonably well referenced and convincing. I did not take from the book that wheat is the cause of an obesity epidemic (though the the possibility is left open), nor did I take from it over-emphasis on gliadin though it was mentioned. Rather I thought that the author advocated the position that wheat has many deleterious effects - often autoimmune related - and that its ill effects are consistently overlooked because wheat is considered intrinsically healthy. It seemed to be a good opening piece to an almost taboo discussion. –  Brian M. Hunt Oct 21 '12 at 23:57

2 Answers 2

My answer can only come from my experience working as a graduate student in a university wheat breeding program. Gliadin is a storage protein1 in the wheat kernel and 1980s research has shown that certain forms of this protein lead to better baking quality, but more recent research shows that it may be more complicated 2.
In our program we did not specifically select for varieties that had higher amounts of any particular protein. The specific goals of the program were adequate baking quality, improved yield, disease tolerance or resistance.

1Wheat and wheat improvement and Genetics of wheat storage proteins and the effect of allelic variation on bread making quality

2Effects of ‘Cheyenne’ Chromosomes on Milling and Baking Quality in ‘Chinese Spring’ Wheat in Relation to Glutenin and Gliadin Storage Proteins

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Welcome to Skeptics! I am not quite sure what you are trying to say with this answer. Can't gliadin stimulate appetite besides having a desirable effect on baking? –  Sklivvz Jan 2 '13 at 23:48
    
While certainly interesting and related, bread quality is irrelevant to the question at hand. –  Anko Jan 9 '13 at 13:10

I suggest reading this: "Demonstration of high opioid-like activity in isolated peptides from wheat gluten hydrolysates", http://www.ncbi.nlm.nih.gov/pubmed/6099562. And then judge for yourself.

OF COURSE the Wheat Industry disputes the findings - just like the tobacco industry said there was "no evidence" that tobacco use caused cancer or that nicotine was addictive.

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Welcome to Skeptics! Please quote a few lines from the paper, and interpret how it answers this question. Also, you need to provide more evidence that the "Wheat Industry" (presumably you mean the Grain Foods Foundation) is wrong than merely an analogy to someone else who was once wrong. –  Oddthinking Dec 6 '12 at 4:26
    
There's already a comment pointing to this article. Nobody seems to be able to explain what it's got to do with the question though... –  Sklivvz Jan 2 '13 at 23:49

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