It's probably been a couple of weeks now, but Kate asked a question about the potential for becoming addicted to gluten. I mean, I think that many of us wish we could eat a juicy doughnut every once and a while, but Kate seemed to think that there is something more to it for some people. Are some people Jonesin' for a doughnut for more reasons than that they smell good around 4:00? I've read up on it while taking a break from getting ready for my dissertation defense and now that I've finished, it seems like a good time to share what I found.
First off, we know the incomplete digestion of gliadin produces peptide fragments that are also known as exorphins. Where that name comes from, I don't know. As I understand it, an exorphin will have comparable action but opposite effects to an endorphin. They interact with the opioid receptors, the mu, kappa and delta receptors, which are located predominantly in the central nervous system (CNS) as well as in the digestive tract.
These are the same receptors that are involved with opium and its purified components morphine and codeine, as well as heroin, which is a semi-synthetic derivative of morphine. Mu receptors generally are responsible for the analgesic effects, respiratory depressant, pupil constriction, euphoric and physical dependence properties. Kappa receptors also affect analgesia, as well as sedation, physical dependences and dysphoria, possibly by inhibiting mu receptors. Delta receptor action is poorly understood, at least when the book I was looking at was written.
An interesting side note that I hadn't been aware of before is the fact that the opioid receptors in the CNS become habituated, whereas the receptors in the digestive tract do not. The consequence of this is that to get the same high, an addict needs to take more drug than they used to, but as they do so the effect of the drug on the gut becomes more and more extreme. When you realized that morphine has been used to relieve diarrhea, it makes me think that perhaps they might need to be taking Alli to balance out the effects.
Biologically, these receptors are activated or deactivated by drugs but they are designed to function in response to chemicals that are made in the body rather than chemicals made in a poppy or a chemistry lab. These endogenous ligands are called endorphins. They are responsible runners high, where a person gains a boost of energy, mental acuity and relief from pain. It isn't clear exactly how this works, because inhibition of runners high using opioid receptor antagonists does not produce the opposite of these effects. Exorphins on the other hand DO cause the opposite effect of a runner's high: loss of energy, loss of mental acuity and the onset of pain. That sounds like a pretty complete explanation of what I feel when I ingest gluten, I'd say.
This is where the speculation and anecdotal evidence begins. I have found that my sensitivity to gluten has increased, rather than decreased as I have been on a gluten free diet. That is, I now get terrible headaches when I eat gluten that I didn't notice having continually before. My speculation is that a similar habituation process can occur with gluten that occurs with heroin. When I ate gluten all the time, I needed more to get the same effect. The difference is that heroin makes you feel good and gluten makes me feel bad. Now that I am off gluten, I have become de-habituated, if that is a word, and am more sensitive.
Second, if gluten peptides are interacting with the same receptors that heroin does, is it unreasonable to assume that for some people they can be habit forming in a similar way. I have often heard that heroin is relatively easy, though extremely messy, to get off of. The withdrawal symptoms are painful and messy, but they end and then the former addict can go on with life. However, approximately 25% of heroin addicts are never free of the craving, and must continue methadone treatment indefinitely.
We do know that aside from the usual withdrawal symptoms, there is something called protracted abstinence syndrome that can last up to six months. It includes depression, abnormal response to stressful situations, drug hunger, decreased self-esteem, anxiety and other psychological disturbances. My book says "Long-term opioid craving might result from a pre-existing or an opioid-induced hypofunction of the endogenous endorphin system. Therefore, to rehabilitate these addicts and keep them in a functional state, low levels of opioid may be necessary." Could there be an "opioid induced hypofunction of the endorphin system" that causes a person to crave gluten forever? I haven't found any research on it in the scientific literature, but it makes sense.
It may be protracted abstinence syndrome that persists for up to six months, and you are giving in and having a slice of Poppa John's pizza within that time frame, thus re-entering the craving cycle, whereas if you just refrained a little longer, you could break out. It may be that there is a persistent physical dependence similar to addiction. Or, it may simply the case that no one sells a good gluten free donut. Someone should do some fMRI studies on this, I think. That isn't my bailiwick, though.
(Information taken from "A Primer of Drug Action" by Robert M. Julien, M.D. Ph.D. 1995.)