Is cheese really addictive?

In our Cheese show we considered the suggestion from the President of the Physicians Committee for Responsible Medicine (PCRM), Neal Barnard, that dairy cheese is addictive. In this 2003 article entitled “Breaking the Food Seduction”, introducing his book of the same name, Dr. Barnard writes:

Cow’s milk—or the milk of any other species, for that matter—contains a protein called casein that breaks apart during digestion to release a whole host of opiates called casomorphins. A cup of cow’s milk contains about six grams of casein. Skim milk contains a bit more, and casein is concentrated in the production of cheese.

I looked into the references from Dr. Barnard’s book that PCRM was kind enough to send. But the analysis I offered in the show was that the idea that cheese is addictive is at best overstated and at worst wrong.

This is why.

First off, a quick biology lesson. We have receptors throughout the cells of our body including our brains. Receptors are like locks that only specific keys can open and cause effects in the cell. We have natural opiates produced by our bodies (e.g. endorphin) . An opiate agonist is a chemical that binds with the opiate receptor and causes effects like analgesia ( decrease in pain sensitivity), feelings of euphoria and can create tolerance and addiction.  It is triggered when an opiate molecule, of a specific size and shape, fits like a key into that receptor’s lock. However, there are some molecules that fit into the receptor but don’t activate it. Opioid antagonists block opioid receptors from activation. As Dr. Barnard’s essay suggests, opioids might regulate preferences for foods high in fat and sugar not because these foods contain opioids but because eating them releases natural opioids (Drewnowski et al 1992).

So Dr. Barard states  proteins in dairy are broken down into opoid molecules called casomorphins. This is definitely true. However, in the breakdown of dairy, opioid antagonistsare also produced which would have the opposite effect and lead cheese to not be addictive. This differs from cheese to cheese (Sienkiewicz-Szłapka et al. 2009):

I would conclude that if these agonistic casomorphins are really important for causing an addiction to cheese we would see a big difference in the popularity of cheeses depending on the ratio of agonistic to antagonistic casomorphins. Unfortunately the authors of this study did not test cheddar – one of the most popular cheeses in the world – but if  it’s anything like the other semi-hard cheeses in the study we would expect it to have a greater percentage of opioid antagonists.

The next problem with the idea of cheese addiction is the question of whether or not the opioid peptides (protein fragments) could pass through the gut into the bloodstream and the brain.

There is evidence that these peptides pass through the guts of infants (casomorphins are also found in human breastmilk) and through their immature blood-brain barrier (which keeps lots of stuff out of the brain that circulates through the blood) but has there been any evidence that they cause morphinelike effects?

There has been a case study linking cow’s milk consumption and sleep apnea but in a larger study of infants who were breast or formula fed they found no difference in average psychomotor development between the two groups.

Another study found markers of human beta casomorphin 8 in the brainstems of human infants. (To correct something I said in the show, these casomorphins are from human breast milk and not dairy).

Given that:

  1. formula fed infants are much more sensitive to peptides
  2. formula fed infants eat a larger proportion of dairy in their diet than most adults (unless someone subsists entirely on dairy)
  3. these peptides would be working on a much smaller body mass than adults
  4. there still isn’t definitive evidence that they are having morphinelike effects

This leads me to think that it is improbable that dairy has addictive properties in adult humans.

There is evidence that casomorphins pass through the gut of adults but, as far as I could find, no evidence that dairy has opiatelike  effects on adult humans. The only thing that came close was this study showing a lowering of blood pressure in those who consumed “sour” milk as opposed to regular milk – however the difference between those milks was not attributed to casomorphins but to other peptides.

One main effect that opiates like morphine have is analgesia (decreased sensitivity to pain). If dairy has enough opiate peptides to create addiction one would expect that dairy would also decrease pain sensitivity. However, I was unable to find any studies relating dairy consumption and pain sensitivity and during my postdoctoral research at the University of North Carolina working with pain data I never saw any questions about dairy in the protocol.

This blog has been pretty far afield from my scientific speciality and I’m grateful for any criticism of my methods or conclusions. But three main pieces of evidence suggest to me that Dr Barnard is in error about the possible addictive properties of dairy.

  1. Dairy has both agonistic and antagonistic opiate peptides and there is no evidence that products with more agonistic peptides are more popular
  2. The effects of bovine casomorphins in infants, those who should be most sensitive to them, are small 
  3. Dairy hasn’t been shown to have opiatelike effects in adult humans

So, why do people have such a hard time giving up cheese? Because fat is high in calories and throughout our evolutionary history, when calories were much scarcer than they are today, fat was the most efficient way to get your calories for the day. Because of this, these foods, and some others (e.g. sweet foods, salty foods), may have a reward system that makes us feel good when we eat them promoting seeking out and eating these foods which throughout our ancestral past led to reproductive success. Nowadays sugar and fat are no longer as rare as they once were but our reward system still amps up when we eat them (see mismatch hypothesis)

I think this is a simpler explanation in addition to explaining my “addiction” to almond butter, dark chocolate and avocadoes. mmm

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About Diana Fleischman

Dr Diana Fleischman co-hosted the show in 2011 and 2012, supplying some American irreverence. Media appearances include discussing atheism on BBC TV's "The Big Questions" and her research on the BBC World Service. She lectures in comparative psychology (the evolution of the mind) at the University of Portsmouth.

17 responses to “Is cheese really addictive?”

  1. @Eat4Health (@leslie_reese) says :

    Love the Devil’s Advocate role that you played here…thanks for sharing the research. It’s easy to understand why everyone gets so confused about what ‘healthy’ is.

    • Diana says :

      Thanks! I’m not sure I played “Devil’s advocate” since I really believed the position of Dr. Barnard until I read the data and then changed my mind. Leaving the data to one side I’m not sure if the idea that dairy is addictive is productive in helping people to quit. Perhaps it makes people approach quitting with greater willpower or, on the other hand, gives them an excuse when they backslide.

  2. Nemo says :

    Sorry, but I find Dr. Barnard much more credible. Then too he has the credentials as well. In any case why would anyone want to use cow’s milk in any form? Yecch.

    • Diana says :

      hi Nemo
      This blog doesn’t endorse eating cheese or drinking cow’s milk. Furthermore, I don’t think the claim that cheese is addictive is a great tool in the arsenal of advocating against dairy. As for credentials, that’s the great thing about the scientific literature. Anyone can read articles and form their own informed opinion about scientific claims with evidence. It’s evidence and reasoning, not having letters after your name, which should make claims compelling.

      • Sophie says :

        Seriously, you dont need letters after your name!! People should be more self-confident.

  3. Philippe says :

    I too used to believe Barnard. But I do have the feeling he’s ready to say a lot of things to promote the vegan way. I’m a vegan. But I know that there are people and organizations out there, PETA being one, that will “lie” to promote their agenda. Recently I’ve had the feeling that Dr. Barnard, who by the way is on the board of PETA, might be using the same technique. What matters for these people is that the animals are saved. That matters to me too and the reason I became vegan was first because I think eating meat is not ethical. Health concerns came second. Whatever your agenda, I don’t think it’s worth it, on the long term, to omit telling the truth ( I guess that’s an euphemism for lying?). Why not simply tell people that cheese is an unnatural food because of its saturated fat content ( up to 70% for some cheese) and that it’s pure poison. That should be enough. No need to talk about addiction. I too haven’t found any scientific evidence or mention about the fact that cheese could be addictive.

  4. georead says :

    News-break: Chronic pain suffers mob supermarket for cheese.

    News-break: New study to test how strong morphine is in cheese. The test subjects will eat a diet of only cheese for a whole month. After which they will be subjected to series of intensive pain tests.

    News-break: Drug addicts break into cheddar factory and make off with a large quantity of cheese.

  5. Joe says :

    The line where the author said “or the milk of any other species, for that matter—” is absolutely 100% not true and I urge you to do more research. Goats milk for instance is A2 Beta-casein and BCM7 “is not released“ on digestion from A2 beta-casein. The issues is related to a peptide called beta-casomorphin-7 (BCM7) and its ONLY found in A1 beta-casein milk. All cows at one time only producted A2 milk, why they don’t now is a whole different topic. There are Dairy’s that have cows that only produce A2 milk so if dairy is your thing hunt those down, but stay away from the American standard milk, its population control milk… Deadly

  6. georead says :

    Check out this fanatical cult from Australia in the link below. They say “Why Cheese is Like “Dairy Crack”: Because It’s Got Morphine In It” – salvation by cheese abstinence

    I wonder why drug addicts haven’t caught on. They could buy up a whole lot of cheese (it’s real cheap) and start reducing down to extract the morphine. Wow they could make a fortune $$$$$$. There’s a lot of money to be made here. Listen up all you drug addicts.

    • Astra says :

      I can’t believe you wrote the above of Paul Godfrey who’s words are in the entire article and who also said:

      “Divine inspiration over 100 years ago said that the effect of cheese is deleterious (harmful, toxic, damaging, adverse, detrimental). Science today finds that actually it gives the same effect as morphine.” Paul Godfrey

      All offshoots are a cult including your website. That entire article is his sermon.

      • georead says :

        Paul has left that cult group and has declared that “it was all a big scam”.

        As for ideas that morphine from cheese has a morphinelike drug affect on the body. I was would like to know if those so confidently preaching these ideas eat any grain products or soya products because these products contain gluteomorphins and soymorphins.

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