In recent years, some research has come out demonstrating that casein in cow’s milk may sometimes break down into peptides called casomorphins. These peptides have opioid structures, leading to the popular (though as of yet unfounded) conclusion that dairy may act like opioids in the human body. Soon the headlines were flying with absurd claims that cheese is like heroin. Some even stupider claims suggest that cheese may be akin to crack cocaine – a comparison that misses the point entirely, since crack cocaine is not an opioid. And the vegan advocates didn’t miss the opportunity to remind us, “See, we told you that milk is bad!”
But is it true? Is dairy really bad for us because of casomorphins? It would seem that by and large the answer is no. Let’s look into this myth a little further.
As we saw in the previous section, milk contains a protein called casein. Under some circumstances, casein can break down into peptides called casomorphins, which have the structure of opioids. The casomorphin that has received the most attention and the one that is blamed (without any evidence to back up the claim) for everything from autism to cancer is beta-casomorphin-7 (BCM7), which can only be formed from milk from cows with the Ai genetic variant. So at this point, the only concern that has been raised is specific to BCM7.
Of interest is that with one exception, the published papers on the subject of BCM7 do not show harmful effects. In fact, they report immuno-modulatory effects. Not only that, but a series of studies (Zhang, Miao, Wang, & Zhang, 2013) show a whole host of protective benefits of BCM7 in diabetic rats. Of course, these are rat studies, and the results don’t always translate well to humans.
The only study claiming that BCM7 is potentially harmful (Tailford, Berry, Thomas, & Campbell, 2003) would be less misleading if the following phrase was added to the title: in rabbits. Perhaps the authors weren’t aware of the fact that rabbits are herbivores, meaning that animal fats and proteins are unnatural for adult rabbits. And while no studies involving nonhuman animals will give an accurate picture of the effects on humans, rabbits are particularly different than humans, whereas rats have more similarities.
That casomorphin should be benign or potentially beneficial for the majority of humans is not surprising. Although the sensationalistic headlines liken casomorphin to heroin, creating a negative association for most people, the reality is that there are a lot of different naturally-occurring opioids that provide valuable benefits to human health.
For one thing, human breast milk contains the human version of BCM7, and there are various investigations into the potential benefits of BCM7 for human infants. Based on the current research, it is reasonable to believe that BCM7 may provide important immuno-modulating properties to the newborn infant with an immature immune system. So the idea that BCM7 is inherently bad turns out to be unfounded.
For another thing, the human body produces lots of opioids naturally. Perhaps the most famous type of endogenous opioid is the endorphin, but there are others, including enkephalins, dynorphins, and endomorphins. All of these substances produced naturally in the body provide important health benefits ranging from pain relief to appetite regulation to immune modulation to sleep and temperature regulation. So it is disingenuous to suggest that all opioids are necessarily bad for health.
Oh, and another thing, despite the emphasis on casomorphins, which are opioid agonists, dairy also contains opioid antagonists. That means that milk contains substances that naturally oppose the actions of BCM7. These substances are not well studied, so not a lot can be said about them, but it is reasonable to assume that there is some sort of balancing act that goes on.
Of course, it would be similarly disingenuous to suggest that casomorphins and specifically BCM7 are always perfectly benign. Some people may react badly to them. In particular, it seems that those with increased intestinal permeability may be at risk for negative effects. So some people may genuinely be better off, at least in the short term, without Al dairy foods in their diets. And anyone concerned about any potential negative effects who still wants to include dairy in their diet may want to seek out A2 milk from traditional breeds of cows.