Casein: A Troublesome Protein Found in Dairy Products

Quite recently I put up an article here on the site in which I talked about the fatty acid profile of dairy products, pointing out that dairy foods have a lipid structure that differs markedly from that of the foods that we humans are evolutionarily accustomed to deriving our fats from, and that this is one of many reasons why I’m reluctant to follow in the footsteps of those people within the ancestral health community who’ve embraced cheese, butter, and/or other types of dairy products.

In today’s article, I thought I’d talk about another reason why I favor a nutritional route that lies closer to the one our hunter-gatherer forebears travelled than the route that pastoralists and dairy-lovers have gone down, which is that dairy foods contain a troublesome mix of proteins. In other words, it’s not just the fatty acid composition that’s problematic, the protein composition is as well.

I’ve already talked at length about whey protein here on the site and the threats it poses, including its effects on IGF-1 production, gut microbiota composition, and skin health. In today’s article, I thought I’d shift my focus onto casein – the second major group of proteins found in milk – and the issues it presents.

What role has milk proteins historically played in the human diet?

It’s safe to assume that we humans are generally able to deal with the protein structures that are found in foods such as meat, fish, and eggs in a safe and effective manner, given that such foods have been a part of our dietary repertoire for a very long time. The same cannot be said for other types of proteins that are inherent to food groups that have only recently (from an evolutionary point of view) been introduced into the human food chain, such as cereal grains and dairy products.

Within the evolutionary health community, much attention has been paid to the impact that gliadin, wheat germ agglutinin, and other types of proteins found in cereal grains have on the human physiology. It’s widely recognized among evolutionary health aficionados that such compounds pose a threat; however, for some reason, many of the people who recognize this threat seem to largely or completely disregard the fact that dairy foods also contain a list of troublesome proteins.

Part of the reason why this is the case is likely that cereal grains have evolved protective structures, intended to inhibit predation via their toxicological effects. Mammalian milk, on the other hand, doesn’t contain such structures, as it is generally reserved for the young of each mammalian species and is rarely gained access to or exploited by unrelated organisms. However, that doesn’t mean that there’s no reason to be concerned about the proteins that are found in cow’s milk (or the milk of sheep, goats, or any other animal for that matter).

The key thing to recognize is that the mix of proteins that’s found in dairy foods differs markedly from the one that’s found in foods of non-milk origin, such as meat, fish, and eggs. Up until very recently in our evolution, whey and casein proteins were not a part of the adult human diet. These groups of proteins have traditionally been reserved for young mammals, in which they serve a unique purpose. Among other things, they contribute to shaping a gut microbiota profile that is desirable early in life and promote skeletal and muscular growth. No wonder bodybuilders are so fond of these compounds. 

The exact types and mix of proteins that are found in milk differ both between species and individuals. Human milk, for example, has a different ratio of casein/whey proteins than cow’s milk. It’s not surprising that such variations exist, as the milk of each species has been specifically designed, via natural selection, to meet the needs of the young of that species.

Some of the physiological effects of casein exposure

In light of the things mentioned above, it’s reasonable to hypothesize that the consumption of casein-rich foods such as cheese and cow’s milk has several adverse physiological effects, which may, over time, contribute to causing major disease. As we turn to the scientific record, it quickly becomes clear that this is a valid assumption. In this section I’ll discuss some of these effects, including potential reasons why they would be desirable in a young, breastfeeding mammal.

One of the major issues with casein has to do with its effects on our brains. Some of the peptides that result from the processing (e.g., fermentation) and digestion of dairy foods behave like opioid receptor ligands, binding to opioid receptors in the brain (1, 2). The resultant effects are obviously not going to be as potent as those of for example a drug like heroine; however, they will be significant, particularly if large quantities of exorphins, AKA exogenous opioid peptides, are taken in. In this sense, casein resembles gluten.

There are several plausible reasons why natural selection has shaped the casein-brain connection in the way it has. The most likely explanation is probably that the ‘addictive’ effects that casein peptides have on the brain contribute to causing breastfeeding younglings to continually return to their mother’s breasts in search for more milk. In other words, it keeps them coming back for more food, something that’s obviously beneficial in the context of survival and reproduction, as it enables the development of a strong, healthy animal that may one day go on to get children of his or her own. Additionally, casein peptides could potentially help calm the infants down, relieve pain, and or bring about a feeling of well-being via their attachment to opioid receptors.

While it’s perfectly normal, from an evolutionary point of view, for the human brain to be exposed to the proteins that are found in human breast milk early in life, during lactation, it’s very much irregular for a human being to be exposed to high levels of the protein structures that are present in the milk of another mammalian species throughout the lifetime. This helps explain why such exposure has been associated with the development of certain neurological disorders of the brain, such as autism and schizophrenia (3, 4, 5, 6, 7).

Additionally, given the novelty of such exposure, one would expect it to be liable to cause an immune reaction. In most individuals, this reaction is probably mild (albeit not negligible); however, in sick individuals with compromised intestinal barriers, it’ll likely be of greater severity. This has been proven to be the case, in the sense that casein consumption has been implicated in several aberrant immunological responses and inflammation-related disorders, including type-1 diabetes, celiac disease, and cardiovascular disease (8, 9, 10, 11, 12, 13, 14, 15).

Most of the research that has been conducted to date has focused on the A1 variant of β-casein – the most common type found in cow’s milk in Europe (excluding France), the United States, Australia, and New Zealand (16) – which is thought to be more troublesome than the rarer A2 type, in part because it, upon digestion, gives rise to the peptide β-casomorphin-7, which has been implicated in various aberrant physiological states. Personally, I think this distinction between the two types of proteins is less significant than it’s been laid out to be. Both variants are new additions to the human diet and likely to cause harm.

Given that proteins of the casein family only makes up a fairly small part of most people’s diet and are generally taken in in combination with other nutrients, it’s safe to assume that such harm in general is subtle, as opposed to severe. This is important to note, as it helps explain why the evidence pertaining to the link between the intake of bovine casein and conditions such as cardiovascular disease, which develops over many years, isn’t conclusive, showing clear-cut causal associations.

The casein content of dairy foods

Casein makes up about 80% of the total proteins found in cow’s milk. When it comes to the exact protein composition and niveau of different dairy products, there’s variation across the spectrum of products that exists and also within each category of products, largely as a result of differences in how the products are manufactured.

Certain processing procedures, such as lactic acid fermentation, can help mitigate or eliminate some of the problems with milk, such as the miRNA issue. Some combinations of bacteria could potentially also reduce the problems associated with casein; however, it’s important to recognize that many fermented dairy products contain very high concentrations of protein; cheese being a prime example.

This helps explain why some people say they are “hooked on cheese”. Personally, I’ve noticed that my cognitive function and sleep suffer when I take in significant quantities of protein-rich dairy foods such as cheese. Back in the day when I used to eat casein-rich cheese a lot more regularly than I do now, I also noticed that it is a very addictive that has a potent impact on the brain. I know others have experienced the same.

What about the studies that seem to show that the consumption of various phosphoproteins of the casein family is beneficial?

A number of studies have shown that the consumption of milk proteins, such as in the form of whey or casein protein supplements, has anabolic and immunoregulatory effects (e.g., 14, 17, 18, 19). These effects are commonly interpreted as being beneficial.

I think that’s a mistake.

Such effects are simply the effects that one would expect to see, given what we know about the nature of milk. Its very purpose in nature is to have that kind of an impact, so as to support and promote the development of young mammals.

The key message that I’m trying to get across is that it’s not ‘natural’ for an adult human being to be exposed to the complex mix of growth-stimulating, hormone-regulating compounds that are found in milk. Our biology is certainly not primed for it. In other words, I’m of the belief that the results of nutritional studies have to be interpreted in light of biology and evolutionary science. We need to pay attention to how things work in nature and the adaptive processes of evolution.

Primary takeaways

Part of the reason why people within the evolutionary health community are critical of bread, pasta, and other grain-based foods is that such foods contain a variety of proteins (e.g., gliadins, lectins) that have been shown to increase gastrointestinal permeability, illicit inflammatory responses, and/or otherwise have a negative physiological impact. However, for a number of reasons, much less attention has been paid to the threat that milk proteins pose to human health.

It’s often ignored that whey and casein proteins have historically been reserved for young mammals, in which they promote muscular and skeletal growth and have immune-related effects, and that continued exposure to these compounds throughout the lifetime may adversely affect the quality of one’s sleep and brain function, and increase one’s risk of developing a variety of health problems and diseases. This is not to say that it’s very harmful to eat some cheese or drink some milk every now and then; however, it’s arguably not a good idea to make such foods a significant part of one’s habitual diet.