What are the opioid peptides in cheese and how do they affect us?

December 25, 2025 •

4 min read

In a 2015 study, researchers found that heavily processed foods, including cheese, ranked high on a list of items promoting addictive eating behaviors. This phenomenon is often attributed to the opioid peptides in cheese, specifically casomorphins, which are protein fragments with mild opiate-like effects.

Quick Summary

The digestion of the milk protein casein releases opioid peptides called casomorphins, which can bind to the brain's dopamine receptors and cause a mild euphoric effect, reinforcing cravings. The concentration of these peptides can be higher in cheese than in milk, and they may have different effects based on individual genetics and intestinal health.

Key Points

Casomorphins are Opioid Peptides: Digestion of casein, the main milk protein, releases peptides called casomorphins that can have a mild opioid effect.
Dopamine and the Reward Center: Casomorphins bind to opioid receptors in the brain, triggering a dopamine release that enhances feelings of pleasure and reinforces cravings for cheese.
A1 vs. A2 Beta-Casein: Milk from cows with the A1 beta-casein variant releases more of the opioid peptide BCM-7, which is a subject of health research and debate.
Gut Health is a Factor: For casomorphins to exert systemic effects, they must pass through the intestinal wall, a process influenced by gut permeability and the enzyme DPP4.
Not a True Addiction: The effect of casomorphins is mild and not comparable to drug addiction. Cravings are also driven by fat and salt content.
Potential Health Implications: Research has explored controversial links between casomorphins and conditions like autism, type 1 diabetes, and heart disease, though conclusive evidence is limited and complex.
Moderate Intake for Most: For the majority of people, moderate consumption of cheese is safe and nutritious. Those with sensitivities should monitor their individual response.

Understanding the Opioid Peptides in Cheese: Casomorphins

For many, cheese is an irresistible treat. But have you ever wondered why it's so easy to overindulge? The answer lies in the specific protein makeup of dairy products. During digestion, the main protein in milk, casein, is broken down into smaller compounds known as casomorphins. These are the opioid peptides in cheese that can have a physiological effect on your body.

The Science Behind Casomorphins

Casomorphins are exogenous (food-derived) peptides that can act on the same opioid receptors in the brain as powerful drugs like morphine, albeit with a much milder effect. This interaction triggers the release of dopamine, a neurotransmitter associated with pleasure and reward, which can reinforce the desire to eat more cheese. This reward-based mechanism is thought to have an evolutionary purpose in mammals, encouraging infants to continue consuming their mother's milk.

One of the most studied of these peptides is beta-casomorphin-7 (BCM-7), primarily released from the A1 variant of beta-casein found in the milk of some cows. However, other types of beta-casomorphins (BCM-4, BCM-5, BCM-6, BCM-9), as well as opioids from other milk proteins like lactoferroxins and casoxins, also exist.

The A1 vs. A2 Beta-Casein Distinction

Not all dairy is created equal when it comes to casomorphin production. A significant area of research revolves around the genetic difference in cows producing A1 or A2 beta-casein protein.

A1 Beta-Casein: A genetic mutation in some European cattle led to the A1 variant. When this protein is digested, it more readily releases the opioid peptide BCM-7.
A2 Beta-Casein: This is the original, ancestral form of beta-casein found in human, sheep, goat, and certain breeds of cattle's milk. Its digestion does not lead to the significant release of BCM-7. Some studies suggest A2 milk may be easier on the digestive system for some individuals.

How Casomorphins Cross the Gut Barrier

For casomorphins to have an effect on the brain, they must first pass through the intestinal wall into the bloodstream. This process is highly dependent on an individual's gut health. A healthy gut with a strong intestinal barrier typically prevents these peptides from being absorbed in significant quantities. However, in individuals with compromised intestinal permeability, also known as 'leaky gut', these opioid peptides can pass into the circulation more easily, increasing their systemic effect.

Another factor is the enzyme dipeptidyl peptidase-4 (DPP4), which normally breaks down casomorphins. Some individuals have lower DPP4 activity, making them more susceptible to the effects of these food-derived opioids.

Potential Health Implications and Controversies

While cheese consumption is generally considered safe and nutritious, the topic of casomorphins has sparked debate, with some research exploring potential links to various health conditions.

A Comparison of Casomorphin-Related Claims vs. Mainstream Science


Aspect	Claims Linking Casomorphins to Health Issues	Mainstream Scientific Consensus
Autism & Schizophrenia	Some alternative theories propose a link between casomorphins (and gluten-derived opioids) and symptoms of autism and schizophrenia.	Evidence from dietary trials supporting this is inconclusive and largely lacks rigorous double-blind study design.
SIDS (Sudden Infant Death Syndrome)	Early studies suggested a link between BCM-7 and apnea in infants, based on findings in animal models and the presence of casomorphins in SIDS victims.	The evidence remains observational and causal links have not been established. The role of different milk types (A1 vs A2) is a factor in ongoing research.
Cardiovascular Disease	Some epidemiological studies in the 1990s showed correlations between A1 beta-casein intake and the incidence of cardiovascular disease.	While some animal studies show a link, the correlation has not been definitively established in human trials and remains controversial. The effects are complex and multifactorial.
Digestive Issues	Many individuals report digestive discomfort that improves on a dairy-free diet. Some of this may be linked to the inflammatory effects of casomorphins.	Casomorphins, especially BCM-7, are acknowledged to delay intestinal transit and potentially increase gut inflammation, confirming some patient experiences.
Addictive Behavior	The mild opiate-like effect of casomorphins is cited as a reason for intense cheese cravings and "addictive" eating.	The effect is significantly milder than pharmaceutical opioids, and cravings are not considered a true addiction. Other factors like fat, salt, and palatability are major contributors to cravings.

What does this mean for cheese lovers?

The existence of casomorphins doesn't mean you should fear cheese. For most healthy people, a moderate intake of cheese is a nutritious part of a balanced diet, offering calcium, protein, and other vital nutrients. The addictive qualities are mild and the pleasure derived is similar to that of other palatable foods. Concerns typically arise for specific populations, such as those with existing gut permeability issues or certain genetic predispositions.

Ultimately, understanding what are the opioid peptides in cheese allows for more informed dietary choices, particularly for those who experience sensitivity to dairy or are exploring the science behind food cravings. https://pmc.ncbi.nlm.nih.gov/articles/PMC8345738/

Conclusion: Navigating Casomorphins in Your Diet

In conclusion, the opioid peptides in cheese are real, but their effects are far from a drug-like addiction for the average consumer. They are natural protein fragments called casomorphins, which can bind to brain receptors and cause mild pleasure, reinforcing the desire for more cheese. The concentration and impact of these peptides can vary based on the type of cheese, the beta-casein type in the milk (A1 vs. A2), and an individual's digestive health. For those with compromised gut health or specific sensitivities, casomorphins may contribute to digestive or inflammatory issues, but for most, they are part of what makes cheese so enjoyable. As with all dietary choices, moderation and awareness of your body's individual response are key.

Frequently Asked Questions

No. The opioid effect of casomorphins is very mild and not comparable to the potency of pharmaceutical opioids. Cravings for cheese are more related to its high fat, salt, and flavor profile, combined with a subtle dopamine release, rather than a true drug-like addiction.

A1 milk, from certain European cattle breeds, releases significantly more of the opioid peptide BCM-7 during digestion than A2 milk, which is the original form of milk protein. Research has focused on A1 milk and BCM-7 due to its higher potential for opioid effects.

Yes. The process of making cheese, especially aging and fermentation, involves enzymatic breakdown of casein. This proteolysis can lead to the release of casomorphins, potentially increasing their concentration in some finished cheeses.

Some alternative theories and anecdotal evidence suggest a casein-free diet may help with autism and gut issues. However, scientific evidence from rigorous clinical trials is still limited and controversial, though some studies suggest that casomorphins can contribute to digestive inflammation in sensitive individuals.

Cheese is a good source of protein and calcium, important for bone health. Some varieties contain probiotics, which are beneficial for gut health, and other healthy fats like conjugated linoleic acid (CLA), which may lower inflammation.

Yes, research indicates that bovine casomorphin (bBCM7) can cross the blood-brain barrier via a specific carrier mechanism, allowing it to interact with opioid receptors in the brain and potentially influence mood and behavior.

For most people with healthy digestion, the effects are minimal. The most effective way to reduce casomorphin intake is to consume dairy from A2 cows, sheep, or goats, as their milk produces significantly less BCM-7. Alternatively, non-dairy cheese substitutes can be used.