What Foods Contain Casomorphin? A Comprehensive Guide

December 25, 2025 •

3 min read

Casomorphin is a peptide derived from the milk protein casein that is known to act on opioid receptors in the brain, though its effects are much milder than pharmaceutical opioids. Its presence varies significantly across different types of dairy. This comprehensive guide details what foods contain casomorphin and the factors influencing its concentration.

Quick Summary

This article explores casomorphin, an opioid-like peptide found in dairy, particularly cow's milk and its products. It explains how casomorphin is released during digestion and highlights the distinction between A1 and A2 milk varieties. Key dairy foods containing casomorphin are identified, clarifying how processing and dairy source affect its levels.

Key Points

Source of Casomorphin: Casomorphin is a peptide released during the digestion of casein, the main protein in milk.
A1 vs. A2 Milk: Casomorphin (specifically BCM-7) is primarily formed from the A1 beta-casein variant found in many conventional cow's milk products, but not from the A2 variant.
Foods with Casomorphin: Common sources include conventional cow's milk, cheeses, yogurt, and other dairy products made with milk from A1-genotype cows.
Cheese Concentration: Due to its high casein content, cheese typically contains higher concentrations of casomorphin compared to milk.
Other Mammals: Milk from goats, sheep, and humans contains the A2 beta-casein variant and does not release significant amounts of BCM-7.
Health Effects Debate: The health implications of casomorphin are a subject of ongoing research, with some studies suggesting minor gastrointestinal effects in susceptible individuals, while other reviews question its overall impact.
Dietary Choice: Choosing A2 milk or non-dairy alternatives is an option for those wishing to avoid casomorphin, especially individuals with digestive sensitivities.

What Exactly is Casomorphin?

Casomorphin is a protein fragment, or peptide, formed during the digestion of casein, the main protein in milk. The most studied type, beta-casomorphin-7 (BCM-7), is released from the A1 variant of beta-casein. While technically an opioid peptide, its potency is significantly lower than other opioids. Research continues on its potential effects, especially on the gastrointestinal system and possible neurological impacts.

The A1 vs. A2 Milk Distinction

Casomorphin presence is linked to the type of beta-casein in milk, which is determined by the cow's breed. This difference centers on a single amino acid at position 67 of the beta-casein chain.

A1 Beta-Casein: Common in milk from breeds like Holstein-Friesian. It has a histidine at position 67, promoting BCM-7 release during digestion.
A2 Beta-Casein: Found in milk from breeds like Jersey and Guernsey, and all other non-bovine mammals, including humans. A proline at position 67 in A2 creates a stronger bond that prevents BCM-7 release.

Casomorphin concentration varies based on the type of casein, with A1 cow's milk being a source, while A2 milk does not contain significant amounts. Foods containing casein can potentially release casomorphin. Common sources include conventional cow's milk, which often mixes A1 and A2 casein. A2 milk from cows producing only A2 beta-casein does not release BCM-7 during digestion. Milk from goats and sheep contain A2 beta-casein and are not known to produce significant BCM-7. Cheese, with its higher casein concentration, can be a significant source, especially hard, aged cheeses from A1 milk. Soft cheeses may also contain levels of casomorphin. Other dairy products like yogurt and ice cream can also contain casomorphin. However, whey protein is not a significant source.

The Health Context of Casomorphin

Research on casomorphin's health effects is ongoing. Some studies suggest a link between BCM-7 and issues like gastrointestinal discomfort or inflammation in sensitive individuals, while others find no significant negative effects.

Gastrointestinal Effects: BCM-7 may slow gut motility, potentially causing discomfort for some.
Neurocognitive Links: Theories exist regarding its mild opioid activity and neurological conditions, but human evidence is lacking.
Cardiovascular Disease: Historical studies suggested a link to A1 milk and heart disease, but recent reviews by EFSA question these claims.

Most people have consumed A1 milk for centuries without widespread adverse effects. Health implications appear minor for healthy individuals, but those with sensitivities might benefit from A2 milk or a casein-free diet. More details on casomorphin quantification and occurrence in dairy products can be found in research like {Link: MDPI https://www.mdpi.com/2673-9976/26/1/125}.

Factors Influencing Casomorphin Content

Factors affecting casomorphin levels in dairy:

Cow's Genotype: A1 vs. A2 producing cows is the most important factor.
Product Processing: Methods like cheese aging can impact casomorphin production.
Digestion: Casomorphin release during digestion depends on enzymes and the individual's system.

Comparison Table: A1 vs. A2 Milk Properties


Feature	A1 Milk (Conventional)	A2 Milk	Human Milk	Goat/Sheep Milk
Primary Beta-Casein Variant	A1	A2	A2	A2
Casomorphin (BCM-7) Release	Yes, during digestion	No, due to stronger peptide bond	Not significant (weaker version, lower quantity)	Not significant
Associated with Casomorphin Concerns	Yes	No	No	No
Common Sourcing	Holstein, Friesian breeds	Jersey, Guernsey breeds, specific A2-only dairies	Exclusively from humans	Goats, sheep
Potential Digestibility	May cause discomfort in sensitive individuals	Often perceived as easier to digest by some	Generally well-tolerated by infants	Similar to A2 cow's milk

Conclusion: Navigating Casomorphin in Your Diet

Understanding the A1 and A2 distinction is key for those concerned about casomorphin. Choosing A2-only products or milk from goats or sheep can minimize exposure. Cheeses and other concentrated dairy from conventional cows will have higher casein and potential casomorphin. While research continues, the consensus suggests minimal effects for most. Individuals with sensitivities may consider their dairy sources.

Non-Dairy Alternatives

To fully avoid casomorphin, plant-based milks (almond, soy, oat) and plant-based cheeses and yogurts are excellent options, as they contain no casein.

The Bottom Line on Casomorphin

Casomorphin is a natural bioactive peptide, not a dangerous substance. Its presence in dairy depends on the milk source. Most people tolerate conventional dairy well. For those with digestive sensitivities, A2 milk or non-dairy options can be helpful strategies, allowing informed dietary choices regarding this natural milk component.

Frequently Asked Questions

The primary food source of casomorphin is dairy products derived from cows that produce the A1 beta-casein variant. These include most conventional cow's milk, cheese, and yogurt.

A2 milk contains casein, but it is the A2 beta-casein variant. This variant is not easily broken down into the opioid peptide BCM-7 during digestion, so A2 milk does not contain significant amounts of casomorphin.

Cheeses are generally high in casein, and thus have the potential for casomorphin formation. The amount varies depending on the source of the milk (A1 vs. A2) and the cheesemaking process. Cheeses from A1 milk will have more casomorphin.

Human milk contains its own version of beta-casomorphin, but it is much weaker and more easily broken down than the bovine BCM-7 derived from A1 cow's milk. Human milk is of the A2 type.

Some studies have explored links between casomorphin, particularly BCM-7, and potential gastrointestinal issues, inflammation, and neurological effects. However, the overall health impact is debated, and a recent authoritative review questioned the evidence for negative human health effects.

Milk from goats and sheep is predominantly of the A2 type beta-casein, similar to human milk. Therefore, these milks do not release significant levels of the bovine BCM-7.

For those avoiding casomorphin, plant-based milks like almond, soy, oat, or rice milk are excellent alternatives. Similarly, plant-based cheeses and yogurts are available and are free of casein.

Some dairy brands specifically market their products as 'A2 milk.' If a product doesn't explicitly state it is A2, it is safest to assume it is a mixture of A1 and A2 milk, and thus contains casomorphin potential.