Is casein in cheese an opiate?

November 22, 2025 •

3 min read

A common claim is that pizza, a cheese-heavy food, is among the most craved foods. However, is casein in cheese an opiate, or is the science more complex?

Quick Summary

The relationship between the milk protein casein and casomorphins, opioid-like compounds, is investigated. This explores how these peptides affect the brain's reward system, and whether this constitutes addiction.

Key Points

Casein's Opiate-like Effect: Casein, a protein in cheese, breaks down into opioid peptides (casomorphins) during digestion.
Dopamine Release: Casomorphins can bind to opioid receptors in the brain, triggering dopamine release, contributing to the pleasure of eating cheese.
Not a Drug Addiction: The effect of casomorphins is mild and not comparable to clinical drug addiction; labeling cheese as an opiate is a sensationalized claim.
Concentrated Protein: Cheese has a higher concentration of casein than milk, delivering a higher dose of casein and casomorphins.
Other Factors at Play: Cheese cravings also involve high fat, salt, appealing texture, and psychological associations.
Individual Sensitivity: Genetic variations in casein digestion can affect casomorphin production, potentially leading to gastrointestinal issues in sensitive individuals.

The Casomorphin Connection: A Closer Look

At the center of the debate about cheese's 'addictive' properties is casein, the main protein found in milk and, by extension, cheese. During digestion, especially in the stomach, casein is broken down by enzymes into smaller protein fragments called casomorphins. These casomorphins are, in fact, opioid peptides. This is a natural, biological process designed to have a calming effect on infant mammals, including humans, to promote breastfeeding and bonding.

How Casomorphins Interact with the Body

These casomorphins can bind to the same opioid receptors in the brain that respond to narcotics. This interaction can trigger a mild, pleasurable feeling and a dopamine release, which is the brain's natural reward system. This is the underlying biochemical reason for why cheese and other dairy products might be craved. The rewarding sensation encourages consumption, serving the evolutionary purpose of ensuring nutrient intake for offspring.

The Difference Between 'Opiate-Like' and 'Addictive'

While the presence of opiate-like peptides in cheese is a fact, labeling cheese an opiate is highly misleading and sensationalized. The potency and effect are vastly different from street drugs. The term 'food addiction' itself is controversial within the scientific community, though studies using the Yale Food Addiction Scale have explored addictive-like eating behaviors, with highly processed foods often ranking high. It is crucial to distinguish between a mild, natural reward mechanism and a clinical drug addiction that leads to severe dependency and withdrawal.

Factors Influencing Cheese Cravings

The opiate-like effect of casomorphins is not the only reason people crave cheese. Other factors include:

Concentration: Cheese contains a much higher concentration of casein than liquid milk, which means more casomorphins are released.
Fat and Salt Content: Many cheeses are high in fat and salt, two components known to make foods highly palatable and rewarding.
Texture: The unique mouthfeel of different cheeses also plays a role in sensory appeal and craving.
Genetics: Individual genetic variations in how enzymes break down casein can influence the quantity and type of casomorphins produced, such as between A1 and A2 milk variants.
Psychological Association: Cheese is associated with comfort food and social gatherings, reinforcing the positive psychological connection.

Casomorphins: Beyond the Reward System

Research into casomorphins and their physiological roles is ongoing and complex, with some suggesting additional effects in sensitive individuals.

Casein Variants and Their Peptides

Different variants of beta-casein, such as A1 and A2, produce different types of casomorphins during digestion. The A1 variant, for example, is more likely to release Beta-casomorphin-7 (BCM-7), which has stronger opioid-like properties than BCM-9, the peptide more commonly associated with A2 milk. Some research suggests that BCM-7 may be associated with various gastrointestinal and other inflammatory issues in susceptible individuals, though more research is needed.


Feature	Casomorphin (from Casein)	Classic Opiates (e.g., Morphine)
Potency	Very low; mild, natural effect.	Very high; powerful psychoactive effect.
Binding Affinity	Binds to opioid receptors, but weakly.	Binds strongly to opioid receptors.
Clinical Addiction	No; no clinical dependency or withdrawal syndrome.	Yes; leads to physical dependency and withdrawal.
Reward System	Triggers mild dopamine release alongside other food factors.	Powerful, direct trigger of the dopamine reward system.
Source	Digestion of a natural food protein.	Pharmaceutical or illicit drug.

Conclusion: The Truth Behind the Cheese Craving

The idea that cheese is a drug is an overstatement. While the milk protein casein breaks down into opioid-like peptides called casomorphins, their effect on the human brain is extremely mild compared to actual narcotics. These peptides, combined with the high fat, salt, and pleasing texture of cheese, create a powerful and enjoyable sensory experience that can lead to strong cravings. For most people, a love of cheese is simply a preference for a palatable, rewarding food, not a chemical dependency. However, individuals sensitive to dairy may experience gastrointestinal or inflammatory responses related to these peptides. Understanding the science allows for a more nuanced perspective on our relationship with food, separating a simple craving from a dangerous addiction. For more in-depth information, the European Food Safety Authority (EFSA) provides a comprehensive look at the health implications of casomorphins.

Frequently Asked Questions

No, this is a highly sensationalized claim. While cheese contains mild opioid-like compounds called casomorphins, their effect is not comparable to the physical dependency and withdrawal associated with narcotics.

A casomorphin is an opioid peptide, a small protein fragment, that is released when the milk protein casein is digested. It is not a classic opiate but has a mild opiate-like effect on the body.

Intense cheese cravings result from factors like the mild dopamine release triggered by casomorphins, high fat and salt content, and the unique, pleasurable texture of cheese.

For most, cheese is a safe and nutritious food providing protein, calcium, and other minerals. The opiate-like effect is a normal biological function. Issues are most common for those with dairy allergies or sensitivities.

Yes, different genetic variants of casein, such as A1 and A2, produce different types and quantities of casomorphins upon digestion. Some research suggests BCM-7 from A1 milk may have stronger effects than BCM-9 from A2 milk.

After casein is broken down into casomorphins, they can bind to opioid receptors in the brain. This process activates the brain's reward center, releasing dopamine and creating a feeling of pleasure.

All dairy products contain casein and thus the potential to form casomorphins. However, cheese has a much higher concentration of casein than liquid milk, making the effect more pronounced.