What Is Casein?

Casein is a milk protein used as a dietary supplement

Casein is a protein found in milk and dairy products. It accounts for roughly 80% of the protein in milk, cheese, and yogurt. (The other 20% is whey.)

Casein is also sold as a protein powder dietary supplement. It is commonly used by bodybuilders to promote exercise recovery and increase muscle size. Casein is also found in dairy-based baby formulas.

This article discusses casein, its uses, and potential health benefits. It also explains possible side effects of casein and what to look for when buying casein-based protein supplements.

Dietary supplements are not regulated like drugs in the United States, meaning the Food and Drug Administration does not approve them for safety and effectiveness before products are marketed. When possible, choose a supplement that has been tested by a trusted third party, such as USP, ConsumerLabs, or NSF.

However, even if supplements are third-party tested, that doesn’t mean that they are necessarily safe for all or effective in general. It is important to talk to your healthcare provider about any supplements you plan to take and to check in about any potential interactions with other supplements or medications.

Supplement Facts

  • Active ingredients: Calcium, peptides, amino acids
  • Alternate name: Sodium caseinate
  • Legal status: Available over the counter
  • Suggested dose: 20 to 40 grams before or after workouts
Chocolate-flavored protein powder with casein
 Gabriel Vergani / EyeEm / Getty Images

Uses of Casein

Casein is a complete protein. This means it contains all of the essential amino acids required by the human body. In its purest form, casein is a white-colored solid with no taste. All mammals produce casein as a component in milk for their offspring.

Human breast milk consists of 40% casein and 60% whey, while cow's milk protein is 80% casein and 20% whey. Since casein binds to calcium and phosphorus, milk is a good source of these vital minerals.

Casein is a milk protein that's produced by mammals.

The popularity of casein supplements for the average adult might be more hype than it's worth. For most people, protein deficiency is rare, and supplements are unnecessary.

Keep in mind that supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or doctor. No supplement is intended to treat, cure, or prevent disease.

Exercise Recovery and Muscle Building

In its isolated form, casein is used as a protein supplement. Bodybuilders may ingest casein products immediately after a workout or before going to bed to promote exercise recovery.

As a protein supplement, casein supplies muscles with the full range of amino acids required for exercise recovery and strength building. After a challenging workout, your body repairs the small tears created in your muscle fibers to build them back to become bigger and stronger.

In addition to serving as a complete protein, casein is used by bodybuilders because of its slow digestibility. Soy protein and whey protein are released into the bloodstream quickly, while casein takes about six to seven hours to digest fully.

Casein's reduced rate of digestion steadily supplies amino acids to damaged muscle tissue for an extended time after a workout, promoting better recovery. Slow digestion also contributes to satiety, helping you feel full for longer and curb unhealthy food cravings.

Proper sleep and adequate protein intake are critical for muscle recovery. Casein products work by providing an extra boost of protein to support muscle tissue.

Bone Health

Casein-rich dairy foods are also good sources of calcium. Most adults require between 1,000 milligrams (mg) to 1,200 mg of calcium per day. Given the dual importance of adequate calcium and protein intake for bone health, casein-rich foods may help in the prevention of osteoporosis.

Food Industry

Casein is a primary component in cheese-making. It is also used to create infant formulas as a substitute for breast milk.

What Are the Side Effects of Casein?

For most people, casein supplements are probably safe. Most healthy adults do not experience side effects when taking casein at appropriate doses.


Casein may not be suitable for everyone. It is always a good idea to discuss supplement use with your doctor before adding a new supplement like casein to your routine.


Cow's milk is one of the most common food allergens, which can pose a problem for formula-fed infants. Milk allergies usually start during infancy or early childhood, but they can also develop later in life.

If a baby is allergic to cow's milk, their healthcare provider may suggest a hydrolyzed casein-based formula. Although its bitter taste isn't always preferred, hydrolyzed casein can help babies with allergies get the nutrients needed during critical growth periods.

If you have an allergy to milk, ask your healthcare provider whether you should have testing to detect the specific proteins responsible for your allergy. It's possible to be allergic to other proteins in milk, like whey, but not casein.

Nonetheless, it's best to play it safe. See an allergist to help determine the root cause of your milk allergy before risking your luck with casein.

Allergic reactions to milk should not be confused with lactose intolerance. Many people are intolerant to lactose (milk's natural sugar) but will tolerate the casein in yogurt or cheese just fine. An allergy to cow's milk is more likely to cause symptoms like hives, chest tightness, or dizziness, whereas lactose intolerance does not.


Some researchers have suspected a potential relationship between casein consumption and autism, but this is debated. Parents and caregivers often provide variations of casein-free meal plans to children with autism in an attempt to encourage typical development and reduce challenging behaviors.

Some families claim significant behavioral improvements while adhering to a casein-free meal plan, but the evidence is still largely inconclusive. As a result, it's not accurate to assume that casein is a cause for concern in children with autism.

Dosage: How Much Casein Should I Take?

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.

A typical dose of casein is between 20 and 40 grams daily. However, how much you should take depends on variables like age and general health.

What Happens If I Take Too Much Casein?

The ingestion of more calories than the body needs, whether from casein-based protein sources or not, can still result in unhealthy weight gain.

It's also worth noting that high protein intake from casein or other supplements can be dangerous for some individuals, particularly those with impaired kidney function. Adding a protein supplement can put dangerous stress on already-weakened kidneys.

How To Store Casein

Protein powders have been found to have a shelf life of around 18 months when kept at temperatures below 80 degrees F. Make sure to keep casein powder in a sealed container.

Try to use casein powder before the expiration date, but note that expired doesn't necessarily mean the casein isn't safe to consume. It does, however, mean that the casein may have lost protein content.

Frequently Asked Questions

  • Is casein addictive?

    Casein is mildly addictive and the reason many people crave cheese. During digestion, casein—a protein that is plentiful in cheese—gets broken down into casomorphins. These opioid-like peptides attach to dopamine receptors in the brain.

    This prompts the release of dopamine—a feel-good neurotransmitter linked to reward circuits. This causes your brain to associate casein (and cheese) with pleasure, resulting in cravings for more casein.

  • Does casein help you sleep?

    Possibly. Casein contains the amino acid tryptophan, which can help to promote sleep. Some people recommend having a casein protein shake before bed to get a better night's sleep.

  • What is the difference between casein and whey?

    Both casein and whey are proteins derived from milk. Whey digests quickly, making it ideal for before workouts. Casein digests slowly and will help you to feel full longer. Both help to repair and build muscles.

Sources of Casein and What To Look For

Casein is available as a supplement, but it is also present in dairy products. Healthcare providers typically recommend whole foods over supplements since whole foods are more nutrient-rich.

Food Sources of Casein

A cup of whole milk has about 300 mg of calcium, much of which is found in casein. It also contains about 8 grams of protein.

You can also get casein from cottage cheese and yogurt. A cup of 2% fat cottage cheese contains about 225 mg of calcium and 24 grams of protein. A cup of whole milk Greek yogurt contains about 235 mg of calcium and 19 grams of protein.

Casein Supplements

As a supplement, casein usually comes as a powder. It can be mixed with water or milk to make a protein shake. It can be purchased in various flavors such as chocolate and vanilla for palatability.

Legality of Casein

Despite its muscle-building benefits, casein is not considered a performance-enhancing drug. Casein's natural presence in dairy classifies it as a food product, even when taken in supplement form.

When athletes use casein, there is no associated risk of legal ramifications, such as those associated with steroids or stimulants.


Casein is a protein found in dairy products. It is often used by bodybuilders to support exercise recovery. Because it contains calcium, it may also support bone health.

Casein should not be used by people with milk allergies. It is always a good idea to talk to your healthcare provider about adding casein or any other supplement to your routine.

A Word From Verywell

Casein can offer several benefits, especially for infants or for adults who do resistance training. A casein supplement can support muscle growth, but in many cases, it's not necessary. If your meal plan includes enough protein from food sources like eggs, meat, seafood, or soy, there's a good chance you're already getting what you need.

Nonetheless, a casein-based protein supplement might be a great choice for those trying to gain weight or struggling with a poor appetite. Only you (and your healthcare provider) can decide which foods and supplements will best support your unique needs.

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Anastasia Climan, RDN, CD-N
Anastasia, RDN, CD-N, is a writer and award-winning healthy lifestyle coach who specializes in transforming complex medical concepts into accessible health content.