Whey protein and casein protein are often spoken about together but not everyone knows the difference between them. In this blog, we’ll help you understand exactly what casein protein powder is, where it comes from, and its health benefits, so you can make an informed choice about the protein powders you incorporate into your routine.

Like whey protein, casein is a dairy protein which comes from cow’s milk. While whey protein is the by-product liquid from curdling during cheese-making, casein comes from the solid curds separated out in the same process, sometimes used for making cheese. 

Casein accounts for around 80% of the total protein in milk, while whey makes up the other 20%. (1) It’s a protein that’s also found in human breast milk, making up around 30% of the protein content. (2)

How is casein protein powder made?

Once milk has been collected, and the solid curds separated from the liquid whey, they are washed with water, drained, dried, and then ground into a powder.

One common form of casein protein is micellar casein, which is the natural, unaltered form of casein that maintains its structure during processing. Other forms of casein, like hydrolysed casein, undergo processing that breaks down the proteins for faster digestion. (3)

We can think of whey and casein as siblings. Both are high-quality proteins derived from milk, meaning they come with some similarities, but they also have their differences.

Here’s your lowdown on what this might mean for which you choose:

Similarities

Complete amino acid profile

Both casein and whey protein are excellent sources of all nine essential amino acids – named as such because our bodies cannot produce them, so we must get them from our diet. Both also contain good amounts of the three branched-chain amino acids (BCAAs), leucine, isoleucine, and valine.

Casein is slightly higher in amino acids like histidine, methionine, and phenylalanine, while whey is higher in leucine. (4)

High-quality protein sources

Both proteins have high bioavailability, meaning they are absorbed and utilised by the body quite easily, broken down into amino acids for muscle support and bodily functions. (5)

Differences

Digestion and absorption rates

Although both casein and whey are utilised by the body in similar ways, their main difference is the rate at which they’re broken down and absorbed.

Compared to whey protein, casein is digested and absorbed at a slower rate. Some research suggests that this is because casein forms a gel in our stomachs once consumed, meaning it can take nearly twice as long to digest and absorb as whey. (6)

Research has also shown that the levels of amino acids in your blood stay elevated for up to 5 hours after consuming casein, but only for around 90 minutes after consuming whey. (7)

Timing of intake

Given its slower absorption rate, many people use casein before going to bed as a form of slow-release protein. (8) Whey protein, on the other hand, can generally be added to your diet at any time of the day, owing to its fast digestion and quick delivery of nutrients to the body. (9)

For individuals with lactose intolerance or sensitivity to dairy, casein and whey protein may not always be well-tolerated. There’s growing interest, though, in A2 casein, which may offer a more digestible alternative for those with dairy sensitivities.

A2 casein refers to a type of protein found in cow’s milk that comes from A2 cows, which produce only the A2 beta-casein protein, as opposed to the more common A1 beta-casein. Studies suggest that A2 casein may be easier on the digestive system for some people, potentially reducing the bloating, inflammation, and discomfort that can sometimes come from consuming regular dairy-based proteins. (10)

Coincidentally, whey protein doesn’t differ whether it’s from A1 or A2 cow’s milk from what we’ve found. You can read more about this here.

When it comes to choosing a protein powder, casein offers a few unique advantages which make it suitable for a range of health goals:

Complete protein source: As we’ve seen, casein protein is a complete source of protein, full of all the essential and branched-chain amino acids your body needs to thrive. Alongside whole food protein sources, you can be sure you’re getting all the right building blocks from a serving of casein protein powder.

Steady protein release: One of the most notable benefits of casein protein is its slow, steady release of amino acids. Unlike a faster-absorbing protein, a casein protein shake allows for sustained protein support over several hours. This makes it ideal for maintaining muscle health between meals or overnight. (11)

Long-lasting satiety: Protein is known as one of the most satiating nutrients (12) and casein protein in particular may help you feel fuller for longer. (13) This is particularly useful for those who are looking to manage their weight or stick to a healthy eating routine.

Supports bone health: Many casein protein powders are a good source of calcium, an essential mineral for maintaining strong, healthy bones. (14)

Bioactive compounds: Casein protein also contains bioactive peptides which have been studied for their positive effects on lowering blood sugar. (15)

As with any protein powder, there are some drawbacks to consider in your decision-making. Some of the below might make casein less suited to your needs:

Slower absorption: Although casein’s slow-digesting properties are often viewed as an advantage, this may not be ideal for those looking for a quick protein boost. Whey protein, for example, may be a better choice when rapid amino acid delivery is beneficial.

Dairy sensitivity or allergies: While those with lactose intolerance may be able to use casein without any issues, as much of the lactose is removed, those with a milk allergy and therefore casein protein would need to avoid it. (16) 

Amino acid profile: Casein is a complete protein source but compared to whey, it contains less of the BCAA leucine, which is key for muscle support. (17)

Casein protein powder offers its own set of benefits thanks to its slow absorption rate, making it an excellent option for those seeking sustained protein delivery to the muscles and body. Whether you're looking to maintain muscle mass, feel fuller for longer, or add more calcium to your diet, casein is a high-quality protein source worth considering.

However, if you're sensitive to dairy or looking for higher leucine levels, whey protein or plant-based alternatives might be better suited to your needs. As always, the best protein powder is the one that fits your specific dietary requirements and health goals.