If you’ve ever read the ingredient list on a protein supplement such as a protein bar, you’ve likely seen the term “milk protein isolate.”

Milk protein isolate is a type of protein supplement made from skim milk. Manufacturers often add it to high protein foods and supplements as a cost-effective way to increase their protein content with little effect on flavor.

Milk protein isolate contains a blend of casein and whey proteins in a ratio similar to the ratio found in cow’s milk.

This article provides an overview of milk protein isolate, including its nutrition and benefits and how it differs from other protein supplements on the market.

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Photography by Aya Brackett

Milk protein isolate is a protein product derived from skim milk powder.

Manufacturers make it using filtering processes, such as microfiltration, ultrafiltration, and diafiltration. These remove all or most of the minerals and the lactose, a type of sugar naturally present in milk-based products (1).

The result is a powder that is at least 90% protein. There are two main types of protein in milk, casein and whey, and milk protein isolate contains both of these.

You might be familiar with whey protein powder and casein protein powder supplements. Unlike milk protein isolate, these contain only a single type of protein.

Milk protein isolate has a similar ratio of casein and whey protein to the ratio found naturally in milk — 80% casein to 20% whey (2, 3).

Because it contains much more casein than whey, milk protein isolate is slow to digest, like casein. On the other hand, if you take whey protein on its own, your body absorbs it readily and it rapidly spikes the amino acid levels in your blood (4).

Milk protein isolate is made differently from other milk-based protein powders, such as casein powder or whey powder. It’s made from skim milk, whereas whey and casein powders are made from the whey and casein portions of milk, respectively.


Milk protein isolate is made from skim milk powder through filtration processes. It has a similar protein composition to milk, with 80% of its protein from casein and 20% from whey.

Milk protein isolate has a healthy nutritional profile, which means it could be an excellent addition to your diet.

Here’s a breakdown of the nutrition of milk protein isolate per standard 1-ounce (30-gram) scoop (5):

  • Calories: 110
  • Protein: 25 grams
  • Fat: 1 gram
  • Carbohydrates: less than 1 gram

Milk protein isolate has a similar amino acid profile to milk. It contains all nine essential amino acids — those that your body cannot produce by itself (6).

This makes milk protein isolate a healthy addition to products like protein bars, meal replacement powders, and protein-fortified foods like high protein yogurts.

Milk and milk protein isolate are rich in branched-chain amino acids (BCAAs), which may help promote muscle growth and performance. This includes the important BCAA leucine, which appears to be the most beneficial amino acid for muscle growth (7, 8).


Milk protein isolate is an excellent source of protein and contains all the essential amino acids your body needs. It’s also a good source of branched-chain amino acids, such as leucine, which are important for muscle growth and recovery.

Milk protein isolate is high in protein and has properties that are linked to health benefits.

Slows digestion

Milk protein isolate is made up mainly of casein protein. Your body takes a while to digest and absorb this protein because the casein proteins change texture and become firmer in your stomach, causing their amino acids to be released at a slow, sustained rate (4).

The slow and steady supply of amino acids that casein provides as it digests may help maintain your muscles. This means milk protein isolate may help prevent muscle breakdown.

That’s why experts suggest it’s best to take casein protein before going to sleep, so it supplies you with a steady dose of amino acids while you’re without food. It may be especially helpful for building muscle mass after resistance training exercise earlier in the day (9).

Can help you build muscle mass

Milk protein isolate is high in protein and amino acids, which means it’s great for muscle growth.

It contains all nine essential amino acids your body can’t produce naturally, and it’s a good source of the amino acid leucine, which helps start muscle protein synthesis (10).

If you’re looking to build muscle mass, milk protein isolate can be a helpful option.

For example, a study in 16 healthy middle-aged men found that milk protein had a similar effect to whey protein in stimulating muscle growth (11).

In addition, research suggests that milk protein may stimulate muscle growth at a faster rate than casein protein and over a longer period of time than whey protein (12).

Compared with plant-based proteins like soy protein, milk proteins appear to be more effective at promoting muscle growth (13, 14).

May help you lose weight

Milk protein isolate is a rich source of protein, which is a key nutrient for fat loss.

Research suggests higher protein diets can increase the production of hormones that help curb your appetite, such as peptide YY (PYY) and glucagon-like peptide-1 (GLP-1). They may also reduce levels of hunger hormones, such as ghrelin (15, 16, 17).

Increasing your protein intake can also boost your metabolism and help you burn more calories.

That’s because your body burns more calories when breaking down protein than when breaking down other types of food. The breakdown of protein stimulates processes that burn more calories, such the production of glucose from protein (18, 19).

Plus, milk protein isolate may be more filling than other types of protein, such as whey. This is because it contains a high proportion of casein protein, which your body digests more slowly and which may keep you feeling fuller longer (20).

Other health benefits

Aside from helping you feel full longer and contributing to changes in your body composition, milk protein isolate may have other benefits, such as:

  • Improved bone strength. Research suggests that taking a milk-based protein regularly may help increase bone density by promoting bone growth and fighting bone breakdown (21, 22).
  • Immune benefits. A review of 16 studies found that regularly consuming dairy products had a significant anti-inflammatory effect in people who had overweight or obesity and metabolic syndrome or type 2 diabetes, as well as in people who did not (23).

Research suggests that milk protein isolate offers several potential benefits, such as aiding muscle growth, promoting fat loss, strengthening bones, and boosting immunity.

Although milk protein isolate has many benefits, it may cause issues for some people.

For starters, milk protein isolate is unsuitable for people with a cow’s milk protein allergy (24).

Consuming too much milk protein isolate may cause digestive issues, such as bloating, flatulence, cramping, and nausea. However, most people can tolerate a moderate intake of 1–2 scoops in one sitting.

Although milk protein isolate is relatively low in lactose, some people with a lactose intolerance may experience undesirable side effects when taking milk protein isolate.

Additionally, milk protein isolate is not as widely available as other protein supplements — such as whey, casein, egg, pea, hemp, and brown rice protein — so it may be harder to buy.


Milk protein isolate is unlikely to cause side effects for most people, but it’s unsuitable for people with a cow’s milk allergy. In excessive doses, it may cause digestive issues.

Milk protein isolate is relatively cheap, versatile, and easy to add to your diet.

Its neutral flavor makes it easy to add to foods to boost their protein content. That’s a key reason companies often add milk protein isolate to protein supplements such as protein bars.

You could add milk protein isolate to smoothies, casseroles, cereals, and soups.

Because it digests slowly, milk protein isolate may be helpful to take before bed or right before a time period when you’re likely to be without food. Your body will digest it over a longer period, helping you stay full.

That said, it’s perfectly fine to take milk protein isolate at any time of the day.

One way to take it is to mix 1–2 scoops (approximately 25–50 grams) of milk protein isolate powder with water and drink it close to bedtime.


Milk protein isolate is highly versatile and easy to incorporate into dishes due to its neutral flavor. Its high casein content makes it ideal as a nighttime protein supplement. However, you can enjoy it at any time of day.

Milk protein isolate is a protein product made from skim milk powder.

Manufacturers often add it to protein supplements to boost their protein content, maybe because it has a neutral flavor and is relative cheap.

Due to its high protein content, milk protein isolate may offer some health benefits, such as aiding muscle growth, promoting fat loss, and strengthening bones. It also has a high casein content, which may help combat the breakdown of muscles — especially overnight.

Its neutral flavor makes it highly versatile and easy to incorporate into your diet. You can add it to many dishes, such as smoothies, soups, casseroles, and cereals, to boost their protein content.