What is Milk Protein made of and how does it Work? Lets Find Out

Milk Protein – Whether you are a beginner or advanced in training, you have surely searched for more information on the topic. If you want to find out why milk protein enjoys such popularity, what are the types and benefits of taking it, keep reading.

What is milk protein

Milk proteins, as the name suggests, are the proteins (proteins) that make up milk, and most often, when talking about milk protein, one is referring to that from cow’s milk (as in this article).

As you know, proteins are an essential macronutrient that has a building function and without which we practically cannot exist.

Milk is among the oldest and most widely consumed foods worldwide. It is a source of high quality protein and one of the most important sources of bioactive peptides.

Milk is a liquid food (87% water content) that contains a total of 13% solids and about 9% solids without fat.

Milk is a food rich in valuable nutrients with important nutritional value due to its content of:

  • calcium,
  • vitamin D,
  • milk protein,
  • vitamin B12,
  • vitamin A,
  • riboflavin,
  • potassium,
  • phosphorus.

The total protein content of cow’s milk is approximately 3.5% by weight (36 g/l).

Difference between whey and milk protein

Whey protein is actually a type of milk protein and is probably the first thing people think of when it comes to protein powder in supplement form.

The other main type of protein in milk is casein. Let’s take a closer look at these so that one can assess when and why to take each.

Milk protein – composition

The main proteins in milk are casein and whey protein.

  • Casein represents approximately 80% (29.5 g/l) of the total protein in cow’s milk, and whey protein is about 20% (6.3 g/l).

Through a series of processes, these two proteins can be separated and made into the form of a dietary supplement.

Casein has earned the name “slow protein” and whey “fast protein”.

The main reason for the slow absorption of casein is its coagulation. When dissolved in water and drunk, casein forms a gel-like substance, apparently more difficult to digest. This slows the emptying of the stomach and the flow of amino acids into the blood.

Casein and whey protein – differences

We can highlight the following facts about casein and whey:

  • Although both proteins stimulate protein synthesis, in casein, after training, this stimulus is 2 times less than that of whey;
  • The peak of the most important amino acid, l-leucine, in both proteins is between 30 and 90 minutes after intake. On average about 60 minutes;
  • In casein, the peak of l-leucine is twice as small. This is probably why the stimulus to protein synthesis is also so much smaller;
  • Whey stimulates protein synthesis more, but its effect on muscle breakdown is very small and short-lived;
  • Casein has less effect on protein synthesis, but on the other hand is longer lasting if the casein is micellar. Tests to date show that whey protein enhances protein synthesis more effectively in the first 3 hours after intake, while casein is more effective after the third hour and persists until the seventh hour;
  • Research shows that casein reduces protein breakdown by about 30%. Unfortunately, this is a whole-body breakdown, and it’s not known exactly how much it affects the muscles themselves;
  • More recent research has shown that casein stimulates protein synthesis more in younger individuals, while whey protein is more suitable for older people. Overall, we can assume that casein is not the most suitable protein for people over 50;
  • Casein may have less effect on antioxidant activity, cholesterol and carbohydrate metabolism. The main benefits come from the amino acid L-cysteine, which is in higher amounts in whey protein;
  • Casein aids gut motility to a greater extent and lowers contractions;
  • Casein can cause an allergy that is different from lactose intolerance. In these situations, hydrolyzed whey protein is the best choice.

Following the above facts, it is clearly seen that casein is very much the opposite of whey.

Whey protein or casein?

Whey is best suited for maximum muscle building stimulation when we have the opportunity to eat shortly after. An example is the post-workout shake. Whey protein, especially the isolate and hydrolysolate, is more suitable for two-hour workouts.

Casein is mostly suitable for “guarding” muscles when we won’t have the opportunity to eat for more than a few hours. It can be used more successfully as a replacement for daytime meals or as a “nighttime” protein.

Whey protein is known as a fast and sports protein, which is why it is more widely used by exercisers. Casein is a slower and heavier protein. The most optimal time to take casein is before sleep or during the day as a meal replacement.

Benefits of casein

When the goal is maximum muscle growth, we need to stimulate protein synthesis sufficiently and reduce protein breakdown as much as possible.

This is because the total amount of new muscle tissue we build in a day is equal to the difference between protein synthesis and protein breakdown.

Casein is mostly involved in minimizing breakdown, but we can’t deny its role in synthesis, be it lesser.

Yes, we know that muscle isn’t lost that easily, overnight or over a few hours, but as the saying goes, drop by drop, a boil happens.

Casein is a protein that is derived from the milk of many species; the majority of casein consumption by humans comes from cow’s milk.

Casein is the insoluble part of milk, while whey is the soluble part; the amount of casein in standard milk protein is approximately 80%.

This quality makes it an indispensable supplement, providing a slow but constant flow of amino acids to nourish muscle mass for a long period – for example – at night. By taking milk protein, you provide your body with essential amino acids.

The peak of their release when taking casein is after about 3, up to 4 hours, which is twice as long as the usual time for other proteins. It thus proves to be an excellent anti-catabolic and muscle-protective agent.

On the other hand, this milk protein has the property of gently squeezing the walls of the stomach, creating a feeling of being full. This saves you from constant hunger, which is especially pronounced with prolonged fasting and heavy diets.

Casein protein, like all proteins, is a source of nutritional amino acids.

Because it is an animal source, it contains all essential amino acids in sufficient numbers for proper human functioning at the minimum recommended level of protein intake.

Benefits of whey protein

Here are some of the proven benefits of taking whey protein.

  • Supplemental whey protein intake to daily protein intake during a caloric deficit can further enhance the reduction of subcutaneous fat percentage. This applies to most protein sources and there is no evidence that whey protein is superior to other animal proteins;
  • Increases insulin in the short term after intake. This is typical of all proteins, but whey protein exhibits a stronger effect. However, fasting insulin levels are maintained or reduced;
  • Helps to increase lean muscle mass. This is typical of all types of protein;
  • Increases protein synthesis to a greater extent in the first hours after intake. In the long term, its potency is similar to other animal sources;
  • If taken 30-60 minutes before exercise, whey protein reduces muscle fatigue (DOMS) after exercise. This is also true when taking L-leucine or BCAAs;
  • May enhance strength gain over time as a result of training. The effect is rather long-term and whey protein has no short-term effect on athletic performance;
  • Strong antioxidant activity and increase glutathione levels in the body. It is mainly due to the amino acid L-cysteine;
  • Lowers the hunger hormone ghrelin;
  • Has been noted to improve insulin sensitivity and is more effective than casein, but so far has only been shown in overweight people and during a weight loss diet. It has yet to show a similar effect in healthy athletes;
  • Lowers “bad” and total cholesterol successfully;
  • Lowers peak triglyceride levels after fat intake as well as steady levels throughout the day;
  • Like any type of protein, whey protects against bone mineral loss but does not lead to the accumulation of new bone mineral mass;
  • Reduces appetite. This is typical of any type of protein. The effect is probably weaker than that of casein or protein matrices;
  • Reduces intestinal permeability. Most likely due to high levels of L-glutamine;
  • Helps regulate liver enzymes, but the effect is small. Most likely due to the amino acid L-cysteine;
  • Lowers liver fat more effectively than other proteins.

What milk protein is made of

Whey protein and casein are made from milk.

When a coagulant (a substance that turns proteins into a gel) is added to milk, the casein and whey separate. Whey protein is the water-soluble part of milk and therefore undergoes a specific processing to become a concentrated and powdered protein source.

Whey protein is not a single type of protein but a class of proteins that are named whey according to their common property, which is water solubility and method of extraction.

Whey can be extracted from virtually any type of milk – cow, buffalo, goat, camel, including human milk. Most commercially produced whey protein is from cow’s milk because it is the most abundant and available.


As long as a person has no health reasons not to take milk proteins, they can be part of a complete menu – both in the form of food and in the form of food supplements (protein powder).

The main dairy proteins are whey protein (a class of protein) and casein, each of which has its advantages and disadvantages, so the choice depends on personal preferences and goals.

Whey protein has earned its name as a fast digesting protein suitable for post-workout intake, while casein is considered slow digesting and therefore suitable for bedtime.

However, it is not necessary to be a “slave” to such rules, especially for amateur exercisers, because in practice it is the total amount of protein that is more important for goals and recovery, which should be obtained mainly through food.

Sources used

You may also want to chek out our other post about proteins