Why is casein harmful?

Slow Protein

Sports nutrition adverts persistently that each athlete must have a whole arsenal of large cans with additives - all kinds of protein, amino acids BCAA, creatine, L-carnitine, pre-training boosters and vitamins at doses of 1000%recommended.

The main emphasis of recommendations is made on the use of huge doses of whey protein during the day and on the intake of casein( "slow" protein) at night. I agree with advertising promises, casein protects muscles from decay, as it is digested much slower than usual protein.

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What is casein?

Casein is a complex protein that is the main cow's milk and serves as the main material for curds and cheese. The name is derived from the Latin word caseus - cheese. Casein accounts for about 70-90% of the protein profile of milk, while whey protein does not exceed 2-5%.

The behavior of casein in the human stomach is similar to the behavior of gluten, which is also a complex protein. Both form clots, gluing the contents and, in fact, complicate the digestion of food. Traditionally, both casein and gluten have served as materials for manufacturing technical glues. Is casein a slow protein?

The view on the slow rate of assimilation of casein is based on a scientific study conducted 20 years ago. Sixteen subjects were divided into two groups, which received a different type of milk protein on an empty stomach. Twice per hour the level of amino acid leucine in the blood was removed( 1).

With the use of whey protein, the level of amino acid leucine first increased, peaking at 30-60 minutes, then gradually decreased. In the case of casein, the leucine level first reached a plateau( 60% of the serum protein level), then decreased, but more smoothly.

Whey Protein Vs. Casein

Comparison of casein with whey protein

The graph on the left - the final results of scientific research, on the right - their interpretation in advertising. Despite the fact that the real schedule is more difficult to understand, manipulation is obvious. Advertising significantly overestimates the difference in peak values, exaggerating the degree of decline over time.

It is also important that the recommendation to use casein at night for "muscle conservation" and slowing catabolism has never been tested in the laboratory. This statement of the manufacturers of sports nutrition, based solely on their own opinion on the metabolism of athletes.

Do I need to take casein at night?

The mechanics of the scientific research mentioned above is also far from real life. Subjects did not eat anything 10 hours before the study and 7 hours after taking casein or whey protein. In fact, it is not known how the presence of food in the stomach affects the rate of assimilation.

It is likely that the presence of complex carbohydrates( especially fiber) and fats slows down the absorption of whey protein. Even if you believe that at night muscles need to be "protected"( which is highly unlikely), you can simply take a portion of whey protein together with dinner.

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Casein and gluten: twin brothers

Gluten-damaging interference is gaining momentum every year. Many consider this substance the main enemy, linking with it obesity, weakening of immunity and the development of diseases of the gastrointestinal tract. Partially opinions about the dangers of gluten are also confirmed by scientific research.

However, casein is a twin brother of gluten. Both are indigestible protein, gluing the contents of the stomach. Followers of a healthy lifestyle, who are afraid of 2-3 grams of gluten in a slice of ordinary white bread, can consume 30 grams of a similar substance every day before going to bed.

Casein: the final recommendation of

The use of casein protein for muscle growth is based only on advertising promises and distortion of data, rather than on real facts. Despite the ease of obtaining casein, the price of such a sports supplement is usually higher than the price of the isolate. Influence on health is in question.

In addition, there are pilot studies showing the relationship between the use of casein and the occurrence of cancer. It is revealed that a certain part of people are allergic to this substance. In the absence of more accurate data, we strongly recommend that you abandon casein.


Casein is the key protein of milk, serving as the basis for cheese and cottage cheese. Its benefit as a slow protein is exaggerated, and the health risk is not investigated. In addition, casein should cost several times cheaper than whey protein, but in the form of sports supplements, it is usually much more expensive.

Scientific sources:

  1. Nutritional evaluation of caseins and whey proteins and their hydrolysates, source
  2. Slow and fast dietary proteins differently modulate postprandial protein accretion, source