For bodybuilders, ‘whey protein’ is the magic word. But what exactly is whey protein and might other forms of protein actually be better?

First of all, ‘whey protein’ is also sometimes referred to as lactalbumin. Like casein, it is derived from cow’s milk, which contains approx. 80% casein and only 20% whey protein.

Human beings can ingest amino acids, proteins, and albumins in three forms:

  • as complete proteins, as it is found in many foods;
  • as partially predigested proteins, called hydrolysates, or
  • as free amino acids.

Once these proteins are digested, the amino acids circulating in the blood are the same. There is no difference in quality, but there is a difference in their respective resorption rates in the stomach.

Whey protein is derived through ultrafiltration and is subsequently carefully dried (spray drying). The resulting product is referred to as whey protein concentrate.

When this concentrate is then predigested using enzymes or acids to split the long chains of molecules, the result is “lactalbuminhydrolysate“. Whey protein hydrolysate tends to be a little more expensive than regular whey protein concentrate.

It is also more readily absorbed by the body than concentrate. Enzymatic splicing of proteins is preferable to splitting them by using acids.

Whey protein isolate is derived through a complicated ion exchange process. Albers and Arndt recommend the term “ion-exchanged milk protein” to refer to this type of whey protein. It is reputed to contain less milk protein and sugar, but this has not been confirmed.


As predigested proteins, hydrolysates are resorbed the fastest in the stomach. Similar to free amino acids, human beings can use them almost immediately. Since these proteins have already been split into short tripeptides and dipeptides, they can easily enter the blood stream with the help of transport enzymes.

The lower the molecular weight (expressed in daltons – Da), the better the resorption rate of the amino acid hydrolysate. Hydrolysates with a molecular weight less than 500 Da can be optimally resorbed, but they do have a rather bitter taste 1.

Due to their fast absorption rates, athletes usually prefer to take hydrolysates rather than complete proteins right before or after a training session.

Complete Proteins

Complete proteins, the ones found in milk or meat for example, are made from long chains of molecules. It takes much longer to digest complete proteins than amino acid hydrolysates.

While both Casein and whey protein rank among the complete proteins, they show significant differences in their resorption qualities.

Free amino acids

Important: Individual amino acids are ingested not on account of their resorption rate, but because of their specific actions.

Whey Protein and Casein: A Comparison

CharacteristicCaseinWhey Protein
Biological value77104
Delayed protein absorption34% in 5 hoursno
New protein formation31% in 100 minutes68% in 100 minutes. Zero after 300 minutes
Oxidation of amino acidslowhigh
Improvement of Nitrogen Oxide (NO) levelsvery goodweak
Improvement during diet / weight lossVery good: Decrease in fat tissue by 7,0 Kg in 12 weeksmedium: Decrease in fat tissue by 4,2 Kg in 12 weeks
Other health benefits observed in studiesIncrease of HDL-Cholesterine, decrease of lipoproteins, lower risk of thrombocytesIncrease of HDL-Cholesterine, decrease of triglycerids, lower blood pressure, strengthening of immune system, better Glutathion level in plasma
Glutamine contenthighlow
BCAA contentmediumhigh

Source: Albers K, Arndt T. Handbuch Proteine und Aminosäuren” (Handbook of Proteins and Amino Acids). 2004. P83.

Whey Protein versus Casein: A Study

Absorption rate

One study measured the absorption rates of casein and whey protein. Study participants received either 30 grams of casein or 30 grams of whey protein on an empty stomach (10 hours without food intake). Following ingestion, their blood leucine levels were measured.

Individuals who took the whey protein evidenced the highest levels of leucine in the blood. About one hour after ingestion of the whey protein, blood concentration reached approximately 330 mmol. Participants who ingested the casein registered approximately 240 mmol.

After three hours (approx. 180 minutes), blood concentrations in both groups were about even. However, after this time period, the group who took whey protein showed a drastic drop in leucine blood levels.

After four hours, only a concentration of 100 mmol leucine was recorded. The group that received the casein, on the other hand, evidenced an almost stable concentration of approx. 200 mmol.

Muscle building, muscle breakdown

What athletes might find more important in comparing casein and whey protein, are the respective protein synthesis and protein breakdown properties associated with the two products. It has been observed that ingestion of whey protein stimulates protein synthesis. Casein appears to significantly slow protein breakdown.

In the final analysis, Casein enabled greater building of muscle mass than whey protein. This is why whey protein is often described as an “anabolic” protein, while casein is considered to be an “anti-catabolic” one.

Based on these observations, Bodybuilding-Magazine generally makes the following recommendation: whey protein should be taken in the morning, right before training, casein the night before, when going to bed.

Proportion of single amino acids in whey protein and casein

The proportions of amino acids vary from one protein isolate to the next. In addition to whey protein and casein, this table also provides the amino acid profile of milk protein and soy protein:

Amino AcidWhey ProteinCaseinMilk ProteinSoy Protein
Histidine (ess.)2,22,92,82,3
Isoleucine (BCAA) (ess.)6,85,76,44,5
Leucine (BCAA) (ess.)11,110,410,47,2
Valine (BCAA) (ess.)6,86,86,84,7
Lysine (ess.)9,98,38,36,2
Methionine (ess.)2,42,82,71,3
Phenylalanine (ess.)3,85,15,24,5
Threonine (ess.)8,04,65,13,9
Thryptophan (ess.)2,11,41,41,1
Asparagine & Aspartic acid11,37,37,911,0
Glutamine & Glutamic Acid19,22321,819,2
Values in gramm per 100 gramm of isolated protein. "ess.": essential amino acid. Source: Arndt, Albers: "Handbook amino acids"; p. 93


  1. Albers K, Arndt T. Handbook of Proteins and Amino Acids. 2004. 77
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