What is Casein Protein?
Casein proteins are the primary constituents of animal milk proteins (accounting for roughly 80% of the total protein content), and are often touted for their exceptionally slow rate of digestion and absorption. (1) The specific fractions/types of casein protein (denoted alpha s1/s2, beta and kappa) differ in proportion according to the species from which they're synthesized; the primary source of casein proteins in human nutrition come from dairy cattle. *Throughout the rest of the guide the term “casein” will be in singular form but will encompass all 4 fractions of casein proteins.*
A distinguishing characteristic of casein protein is its insolubility at lower pH (such an environment would be that of stomach acid). The mechanism for casein’s slow absorption arises from its coagulating properties when exposed to stomach acid; the resulting coagulant precipitates and creates a slow, sustained rise of plasma amino acids. (2) It is for this reason that casein protein is suggested to have longer-lasting anti-catabolic properties (upwards of 7-8 hours post ingestion) compared to a rapidly-digesting protein such as whey. (3)
While casein is certainly effective at promoting muscle protein synthesis, one of its differentiating features is the ability to provide a sustained rate of amino acid uptake versus a rapid, transient increase that would arise from whey protein ingestion. (7) Given this, casein may be more beneficial to individuals who are looking for a protein supplement that can provide several hours of nourishment and satiety versus a quicker digesting protein like whey. As noted earlier, this gives casein longer-lasting anti-catabolic properties and is why people often refer to it as the optimal “bedtime” protein; casein’s prolonged digestion helps promote a positive nitrogen balance during extended hours of sleep. However, don’t constrain casein supplementation to just before bed, as it can be beneficial at most anytime of the day, even pre and post workout (*more on this in the When should I take Casein protein section). (8)
Another feature of casein protein is its rich calcium content (*see the Micellar Casein section below for more on why this is). Calcium is an essential mineral for bone health and research has suggested that in can enhance fat loss in overweight subjects. (9) For this reason, individuals that find they struggle to meet their daily quota of calcium intake through food sources could stand to benefit with a casein protein supplement.
Casein proteins are the primary constituents of animal milk proteins (accounting for roughly 80% of the total protein content), and are often touted for their exceptionally slow rate of digestion and absorption. (1) The specific fractions/types of casein protein (denoted alpha s1/s2, beta and kappa) differ in proportion according to the species from which they're synthesized; the primary source of casein proteins in human nutrition come from dairy cattle. *Throughout the rest of the guide the term “casein” will be in singular form but will encompass all 4 fractions of casein proteins.*
A distinguishing characteristic of casein protein is its insolubility at lower pH (such an environment would be that of stomach acid). The mechanism for casein’s slow absorption arises from its coagulating properties when exposed to stomach acid; the resulting coagulant precipitates and creates a slow, sustained rise of plasma amino acids. (2) It is for this reason that casein protein is suggested to have longer-lasting anti-catabolic properties (upwards of 7-8 hours post ingestion) compared to a rapidly-digesting protein such as whey. (3)
Benefits of Casein Protein
The benefits of casein protein are numerous, especially for those who are following an active exercise regimen. Much interest in casein protein and its correlation to muscle hypertrophy arose from early studies comparing fluid milk ingestion to soy proteins. It has been elucidated in a plethora of studies that milk proteins are superior to soy/vegetable proteins in terms of promoting muscle hypertrophy after resistance training. (4, 5) All of the major animal milk proteins (i.e. casein, whey, albumin) are capable of promoting muscle protein synthesis to some degree via activation of the mammalian target of rapamycin (mTOR) pathway and they are complete proteins (meaning they possess all of the essential amino acids). (6)While casein is certainly effective at promoting muscle protein synthesis, one of its differentiating features is the ability to provide a sustained rate of amino acid uptake versus a rapid, transient increase that would arise from whey protein ingestion. (7) Given this, casein may be more beneficial to individuals who are looking for a protein supplement that can provide several hours of nourishment and satiety versus a quicker digesting protein like whey. As noted earlier, this gives casein longer-lasting anti-catabolic properties and is why people often refer to it as the optimal “bedtime” protein; casein’s prolonged digestion helps promote a positive nitrogen balance during extended hours of sleep. However, don’t constrain casein supplementation to just before bed, as it can be beneficial at most anytime of the day, even pre and post workout (*more on this in the When should I take Casein protein section). (8)
Another feature of casein protein is its rich calcium content (*see the Micellar Casein section below for more on why this is). Calcium is an essential mineral for bone health and research has suggested that in can enhance fat loss in overweight subjects. (9) For this reason, individuals that find they struggle to meet their daily quota of calcium intake through food sources could stand to benefit with a casein protein supplement.
Casein Benefits Review:
- Stimulates muscle protein synthesis/activates mTOR pathway
- Is a complete protein source
- May be a useful appetite suppressor since it provides more enduring satiety than a rapidly-digesting source of protein
- Provides anti-catabolic properties for longer periods of time than rapidly-digesting proteins
- Is a rich source of calcium which may be beneficial for bone health and fat loss
- Individuals looking a convenient and quick way to increase protein intake will derive the most benefit out of supplementing with casein protein. These include:
- Bodybuilders & strength trainers
- Athletes
- Vegetarians
- Recreational exercisers and those new to weight/strength training
- Anyone else who is looking for a simple way to get more protein in their diet (*allergies notwithstanding)
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