Casein Protein

Your endeavor to achieve your physique and fitness goals starts with proper nourishment. When you push your body physically the demand for protein can significantly increase; this increased demand can make it cumbersome to meet your protein needs purely with solid food sources such as poultry, beef, eggs, etc.—this is where supplemental sources of protein come in handy.

Many people are familiar with whey protein’s benefits since it is quickly absorbed and highly bioavailable, but casein protein can be an even more viable option in many situations. This guide will serve as a complete resource to supplemental casein protein by expanding on what casein protein is, how it’s produced, its benefits, how it differs from whey protein, who should take it, and which products we recommend.

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)

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)

How is Casein Protein Made?

Casein protein is found in fresh milk produced via mammals. The supplemental forms of casein are produced by various food technology methods including acidification, ultra-filtration, enzymatic hydrolyzation, salification and others. (10) Casein protein powders have a cream-like color and are bland in flavor/odor in their raw state. Casein protein supplements maintain a shelf life of approximately two years when stored in the original sealed container and kept at room temperature. (10)

What are Casein Hydrolysate and Micellar Casein?

Before we discuss the differences between these two forms of casein protein, a fundamental understanding of protein structure and digestion is necessary. Proteins are made up of many peptide bonds that conjoin amino acids via carbon-nitrogen bonds. These bonds are necessarily “lysed” (i.e. split) by the process of hydrolysis which subsequently increases free amino-acid concentrations in the blood. Hence, hydrolysis refers to the splitting of a chemical bond by an H2O molecule.

Casein hydrolysate (also sometimes referred to as hydrolyzed casein) is enzymatically hydrolyzed during processing to improve its rate of absorption. (11) The increase in digestion/absorption rate and amino acid delivery to skeletal muscle tissue arises from the fact that the protein structure is essentially “pre-digested” into smaller peptide fractions from its intact, original structure.

Micellar casein is a soluble, high-quality milk protein powder with a clean flavor. Micellar casein protein can essentially be described as the whole, undenatured form; in nature, most casein protein exists as what’s known as a casein micelle. (1) A casein micelle is a colloidal particle that biologically serves to transport insoluble calcium-phosphate complexes in liquid form to the stomach for clotting and subsequent digestion. In fact, over 90% of the calcium content in skim milk is linked with the casein micelle. (1) For this reason, as aforementioned in the benefits section, casein protein supplements can serve as potent sources of calcium.

How should I take Casein Protein?

Casein protein powder can be used in many applications just like the myriad of other protein powders. Many people like the convenience of having something available on the go so just mixing casein in sufficient fluid (roughly 8oz fluid for every 25g of protein content) with a spoon/blender/shaker is adequate. Due to its chemical properties, casein protein powder will mix a bit thicker than whey protein powders will, and the texture can sometimes be described as a bit gritty.

Furthermore, the characteristic coagulating property of casein protein when it’s exposed to acidic environments and/or high temperatures make it tricky to bake with or add to hot foods since it will tend to be insoluble and clump up. But a great application of casein protein powder (for those who like to get creative in the kitchen) is to make “protein pudding”, also colloquially referred to as “sludge”. Since casein powder will readily gel/thicken up when mixed in minute amounts of liquid this can be a nice treat for those who get tired of always drinking their protein supplements. Find out how to make protein sludge here.

When is the best time to take my casein protein supplement?

Casein protein is versatile and can be used virtually whenever you desire more protein in your diet. They are especially useful when prolonged periods of time without feeding are to be expected (such as before going to bed). Casein protein can also be combined with whey protein to enhance the anabolic response8; if you are seeking a great option for after a workout, try combining whey and casein protein supplements in a 2:1 ratio, respectively.

Whey vs. Casein

Whereas whey protein is readily acid-soluble (and hence creates a rapid increase in plasma amino acid levels), casein coagulates when exposed to acidic solutions and slowly precipitates, resulting in a more sustained rate of digestion. (11) High-quality proteins such whey and casein are capable of promoting muscle protein synthesis post-exercise by activating the mammalian target of rapamycin (mTOR) signaling pathway. (6)

While whey protein on its own has been shown to more effectively stimulate muscle protein synthesis directly after a workout (8), casein may actually serve as a potent adjunct to whey by enhancing the anabolic response to weight training. (6) Don’t think of it as an either-or issue; both casein and whey supplements are your allies in the battle to build your dream physique and they should be used in conjunction with one another.

To read more about whey protein’s, check out our Expert Guide here.

Casein FAQ

Is a casein protein supplement okay if I have an allergy to milk?

Unfortunately casein is not safe for consumption if you have allergic reactions to milk; the proteins in milk are known allergens.

Is a casein protein supplement okay if I am lactose intolerant?

Yes, casein is a protein in milk and has nothing to do with lactose (a sugar component of milk).

Do rice, soy, or almond milks contain casein protein?

No, these are vegetable/grain-based milk products and casein protein is found in animal-derived milk products.

How much protein should I aim for everyday?

This will vary according to your goals, lifestyle and metabolic factors. A good starting point for trainees is 1 gram of protein per pound of lean body mass.

I’m a vegetarian, can I use casein supplements?

Yes, casein supplements are a great source of protein for those abstaining from animal sources of protein.

Can’t I just drink milk instead of buying a casein supplement?

Yes, but it’s actually a better value in terms of price per gram of protein to use a pure casein supplement since milk contains other nutrients like carbohydrates and fats.