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Introduction
Casein is the predominant protein found in milk. While whey makes up about 20% of the protein content in cow milk, casein makes up the other 80% [1]. Casein protein has been used by athletes for decades for its anticatabolic (muscle sparing) properties.
Casein is usually found in three forms, calcium caseinate, micellar casein, and milk protein isolate. Calcium caseinate is considered to be lower quality, while micellar casein and the casein in milk protein isolate are identical. This makes milk protein isolate more economical given a choice between the two. In comparison to whey, casein is not as high quality by some conventional standards of measuring protein quality. The biological value of casein protein is about 70 compared to 100 for whey. However, milk protein has a biological value of over 90. And if we use the PDCAAS, a more modern method of determining protein quality, all three of these proteins (casein, whey, and milk) are on equal footing at 1.00.
What is unique about casein protein is the slow digestion rate. Studies that compare whey and casein administered in the workout period inevitably find that whey protein exerts a far stronger anabolic response in this case [2]. However, when casein is administered at other periods the strength gains are twice of those seen with whey [3]. This is because while whey stimulates protein synthesis much more than casein in the short term, casein causes a sustained release of amino acids, preventing muscle breakdown for a more extended period of time [4]. This makes whey the protein of choice for the workout period, with casein preferable at other times, especially before periods of fasting (such as sleep). Because casein does not have a pleasant taste, a blend of casein and whey is generally used. An additional reason not to completely ditch the whey is that it has a plethora of health benefits that casein does not have, although some peptides in casein do have free radical scavenging activity [5].
Marketing techniques
There are many "sustained release protein" products on the market. However, many of these probably do not contain as much casein as they appear. Companies want to avoid putting too much casein in a product for a few reasons. First, casein is more expensive than whey. Second, casein has a distinct, malty taste which many find unpleasant, and the taste is not easy to mask. However, because a protein with high casein content is sought after, the advertisement may make it appear as though the protein blend contains more casein than it actually does. To tell if a product is high in casein, milk protein isolate or some form of casein should be the first ingredient. Even then, low casein content may be masked by use of many different protein sources. For example, if the ingredients section of a protein lists, in order, milk protein isolate, whey protein concentrate, whey protein isolate, egg protein, and soy protein, the casein content may be lower than 20%.
Recommended sustained release protein products
1. Protein powders
HSN Driver
This is, in my opinion, the highest quality sustained release protein out there. In addition to casein and egg proteins, this product contains other high quality ingredients such as fructooligosaccharides and fish oil. Going by the ingredients, this is also the most sustained release protein blend out there.
Xtreme Formulations Ultra Peptide
The runner up to Driver for best sustained release protein. While Driver does contain some calcium caseinate, this product contains solely high quality protein sources. Additionally, this product costs a few dollars less for the same amount. However, not all of the proteins in Ultra Peptide are slow-releasing – in fact, hydrolyzed whey is one of the fastest releasing proteins there is (although this will be mitigated by the presence of the slower releasing proteins). In my opinion, a dual release protein such as this is ideal for a period such as postworkout, whereas before bed, you want the most sustained release of amino acids possible, so Driver would be a better option.
CytoSport EvoPro
CytoSport, makers of Muscle Milk, tend to make unique products, and this is no exception. However, the main reason that this is one of the better casein products is that it is about the least expensive you can get for the protein content before quality starts to drop. Although not as high quality as the other two protein blends mentioned (for example, some lower quality sweeteners are used, and canola oil is present), this is still a good choice, especially for the consumer wishing to save a few dollars. Also, this protein comes in a wide variety of flavors.
2. Low carb MRPs
Labrada Low Carb Lean Body
A low carb MRP is pretty much like taking a normal protein powder along with a multivitamin. However, for those who like MRPs, or having individually packaged protein, this should be the low carb protein of choice. This MRP is priced reasonably and contains both milk protein isolate and calcium caseinate, along with various forms of whey.
Optimum Complete Protein Diet
For those trying to remove every last carbohydrate from their diet, this contains less carbohydrates (and more fat) than the Labrada product. The casein source is calcium caseinate, and the multiple other protein sources present indicate that the casein content may be relatively low, but this is the option with the lowest price.
3. MRPs
VPX Micellean MRP
This is the only VPX product I will ever recommend. VPX products are usually overpriced and overhyped, and this is no exception. However, in addition to the sustained release protein, this MRP offers carbohydrate sources of a higher quality than most MRPs. Still, the best way to go in my opinion is just to use a protein powder and then add in some raw oatmeal while blending, as this will save a significant amount of money, and you can manipulate the carbohydrate content according to your goals.
Met-Rx Met-Rx Drink Mix
This is more affordable, and going by the ingredients, is probably also higher in casein. Although the carbohydrate source is high GI (maltodextrin), the carbohydrate content isn't excessive.
AST Ny-Tro Pro
Another MRP that is high in casein. The same price as the Met-Rx product, but has more carbohydrates per serving.
4. Weight Gainers
Beverly Mass Maker
I tend to think Beverly charges a bit too much for their products, but they do have a good reputation for high quality. This is also one of the few weight gainers you will find that isn't just whey protein and maltodextrin. The first two ingredients in the protein blend are calcium caseinate and milk protein isolate, and it also contains other slower releasing proteins. Additionally, it contains some carbohydrate sources other than just maltodextrin. If you are taking weight gainers, I would recommend this before bed only, and a cheaper weight gainer for other periods.
Biotest Grow
Some would argue that this is too low in carbohydrates to be considered a weight gainer, but I think it functions well in this respect, especially if one adds some of their own carbohydrates in. At first it might appear more expensive than Mass Maker, but it has twice the protein content per serving, making it significantly cheaper. Although the carbohydrates are low quality, this and Mass Maker are about the only high carbohydrate products which are good sources of sustained release protein.
Conclusions
As a protein source, casein can be of great benefit to the athlete by preventing muscle breakdown. Although there are many products which do not meet up with the claim of offering a high quantity of sustained release protein, there are still a number of good products available for those with a variety of goals.
Casein is the predominant protein found in milk. While whey makes up about 20% of the protein content in cow milk, casein makes up the other 80% [1]. Casein protein has been used by athletes for decades for its anticatabolic (muscle sparing) properties.
Casein is usually found in three forms, calcium caseinate, micellar casein, and milk protein isolate. Calcium caseinate is considered to be lower quality, while micellar casein and the casein in milk protein isolate are identical. This makes milk protein isolate more economical given a choice between the two. In comparison to whey, casein is not as high quality by some conventional standards of measuring protein quality. The biological value of casein protein is about 70 compared to 100 for whey. However, milk protein has a biological value of over 90. And if we use the PDCAAS, a more modern method of determining protein quality, all three of these proteins (casein, whey, and milk) are on equal footing at 1.00.
What is unique about casein protein is the slow digestion rate. Studies that compare whey and casein administered in the workout period inevitably find that whey protein exerts a far stronger anabolic response in this case [2]. However, when casein is administered at other periods the strength gains are twice of those seen with whey [3]. This is because while whey stimulates protein synthesis much more than casein in the short term, casein causes a sustained release of amino acids, preventing muscle breakdown for a more extended period of time [4]. This makes whey the protein of choice for the workout period, with casein preferable at other times, especially before periods of fasting (such as sleep). Because casein does not have a pleasant taste, a blend of casein and whey is generally used. An additional reason not to completely ditch the whey is that it has a plethora of health benefits that casein does not have, although some peptides in casein do have free radical scavenging activity [5].
Marketing techniques
There are many "sustained release protein" products on the market. However, many of these probably do not contain as much casein as they appear. Companies want to avoid putting too much casein in a product for a few reasons. First, casein is more expensive than whey. Second, casein has a distinct, malty taste which many find unpleasant, and the taste is not easy to mask. However, because a protein with high casein content is sought after, the advertisement may make it appear as though the protein blend contains more casein than it actually does. To tell if a product is high in casein, milk protein isolate or some form of casein should be the first ingredient. Even then, low casein content may be masked by use of many different protein sources. For example, if the ingredients section of a protein lists, in order, milk protein isolate, whey protein concentrate, whey protein isolate, egg protein, and soy protein, the casein content may be lower than 20%.
Recommended sustained release protein products
1. Protein powders
HSN Driver
This is, in my opinion, the highest quality sustained release protein out there. In addition to casein and egg proteins, this product contains other high quality ingredients such as fructooligosaccharides and fish oil. Going by the ingredients, this is also the most sustained release protein blend out there.
Xtreme Formulations Ultra Peptide
The runner up to Driver for best sustained release protein. While Driver does contain some calcium caseinate, this product contains solely high quality protein sources. Additionally, this product costs a few dollars less for the same amount. However, not all of the proteins in Ultra Peptide are slow-releasing – in fact, hydrolyzed whey is one of the fastest releasing proteins there is (although this will be mitigated by the presence of the slower releasing proteins). In my opinion, a dual release protein such as this is ideal for a period such as postworkout, whereas before bed, you want the most sustained release of amino acids possible, so Driver would be a better option.
CytoSport EvoPro
CytoSport, makers of Muscle Milk, tend to make unique products, and this is no exception. However, the main reason that this is one of the better casein products is that it is about the least expensive you can get for the protein content before quality starts to drop. Although not as high quality as the other two protein blends mentioned (for example, some lower quality sweeteners are used, and canola oil is present), this is still a good choice, especially for the consumer wishing to save a few dollars. Also, this protein comes in a wide variety of flavors.
2. Low carb MRPs
Labrada Low Carb Lean Body
A low carb MRP is pretty much like taking a normal protein powder along with a multivitamin. However, for those who like MRPs, or having individually packaged protein, this should be the low carb protein of choice. This MRP is priced reasonably and contains both milk protein isolate and calcium caseinate, along with various forms of whey.
Optimum Complete Protein Diet
For those trying to remove every last carbohydrate from their diet, this contains less carbohydrates (and more fat) than the Labrada product. The casein source is calcium caseinate, and the multiple other protein sources present indicate that the casein content may be relatively low, but this is the option with the lowest price.
3. MRPs
VPX Micellean MRP
This is the only VPX product I will ever recommend. VPX products are usually overpriced and overhyped, and this is no exception. However, in addition to the sustained release protein, this MRP offers carbohydrate sources of a higher quality than most MRPs. Still, the best way to go in my opinion is just to use a protein powder and then add in some raw oatmeal while blending, as this will save a significant amount of money, and you can manipulate the carbohydrate content according to your goals.
Met-Rx Met-Rx Drink Mix
This is more affordable, and going by the ingredients, is probably also higher in casein. Although the carbohydrate source is high GI (maltodextrin), the carbohydrate content isn't excessive.
AST Ny-Tro Pro
Another MRP that is high in casein. The same price as the Met-Rx product, but has more carbohydrates per serving.
4. Weight Gainers
Beverly Mass Maker
I tend to think Beverly charges a bit too much for their products, but they do have a good reputation for high quality. This is also one of the few weight gainers you will find that isn't just whey protein and maltodextrin. The first two ingredients in the protein blend are calcium caseinate and milk protein isolate, and it also contains other slower releasing proteins. Additionally, it contains some carbohydrate sources other than just maltodextrin. If you are taking weight gainers, I would recommend this before bed only, and a cheaper weight gainer for other periods.
Biotest Grow
Some would argue that this is too low in carbohydrates to be considered a weight gainer, but I think it functions well in this respect, especially if one adds some of their own carbohydrates in. At first it might appear more expensive than Mass Maker, but it has twice the protein content per serving, making it significantly cheaper. Although the carbohydrates are low quality, this and Mass Maker are about the only high carbohydrate products which are good sources of sustained release protein.
Conclusions
As a protein source, casein can be of great benefit to the athlete by preventing muscle breakdown. Although there are many products which do not meet up with the claim of offering a high quantity of sustained release protein, there are still a number of good products available for those with a variety of goals.