Casein is a form of protein that helps prevent muscle breakdown, increase fullness and improve body composition. Alongside whey, casein protein is extracted from milk (both cow’s milk and human milk contain differing amounts of casein) (1).
While whey protein powder is by far the most popular protein supplement with fitness enthusiasts and athletes, casein protein is also very popular due to slightly different benefits that it offers.
Whey protein is one of the fastest absorbed protein sources around, which is why it is often taken immediately post workout, in the (possibly mistaken) belief that this will speed up protein synthesis. Casein protein on the other hand is much slower when it comes to digestion, due to it forming a “clot” in the stomach and drip feeding nutrients and amino acids into the blood stream over a longer period (2).
This can help keep you feeling fuller for longer, and also help with maintaining raised protein synthesis rates post workout. Many protein shakes now offer combinations of whey and casein protein, finding that this can lead to even greater results than taking either supplement separately (3).
Taking casein protein immediately after a workout can prevent muscle protein breakdown when exercising in a fasted state. Exercising in a fasted state is generally seen as a bad idea, but it used to be promoted as a fantastic way to burn fat.
This belief was pretty much laid to rest by an article by Brad Schoenfeld where he stated that not only is there no increase in fat loss, but due to a lack of energy, the workout will potentially lead to less fat burning as performance will have dropped (4).
But people still do it, often due to training very early in the morning.
If you train in a fasted state, then your body will not have any protein stores to begin protein synthesis. This means that taking some immediately after a workout would be beneficial. A 2009 study found that taking a protein and carbohydrate meal immediately post workout (fasted) will prevent muscle protein breakdown (5).
A combination of whey protein, casein protein, and a carbohydrate source would be perfect.
Casein protein can help you on a diet by protecting fat free mass. For weight loss to occur you need to be in a calorie deficit, that is the only way that you can drop body fat. The bigger the deficit, the faster the fat loss (up to a certain point). This is why crash diets and week long fasts can cause such incredibly fast weight loss results.
The downside of creating a big deficit is that you can actually begin to lose muscle mass (there are of course many other physiological and psychological downsides – which is why crash diets are such a poor nutritional strategy). But even a sensible diet can lead to some muscle loss, the trick is to limit this as much as possible. Studies have shown that increasing protein intake can prevent muscle loss during short term calorie deficit diets.
A 2013 study found that consuming twice as much protein as recommended can protect fat free mass during a short term diet (6).
Whey protein or casein protein, or a combination of both would be perfect for this.
Casein can increase satiety making it perfect for dieting. Satiety is another word for feeling full after a meal, the fuller (or more sated) you feel after a meal the less likely you are to want to eat. This means that foods that can increase satiety after a meal are better on diets. The most satiating food according to the satiety index for common foods is the boiled potato (7).
But high protein foods that are also satiating are better due to their ability to increase your metabolism and protect muscle.
Many studies have compared casein protein powder to whey and other protein powders and have found mixed results, some found casein to be more satiating while others found whey. A 2011 study compared casein, pea protein, whey, and egg albumin (protein powder) to find which was the most satiating (8).
It found that casein and pea protein were significantly more satiating than the other sources.
A 2014 study found that whey protein was more satiating than casein and also more satiating than a carbohydrate supplement (9).
This may seem a bit confusing, and it is.
There doesn’t seem to be much of a consensus on why whey and casein might/might not be more satiating than the other. Casein is slower to be absorbed and travels through the intestines at a slower rate, which makes it work like fiber and theoretically should make it more satiating. But whey may cause a different hormonal response.
A 2008 study explains it like this:
“Different proteins cause different nutrient related responses of (an) orexigenic hormones. Protein-induced satiety coincides with a relatively high GLP-1 release, stimulated by the carbohydrate content of the diet, PYY release, while Ghrelin does not seem to be especially affected, and little information is available on CCK.” (10)
In other words, different protein sources can stimulate different hormones which deal with appetite, but at the moment science is not certain which proteins affect which hormones. On the other hand, a study in 1998 failed to find any difference between protein types, and instead posited that protein intake is more important (how much protein you have) (11).
They also suggested that because you usually consume protein as part of a meal the other foods will influence satiety overall. Of course, this is clearly not the case when taking a casein or whey protein shake as they are taken in isolation. Whatever the science says, one thing is for certain – casein protein can increase satiety and is therefore a good supplement to take while on a diet.
Casein protein powder can help to improve body composition. Due to casein protein being effective at protecting fat free mass during a diet, and improving dieting adherence by increasing satiety, it is perhaps no surprise that casein protein can improve body composition. It is well established that reducing carbohydrates and increasing protein intake can improve body composition, and studies have demonstrated this (12).
A high protein diet can increase thermogenesis (slightly), increase satiety (as we mentioned above) and as a result improve weight loss (13).
Both whey and casein protein have been shown to do this, particularly when combined (milk protein). A 2013 study found that milk protein can improve metabolic health and reduce body fat (14).
Casein protein taken before bed can improve post-exercise recovery. A 2012 study looked at post-exercise recovery and casein protein (15).
The study involved 16 healthy young men who all performed a resistance workout (free weights and machines) at 8pm after consuming a standard diet.
30 minutes before sleep (11:30pm) they took either 40g of casein protein powder, or they took a placebo. The study measured their blood and muscles to assess how much protein synthesis occurred during sleep (7.5 hours). The study found that casein protein taken immediately before bed (or within a 30 minute window if you want to be specific) increased whole body protein synthesis rates and improved the subjects’ net protein balance. An increase of 22%.
One of the reasons for casein being so effective pre-bed is that it is slow releasing, because casein has slower motility than whey protein, it can spend more time releasing amino acids (particularly Leucine) into the blood. This means that it can elevate protein synthesis for longer than whey protein (16).
Casein protein may help improve sleep quality. A lot of articles and fitness professionals claim that casein is good for improving sleep quality, but there is surprisingly little evidence for this. One of the main reasons why casein is said to improve sleep is that it contains tryptophan. This is an amino acid that helps regulate sleep, but only 1.1% of casein is made up of tryptophan (17).
There are other foods (such as egg whites) that contain much higher quantities of tryptophan than casein.
In fact it might not have anything to do with tryptophan, casein may help improve sleep quality because it contains a peptide called AlphaS-1 Peptide. This peptide is known for reducing anxiety (called an anxiolytic) and reduce stress.
A study on rats suffering from chronic stress found that AlphaS-1 peptide found in casein protein helped to improve sleep (18).
You could also theoretically claim that casein protein may help reduce stress and anxiety too, but there are no human studies that confirm this.
Casein protein can help build muscle. The link between protein supplementation and muscle mass is well known. Provided you are performing adequate exercise whey or casein protein will absolutely help increase muscle mass.
A systematic review on the effects of protein supplements on muscle mass found that protein supplementation can enhance gains in muscle mass (hypertrophy) and strength, it also found improvements in aerobic and anaerobic performance (19).
Provided there is enough stress on the muscles from resistance exercise of course.
A 2012 study looked at the effect of protein supplementation on the muscle mass of both young people and older people (20).
It found that prolonged exercise, combined with whey, casein, or a combination of whey and casein led to significant increases in both populations.
A similar study found that whey and casein protein were more effective than soy protein when it came to muscle accretion in both young and elderly people (21).
There was an interesting study that looked to find the best protein supplement, comparing whey, casein, bovine colostrum (also a milk protein), and soy protein. They found that:
“In athletes supplementing their diets with additional protein, casein has been shown to provide the greatest benefit for increases in protein synthesis for a prolonged duration. However, whey protein has a greater initial benefit for protein synthesis. These differences are related to their rates of absorption. It is likely a combination of the two could be beneficial” (22).
Casein protein can help build greater strength when combined with resistance exercise. If casein protein can increase muscle mass, then it stands to reason that it can also help build strength too. A 2013 study found that a combination of resistance exercises and pre and post workout protein shakes led to changes in performance, they found no difference between casein and whey protein (23).
A 2006 scientific review article found that combining whey and casein protein led to the greatest gains in strength and fat free mass over a 10 week period (24).
A similar study in 2005 found that milk protein (a combination of whey and casein) combined with a 12 week training program led to greater gains in strength and hypertrophy than a soy based protein (25).
Due to casein being free of lactose, a lot more people are able to consume it than they are other dairy protein sources. But you can still be allergic to it if you have a dairy allergy. The side effects of this can be nausea, bloating, headaches, and similar minor complaints, but nothing too serious.
One issue that has surfaced recently is contamination, a recent study by the clean label project found that many protein powders had levels of lead, cadmium, and BPA within them (26).
Now there should be some context given here, while the levels were higher than expected, they were still well within safe levels. Secondly, milk and egg based proteins (including casein) were found to be much safer than vegan and plant based protein powders.
The only other issue is casein protein contributing to a very high protein diet. There is a lot of debate at the moment on whether high protein diets are safe or not. The worry about kidney problems occurring has finally been laid to rest (protein will not affect healthy kidneys at all) but some studies indicate that lower protein diets lead to a lower risk of mortality in under 65s (27).
That same study also found that people who were over 65 actually benefited from higher protein, possibly due to the increased requirement of Leucine in the elderly (28).
How much protein you require is influenced by many factors, whether you are young or old, whether you are active or inactive (studies have shown that athletes require twice as much protein as sedentary people (29).
If you are looking to build muscle, or lose weight can also affect this. Your body weight, and muscle mass can also have an impact, as can your gender.
Examine probably gives the best advice – due to it only considering studies performed on humans, and aiming their information at a variety of individuals.
They break up society into three groups: Athletes and highly active people (1.5-2.2g/kg), people attempting to lose weight while preserving muscle mass (1.0-1.5g/kg), and sedentary people who are not looking to change their body composition (0.8g/kg and up) (30).
Q: When should you take casein?
A: Because casein is a slow digesting protein, its best suited to take it before bed ow as a meal replacement instead of post workout.
Q: Can you be allergic to casein?
A: If a glass of milk or a slice of pizza causes swollen lips, hives, or other significant symptoms, you may have an allergy to casein, a protein in milk. Another milk protein associated with food allergies is whey. Some people are allergic to both casein and whey
Q: Is whey or casein better?
A:Whey is considered a “fast” protein, because it is rapidly digested in as little as an hour, whereas casein is a “slow” protein that is digested over several hours. Neither is better than the other as they serve different purposes.
Q: Do eggs contain casein?
A: Eggs do not contain casein, though some dishes that contain eggs may have it, depending on ingredients.
Q: What foods have casein in them?
A: Because casein is a protein, it’s found mostly in dairy products with moderate-to-high protein content such as low-fat milk, yogurt, kefir and cheese.
Q: Is it ok to take casein in the morning?
A: Yes, anytime that isn’t post workout is ideal for casein.
Q: Is ghee free of casein?
A: Ghee or clarified butter (also known as drawn butter) is a casein free alternative to regular butter. Both ghee and clarified butter have the milk proteins casein and whey removed and what remains is butter fat.
Casein protein is a great protein supplement for people looking to build muscle, increase strength, preserve muscle, or lose weight. It appears to have a few benefits over whey protein when it comes to satiety and protein synthesis, but whey has other benefits that casein doesn’t.
There seems to be a growing consensus that combining whey and casein together leads to better results. You could either take a scoop of each, or have a whey protein shake post workout, and a casein protein shake before bed. Lots of supplement companies pre-mix the two together, but find the option that provides the best value for money and protein per serving.
There are essentially no side effects to taking casein, unless you have a lactose or dairy allergy. The fear of contamination is overblown, particularly for animal sources of protein. But you can always check the clean label project website to find which products have the lowest levels (31).
If you are an athlete, bodybuilder, or just someone who goes to the gym twice per week, there are many benefits to taking casein. Even sedentary people will benefit from casein, with increased satiety, an improved metabolism, and better sleep (possibly).