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What is casein and why is it the pre-sleep protein king?
We know pre-sleep protein is important, but does the protein source matter? The two most popular and well researched protein powder sources are casein and whey.
Both of these proteins are derived from milk, yet they differ significantly in their capacity for maximising night-time anabolism. Both whey and casein are still high quality, complete proteins (meaning they contain all the essential amino acids for building new muscle protein) and are digested and absorbed readily.
We know that a high protein diet is effective for seeing improvements in muscle mass and recovering post workout. But did you know that adding in a night time protein shake could deliver even better results?
To make whey and casein, special enzymes are added to warmed milk, causing the milk to coagulate and separate into solid and liquid portions. The liquid is the whey (which is washed and dried into powder), while the remaining curds are washed and dried to form casein powder. Now the rates of digestion and absorption is where these two proteins really differ. While whey digests quickly and may be a wise choice post-workout to cause a rapid increase of amino acids in the bloodstream, casein is digested very slowly, gradually releasing amino acids into the bloodstream over many hours. This is why you might notice that casein protein does not digest as well or as fast in your shaker. This is also why casein is a standout choice for a pre-sleep protein, keeping a relatively stable and high level of aminoacidaemia (concentration of amino acids in the blood) while you’re not eating for 6-10 hours.
To learn more about the difference between whey and casein proteins, check out our blog on fast and slow release proteins.
Pre-sleep casein after evening workouts leads to more muscle mass and strength gains
It is important to note that protein consumed before sleep is digested and absorbed exactly the same time as when we are awake. The muscle still responds to a high concentration of amino acids in the blood during sleep by increasing muscle protein synthesis.
In a previous 12-week study this point was highlighted when a group consuming casein protein before sleep, after an evening weight training workout gained more strength and muscle mass than a group performing only the weight training, without the casein before bed.
A 12 week study found that consuming casein protein before going to bed leads to increased muscle mass and strength gains
Late night protein doesn’t slow rates of fat loss while sleeping
It seems as though many lifters and athletes out there are hesitant to consume protein (or any calories for that matter) late at night in fear of disrupting body fat loss during sleep. However, the research tells us we have no reason to be frightened from late night protein.
A number of studies have indeed shown that supplemental protein before bed does not negatively impact rates of lipolysis (release of body fat into the blood) or fatty acid oxidation (fat burned for energy). Interestingly, in a small study of 11 active men, a pre-bed casein shake actually INCREASED rates of fat oxidation the next day. I think we can say at the bare minimum, that pre-bed protein, particularly casein, won’t make you fat while you sleep.
Will having a casein shake right before bed interrupt my sleep?
Thankfully, several research studies have shown that pre-bed protein consumption has no effect on sleep quality scores or sleep onset latency.
Why sleep is a special opportunity for muscle growth and recovery
We know new muscle tissue only grows, or existing muscle tissue repairs when the amino acids from protein (the building blocks) are available in the bloodstream. This is akin to muscle glycogen storage only occurring when there is available glucose in the bloodstream. But for protein it isn’t so simple, the body doesn’t store and release amino acids to maintain a constant circulation in the blood. Glucose does, otherwise, we would go hypoglycaemic and die! And so, a slow-digesting protein, a steady supply of amino acids into the blood while you sleep could significantly improve protein intake distribution over 24 hours, preventing levels from falling to a degree which might risk catabolism.
In a survey of over 500 athletes, the researchers found that the athletes were typically consuming at least 1.2g of protein per kg of body weight per day, however, on average were only consuming a total of 7g of protein in their final evening snack. This means it’s highly likely that while daily protein requirements may be met, low levels of amino acids in the blood during sleep may compromise night-time muscle growth.
Having a slow release protein before sleep will help to prevent muscle catabolism and instead helps with muscle repair and growth
If I have more protein at night, won’t that just mean I need less during the day?
Not exactly. In one study consuming 60g of protein powder before sleep did not change the muscle protein stimulus response to a high protein breakfast the next morning. This tells us that the muscle growth effects of night-time protein appear to be additive.
Additionally, for those not tracking calories, having a night-time casein shake doesn’t appear to affect appetite the next morning. Which means you don’t have to worry about not being able to stomach a high protein (or high calorie if need be) breakfast.
The bottom line? Prioritise protein for your goals
Your total daily protein intake is still going to be the strongest predictor of how much strength and muscle you gain from your weights program. With that said, having a more even spread of this protein intake over 24 hours preventing amino acids from reaching low levels in the blood is likely to prevent catabolism and/or enhance anabolism compared to only consuming faster digesting proteins during waking hours.
Casein protein is your best option for a pre-sleep protein, as amino acids are gradually released into the bloodstream over many hours. Perfect for when you’re asleep and not eating. A worthy investment for anyone looking for a small edge on top of the competition.
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Joy JM, Vogel RM, Shane Broughton K, et al. Daytime and nighttime casein supplements similarly increase muscle size and strength in response to resistance training earlier in the day: a preliminary investigation. J Int Soc Sports Nutr. 2018;15(1):24. Published 2018 May 15. doi:10.1186/s12970-018-0228-9
About the author
Jackson is a PhD candidate, accredited Sports Nutritionist, and competitive bodybuilder and boxer. He currently works at the School of Human Sciences, where he has completed a BSc in Sports Science and in Exercise & Health, and an Honours in Exercise Physiology. Jackson is also completing his PhD in the field of Nutrition where he is directing the first randomised controlled trial investigating the effects of intermittent vs continuous dieting on fat loss, muscle retention and muscle performance in resistance trained athletes.
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