Whey Or Casein At Night? | Benefits Of Protein Shakes Before Bed

By Christopher Tack, Clinical Specialist Physiotherapist

When is the best time to take a protein shake?

Commonly, post workout supplementation is considered to optimise the muscle growth response during an “anabolic window” after you work out (1). However, there seems to be an ongoing conversation regarding whether the period of fasting, which occurs overnight as you sleep, has a detrimental effect on muscle gain. Does having a protein shake before bed can counteract this potential problem and facilitate more muscle growth?

This article aims to answer that question so you can understand whether pre-sleep protein is essential or just a waste of your supplements.

Whey vs. Casein

We all know that in order to sustain or gain muscle, we have to ensure a balance of protein synthesis vs degradation is tipped towards positive (19).

Generally, protein balance will start to become negative in the absence of food intake, such as during sleep (2-4). It’s a reasonable assumption that the reduction in availability to amino acids will halt muscle-protein synthesis rates and lead to degradation.

Protein powder supplements are a popular and, importantly, convenient method of boosting protein levels at the right time (5). For the purposes of this article, we’ll consider whey and casein protein as the two key options for before-sleep supplementation.


Most modern whey proteins available are whey varieties, of which there is isolate, concentrate and hydrolysate. Whey is considered the highest quality protein source due to its high concentration of branched-chained amino acids and fast acting response to promote muscle protein synthesis (5-6).

To prevent our muscles being in a negative net protein balance and potentially beginning to break down, it’s thought that we need a slow-digesting protein source to continuously fuel them. Whey protein is known to be digested faster than casein protein, so may not be the ideal supplement before bed, unless you’ve just trained.


The next most commonly consumed form of protein powder is micellar casein protein. Whilst whey protein makes up around 20% of total milk protein, casein protein is the predominant form of protein in milk. Casein protein is the curd portion of milk, which is produced as part of the cheese-making process. Just as whey is a high quality form of protein, so is casein due to its variety of essential amino acids (7).

The Difference Between Whey & Casein?

The difference between casein and whey is the speed at which their amino acid load is released into the blood stream. Simply put, casein has a slower digesting time, meaning it releases its amino acids over a longer period (8-9).

This will result in a prolonged period of positive net protein balance. The benefit of this is a reduction in the impact of muscle protein breakdown, particularly during periods of fasting (such as during sleep) (8-9).

Interestingly, most studies comparing casein to other forms of protein (usually whey and soy) usually promote whey as the key protein for muscle-protein synthesis, which is usually the main reason people consume such supplements. Such studies (10-11), however, will predominantly examine the immediate or short-term response of protein consumption, and if measurements are extended over several hours, casein demonstrates a prolonged beneficial effect which other proteins do not (12).

Casein or Whey?

Strictly speaking, your preferred choice of protein type is dependent upon your objective. Post-workout muscle-protein synthesis has been found to be greater following consumption of whey protein compared to casein (13).

However, casein has been found to be beneficial due to its different rate of absorption by our gut, and the impact this rate has on postprandial protein balance.


One study (8) examined the effect of consuming both whey and casein protein as the protein source in a single meal. They measured a number of physiological properties (including protein balance and the use of leucine in the body).

They noted a variable response to each of the protein types: whey induced a large increase of amino acids over a shorter period of time, whilst casein elevated amino acid concentration by a lesser amount but for a longer duration of time. The authors of this study suggested that this was due to slow gastric emptying, and which leads to greater inhibition of muscle-protein breakdown (34%).

Therefore, whilst whey had a 37% greater immediate increase in muscle-protein synthesis (MPS), casein managed protein balance by having a smaller impact on MPS and a greater attenuation of protein degradation.

Protein Timing | Does It Matter?

The previous study mentioned outlines the theory behind why people choose to consume a source of protein (usually casein) before bed. However, does this theory hold water? In order to discuss this we need to examine whether timing of protein consumption is likely to show benefit.

The “yes, timing is important” camp will argue that timing of protein consumption is essential on two specific occasions: post work out and prior to periods of fasting.

It is well recognised that active people will have a greater demand for protein from their diet and supplements due to the elevated levels of protein oxidation and breakdown occurring during exercise (14-15), and to ameliorate the responses of muscle protein regeneration vs proteolysis (breakdown) during recovery (16-18).

They would consider it wise to strategically plan protein intake as an integral part of their training, recovery and nutrition regimes (19). We should consider then, what evidence is there to support the theory that pre-bed protein consumption will give us added benefits?

Pre-Bed Protein Shake Benefits

It is evident that the reduction in available amino acids during periods of fasting, like over night during sleep, will prevent a rise in muscle protein synthesis (20).

Researchers have evaluated the impact of protein ingestion prior to subsequent overnight recovery on a number of variables including:

Protein synthesis rates (21)
Net protein balance levels (22)
Measures of strength and hypertrophy
✓ Measures of recovery (20)

Let’s break these down a little.

#1 Protein Synthesis

One study (21) examined a group of 16 recreationally active young males and measured overnight recovery following a single bout of resistance exercise including chest press, shoulder press and lat pull down exercises. Prior to sleep the group members were either given a dose of 0.15g per kg of body weight of casein hydrolysate protein (85.3% concentration) or a placebo.

Their results found that this protein dose was both effectively digested and absorbed; and significantly elevates whole body protein synthesis rates compared to the placebo supplement. In fact functional rates of protein synthesis were 22% greater in the casein protein group.


#2 Strength & Hypertrophy

The aforementioned research group (led by Luc Van Loon from the Maastricht University in the Netherlands) also performed a study which examined the benefits of pre-sleep protein digestion on physical measures of strength and hypertrophy (23).

In this particular study they randomly assigned 44 young men to either a 27.5g protein group (13.75g casein hydrolysate + 13.75g casein) or a placebo beverage which the would take highly before sleep. They then all underwent a 12 week progressive training programme.

They used dual energy X-Ray absorptiometry and CT scan to measure hypertrophy; and muscle biopsy to assess muscle fibre type pre and post exercise. Strength was evaluated by 1 rep max testing.

Their results amazingly indicated that pre-sleep protein supplementation with casein facilitated a 26% increase in 1 rep max strength compared to placebo!

✓ Additionally quadriceps muscle bulk had a 75% greater increase in cross sectional area in the casein group, and there was a significantly greater increase in fast twitch muscle fibres in this group also.

This highlights the real world impact of protein supplementation before bed, and gives greater evidence to support the benefits of prolonging a positive protein balance overnight.

#3 Increases Metabolism

A final piece of evidence in support of the importance of protein timing before sleep evaluates the effect of protein on our metabolism (24).

This study took a group of 11 young men with an average body fat percentage of 16%. These individuals were randomly allocated to various groups where they were either given 30g of whey protein, 30g of casein protein, 33g of carbohydrates or a placebo supplement, infested 30 minutes before sleep.

They then took measurements of resting energy expenditure (REE) immediately upon waking between 5am and 8am the next morning. Their results showed that protein consumption (both whey and casein) showed a significantly greater level of REE which was 5% greater than placebo.

This indicates positive benefits to pre-bed protein consumption on next morning metabolism, giving you another reason to consider a night time protein shake!

Is Night-Time Protein The Key?

It would be remiss of us to not recognise that in contradiction to the theories supporting the timing of pre-sleep protein ingestion, there are also theories which suggest timing of protein intake is less important.

For example a 23 study meta-analysis of 525 people (25) concluded that any beneficial changes to strength and hypertrophy relative to protein consumption where more attributable to total protein consumption, rather than when it was consumed. They found that as long as protein consumption over the period of the day met a sufficient level (approximately 1.6g per kg), timing had minimal influence on muscle synthesis and net protein balance.

Of course the extra benefit of night time protein consumption is that it gives you an additional dose of protein which will elevate total protein consumption. As such it is difficult to differentiate which is the true theoretical basis of the physical benefits seen.

Pre-Bed Protein Shakes | Benefits for Sleep

Aside from the timing debate, I am also interested in whether consuming protein pre-sleep gives any extra benefits.

For example, it has been found that protein consumption assists with uptake of the amino acid L-tryptophan into the brain (26).

L-tryptophan is a precursor to the neurotransmitter, 5-Hydroxytryptophan (5-HTP) which is one of the key neurotransmitters associated with the sleep cycle (27).

This relationship has led researchers to examine the effect of dietary manipulation on sleep. One study found that diets, where the macronutrients were manipulated to be 56% protein, 22% carbohydrates and 22% fat, led to fewer waking episodes and improved sleep (28).

These results were supported further by a recent study which examined dieting of overweight individuals and showed improved global sleep score when more protein was included in their diet (29).

As such, it is evident that diets high in protein may result in improved sleep quality and general sleep experience, giving us just another reason to up our protein intake just before bedtime (30).

Take Home Message

Most people accept the benefits of timing your protein intake, particularly immediately post workout to increase MPS. However less stock is placed on the prevention of muscle protein degradation overnight.

The truth is that protein consumption guidelines advise a combination of fast (whey) and slow (casein) protein intake to optimise muscular responses (19). In fact many manufacturers will now blend both protein types into one product, which is considered the best approach to protein supplementation (31).

Even if you do not buy the concept that protein timing is important, at least using a pre-bed shake will do is give you an extra dose of valuable protein.


Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.

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Lauren Dawes

Lauren Dawes

Writer and expert

Lauren is an English Literature graduate originally from the South. She’s always loved swimming, has discovered the power of weight training over the past few years, and has lots of room for improvement in her weekly hot yoga class. On the weekends she’s usually cooking or eating some kind of brunch, and she enjoys trying out new recipes with her housemates – especially since shaking off student habits, like mainly surviving off pasta. Above all, she’s a firm believer in keeping a balance between the gym and gin. Find out more about Lauren’s experience here: