In 30 seconds
- With 40 g of casein before bed, overnight muscle protein synthesis was 22% higher than with placebo in young men who had trained.
- In a 12-week trial, 27.5 g of protein every night led to more strength and 75% more quadriceps growth than a calorie-free placebo.
- In men aged 72, 40 g raised overnight muscle protein synthesis and 20 g did not: the amount counts.
- Protein before bed did not worsen sleep quality or change appetite the next morning.
Yes: having protein before bed increases muscle protein synthesis overnight, and in a 12-week trial it led to more strength and more muscle. The key is the amount, about 40 g, and making it fit into your total protein for the day. This is what the studies say.
Why at night
While you sleep you go many hours without eating, and muscle protein synthesis during sleep is particularly low 4. The idea is simple: use that gap to give your muscles building material.
The question was whether protein is digested properly while you are asleep. Tracer studies have answered it: the protein you take before bed is digested and absorbed during the night, and its amino acids reach the muscle 1 2.
Level of evidence by outcome
| Outcome | Evidence | What the data show |
|---|---|---|
| More muscle protein synthesis overnight | High | With 40 g of casein, in young people after training and in older adults. It is digested and absorbed while you sleep. |
| More muscle and strength with training | Moderate | Positive in a 12-week trial with 44 young men; the protein group had more protein per day. |
| Effective amount of about 40 g | Moderate | In older adults, 20 g did not raise overnight synthesis and 40 g did. |
| Sleep and appetite | Moderate | No effect on sleep quality or on appetite the next morning. |
| More muscle in older adults in the long term | Preliminary | Few studies; with 20 g of whey protein there was no extra gain in 12 weeks. |
The rating is our own, based on the number of studies, their quality and the consistency of the results.
The key studies
| Study | Type | Sample | Outcome |
|---|---|---|---|
| Res et al., 2012 | Tracer trial | 16 young men who trained in the evening | 40 g of casein before bed: 22% more muscle protein synthesis overnight and a positive protein balance. 1 |
| Snijders et al., 2015 | 12-week trial | 44 young men who did strength training | 27.5 g of protein every night: more strength and more muscle, with 8.4 cm² more quadriceps compared with 4.8 cm² with placebo. 3 |
| Kouw et al., 2017 | Tracer trial | 48 men with an average age of 72 | 40 g of casein raised overnight muscle protein synthesis; 20 g, with or without leucine, did not. 2 |
| Holwerda et al., 2018 | 12-week trial | Older men who did strength training | 20 g of whey protein with 1 g of leucine before bed did not add more muscle or strength. 5 |
| Joy et al., 2018; Antonio et al., 2017 | Trials | Adults who exercised | With the same total protein, taking it during the day or at night led to similar gains in muscle mass. 5 |
| Reis et al., 2021 | Systematic review | 9 studies | Positive results in young men who exercise, with 20-40 g of casein about 30 minutes before bed. In older adults, long-term data are insufficient. 6 |
The first study
What the study night looked like
The first study: 22% more
In the study that opened this line of research, 16 young men did strength training at 20:00 and had a recovery meal at 21:00, with 20 g of protein and 60 g of carbohydrates. At 23:30, before going to sleep, they took 40 g of casein or a placebo 1:
- Overnight muscle protein synthesis: 22% higher with casein.
- Whole-body protein balance: positive with casein and negative with placebo.
In other words, with the protein the body spent the night building rather than breaking down 1.
12 weeks of strength training
Protein every night versus a calorie-free placebo
Twelve weeks: more strength and more muscle
The next step was to see whether that translated into results. In one trial, 44 young men did strength training for 12 weeks. Every night, half took 27.5 g of protein with 15 g of carbohydrates, and the other half a calorie-free placebo 3:
- Maximum strength: the gain was greater with protein: +164 kg compared with +130 kg with placebo, in the 1RM tests.
- Quadriceps: grew by 8.4 cm², compared with 4.8 cm² with placebo.
- Fast-twitch fibres (type II): grew more than twice as much.
An important nuance: the placebo had no calories, so the protein group was getting more protein in total 6. When daily protein is matched, taking it at night or during the day gives similar results in muscle mass, according to two later trials 5.
The practical takeaway: the night is an excellent time to add protein, especially if you find it hard to reach your daily figure.
In older adults, the amount is what counts
With age, muscle responds less to small servings. In a trial with 48 men with an average age of 72, casein before bed was compared in different amounts 2:
- 20 g: no significant increase in overnight synthesis.
- 20 g with 1.5 g of leucine: no increase either.
- 40 g: muscle protein synthesis 33% above placebo.
This fits with what was seen later: in older men who did strength training, 20 g of whey protein with leucine before bed did not add more muscle over 12 weeks 5. As you get older, if you have protein at night, make it a generous serving. We go into more detail in protein in older adults.
How much before bed
The amount that has been studied
How much and which type
- Amount: the researchers who have studied it most suggest at least 40 g before bed 4. The International Society of Sports Nutrition talks about 30-40 g of casein 7.
- Timing: in the studies, about 30 minutes before going to bed 6.
- Type: almost all the studies used casein, the slow protein in milk 6. There are fewer data with whey protein.
- Even better if you have exercised that day: prior exercise makes your muscles make more use of the night-time protein. In one study, 76% more of the amino acids from the serving were incorporated into muscle fibre 5.
A practical tip: if your protein is whey, make it with milk. Four-fifths of the protein in milk is casein 8. You will find more ideas in what to have before bed if you train.
What about sleep, appetite and fat?
- Sleep: protein before bed did not change the time taken to fall asleep or sleep quality, in either young or older people 5.
- Appetite: it did not change appetite the next morning either 5.
- Fat: according to the International Society of Sports Nutrition, casein before bed raises muscle protein synthesis and energy expenditure without slowing the mobilisation of fat 7.
Your daily total is still what matters most
Your night-time protein adds to the rest of the day rather than replacing it. The ISSN recommends 1.4-2.0 g of protein per kilo a day if you exercise, in servings of 20-40 g every 3-4 hours 7. The serving before bed can be the last one in that distribution.
Work out your figure with the protein calculator, and if you want to know how much the clock matters, you have it in the anabolic window.
What the regulations authorise
For foods that are at least a source of protein, the EU authorises these claims 9:
- Protein contributes to a growth in muscle mass.
- Protein contributes to the maintenance of muscle mass.
- Protein contributes to the maintenance of normal bones.
A varied and balanced diet and a healthy lifestyle are important.
And our protein?
Our Gourmet Isolate Protein is whey protein isolate with a chocolate flavour. One 50 g serving, two scoops, provides 42.8 g of protein, in line with the 40 g used in the studies, with 0.2 g of sugars. Made with milk, it also adds the casein from the milk. It contains milk and soya.
Frequently asked questions
Is it good to have protein before bed?
If you exercise, it can help. With 40 g of casein, overnight muscle protein synthesis was 22% higher, and in a 12-week trial protein before bed led to more strength and more muscle than a calorie-free placebo.
How much protein should you have before bed?
The researchers who have studied it most suggest at least 40 g. The International Society of Sports Nutrition talks about 30-40 g of casein. In older adults, 20 g was not enough.
Does whey protein work before bed?
Most studies used casein, the slow protein in milk, and there are fewer data with whey protein. If you have your whey shake at night, making it with milk adds casein: it is four-fifths of the protein in milk.
Does eating protein at night make you put on fat?
According to the International Society of Sports Nutrition, casein before bed raises muscle protein synthesis and energy expenditure without slowing the mobilisation of fat. In the studies, it did not increase appetite the next morning either.
Does protein before bed affect sleep?
No. In the studies, it did not change the time taken to fall asleep or sleep quality, in either young or older people.
Sources
- Res PT, Groen B, Pennings B, et al. Protein ingestion before sleep improves postexercise overnight recovery. Med Sci Sports Exerc. 2012;44(8):1560-1569. View publication
- Kouw IWK, Holwerda AM, Trommelen J, et al. Protein ingestion before sleep increases overnight muscle protein synthesis rates in healthy older men: a randomized controlled trial. J Nutr. 2017;147(12):2252-2261. View publication
- Snijders T, Res PT, Smeets JSJ, et al. Protein ingestion before sleep increases muscle mass and strength gains during prolonged resistance-type exercise training in healthy young men. J Nutr. 2015;145(6):1178-1184. View publication
- Trommelen J, van Loon LJC. Pre-sleep protein ingestion to improve the skeletal muscle adaptive response to exercise training. Nutrients. 2016;8(12):763. View publication
- Snijders T, Trommelen J, Kouw IWK, Holwerda AM, Verdijk LB, van Loon LJC. The impact of pre-sleep protein ingestion on the skeletal muscle adaptive response to exercise in humans: an update. Front Nutr. 2019;6:17. View publication
- Reis CEG, Loureiro LMR, Roschel H, da Costa THM. Effects of pre-sleep protein consumption on muscle-related outcomes: a systematic review. J Sci Med Sport. 2021;24(2):177-182. View publication
- Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20. View publication
- Tetra Pak. Dairy Processing Handbook, chapter “The chemistry of milk”. View publication
- Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product.
