You’ve heard that taking a protein shake before bed will help you build muscle faster.
But you’ve also heard that doing so is a waste of time, and that protein timing is irrelevant. Just hit your macros by the end of the day and you’ll be fine.
Will drinking a protein shake before bed give you more muscle by morning? Or is it all just a ruse to get you to buy fancy protein supplements that you don’t really need?
Here’s a closer look at both sides of the story.
The Case For Taking a Protein Shake Before Bed
The idea behind taking a protein shake before bed, usually one containing a slow-release source of protein such as casein, is that it “drip feeds” amino acids to your muscles throughout the night, helping them recover and grow while you sleep. You’ll wake up with a little more muscle than you had the day before.
The story starts back in the 1990s, with a series of studies published by a group of French scientists, led Yves Boirie. Boirie and his team took a group of healthy subjects, gave them a protein supplement containing whey or casein, then looked at how quickly each of the supplements was digested .
Whey protein caused amino acid levels in the blood to increase rapidly, peaking after one hour and dropping back to normal after four hours. Casein, on the other hand, caused a much slower rise. A lower peak was reached after around one hour, but this level was maintained for almost seven hours.
Although much was made of this research at the time, particularly by companies selling “slow release” protein supplements containing casein, the design of the study limits the conclusions we can draw.
For one, the research looked at protein synthesis and breakdown in the whole body rather than in the muscle (known as “mixed muscle” protein synthesis).
Why does this matter?
Muscle isn’t the only thing that contributes to whole body protein synthesis. Protein turnover measured at the whole body level doesn’t tell you what’s happening to muscle protein. One study found a 19% increase in overnight whole-body protein synthesis following a protein/carb supplement, but no change in muscle protein synthesis .
What’s more, different tissues in the body are “turned over” (broken down and resynthesized) at very different rates. Muscle protein, for example, turns over much more slowly than proteins in the gut. Tissues such as tendons and ligaments also have a much slower turnover rate.
In short, measuring protein turnover at the whole body level won’t tell you what’s happening inside the muscle. We know that protein was being synthesized and stored, but we don’t know where.
What’s more, subjects were fasted for over 12 hours being given the protein supplements. Protein synthesis and breakdown rates are very different after an overnight fast than they are during the day after food has been eaten.
Mixing nutrients (such as eating protein with carbohydrate and fat) also changes the rate at which amino acids reach the bloodstream.
Consuming a fast or slow protein as part of a mixed meal, or even a few hours after a mixed meal (where nutrients are still being digested and absorbed), may well give a different set of results. Lifting weights will also have a big impact on the way your body responds to a fast or a slow protein, and can affect protein metabolism for several days.
In short, it’s very difficult to draw any meaningful conclusions about what this research means for people who want to gain muscle. All it tells us is how quickly whey or casein are digested when they’re taken by themselves, after an overnight fast, in untrained, non-exercising subjects.
Pre-Bed Protein Revisited
In 2012 a team of Dutch researchers decided to look again at the impact of taking a protein shake before bed. They found that 40 grams of protein taken 30 minutes before sleep led to an increase in muscle protein synthesis during the night .
In fact, muscle protein synthesis – a key driving force behind muscle growth – was around 20% higher in subjects given the protein supplement compared with a placebo.
A follow-up study by the same team of researchers looked at gains in muscle size and strength over a 12-week period .
Men taking part in the study were assigned to either a placebo or a protein group. The protein group consumed a supplement providing 28 grams of protein and 15 grams of carbohydrate each night before they went to sleep. Group two received a placebo containing no calories.
The supplement contained a 50:50 blend of micellar casein and hydrolyzed casein. While micellar casein is digested relatively slowly, hydrolyzed casein has been partially pre-digested, which means it’s absorbed more quickly than regular casein .
Both groups trained with weights three times per week for a total of 12 weeks. All training sessions were performed in the evening between 8pm and 10pm.
A variety of methods were used to track changes in muscle size. Whole-body muscle growth was assessed using DEXA, while a computerised tomography scan (also known as a CT or CAT scan) was used to look at changes in muscle thickness in the thighs.
The researchers also took a slice of muscle tissue from their subjects and looked at it under a microscope, which allowed them to measure changes in the size of individual muscle fibers. Strength was assessed by measuring the maximum amount of weight that could be lifted once across a total of six exercises.
Did taking protein before sleep have any effect on muscle growth?
Gains in whole-body lean mass, measured by DEXA, were not significantly different between groups.
If DEXA had been the only method used to track changes in muscle mass, we’d come away with the conclusion that there was no difference between the two groups.
However, all other measures of muscular gains were significantly greater in the protein versus the placebo group.
The size of the quadriceps, measured using a CAT scan, increased in both groups. But it was the pre-bed protein group that grew the fastest, gaining 75% more muscle than their counterparts in the placebo group.
Why did a CAT scan show a significant increase in muscle growth, while DEXA did not?
A CAT scan uses X-rays and a computer to create detailed images of the inside of the body. It’s far more sensitive than DEXA when it comes to detecting changes in muscle mass. In one study, a CAT scan shows that a strength training program led to a 6% increase in thigh muscle area, while DEXA registered no change in muscle mass .
Changes in muscle fiber size were also greater in the pre-bed protein group. In fact, the increase in type II muscle fiber size seen in the protein group was more than double that of the placebo group.
In addition, maximal strength across all six exercises increased by 361 pounds (164 kilograms) in the protein group – a 26% increase compared to the placebo group.
At first glance, this study appears to support the use of a protein shake before bed.
However, all research comes with limitations, and this trial is no different. The main problem is that protein intake wasn’t matched between the groups.
Subjects in the placebo group consumed, on average, 0.6 grams of protein per pound (1.3 grams per kilogram) of bodyweight per day. The addition of 28 grams of protein before bed raised their average protein intake to 0.9 grams per pound (1.9 grams per kilogram) of bodyweight.
The fact that the protein group ended up consuming almost 50% more protein than the placebo group does make it a little tricky to interpret the results.
We don’t know if it was the time at which the protein was consumed, or simply the extra protein itself, that was primarily responsible for the additional gains in size and strength.
The researchers themselves point out that “ingestion of the protein supplement before sleep was not compared with other time points of ingestion. As such, we can only speculate on the surplus benefit(s) of the protein supplement being provided before sleep as opposed to other time points throughout the day.”
The 2012 study had the same weakness – total daily protein intake was around 40 grams higher in the group given protein before bedtime.
Both studies provide some support for the idea of taking a protein shake before bed. But the fact that protein intake wasn’t matched between groups is a problem. We don’t know if it was the additional protein, or the time at which it was consumed, that was primarily responsible for the additional gains in size and strength.
The Case Against Taking a Protein Shake Before Bed
When daily protein intake is matched, there’s very little evidence to show that taking a protein shake before bed will help you build muscle any faster.
When a team of US researchers put the idea to the test, they found no difference in muscle growth with a protein shake before bed compared to the same amount of protein consumed during the day .
They took a group of recreationally active young men, and assigned them to one of two groups. Both groups lifted weights four times a week for ten weeks, and took a daily casein supplement providing 35 grams of protein. This bumped up their daily protein intake to around 0.9 grams per pound (2 grams per kilogram) of bodyweight, which is more than enough protein for anyone wanting to build muscle .
The only difference was in the timing of the protein. One group took the supplement during the day, while group two took it shortly before going to bed.
Lean body mass (a reasonable proxy for muscle mass) increased to a similar extent in both groups. Ultrasound scans also show similar gains in muscle thickness. What’s more, there was no significant difference in strength gains on the leg press and bench press between the two groups.
In short, given enough daily protein, a pre-bed casein supplement worked no better for muscle growth than the same amount of casein taken during the day.
Other studies report much the same results. In one trial, eight weeks of supplementation with two scoops of protein powder (providing 54 grams of casein) 90 minutes or less prior to sleep delivered no additional muscle gains compared to the same amount of protein taken in the morning .
One of the limitations with this study is that subjects were instructed to maintain their usual training habits. In an ideal world, both groups would have followed the same training program. But that isn’t what happened.
Gains in muscle mass were also assessed using the Bod Pod®, which is one of the least reliable ways to track individual changes in body composition over time.
Researchers from Florida State University also report that a protein shake before bed, be it whey or micellar casein, has no effect on muscle growth after four weeks of training compared to the same amount of protein eaten earlier in the day .
Will Drinking a Protein Shake Before Bed Help You Lose Weight?
Some say that taking a protein shake before bed will “boost your metabolism” and help you lose fat faster. This claim is based on the finding that pre-sleep protein raises your metabolism the following morning compared to eating nothing [11, 12, 13].
However, this doesn’t mean that taking a protein shake before bed will help you lose fat any faster.
For one, the finding that pre-sleep protein raises your metabolism doesn’t show up in every study. In one trial, a casein supplement providing 30 grams of protein had no effect on fat metabolism, metabolic rate, or appetite the following day .
In another, a bedtime glass of milk containing 10 or 30 grams of protein had no effect on metabolism the following morning . Pre-sleep carbohydrate has also been shown to raise metabolism the following morning . It’s not something that’s unique to protein.
What matters when it comes to losing fat is the amount of fat burned over a period of weeks and months. As long as you account for it in your daily calorie budget, taking a protein shake before bed isn’t going to have a big impact on your rate of fat loss one way or the other.
Summary: Is It A Good Idea To Eat Protein Before Bed?
To sum up, taking a protein shake before bed is something I’d put in the “worth a try” category. It certainly isn’t going to hurt your results. However, assuming that the rest of your diet and training program is in order, it’s probably not going to help much either.
If pre-bed protein is something you want to try, researchers think that at least 40 grams of protein is required to maximize the rate of muscle protein synthesis during overnight sleep, and that a variety of high-quality animal-based protein sources (i.e. whey, casein, chicken or beef) will do the job, with relatively minor differences in effectiveness between protein types .
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