Muscle is crucial for health, performance, and (let’s face it) to look good.
Although resistance-based exercise is extremely helpful to increase the anabolic potential of muscle tissue, the anabolic effects of nutrition are ultimately driven by the incorporation of dietary protein into skeletal muscle proteins .
This makes an adequate dietary protein intake essential in order to stimulate muscle protein synthesis .
For muscle growth to occur, net muscle protein synthesis has to be larger than net muscle protein breakdown at the end of the day. Accordingly, nutrition has the largest influence on changes in muscle protein synthesis and muscle protein breakdown .
The current recommended daily protein intake for the average person is 0.8 grams of protein per kg of body weight.
However, these recommendations are only stated as a means to aid normal metabolic function and maintain protein balance, and are not optimized for people undertaking physical activity and wanting to gain muscle mass.
For this reason, it is logical to assume that people in this category require a higher protein intake to ensure they have a pool of “free” amino acids that may be used for muscle-building purposes.
After all the body will always preferentially use dietary protein to satisfy the metabolic need for survival as opposed to supporting muscle gain. This makes an abundance of dietary protein a necessity for building muscle .
So how much protein do you need to gain muscle, and how much do you need to optimize muscle growth?
A Complex Topic that Depends on Many Factors
The amount of dietary protein needed to gain muscle is determined by several dietary factors, including:
- The quality of the protein source
- The amount of protein ingested
- The timing of protein intake
- The pattern and frequency of protein intake
All of these factors can independently and synergistically impact rates of protein digestion and amino acid absorption, the delivery of amino acids to muscle cells, and ultimately the amount of muscle protein synthesis.
1. Protein Quality
As foods have different ratios and concentrations of amino acids, protein sources differ in their capacity to stimulate muscle protein synthesis.
The main properties that determine the anabolic effect of a protein source are it’s digestion rate and amino acid composition – particularly leucine.
In general, animal-based foods are recognized as a superior source of protein because they have a complete composition of essential amino acids, with high digestibility (>90%) and bioavailability.
Plant proteins do still offer a complete set of amino acids (despite the myth that they don’t), however they do vary considerably in their quantities of certain essential amino acids. Plant foods, on average, tend to be lower in amino acids such as leucine, methionine, and cysteine.
Since leucine is the main amino acid which signals for anabolic processes to start, this will significantly impact on protein synthesis rates from a given protein source .
In addition, the digestibility and bioavailability of plant proteins is lower than those from animal sources due to the potentially high content of dietary fiber and protease inhibitors .
2. Protein Distribution
To many people’s surprise, protein-induced increases in muscle protein synthesis are limited in duration after a meal. In general, dietary protein can increase muscle protein synthesis for ~3 hours before returning to normal levels, despite sustained amino acid availability and intramuscular anabolic signalling.
This is termed the “muscle full effect” and occurs when a meal contains ~2.5 grams of leucine and ~10 grams of essential amino acids   .
Considering this, it is important to have regular protein feedings to ensure muscle protein synthesis is being frequently stimulated throughout a 24-hour period.
The science is not yet conclusive, but it is estimated that the consumption of ~3 evenly distributed meals a day each containing ~25–50 grams of high-quality protein is optimal for the stimulation of 24 hour muscle protein synthesis .
20 grams of protein gives a near-maximal increase in muscle protein synthesis after resistance training, but raising this to 40 grams leads to superior results by ~10%  .
The exact amount of protein per meal may change depending on gender and body composition, so a more accurate recommendation of 0.25-0.40 grams of protein per kg of bodyweight may also be used.
This goes against the mindset of “the more, the better”, and in fact the distribution of protein throughout the day may be just as important as protein dose and source.
Following on from the general recommendation to spread out protein-containing meals, a further step can be taken to specifically target the times in the day where people may get the most bang for their buck with protein ingestion:
- Protein intake immediately post-exercise may have a more beneficial response compared to other times in the day, as it will quickly reverse muscle protein breakdown from exercise and quickly initiate muscular repair. Studies support this, showing that protein ingestion immediately after exercise is more effective than protein ingestion 3 hours post-exercise .
- Ingestion of a high-protein meal before sleep may be especially important as sleep requires a long period of fasting with no opportunities to stimulate muscle protein synthesis. By consuming a high-protein meal before sleep, this will ensure the fasting period does not need to be longer than it already is .
The responsiveness of muscle protein synthesis to protein ingestion significantly deteriorates with advancing age. This is referred to as “anabolic resistance” .
Specifically, the muscle protein synthesis response is ~30% lower in older adults (>50 years old) compared to young adults .
This indicates that the skeletal muscle of older individuals does not lack the capacity for inducing a maximal anabolic response, but rather is less efficient.
As such, this suggests that the relative amount of protein required to maximally stimulate muscle protein synthesis is ~30% higher in older adults  .
4. Training Status
Considerable evidence has shown that the amplitude and duration of increases in muscle protein synthesis post-exercise is dependent on an individual’s training status – trained versus untrained .
The total muscle protein synthetic response is decreased in trained subjects compared to untrained subjects, hence why it is harder for more muscular individuals to add additional muscle mass.
This also makes for a logical explanation as to why untrained people can make faster much gains than experienced lifters (“newb gains”).
What Does The Research Support?
The problem with the research in relation to this question is that it focuses on protein recommendations in order to maximize muscle gains as opposed to the minimal amount needed for muscle growth to occur.
Regarding the best protein intake range for muscle growth to be optimized, this appears to be in the range of 1.3-1.8 grams of protein per kilogram per day, consumed as 3-4 well distributed meals with high-quality protein sources .
The reason for such a large range is because of all the factors which have previously been mentioned that clearly have a large impact on muscle protein synthesis responses.
For example, high-quality protein sources require less total protein to induce the same response as higher intakes of low-quality sources.
This makes the topic extremely complex with no “true” answer, as it depends on a range of variables that affect the context of the situation.
As for the minimum amount of protein needed to see some amount of muscle growth occur, this is likely just any amount over the amount needed for daily metabolic processes – ~0.8 grams of protein per kilogram of bodyweight.
What Is The Best Practical Advice?
If you are wanting to gain muscle, some simple advice would be to focus on ingesting ~1.5 grams of protein per kilogram of bodyweight per day.
This total quantity should be split into at least 3 protein-rich meals, distributed evenly throughout the day, consisting of high-quality protein sources such as meat, fish, dairy, and legumes .
If possible, try to get some of these protein meals for immediately post-exercise and also before bed.
People looking to gain muscle require higher protein intakes than standard recommendations as they need to have spare protein and amino acid stores to contribute towards muscle building.
In theory, any amount of protein above the requirements needed for metabolic function and health will aid muscle growth.
However, the discussion about “optimal” protein intakes to maximize muscle growth is a separate topic and depends on many variables such as protein quality, protein distribution, training status, and age.
Based on the current evidence it is best to stick to a daily protein intake of ~1.5 grams per kilogram of bodyweight to ensure muscle growth – provided other nutritional protocols are in place.