Muscle Gain Nutrition Considerations (Part 2): Optimising Protein Intake
In your pursuit of muscle gain it is important to understand the importance of protein intake. Part two of this article series shall therefore delve into the why, what, when and how for those individuals that wish to optimise their muscle building efforts. However, first a little theory to set the scene to educate you upon how the muscle magic happens.
I want to first introduce you to two key processes:
- MUSCLE PROTEIN SYNTHESIS (MPS)
- MUSCLE PROTEIN BREAKDOWN (MPB)
A common analogy used to explain the importance of protein is to consider amino acids as building blocks (e.g. lego) and your muscle as a wall.
MPS is the process of building the wall by adding bricks (protein), whereas MPB is the removal of bricks (protein).
When at rest, and in a fasted state, the rate of MPB is greater than MPS, which results in a negative net protein balance. However, when protein is consumed there is a transient increase in MPS above rates of MPB, resulting in a positive net protein balance. Following resistance exercise MPS rates are primed for an increased sensitivity to protein feeding. Following resistance training the elevated rates of MPS remain above resting levels for 48hrs within non-resistance trained individuals, whilst persisting for up to 24hrs in resistance trained individuals. It is the repeated accumulation of resistance training, protein feeding and periods of positive protein balance over time that leads to muscle hypertrophy (increase in muscle size).
Okay so we have covered what the importance of MPS and MPB and their role in the development of muscle, but what happens to these processes during energy restriction? When within an energy deficit MPS has been found to be the main adaptive mechanism with a decrease in MPS rates found, with MPB pretty much unchanged. Why is MPS reduced in such conditions? Building muscle is a energy costly process and it is proposed that in the face of energy restriction your body induces a “compensatory decrease in energy-consuming processes …with a greater relative proportion of amino acids catabolised for energy production“. A focus of the nutritional and training intervention should therefore be to minimise the decline in MPS. How can this be achieved? Simply by implementing a resistance training programme and an elevating protein intake above maintenance needs.
DAILY PROTEIN INTAKE
The recommended daily intake for protein is 0.8g per kg of body mass with such intake deemed adequate to cover the needs of 97.5% of the population. However, it is important to highlight that this is the intake to avoid protein insufficiency and therefore cannot be considered applicable to athletes, especially those seeking optimal adaptation to resistance training.
For individuals engaged in resistance training when in eating at maintenance or in a calorie surplus, a protein intake of 1.6 – 2.2g per kg of body mass is recommended. However, as discussed in the previous section, daily protein intake is suggested to be higher when in a calorie deficit at roughly 2.3-2.7g per kg of body mass. For those basing intake upon fat-free mass, then a total protein intake of 2.3-3.1g per kg of fat-free mass may be considered.
Interestingly, a recent research review highlighted the benefits upon body composition via different pathways when consuming higher dietary protein intakes. Where possible an emphasis should be placed upon quality weight loss, with a decrease in fat mass and increase in fat-free mass (or its maintenance/minimised loss if very lean). Three key influences upon such an approach include:
Satiety – Protein consumption can influence neural and hormonal pathways that influence appetite. For individuals that are therefore reducing energy intake, increasing protein consumption can aid the feeling of fullness.
Thermic Effect of Food – Of all the macronutrients (carbohydrate, fat and protein) protein expends the greatest amount of energy with regards to its digestion and absorption. Therefore, increasing the contribution of protein within dietary intake will increase energy expenditure.
Fat-Free Mass – To stimulate muscle protein synthesis requires the ingestion of protein (amino acids), particularly high quality protein sources (e.g. eggs, dairy, meat, chicken, turkey, fish), which are rich in essential amino acids. The combination of resistance training and protein intake further enhances the MPS response. The maintenance, or in some instances increase, of muscle mass, is not only desired for performance or aesthetic reasons, but also for our health.
INDIVIDUAL PROTEIN DOSE
So, how much protein is required in a single meal or snack to optimise the MPS response? Is this a saturable process? Initial research suggested that the consumption of 20g of protein (around 0.25g per kg of body mass) was found to maximally stimulate MPS, with no statistically significant benefit by ingesting a larger 40g protein dose amongst healthy individuals with a range of training experience and trained individuals. With MPS found to be optimised at 20g, protein intakes higher than this were oxidised at a higher rate or utilised for other processes within the body. However around a 10% mean increase in MPS was seen when consuming 40g as opposed to 20g, which suggests there may be some additional benefit for those looking to leave nothing on the table with regards to their gains. Interestingly, recent research has suggested that a 40g protein dose is superior to 20g in optimising MPS post whole body resistance training, with the 40g dose displaying a 20% greater response. It is important to highlight that the greater amount of muscle mass recruited in this study (whole body resistance training) compared to the previous (lower body training only) may have therefore required a greater demand for protein to optimise MPS.
ALTHOUGH INITIAL SUGGESTIONS STATED THAT A PROTEIN DOSE OF 0.25G PER KG OF BODY ASS WOULD OPTIMISE MPS, THIS HAS SINCE BEEN INCREASED TO 0.4G PER KG OF BODY MASS TO ACCOUNT FOR INTER-INDIVIDUAL VARIATION.
Protein content of common foods:
Protein content of common vegetarian protein sources:
Protein is comprised of building blocks, otherwise knowns as amino acids. There are 20 amino acids, with 11 considered non-essential (synthesised within the body) and 9 essential (required via dietary intake).
(1) Essential Amino Acid (EAA) Composition
EAA play an important role in the stimulation of MPS, with 10g of EAA (equating to 20g protein) found to optimally stimulate MPS (Cuthbertson, 2005). The EAA composition of a protein source is therefore predictive of its ability to stimulate MPS. However, “the leucine content of a protein is the strongest determinant of the capacity of a protein to affect MPS and likely hypertrophy”.Why is this so? Well, the EAA Leucine is often refereed to as the metabolic trigger that triggers a rise in MPS. Therefore, it is important that if looking to optimise MPS you consume foods rich in all EAA, with Leucine being of particular importance.
(2) Digestive/Absorption Properties
Quite simply, this refers to how quickly a protein source can be broken down, enter the blood and be utilised by muscle for MPS. Rapid digestion to enable an increase amino acids and in particular leucine to trigger MPS.
When compared to animal-based protein, plant-based sources are typically of a lower EAA content – see the table above. Additionally, plant-based protein have a lower digestibility than animal protein sources. Therefore, via the previously discussed criteria of assessing protein quality, plant-based protein sources can be considered of lower quality. However, this is not to say they cannot be of use – they certainly can and they can make up some quite tasty meals! However, you have to be a bit more mindful of putting your meal together, as a common solution is to combine sources to build a complete EAA profile. If incorporating plant-based protein sources within your dietary intake, it is important to mindful that you will require a greater overall protein serving to match the EAA content of that seen in an animal protein source. Note that the the lower content of protein/EAA seen within the majority of plant-based protein sources typically also come with a higher kcal content, typically via increased carbohydrate.
A common misconception when it comes to protein intake is the belief that more is better. You may have seen at some point the individual with the Tupperware cramming in some protein on the hour. Such people are of the belief that continually consuming protein via high meal frequencies will continually stimulate MPS and lead to continued muscle mass gains – if only!!
The ‘muscle full effect’ suggests that in the face of continued protein feeding the muscle will eventually become refractory once maximally stimulated, with excess protein either oxidised for energy or utilised for other roles within the body. Following the consumption of a saturable dose of protein, a 30 minute lag follows before a large increase in MPS, which peaks around 90 minutes before returning to baseline at roughly by 120mins, highlighting the transient nature of MPS . This is where the basis for protein feeding every 3-4 hours has been suggested to maximally stimulate rates of MPS.
As analogy let’s take a light bulb …
Interestingly, recent research within Australian rugby players found that “there was no clear effect of increasing protein distribution from approximately 4 to 6 eating occasions on changes in lean mass during a rugby preseason”. If creating a hierarchy of importance when dieting, ensuring daily protein targets are met would be of greater priority than distribution and timing. However, an individual looking to leave no stone unturned in their pursuit of optimising their muscle mass may opt for distributing 4 protein containing meals/snack, with consumption every 3-5 hours and an additional pre-bed casein feeding.
‘The anabolic window’ is a time period of great notoriety, particularly amongst resistance training individuals, where the timing of protein pre and post-training is considered immediately necessary for super-compensated muscular repair and remodelling.The increased sensitivity of MPS to protein feeding following resistance training highlights that protein consumption following resistance training is of importance for those individuals with goals regarding increased muscle mass. However, such a short window of anabolic opportunity is not as narrow as the often mentioned 30-60 minute window.
Based upon the research it has been put forward that the timing and contents of the pre-workout meal dictate the timing needs of the next protein feeding due to the time course of digestion and absorption. The closer the meal is consumed to the training bout, the longer the time needed for post-training protein consumption due to the sustained delivery of amino acids. Based upon previous findings of muscle protein stimulation every 3-4 hours, and the typical resistance training bout of most individuals lasting 60 minutes, individuals wishing to optimise their muscle gain efforts may look to consume protein 90mins pre-training and ensure protein within 90 minutes following training. This can be adjusted based upon personal preference with regards to how close or far away you wish to consume a protein dose pre-training. Individuals opting for a large mixed meal (containing both protein and carbohydrate) should be aware that this may be digested and absorbed over a longer period of time (roughly up to around 5-6 hours). This may further decrease the necessity for immediate post-training protein consumption if consuming a meal a couple of hours pre-training. For example, again based upon a 60 minute training session, if consuming a decent sized mixed meal 2 hours pre-training, one would look to consume protein within the 2-3 hours following training. In the scenario that an individual opts to train fasted first thing in the morning prior to work there should be an increased emphasis upon the timing of protein soon after the completion of training, likewise those individuals who have not consumed a large mixed meal within the previous 5-6 hours.
It is important to remember …
The consumption of protein prior to sleep is a strategy of great interest amongst the strength training population. This strategy was put forward based upon the principle that the overnight period presents an extended fasting period where an individual would be expected to be in a negative protein balance (MPB > MPS). Therefore, to promote a positive protein balance whilst sleeping it has been suggested to ingest a casein based protein feeding (slow release protein) at a higher dose (around 30-40g) than that recommended for a daytime dose, which equates to roughly 0.5-0.6g per kg body mass. A popular approach is to integrate dairy based foods (e.g. greek yogurt) into this feeding opportunity (food-first approach where possible), or for those that wish not to opt for food a casein based protein supplement could be utilised.
The infographic below summarises the key considerations for individuals looking to optimise their protein with the goal of muscle gain: