Protein for Strength Athletes and Bodybuilders – How Much, How Often, and What Kind

The term “protein” is derived from the Greek word for primary. This meaning is true especially for athletes, bodybuilders and strength athletes with the goal to increase performance, muscle size and strength. Protein is the primary dietary driver for anabolism. This article will make sure you know everything you need to know about how protein can help you in your athletic endeavours.

Basic Functions of Protein and Muscle Growth

Protein is required for the maintenance, repair and synthesis of every cell in the body, but is also vital for athletes to promote training adaptations and recovery.

Dietary protein is used to synthesize new tissue and to repair breakdown of tissue, and is required to promote growth. For athletes, this often refers to muscle protein, to stimulate the synthesis of new muscle protein and to reduce muscle protein breakdown.

During periods of energy balance, the skeletal muscle mass of an untrained adult individual remains relatively unchanged over time. Regular physical activity, especially resistance training, increases muscle protein synthesis, as does protein ingestion. The combined effect of exercise and protein ingestion is greater than the sum of its parts. Over time, the combination of resistance training and protein-rich feedings translates to muscle growth.1

Protein is made up of building blocks called amino acids. Out of the 21 amino acids used to make the proteins required for health, growth, and repair, 9 are considered essential. Essential means that these amino acids cannot be synthesized in the body but have to be provided through dietary means. These 9 essential amino acids are also the ones required for muscle growth and muscle protein synthesis.

Ten grams of essential amino acids plus 10 grams of non-essential amino acids do not provide a more robust stimulation of muscle protein synthesis than 10 grams of essential amino acids alone. This indicates that non-essential amino acids are not required to promote muscle protein synthesis.2 3

Beyond acting as substrates for protein synthesis, amino acids also serve as triggers to initiate an anabolic response, both at rest and post-exercise. Following protein ingestion, plasma amino acid levels increase, regulating signal mechanisms that initiate protein synthesis in skeletal muscle.4

Protein does not need to be ingested in combination with other macronutrients in order to stimulate muscle protein synthesis maximally. When ample amounts of protein is provided, adding carbohydrate does not further stimulate muscle protein synthesis.5

Insulin is required for the amino acid-stimulated muscle protein response to protein feedings, but this is not due to any effect on muscle protein synthesis by insulin per se. Rather, insulin increases amino acid availability, but this effect requires only fasting levels of insulin.6

Insulin reduces muscle protein breakdown, but this effect plateaus at relatively low levels of insulin, achievable by protein ingestion alone.7 8

Protein Recommendations for the General Population and Athletic Adults

For many decades, protein recommendations for active adults and athletes were static and focused mainly on overall total daily protein intake and sport-specific requirements. Current recommendations have evolved to reflect the needs of the individual athlete depending on body composition, training goals, health and the acute requirements of a training session.

More attention has also been given to protein periodization in recent years, including meal frequency, timing of protein intake in relation to training sessions, and protein distribution over the course of the day.

The European Food Safety Authority (EFSA) Population Reference Intake (PRI) for protein is 0.83 grams of protein per kilogram of body mass per day.9 The US recommendeded daily intake is 0.8 grams of protein per kilogram of body mass per day.10 These are not the amounts recommended for optimal health and performance, but rather the amounts required to cover basic protein needs for 98% of the population.

These recommended amounts are based on nitrogen balance calculations, a method that has been criticized in recent years. Studies using the indicator amino acid oxidation (IAAO) method to calculate protein requirements have indicated that recommendations should be up to 50 % higher for the optimal health of the general population. This would bring general protein requirements up to 1.2 grams of protein per kilogram of body mass per day.11

Elderly individuals have a diminished anabolic response to feeding and exercise. In this population, 1.0 to 1.3 grams of protein per kilogram of body mass per day is likely needed to optimize health and physical function.12

Protein Requirements for Athletes

When the current RDI values were set, the notion of consumption beyond what is considered adequate to optimize training adaptations was not considered.

There are studies that indicate that athletes who habitually engage in endurance or resistance training have higher protein requirements than their sedentary counterparts.13

Resistance training might increase protein requirements to meet the need for more protein to form new muscle protein, initiate muscle protein synthesis, and repair damaged muscle protein. Endurance training increases amino acid oxidation, especially leucine oxidation, which would translate into an overall greater requirement for dietary protein.

A review article from 2011 recommends that athletes consume 1.3-1.8 gram of protein per kilogram of body mass per day to maximize muscle protein synthesis during periods of energy balance or above. It was also concluded that athletes should increase their protein intake to 1.8-2.7 grams per kilogram of body mass per day to ensure that muscle mass is maintained during hypoenergetic diets.14

Protein Requirements for Bodybuilders and Strength Athletes

Bodybuilders and strength athletes seeking to maximize the anabolic response to training might benefit from even higher protein intakes. A 2018 meta-analysis concluded that a total protein intake of 1.62 grams of protein per kilogram of body mass per day maximized training-induced gains in fat-free mass.15

A recent study which aimed to assess the protein requirements of young male bodybuilders using IAAO-testing found that protein oxidation plateaued at an average intake or 1.7 grams per kilogram of body mass per day.16

This indicates that this amount would be needed to optimize the anabolic effects of total daily protein intake. However, there seems to be some variability in individual protein requirements, and the upper end of the confidence interval in this study reached 2.2 grams of protein per kilogram and body mass per day. This was measured during a rest day, so the requirements on a training day could potentially be even higher.

These results suggest that 1.6-1.7 grams of protein per kilogram and body mass per day is enough to cover the protein requirements of most strength athletes, but individual variability might increase this to 2.2 grams per kilogram and body mass per day.

Protein Per Meal

There are only a few studies that have examined how much protein can be utilized to synthesize new muscle protein per meal.

Two studies have determined that 20 grams of either egg or whey protein maximally stimulate muscle protein synthesis after resistance training.17 18 Increasing the amount of protein in a single dose beyond 20 grams only resulted in increased amino acid oxidation and ureagenesis. The amount of protein that maximized post-exercise protein synthesis in these two studies also resulted in maximizing muscle protein synthesis at rest.

The training session employed in these two studies only targeted a single muscle group. A 2014 study showed that after a whole body workout, 40 grams of protein further stimulated muscle protein synthesis.19. Double the amount of protein did, however, not double the muscle protein synthetic response, but rather increased it a further 22%.

Measuring muscle protein synthesis following whole food intake, a 2009 study found that 90 grams of protein from lean beef did not produce a more pronounced anabolic response than 30 grams, despite a threefold increase in energy content.20

In elderly individuals, larger doses of protein per intake might be needed to maximize rates of muscle protein synthesis. One study found that older adults need higher protein doses following resistance training to optimize muscle protein synthesis, regardless of how many muscle groups are worked in a training session. While post-exercise rates of muscle protein synthesis plateaus with 20 grams of protein post-exercise in young individuals, 40 grams of protein is likely needed to achieve the same effect in the elderly.21

Given that the amount of protein required to maximize muscle protein synthesis seems to be around 20-30 grams of protein, it might be prudent to target multiple moderate-sized meals rather than one or two larger meals if the goal is to optimize muscle growth.22

The “muscle full”-effect further supports this notion. When high plasma leucine concentrations are sustained over a long time through multiple close protein feedings, there is a refractory response where muscle protein synthesis decreases to basal levels despite high amino acid availability.23 Therefore, an ingestion pattern of moderate-sized servings of protein spread out over the course of the day will maximize the anabolic response to each individual feeding.

Read more: How Much Protein from a Single Meal Can Your Body Use to Build Muscle Mass?

Protein Timing

In the fasted state, muscle protein breakdown exceeds that of muscle protein synthesis. Exercise increases both muscle protein synthesis and muscle protein breakdown, but muscle protein balance remains negative until amino acids are available. Even without amino acid availability, however, muscle protein balance is improved following resistance training, due to a larger increase in muscle protein synthesis.24

Many studies have provided evidence that resistance training in combination with feeding acts in synergy to provide a more substantial anabolic response than either training or feeding alone. Most research have focused on post-exercise nutrition, with amino acids or intact protein provided immediately or in the hours following training.

Post-exercise, there seems to be a dose-dependent muscle protein synthesis response to amino acid intake, plateauing at 10 mg of essential amino acids in a single bolus intake.25 Early studies used free amino acids, but later research has revealed that intact proteins, from protein supplements like whey protein powder as well as from food sources like eggs, beef, soy, and whole milk provide the same effect, as long as the essential amino acid content is equivalent.

Studies on how post-exercise protein supplementation translates into actual muscle hypertrophy and strength gains provide ambiguous results. While some studies show improved body composition and increased strength as the result of post-exercise protein supplementation, others do not report any advantages with such a protocol compared to protein intake during other times of the day.

A meta-analysis found that protein intake within an hour after a workout had significant effects on muscular hypertrophy compared to a delayed feeding. This advantage disappeared after controlling for total dietary protein intake, however. In studies showing increased rates of muscle growth as the result of post-exercise protein intake, the protein supplementation also increased the total protein intake compared to control groups.26

It is well known that post-exercise protein intake results in a rapid increase in amino acid levels in the blood and activates signaling pathways which regulate muscle protein synthesis. However, it is unclear if immediate post-exercise nutrition confers any significant advantage over consuming the same amount of protein at some other time.

Similar rates of post-exercise muscle protein synthesis have been observed when essential amino acids or protein are provided immediately before a workout instead of afterwards. Not many studies have examined the effects of pre-exercise protein intake, but one 2017 article showed similar effects on muscular adaptations from post- and pre-exercise protein supplementation.27

It is unknown if this translates to different gains in strength and muscle mass over longer periods of time compared to post-exercise feedings, or if protein intakes both before and after a workout would confer any unique benefits.

If resistance training is performed in the fasted state, it might be advantageous to ingest some form of protein within a reasonable time following the training session to turn the negative muscle protein balance of the fasted state into a positive one. If the training session is performed in the hours following a normal meal, amino acid availability is likely already high enough so that another pre-exercise protein feeding would not confer any additional benefits.28

The total daily amount of protein is likely to be the major determining factor regarding the hypertrophic effects of protein intake, while timing of a single protein intake in relation to a training session might confer some additional benefits. Following exercise, amino acid sensitivity is increased for up to 24 hours,29 which means that the synergistic effects of resistance training and protein intake last a long time, although it is likely to be highest during the first hours post-exercise.

Protein Sources

The most common protein-rich foods include the meat of ruminants, fish, poultry, seafood, and game, but also products procured from animals, such as dairy and eggs, and plant-based foods like legumes, nuts, and seeds. Animal sources of protein are the ones containing the highest amounts of essential amino acids, the amino acids needed to stimulate muscle protein synthesis.

L-leucine in particular stands out as the amino acid that initiates the anabolic response to feeding. Animal protein sources generally have a higher leucine content than vegetable sources. To produce a robust stimulatory effect on muscle protein synthesis, at least 3 grams of leucine must be ingested in a single meal.30 This is called the “leucine threshold”.

Traditionally, plant-based protein sources have been considered less valuable for muscle protein synthesis, and while this might be true on a gram-for-gram basis, increasing the amount of protein in a given meal might also increase the anabolic potential to equal that of animal protein. Other strategies to augment the anabolic properties of plant protein include combining multiple protein sources, or adding amino acids to a lower quality protein source.31

It is not necessary to combine different plant-based protein sources in a meal to ensure a sufficient amount of essential amino acids for the general population.32 However, it is not known if this is also the case for bodybuilders and strength athletes seeking to maximize training adaptations.

When a suboptimal amount of protein is ingested, the lower anabolic response might be rescued by adding enough leucine to the meal to reach the leucine threshold.33 Thus, simply eating more of a plant-based protein until the leucine threshold is reached would make its efficacy equal to that of a protein source with a higher leucine content.

Most research on the muscle protein synthetic response to protein ingestion in relation to resistance training has focused on powdered protein sources. These include whey protein, casein protein, soy protein, beef protein, pea protein, and egg protein. They all seem to effectively stimulate protein synthesis following exercise, and while leucine-rich proteins like whey generally provide a more robust stimulation of muscle protein synthesis, increasing the amount of protein from other sources might negate that difference.

When similar amounts of protein is consumed, however, leucine-rich protein sources like dairy promote larger gains in muscle protein, and the  habitual consumption of such sources likely leads to greater muscular hypertrophy.34 (26)

The amount of research on the consumption of whole foods following a training session is limited. Two studies indicate that it is a viable alternative to powdered nutrition.35 36. After the consumption of whole milk following resistance training, one study demonstrated a greater amino acid uptake across the exercised leg compared to skim milk. This should presumably also translate into greater muscle protein synthesis. Similarly, another study showed a greater post-exercise muscle protein synthetic response when whole eggs were consumed compared to egg whites, even when the protein content was matched.

A healthy diet should include various protein sources as part of mixed meals, where protein is co-ingested with other macronutrients and micronutrients for a complete approach to nutrition. When convenience demands it, such as following a training session, protein supplements offer a practical alternative.

Protein Safety

Concerns about high protein diets in regards to kidney damage and increased excretion of calcium still exist. Results from studies on renal patients have been extrapolated to include healthy, active individuals, regardless of the fact that no evidence indicating harmful effects of a high protein intake in a healthy population exists.

The World Health Organization has published reports indicating that there is no evidence linking protein intake to renal disease.37

Short-term studies indicate that a protein intake of 3-4 grams of protein per kilogram of body mass per day does not result in any clinical side effects. A year-long study did not show any harmful effects on liver or kidney function or blood lipids when participants consumed 3.3 grams of protein per kilogram of body mass per day.38

Recent epidemiological studies suggest that a high (>20% of the energy intake) protein intake might increase the risk of cancer and type 2 diabetes, but these studies do not establish causation and do not take into account the quality of the protein sources, for example processed meats, which are known to have detrimental health effects.

Key Points

  • During periods of positive energy balance, a protein intake of 1.6 to 2.2 grams of protein per kilogram of body mass per day will be sufficient for the vast majority of strength athletes to sustain muscle growth.
  • During periods of energy restriction, up to 2.7 grams of protein per kilogram of body mass per day might be required to curtail the loss of fat-free mass.
  • The optimal dose of protein to maximize acute muscle protein synthesis seems to be 20-40 grams of protein per serving, depending on age and training status.
  • Protein intakes up to 3.3 grams of protein per kilogram of body mass per day for at least a year do not seem detrimental to any health markers in healthy individuals.
  • Total protein intake is the most important consideration, while details like protein timing and distribution might confer additional, but smaller, benefits.

Take-Home Message

Protein is important. Make sure to consume enough of it.

References

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  2. J Nutr Biochem. 1999 Feb;10(2):89-95. Nonessential amino acids are not necessary to stimulate net muscle protein synthesis in healthy volunteers.
  3. J Nutr. 2006 Feb;136(2):525S-528S. Skeletal muscle protein metabolism and resistance exercise.
  4. Int J Sport Nutr Exerc Metab. 2007 Aug;17 Suppl:S47-57. Role of amino acids and peptides in the molecular signaling in skeletal muscle after resistance exercise.
  5. Am J Physiol Endocrinol Metab. 2007 Sep;293(3):E833-42. Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis.
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  7. Diabetologia. 2016 Jan;59(1):44-55. Role of insulin in the regulation of human skeletal muscle protein synthesis and breakdown: a systematic review and meta-analysis.
  8. Am J Physiol Endocrinol Metab. 2008 Sep;295(3):E595-604. Disassociation between the effects of amino acids and insulin on signaling, ubiquitin ligases, and protein turnover in human muscle.
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  19. Physiol Rep. 2016 Aug;4(15). The response of muscle protein synthesis following whole-body resistance exercise is greater following 40 g than 20 g of ingested whey protein.
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  27. Peer J. 2017; 5: e2825. Pre- versus post-exercise protein intake has similar effects on muscular adaptations.
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  34. The American Journal of Clinical Nutrition, Volume 85, Issue 4, April 2007, Pages 1031–1040. Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage.
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