The Science Behind Protein’s Role in Muscle Building
Amino acids are major nutrient regulators of muscle protein turnover. After protein ingestion, hyperaminoacidemia stimulates increased rates of skeletal muscle protein synthesis, suppresses muscle protein breakdown, and promotes net muscle protein accretion for several hours.
What’s fascinating about this process is how your body treats protein like a construction crew receiving blueprints and materials. Each amino acid has a specific job, working together to rebuild damaged muscle fibers stronger than before. Think of it like renovating a house – you need the right tools and materials at the right time to create something better than what was there originally.
Protein is made up of amino acids that act as building blocks for cells and tissues in the body. When a person eats protein, it is digested and broken down into amino acids, which are involved in many processes in the body, including tissue growth and repair, immune function, and energy production. Muscle proteins are continuously broken down and rebuilt. In order to build muscle, a person must consume more protein than what is broken down.
Optimal Protein Intake for Maximum Muscle Development
One 2020 meta-analysis published in the journal Nutrition Reviews found that protein intakes ranging from 0.5 to 3.5 g per kg of body weight can support increases in lean body mass. In particular, researchers noted that gradually increasing protein take, even by as little as 0.1 grams per kilogram of body weight per day, can help maintain or increase muscle mass. The rate of increase in lean body mass from higher protein intakes rapidly decreased after 1.3 g per kg of body weight was exceeded.
Here’s where things get interesting – the old standard recommendation of nearly one gram per kilogram just doesn’t cut it for active individuals. While it is difficult to give exact figures due to varying study results, the optimum amount of protein for muscle-building appears to be between 1.2 and 1.6 g per kg of body weight. This means a 180-pound (81.8 kg) male, for example, would need to consume between 98 and 131 g of protein daily, combined with resistance training, to support muscle growth.
It is increasingly evident, however, that protein intake of at least 1.4–1.6 g/kg/day would be more appropriate for active individuals attempting to optimize training adaptations. It should be noted, however, that total daily caloric and protein intake over the long term play the most crucial dietary roles in facilitating adaptations to exercise.
Complete vs Incomplete Proteins: Understanding the Difference
Complete proteins includes the nine essential amino acids our bodies can’t make and are typically found in animal source proteins. Incomplete proteins are from plant-based proteins, which have a few of the nine essential amino acids but not all of them. If you don’t have the nine essential amino acids in your system, you’re missing a piece for proper protein metabolism.
Think of essential amino acids like a master key ring – if you’re missing even one key, you can’t unlock the door to optimal muscle protein synthesis. Eggs contain all of the essential amino acids, making them a complete protein source. Eggs are also a source of vitamins, minerals, healthy fats, and antioxidants.
For example, eating a peanut butter sandwich is a way of matching up incomplete proteins to make a whole. The whole grain from the bread doesn’t have all the essential amino acids but neither do peanuts. Together, they fill each other’s gaps and make-up the essential amino acids your body needs.
While the majority of complete proteins come from animals, one plant-based protein has all nine amino acids, and that’s soy, which is found in tofu, edamame, tempeh or miso. In fact, Matt says beans are a protein powerhouse, because they’re easily matched with other nutrients to make-up the essential amino acids.
The Power of Essential Amino Acids in Recovery
This study tests the hypothesis that a dose of 6 g of orally administered essential amino acids (EAAs) stimulates net muscle protein balance in healthy volunteers when consumed 1 and 2 h after resistance exercise. What researchers discovered was remarkable – even small amounts of essential amino acids could dramatically influence muscle recovery.
Net muscle protein balance (NB) increased proportionally more than arterial AA concentrations in response to drinks, and it returned rapidly to basal values when AA concentrations decreased. Area under the curve for net phenylalanine uptake above basal value was similar for the first hour after each drink (67 +/- 17 vs. 77 +/- 20 mg/leg, respectively).
The main finding of this study was that, in contrast to our hypothesis, LEAA supplementation three times per day was not more effective than placebo at enhancing integrated MyoPS over 96 h following an unaccustomed bout of RE in recreationally active men consuming a controlled diet with 1.2 g/kg/d of protein. However, consistent with our hypothesis, LEAAs moderately improved recovery from post-RE muscle damage, which interestingly did not correlate with changes in MyoPS.
This finding challenges the traditional thinking that more muscle protein synthesis automatically equals better recovery. Sometimes the body’s repair mechanisms work in ways we don’t fully understand yet.
Fish and Omega-3s: The Unsung Heroes of Muscle Health
Salmon is a great choice for muscle building and overall health. Each 3-ounce (85-g) serving of salmon contains about 17 g of protein, 1.5 g of omega-3 fatty acids, and several important B vitamins. Omega-3 fatty acids play an important role in muscular health.
Research suggests that taking 2 g of omega-3 fatty acid supplements per day may help build muscle mass. This isn’t just about the protein content – the omega-3s themselves have muscle-building properties that work independently of the protein.
Additionally, tuna provides large amounts of omega-3 fatty acids, which may support muscle health. This may be beneficial for older adults because it could help slow the loss of muscle mass and strength that occurs with age.
Think of omega-3s as the oil that keeps your muscle-building machinery running smoothly. Without adequate amounts, even the best protein in the world won’t work as effectively.
Plant-Based Proteins: Building Muscle Without Meat
There’s some debate about how well plant protein stacks up against animal protein for muscle growth. Some research suggests that animal protein is better. Animal protein sources contain all essential amino acids and may be easier to digest than plant protein.
However, this doesn’t mean plant-based athletes can’t build impressive muscle mass. You can also get essential amino acids from plant-based foods. However, most plant-based proteins do not contain all of the needed essential amino acids, and so are called incomplete proteins. If you avoid animal proteins, the best way to ensure you are consuming a healthy mix of amino acids is to enjoy a variety of plant-based proteins through the day.
Quinoa is a plant-based protein source that is also a complete protein. A cup of cooked quinoa provides about 8 grams of protein and 5 grams of fiber. Quinoa is also a good source of minerals such as manganese, phosphorus, and copper.
The key is strategic combining and timing. Plant-based athletes often need to be more thoughtful about their protein choices, but with proper planning, they can achieve remarkable results.
The Role of Casein in Overnight Recovery
There are two proteins in milk – whey and casein. Whey is the watery part and casein is the curds. Whey is digested more quickly than casein and has all the essential amino acids, including leucine, which is important in muscle protein synthesis.
Casein is digested more slowly and helps stop muscle protein breakdown. Some people drink a casein shake before bed, since there’s muscle breakdown overnight when you’re not eating.
Pre-sleep casein protein intake (30–40 g) provides increases in overnight MPS and metabolic rate without influencing lipolysis.
This slow-release property makes casein like a time-release medicine for your muscles – it provides a steady stream of amino acids throughout the night when your body is doing most of its repair work. While you sleep, casein continues working, ensuring your muscles have the fuel they need for recovery and growth.
Hydrolyzed Proteins: Pre-Digested for Faster Absorption
This form of whey therefore appeals to those wanting to maximise muscle growth as the amino acids are available for the body to use for muscle repair more quickly post-workout. Hydrolyzed proteins have been partially broken down, making them easier to digest and absorb.
There are three main types of whey protein: whey protein concentrate (WPC), whey protein isolate (WPI) and whey protein hydrolysate (WPH). WPI goes through further processing to remove more fats and carbohydrates, resulting in a higher protein concentration. WPH is pre-digested, making it easier to absorb.
Had thirteen trained male cyclists complete a simulated 60-km time trial where they ingested either carbohydrate or carbohydrate and protein hydrolysate at equal intervals throughout the race as well as at the conclusion of the race. The authors reported that co-ingestion of a carbohydrate and protein hydrolysate improved time-trial performance late in the exercise protocol and significantly reduced soreness and markers of muscle damage.
It’s like having your protein pre-chewed by science – your body can immediately put these amino acids to work without having to spend energy breaking them down first.
Muscle Protein Synthesis vs. Daily Protein Goals
Strategic ingestion of high-protein dairy milk during a resistance training program increases lean mass, strength, and power in trained young males. We assessed the relationship of changes in upper and lower body lean mass with muscle strength, endurance and power responses following two high protein diets (1.6 or 3.2 g.kg-1.d−1) during 16 weeks of either concurrent training (CT) or resistance training (RT) in resistance-trained young males.
What’s interesting about recent research is that doubling protein intake doesn’t necessarily double the results. Changes in muscle strength, endurance and power adaptation responses following 16 weeks of either CT or RT with different high protein intakes were not associated with changes in lean mass in resistance-trained young males. Changes in muscle strength, endurance and power adaptation responses following 16 weeks of either CT or RT with different high protein intakes were not associated with changes in lean mass in resistance-trained young males. These findings indicate that muscle hypertrophy has a small, or negligible, contributory role in promoting functional adaptations with RT or CT, at least over a 16-week period.
A single bout of RE can sustain measurable increases in postabsorptive MPS soon after RE cessation and up to 48 h post-RE. This extended window of elevated protein synthesis means your muscles are actively rebuilding for much longer than most people realize.
Think of muscle protein synthesis like a slow-cooking process – once you turn up the heat with resistance training, it keeps cooking at a higher rate for days, not hours.
The Saturation Point: When More Isn’t Better
Originally, this information came from a 2013 study where participants experienced greater muscle growth when fed 20 grams of protein four times per day (Areta et al., 2013). However, both groups had much lower protein intake than is currently recommended, and the researchers utilized whey, a fast-absorbing protein source that quickly saturates receptors in the intestinal wall. However, when eating slower absorbing protein sources, such as those that come in a varied diet of meats, eggs, beans, dairy, and plant-based protein, the 25-gram limit does not seem to apply (Morton et al., 2018).
However, infusion-based studies in rats and humans indicate that the postprandial rise in MPS from ingesting amino acids or a protein-rich meal is more transient, returning to baseline within 3 hours despite sustained elevations in amino acid availability. It thus has been hypothesized that a “muscle full” status can be reached where MPS becomes refractory, and circulating amino acids are shunted toward oxidation or fates other than MPS.
This “muscle full” concept is like trying to fill a glass that’s already overflowing – at some point, additional protein doesn’t contribute to muscle building but gets used for other purposes or simply eliminated. The key is finding that sweet spot where you’re providing enough fuel without wasting resources.
Recovery Markers: Beyond Just Muscle Growth
The impact of dietary protein supplementation on recovery from resistance exercise-induced muscle damage: a systematic review with meta-analysis. Eur J Clin Nutr. Recent research has expanded our understanding of how protein contributes to recovery beyond simple muscle building.
For example, studies have reported positive effects of protein supplementation on post-RE muscle soreness but not muscle strength, muscle strength but not muscle soreness, or neither. The variability may be explained by differences in protein supplement type (whey protein, milk protein, or BCAAs), supplementation timing (before exercise, after exercise, multiple times per day), exercise protocol, overall macronutrient intake, and/or the overreliance on parametric statistics and lack of effect size analysis. In the present study, effect size analysis revealed that LEAAs had small to moderate effects on reducing muscle soreness, and moderate to large effects on preserving muscle torque production that reached statistical significance when peak torque measures were summated.
It’s becoming clear that protein’s benefits extend far beyond what we can see in the mirror – it affects how you feel during training, how quickly you recover between sessions, and how well you perform under fatigue.
The Practical Reality of Protein Intake
Despite all the science and research, the practical application often comes down to consistency and convenience. As athletes, schedules can be rigid, and time is finite. When thinking through a practical nutrition plan, zoom out and ask yourself, “What structure and eating schedule will lend itself to maximum consistency and intake?” If you’re not a big breakfast eater, you could try plugging in 12-16 ounces of chocolate milk or 6 ounces of Greek yogurt. Or if you’re too busy to eat lunch, make sure to add a dose of protein following your workout to make up for the deficit. Where protein is concerned, a sufficient amount is key, in whatever distribution works best for your lifestyle.
For untrained individuals, consuming supplemental protein likely has no impact on lean mass and muscle strength during the initial weeks of resistance training. However, as the duration, frequency, and volume of resistance training increase, protein supplementation may promote muscle hypertrophy and enhance gains in muscle strength in both untrained and trained individuals. Evidence also suggests that protein supplementation may accelerate gains in both aerobic and anaerobic power.
The best protein strategy is the one you can stick to long-term. Whether that’s three large meals with substantial protein or six smaller protein-containing snacks throughout the day, consistency trumps perfection every time.