The Importance of Protein. Part 1

News Written by Richard Harris

Protein. Good for my muscles, right?


Protein is arguably the most important of the three macronutrients. Amongst being good for our muscles, protein is crucial for good health, immunity and for maintaining optimal body composition.

The first part of this ‘importance of protein’ series focuses on protein for high intensity exercise and muscle growth.

High Intensity Exercise

Good nutrition is vital for intense exercise, enabling suitable recovery between sessions, allowing you to benefit from training adaptations.

Adequate energy should derive from a wide variety of foods that provide carbohydrates, proteins, fats and micronutrients (vitamins and minerals). However, typical diets feature lower than ideal protein intakes, especially those involved in regular intense exercise. We in the UK tend to consume much of our daily protein at dinner. For optimal ‘gainz’ and performance improvements, this just doesn’t cut the mustard!

Why is protein important?

Proteins provide the building blocks of life. Most tissues and cells are devised from some form of protein i.e. tendons, ligaments, skeletal muscle, blood vessels.

Protein, when consumed, is broken down into amino acids of which there are 20; 11 non-essential (produced by our bodies) and 9 essential (EAAs). EAA’s need to be consumed within our diets (3).

High Quality Protein

Protein quality is just as, if not more important than quantity. Not all proteins are created equal. Protein quality is assessed on its bioavailability, which according to the International Society of Sports Nutrition (ISSN) (4) means:

“The amino acid bioavailability of a protein source is best conceptualized as the amount and variety of amino acids that are digested and absorbed into the bloodstream after a protein is ingested.”

In other words, how much of the protein you consume is utilised by the body.

Sources of Protein

Proteins derived from milk, specifically whey isolate and casein proteins are rated the highest quality due to their EAA content (5). Furthermore, milk proteins contain high amounts of Leucine, a branched chain amino acid (BCAA) that is a vital component in promoting muscle protein synthesis (MPS) (6, 7, 8), the process that creates muscle growth and repair.

Casein protein has consistently been highlighted as a fantastic overnight protein source. Taken 30 minutes before sleep, casein helps boost MPS during the night and the following morning, promoting lean mass growth (26, 27).

Eggs are another fantastic source of EAAs and Leucine. It was once thought eggs contained high levels of cholesterol. Whilst true, the link between egg intake and heart disease has long been debunked (9).

Other sources include flesh proteins; lean beef, poultry, fish, which all contain high amounts of EAAs as well as several important micronutrients (3).

What about plant-based proteins?

Complete* plant-based proteins contain lower levels of EAAs, especially Leucine, whilst having a lower bioavailability rating. They’re also lacking in important micronutrients (3). However, a well thought out nutritional plan, combining several plant-based proteins and supplements will provide complete protein and EAA consumption for vegetarians/vegans, optimising muscle growth (3).

Of the plant-based protein sources, soy is the most well researched (10). Whilst a complete protein, soy stimulates MPS far less than milk or animal proteins (11) due to its much lower content of Leucine (12). A more suitable plant-based source of protein is rice protein. A recent study assessed both rice and whey protein powders, finding remarkably similar adaptations in terms of lean mass gains (13).

How much protein?

The UK’s current dietary reference value is set at 0.8g of protein, per kilogram bodyweight, per day (g/kg/BW/day) for adults (2). However, plenty of evidence now suggests this number is low and lacks consideration of the individual, their needs, their training volume/intensity, current weight etc (1).

There are several journals/organisations with differing recommendations, and we’ve summarised these below:

  • Sedentary individuals should aim for 1.2 – 1.8g/kg/BW/day (14)
  • The ISSN suggests training athletes should aim for 1.4 – 2g/kg/BW/day (3).
  • If you’re of healthy weight, active, and wish to build muscle, aim for 1.4 – 3.3 g/kg/BW/day as recommended by Examine (15).

Evidence suggests higher protein intakes may not necessarily lead to greater skeletal muscle growth, however will be taken up by other tissues in the body (19), flaying the ‘protein wastage’ myth.

Most recommendations are based on studies using whey protein, meaning it’s important to consume proteins of a similar quality to obtain the relevant protein intake. Furthermore, the above recommendations fall within the accepted protein contribution toward our total daily macronutrient intake; 10 – 35% (25).

Per meal protein

Research now suggests our per meal protein consumption is the most important factor influencing MPS; protein accretion (muscle growth) only occurs in a protein fed state (3). Previously it was thought that MPS peaked with a consumption of 20 – 25g protein per meal (16, 17). However, new evidence highlights greater MPS from a consumption of 0.4 – 0.55g/kg/BW/meal of high-quality protein, over a minimum of 4 meals (18), equating to a consumption of 1.6 – 2.2g/kg/BW/day.

To get the most from your training, it’s important to space your protein out throughout the day, which brings us on nicely to our next topic!

Protein Timing

Evidence use to claim a ‘window of opportunity’ of consuming protein immediately following exercise. Several authors have sought to debunk this theory however evidence is clear that consuming protein around exercise, in EAA or whole protein form (whey protein, eggs etc) leads to greater gains in lean mass and improvements in sporting performance (20, 21).

It is believed that MPS rates elevate and peak within 3 hours of finishing exhaustive exercise, whereby skeletal muscles’ sensitivity to protein is also elevated (6), suggesting the ‘window of opportunity’. Furthermore, MPS levels remain elevated for 24 hours post exhaustive exercise (22), provided adequate protein is consumed. It would seem reasonable then to suggest that consuming protein immediately after exercise will at the very least have a neutral benefit, if not a significant one, forming part of your daily protein consumption (3).

Protein ‘Balance’

Exhaustive exercise places the body in what’s known as a ‘negative protein balance’, i.e. breaking down skeletal muscle (3). However, providing an immediate feed of protein, and further protein feeds every 3 – 4 hours (minimum of 4 meals per day) will place the body in a net 'positive protein balance', promoting growth and recovery (18). The ISSN recommends adding protein to carbohydrates at a carbohydrate to protein ratio of 2-4:1 (3) for optimal recovery from exhaustive exercise. This results in increased glycogen resynthesis and ultimately improved performance.

Is a high protein diet safe?

Evidence is now clear that unless you have a pre-existing liver or kidney illness, high protein intakes are completely safe for healthy, exercising individuals (23, 24). Bring on the gains!

Take home message

Just in case the above has bamboozled you, below is a summary of the key points relating to this topic:

  • Consume your protein evenly throughout the day, through a minimum of 4 meals, maximising MPS, maximising lean mass growth and retention,
  • Protein intake per day: Aim for 1.4 – 2.0g/kg/BW/day (even up to 3.3g when in a calorie deficit),
  • Protein intake per meal: 0.4 – 0.55g/kg/BW,
  • Intake targets will make up 10 – 35% of your daily macronutrient intake,
  • High quality protein sources are key; providing the EAAs discussed, including 1 – 3 g Leucine per meal, promoting and maintaining elevated MPS,
  • Combining protein with carbohydrates post exercise will help with reducing muscle soreness, replenishing glycogen levels as well as contributing toward your daily protein intake target.

All that’s left to say now is, don’t forget to train, and with intensity!

Team MPN


* complete proteins are those that contain all 20 amino acids


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