Why is protein important? What are the benefits?

Table of contents:

• What does protein do?
• Daily protein intake
• Benefits of protein
• Should I take a protein supplement?
• Take aways

What does protein do?

Protein is one of the 4 macronutrients that once digested, is broken down into subunits called amino acids.

Protein has a structural role – for example, to make cells, tissues, muscles and bones. And a functional role – enabling all of the different processes and reactions to take place in the body, for example muscular contraction.

Enough protein is critical general health and wellbeing– from bone health, to cognitive health to immune health (1).

Some examples of what protein does:

• Growth and maintenance of cells and tissues: any muscle or tissue that undergoes growth/repair breaks down protein and requires more protein
• Structural: the protein collagen is a critical part of bone, tendons, ligaments and skin
• Reactions and processes: require proteins known as enzymes – think muscular contraction, energy generation, digestion
• Generation of energy: it can be used to make energy (ATP) 
• Acts as a chemical messenger: proteins are hormones, for example human growth hormone which stimulates the growth of tissues
• Fluid balance: helps to maintain the fluid balance between the blood and tissue
• Part of the immune system: forms antibodies which help protect the body
• Transports and stores nutrients: for example haemoglobin which transports oxygen in the blood, is a protein. 

Daily protein intake

Although the recommended daily allowance (RDA) is 0.8 g/kg/day (2), this is considered necessary to prevent being deficient. However, having sufficient protein intake may not be the same as optimal intake – more and more research suggests that a greater intake is beneficial.

If you are active, a dietary protein intake of 1.2-2.2 g/kg/day is recommended to support needs – such as muscle repair and recovery (3). Requirements vary depending on the individual. 

Guidelines (g/kg protein/bodyweight):

• Athletes and exercisers: 1.8g/kg may maximise muscle protein synthesis (4) and up to 3g /kg may be beneficial (5)
• Injuries: 1.5g/kg bodyweight (6) to rebuild damaged tissue 
• Fat loss: 1.6-2.4 g/kg (7,8) promotes muscle mass retention during a deficit. If you are very overweight, approx 1.5 g/kg is appropriate and the leaner you are, the higher end of 1.6-2.4 g/kg you should shoot for
• Seniors: those who are older and also more active may benefit from more protein – to improve physical performance without necessarily increasing muscle mass (9)

Benefits of protein 

Build muscle: amino acids are necessary to build muscle mass gains (10, 11, 12)! Without hitting your daily protein intake, you will not have the building blocks to gain. Sure, you need to train, but if you don’t have sufficient circulating levels of amino acids, you won’t be able to build the muscle.

Whilst resistance training upregulates specific factors involved in muscle growth (mTOR) (13), having enough protein distributed throughout the day, enhances this factor (mTOR) (14).

If you’re looking to up your muscle mass, resistance training + hitting daily protein intake is a must! 

Better fat loss: fat loss means you retain lean muscle mass whilst losing bodyweight – therefore protein intake is key. A higher protein intake during a calorie deficit results in a greater proportion of weight loss being fat loss than a lower protein intake (15).  

Increasing protein intake to approximately 35% of macronutrient intake vs 15% is superior for fat loss (16).

Better strength and performance: sufficient daily protein intake and distribution is associated with better strength and performance (10,11,12). Performance benefits are seen for anaerobic power and strength for resistance trained individuals who take a protein supplement (17).

Protein supplementation is also associated with significant improvements in performance for endurance athletes(19). Intense or prolonged bouts of endurance exercise uses considerable amounts of amino acids, specifically leucine and therefore protein supplementation, with a focus on leucine may be beneficial. Consuming a form of branched chain amino acid (BCAA) in specific, during endurance exercise has been shown to improve performance (20) and delay central fatigue (21). 

Weight managament: protein is the most satiating macronutrient – eating a higher proportion of protein within the diet results in less hunger and greater fullness (31,32). Consuming protein increases levels of the fullness substance – GLP-1 and PYY.

Protein is the macronutrient with the highest thermic effect, which means that it costs the most energy to be digested and absorbed. If you’re looking to expend more energy whilst keeping calorie intake the same, simply increase the relative proportion of protein (decreasing the others)! Unlike increasing calories from the other macros, increasing calories from protein may increase overall energy expenditure (29).

Better recovery: training requires energy and involves the breakdown of muscle fibres – adequate energy and protein intake is critical for the body to adapt from training to become stronger (1). Whilst carbs and fats provide energy, protein provides the building blocks (and energy if need be) necessary to rebuild those muscle fibres, repair damaged muscle tissue and build new lean tissue! Ensuring adequate protein intake, along with overall calorie determines an athlete’s recovery. 

Higher protein requirements are also recommended for individuals with any injury – in order to rebuild the lost or damaged tissue (27). A diet high in protein and rich in micronutrients promotes wound healing (28) and consuming BCAA may improve markers of immune health (20). 

Should I take a protein supplement?

Meeting your daily protein intake, followed by distributing it relatively evenly throughout the day are your priorities! Check out Does protein distribution matter for maximising your muscle gains for more info on this.

Although it has been shown that post total-body resistance training, consumption of a protein supplement results in lower rates of whole body protein breakdown (17), overall research indicates that if you are meeting your daily needs and distributing your protein throughout the day, it’s unlikely that a protein supplement will take your muscle gains any further!

If you are training a fair amount, then check out Nutrient timing – what’s the deal and does it matter when you eat. Consuming a protein supplement may be beneficial in preventing decreases in muscle performance and improving delayed onset of muscle soreness (22,23). Marathon runners receiving protein supplements show significantly lower biomarkers of damage and stress than those who didn’t receive protein supplementation (24).

If you train a lot and are on a lower carb diet /keto, protein supplementation post training may be more valuable in the recovery process, improving glycogen replenishment and decreasing symptoms of muscular damage (25). Additionally, taking a protein based drink post work out assists with the rehydration process (26) a critical component of the recovery process.

Take aways:

Protein is a macronutrient with diverse roles: integral to general health, well-being, performance and recovery. It’s necessary for everything – from bone, cognitive and immune health, to the maintenance, building, recovery and repair of muscle tissue.

Adapt your protein intake depending on your individual needs: and shoot for what is optimal for you. If you exercise regularly, are trying to lose weight or gain muscle, are recovering from an injury, or are older, adapt your needs accordingly.

Hitting your daily protein intake has many benefits including: better fat loss and muscle mass gains, easier weight management through reduced hunger and improved strength, performance and recovery.

Related articles

Does protein distribution matter for maximising your muscle gains?

Nutrient timing – what’s the deal and does it matter when you eat?

References

1. Cintineo et al. (2018). Effects of protein supplementation on performance and recovery in resistance and endurance training. 
2. Aragon et al. (2017). International society of sports nutrition position stand: diets and body composition.
3. Thomas et al. (2016). Nutrition and athletic performance.
4. Phillips et al. (2011). Dietary protein for athletes: from requirements to optimum adaptation.
5. Tipton et al. (2004). Protein and amino acids for athletes.
6. Tipton (2015). Nutritional support for exercise-induced injuries
7. Layman et al. (2005). Dietary protein and exercise have additive effects on body composition during weight loss in adult women.
8. Wycherley et al. (2012). Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets: a meta-analysis of randomised controlled trials. 
9. Tieland et al. (2012). Protein supplementation improves physical performance in frail elderly people: a randomised, double-blind, placebo-controlled trial
10. Cermack et al. (2012). Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta-analysis. 
11. Morton et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. 
12. Bosse et al. (2012). Dietary protein to maximise resistance training: a review and examination of protein spread and change theories. 
13. Bodine et al. (2006). mTOR signalling and the molecular adaptation to resistance exercise.
14. Kakigi et al. (2014). Whey protein intake after resistance exercise activates mTOR signalling in a dose-dependent manner in human skeletal muscle.
15. Meckling et al. (2007). A randmoised trial of a hypocaloric high-protein diet, with and without exercise, on weight loss, fitness, and markers of the metabolic syndrome in overweight and obese women. 
16. Metler et al. (2010). Increased protein intake reduces lean body mass during weight loss in athletes.
17. West et al. (2017). Whey protein supplementation enhances whole body protein metabolism and performance recovery after resistance exercise: a double-bind crossover study.
18. Morton et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults.
19. Stearns et al. (2010). Effects of ingesting protein in combination with carbohydrate during exercise on endurance performance: a systematic review with meta-analysis.
20. Kephart et al. (2016). Ten weeks of branched-chain amino acid supplementation improves select performance and immunological variables in trained cyclists.
21. Blomstrand (2001). Amino acids and central fatigue.
22. Cockburn et al. (2010). Effect of milk-based carb protein supplement timing on the attenuation of exercise-induced muscle damage.
23. Cockburn et al. (2013). Effect of milk on team sport performance after exercise-induced muscle damage.
24. Huang et al. (2017). Whey protein improves marathon-induced injury and exercise performance in elite track runners.
25. McLellan et al. (2014). Effects of protein in combination with carbohydrate supplements on acute or repeat endurance exercise performance: a systematic review. 
26. Leiper (1998). Intestinal water absorption-implications for the formulation of rehydration solutions.
27. Tipton (2015). Nutritional support for exercise-induced injuries.
28. Russell (2001). The importance of patients’ nutritional status in wound healing. 
29. Bray et al. (2015). Effect of protein overfeeding on energy expenditure measured in a metabolic chamber.
30. Halton et al. (2004). The effects of high protein diets on thermogenesis, satiety and weight loss: a critical review. 
31. Brennan et al. (2012). Effects of fat, protein and carbohydrate and protein load on appetite, plasma cholecystokinin, peptide YY, and ghrelin, and energy intake in lean and obese men.
32. Leidy et al. (2011). The effects of consuming frequent, higher protein meals on appetite and satiety during weight loss in overweight/obese men
33. Weigle et al. (2005). A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations.