I am sure we have all been asked and asked these types of questions at some point during our journey. Your right to ask them too, building muscle or improving body composition is a tough game and you don’t want to be missing the mark due to a fundamental flaw in your nutrition, through eating to little or even in some cases to much protein! So lets talk science and lets talk studies!
The recommended protein intake for a healthy adult in the U.K and U.S is 0.8g/kg (SACN 2016), it is widely documented that the intake to maintain optimal health exceeds this stated quantity, that has not been revised since 1991 (British Nutrition Foundation, 2016) Whilst speculation on the exact amount remains, the census from an extensive literature review of credible research concludes an intake of 1-1.2g/kg is required daily for those aiming to maintain health and body weight, with the figure increasing to 1.4-1.8g/kg for those engaging in regular exercise and subjected to sporting demands (Rand, Pellett and Young 2003.). With the highest figure of > or equal to 2.2g/kg for those whose aim is to increase muscle density, mass and strength (Tipton and Wolfe, 2001). Yet there are current documents of intakes as high as 4.4g/kg in bodybuilding practises, though this is not recommended in the main (Kim Lee and Choue 2011).
It is recognised that for the average adult (male and female) protein consumption should meet ~20% of total daily kilocalorie intake, increasing to 38-40% of protein for those engaged with regular intense exercise/training (Phillpson 2016). The recommendations stress the importance that the protein quantity is derived from quality protein sources, that provide a high bio-availability and complete amino acid profile.
Whilst increased ingestion of quality protein is beneficial for all populations it is of particular interest to those focusing on increasing muscle mass, strength and power output. An increased requirement for protein during exercise is supported by a wealth of current research, denoting that if optimal protein intakes are not met when partaking in regular exercise an increased excretion of 3-methyl histidine, increased nitrogen urea excretion and down regulation of protein synthesis (MPS) will occur creating a catabolic state (Fluckey and Simmons, 2017). The main causation is due to the increased utilisation of the branch chain amino acids (BCAA) during exercise, yet this can be halted by assuring quality protein intakes are met.
Overwhelming evidence proves that by ensuring the ‘right’ amount of quality protein to create a positive nitrogen balance will provide the perfect environment to illicit muscle growth and repair for those partaking in intense training schedules, demanding exercise and muscle trauma sustained from contact sports (Hayes 2006).
Recognition of higher protein requirements are also required for those reducing bodyfat; be it for competitive, aesthetics or health purposes. When the body is put into a hypocaloric state to breakdown adipose tissue for energy the requirement for protein in increased to prevent an induced catabolic state (Helms 2016). If a catabolic state is present amino acid oxidation will occur that results in muscle breakdown; decreasing muscle mass and metabolic rate (Jahan and Mihan 2017). Protein intake is often over looked when the aim is to reduce body fat, yet optimal intake is essential to ensure a positive nitrogen balance to protect and maintain the lean body mass whilst reducing adiposity (Mihan 2017). Ensuring protein intake and a positive nitrogen balance provides an optimal environment for the ‘Muscle- full’ set point, that initiates muscle protein synthesis (MPS), increases toxin clearance, ensures cell integrity and maximises nutrient uptake for muscle mass (Atherton and Smith, 2012).
Speculation remains to the exact amount of protein the human adult body can uptake in one sitting; the uptake is highly variable due to many factors on both the individual and the protein source ingested. Quantities of 25-50g are credibly documented (Helms 2014), yet by selecting differing sources of protein to control the rate of delivery through ‘drip feeding’ the body over a sustained time period maximal quantity of protein uptake can be achieved. It is acknowledged that various factors can equip the body with the perfect environment to aid maximal uptake of the protein (Guezennec and Krzentowski 2017).
The main factors one derived from literature (both laboratory and observational) included; Protein bio-availability, nitrogen balance, amino acid content, rate of gastric emptying and digestion, protein source, protein quality, optimising gut health through colonisation of microbiota and increasing quantities of digestive enzymes all heavily contribute to full utilisation of dietary macro and micro nutrient uptake.