Since graduating from Brunel University with a masters degree in sports science, Omar Labarta has gone on to work as a personal trainer in strength and conditioning for different fitness companies and high performance centres. He has since embarked on his journey as a self-employed personal trainer launching his own brand OLab Performance. Today, the Spanish-born fitness advocate with 14 years experience in the field teaches classes across London, using a combination of strength conditioning, muay thai and nutrition to improve the health of his clients. Erbology is lucky enough to offer an exclusive article, written by Omar, exploring the role dietary protein has on the health of skeletal muscle mass.
First off, what is skeletal muscle mass?
Skeletal muscle mass (SMM) is an integral body tissue which together with the nervous system and bones is responsible for body movements. Beside its locomotor role, skeletal muscle is the largest site of postprandial glucose disposal, a site for lipid oxidation and an important contributor of basal metabolic rate. Therefore, preservation of SMM is essential in the maintenance of metabolic and locomotive health.
SMM is dictated by the difference between muscle protein synthesis (MPS) and muscle protein breakdown (MPB). In plane words, if MPS equals MPB muscle mass will be maintained, if there is a positive net balance (MPS>MPB) then muscle mass will increase (Hypertrophy) and on the other hand if this net balance is negative (MPS< MPB) muscle mass will be lost (atrophy). Two important factors affecting this balance are amino acid provision from dietary protein intake and resistance training.
What role does protein play?
Protein provides the structural premise to all tissues and organs. During normal daily activity, and especially during exercise, proteins are broken down and in order to repair muscle structure and function you have to feed your body with protein. Furthermore, protein ingestion plays an important role in maintenance of immune function, especially in athletes and physically active individuals (1). Beside the importance of maintaining muscle mass from a health point of view, there is a great interest from recreationally active individuals and athletes in how protein ingestion combined with resistance training augments muscle mass (AKA hypertrophy).
How much protein do we need?
It is clear how essential the dietary protein is in order to maintain a healthy skeletal muscle mass. But how much protein do we need? Does everyone need the same amount? And when’s best to get it? The answer is not easy. What is clear is that recommending a total daily amount of protein is not enough to maintain a healthy SMM system as many variables should be taken in consideration such as age, body mass, exercise modality and inter-individual variability. Furthermore, protein source (quality), dose (quantity) and timing of the ingestion all affect muscle protein synthesis and therefore, they are all important in maintaining or increasing muscle mass. Although more research is needed, below is a brief summary of what the published literature says:
"Protein provides the structural premise to all tissues and organs."
Despite the recommended dietary allowance for protein (RDA) being ~0.8gr/kg of body mass per day (2) for normal adults, literature is rich in studies suggesting that this amount may be inadequate for a) maintaining and increasing muscle mass in individuals in a resistance training programme; b) maintaining muscle health in older adults and in individuals in energy restriction diets (3).
A recent study on this regard (4) showed that 0.24 gr/kg per body mass of protein maximally stimulates MPS in young adults whereas older adults needed 68% more to equal that results (~0.40 gr/kg per body mass protein). A recent review (3) suggests that when muscle mass gain is the goal after resistance training, daily protein intake should range between 1.6 to 2.2 gr/kg/body weight (110-160gr/day for a 70kg adult, ~20gr per meal). This can be achieved by adding a good source of protein to each meal or incorporating high quality protein supplement (i.e. whey). For those individuals involved in a serious resistance training programme the optimal dose will be higher than in less-active individuals and certainly more than a sedentary population. The recommended daily protein intake depends on body mass and therefore heavier athletes need a greater dosage per meal than their lighter counterparts.
In a calorie-restricted diet, the protein intake dose requirements appear to be even higher ~2.3–3.1 g/kg per day, which triples the recommended guidelines (0.8gr/kg), in order to preserve lean body mass, with the leaner individuals with experience in resistance training falling in the higher part of the spectrum. On the other hand, less exercise-advanced subjects should be aiming the lower part of this range (3).
When should you take protein?
A particular study on this regard (5) suggest that protein meals would be, ideally, spread during the day, separated by ~3–5 h to maximize muscle protein synthesis. Timing the protein intake close to exercise is recommended, although not critical, for stimulating a maximal response of MPS.
Furthermore, different studies have shown that the ingestion of casein protein before bed time (~1-3h) increases muscle anabolism (6,7). However, the dose must be higher (~0.5-0.6 g/kg per meal or 30/40gr) in order to stimulate MPS and attenuate the net negative balance produced during the sleep time.
Protein type and quality
It appears that high quality protein such as “Whey” (known for fast digestibility and high content of essential, branched chain and leucine amino acid) stimulates greater rates of protein synthesis than other types of protein (8). Lower quality protein (soya or wheat protein) appears to fail in promoting protein synthesis at the same level as higher quality protein does (9). The key amino acid contributing to MPS is leucine with a recommended dose of ~ 2-3gr. Furthermore, the ingestion of leucine can compensate low quality and quantity of protein sources in promotes MPS (10). Therefore, manipulating the ingestion of this amino acid can be useful for people who struggle to reach the above recommended doses, which is often the case of older adults. Moreover, in calorie deficit diets the protein quality selection should be as high as possible in order to increase its appetite suppression characteristics.
I’ve outlined below a few practical recommendations, taken from the excellent recent reviews by well renowned scientists in the area (3):
– Individuals involved in serious resistance training programmes should have a daily protein intake of ~1.6g/kg per day and up to 2.2g/kg per day
– ~0.3g/kg body weight/per meal (~20g/kg per meal for a 70kg person)
– Young men and likely women with exercise experience should intake ~0.4g/kg body weight after a period of resistance training or rest period.
– Protein meals should be separated by ~3–5 h to maximize MPS (ie. ~0.3/0.4g/kg of body mass of protein in 4 to 5 meals spread during the day)
– Consume of high quality protein with high Leucine content
– In lower quality protein manipulating leucine content can compensate that lack of quality/quantity. This can be useful for populations that struggle to reach the above recommended doses like older adults
– Before bed: increase protein ingestion to ~0.5-0.6 g/kg per meal; casein appears to be a good option
– Individuals in calorie restriction : ~2.3–3.1 g/kg per day of high quality protein.
– Resistance training with high protein intake should be a must in energy restriction individuals seeking to maintain lean mass
Despite the great number of studies focusing on the role of protein in skeletal muscle mass health, more research must be done in order to better understand how protein and its different sources (ie. plant-based) affect different type of populations, especially in females due to the lack of studies with women.
1. Gleeson. Exercise, nutrition and immune function. 2004.
3. Stokes et. al., (2018), Recent Perspectives Regarding the Role of Dietary Protein for the Promotion of Muscle Hypertrophy with Resistance Exercise Training. Nutrients.
4. Moore et al. (2015), Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men. J. Gerontol. A Biol. Sci. Med. Sci.
5. Areta, et. al. (2013), Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. J. Physiol.
6. Groen, et.al. (2012), Intragastric protein administration stimulates overnight muscle protein synthesis in elderly men. Am. J. Physiol. Endocrinol. Metab.
7. Res et. al. (2012), Protein ingestion before sleep improves postexercise overnight recovery. Med. Sci. Sports Exerc.
8. Devries et.al. (2015), Supplemental protein in support of muscle mass and health: Advantage whey.J. Food Sci.
9. Gorissen, et. al. (2016), Ingestion of wheat protein increases in vivo muscle protein synthesis rates in healthy older men in a randomized trial. J. Nutr.
10. Churchward-Venne, et al. (2014), Leucine supplementation of a low-protein mixed macronutrient beverage enhances myofibrillar protein synthesis in young men: A double-blind, randomized trial. Am. J. Clin. Nutr.