TRAIN WITH FFS
In Part 1 of his blogs on Protein, nutrition coach Darragh Henry delves into the science of animal and plant-based protein.
Constantly, as we sit, walk, sleep, swim, or do anything, our muscle mass is in constant flux between muscle protein breakdown (MPB) and muscle protein synthesis (MPS), with the former resulting in catabolism or “atrophy” a.k.a muscle loss, and the later in anabolism or “hypertrophy” a.k.a muscle building. MPS is the primary mechanism of the anabolic response in skeletal muscle, which is stimulated by two primary drivers in combination (Moore & Tang et al., 2009);
1) Nutrition, more specifically a positive nitrogen balance through protein ingestion. Protein is the only macronutrient that contains nitrogen, where-as fat and carbohydrates are only composed of carbon, hydrogen and oxygen.
2) Physical exercise, a systematic resistance-based training plan. This places a tensile stimulus on our muscles, causing them to adapt and grow.
Specific training and nutrition principles will determine the magnitude of skeletal muscle hypertrophy. Focusing our attention on nutrition, firstly the dose of protein is the primary nutrition priority to building muscle mass, with acute stimulation of MPS occurring at roughly 0.4g/kg (Morton et al.2015), with practical recommendations by Egan (2016) stating active adults should aim for 20-40g of protein per meal, to insure a positive nitrogen balance is achieved. The same author summarized daily protein requirements in a 1.2-2.0g/kg lean body mass range, with the latter end of the range recommendation for active adults partaking in resistance training.
Secondly, the quality of the protein is another important nutrition factor, more specifically the leucine content, for stimulating MPS (Moore and Robinson et al.,2009). Protein quality is also dependent upon its kinetics, rate of digestion, absorption of amino acids (AA) and retention in the gut of newly synthesized protein (Luiking et al.,2005).
Protein comes from a variety of animal sources (e.g beef, fish, eggs, and dairy) or plant-based sources (e.g pea, hemp, soy, rice) which differ in the amount of leucine. Previously shown by Van Vliet and colleagues in 2015, as well as Gorissen et al. (2018), that plant-based proteins have a reduced anabolic quality due to the following.
Plant-based sources contain typically 6-8% leucine, compared to animal-based products that contain 8-9%, as well as dairy containing >10% (van Vliet et al., 2015). Leucine is one of 3 branched chain amino acids (BCAA), valine and isoleucine being the other two, and is the most potent stimulator of MPS among the BCAA’s, provided >3g has been ingested (Morton et al.,2015; van Vliet et al., 2015). In the post-prandial period following a bout of RT, the MPS response will be correlated with circulating plasma AA levels (Morton et al.,2015)
Due to ethical, religious, & environmental reasons, vegan & vegetarian diets have received recent popularity in western culture. Currently, clinical and consumer market is directed toward the use of plant-based sources of protein, as a means of preserving or increasing muscle mass. For individuals aiming to increase muscle mass, there is divided opinion as to whether they can achieve such goals, solely with the use of plant-based protein sources, or if used in combination with an omnivorous diet. In part 1 of this blog I will delve into the science to compare the acute response of plant-based protein ingestion vs animal-based protein ingestion in a variety of populations both at rest and post-exercise.
Assessing the literature, elderly subjects (N=30 71±5 years) showed a significantly greater (P<0.001) post-exercise MPS rate when whey protein was ingested, at 20g and 40g doses, compared to soy protein of the same doses (Yang et al.,2012). This led the authors to hypothesis that leucine oxidation rates are higher in soy protein both at rest and post exercise compared to whey protein. Similar findings by Moore and colleagues in young (N=18 22.8±3.9 years) men with RT experience, showed greater MPS rates in the post-prandial period following a bout of RT, with significant differences in the first 30 and 60 minutes (P<0.05), when compared to soy and casein protein sources, with the authors concluding that the availability and content of leucine in whey protein to be the key contributor to significantly greater levels of MPS.
Further research from Wilkinson and colleagues (2007) assessed protein kinetics of isonitrogenous/calorie milk vs soy protein in 8 healthy men, combined with RT in a 3-hour post-prandial period. The RT intervention was dispersed by 1 week, of unilateral leg extensions (comparing the resting leg to exercised leg), with either the ingestion of milk or soy protein following each training bout. A significant difference (P<0.05) was observed in muscle fractional synthetic rate (FSR), favouring milk by 34%.Total AA area under the curve over the 3 hours was significantly greater (P<0.05) in the milk intervention and a positive nitrogen distribution in the 180-mins post ingestion (P<0.01), where the soy ingestion had a negative nitrogen balance after 120 mins post ingestion. The authors propose that the difference in net uptake of AAs in the exercised leg was influenced by the digestion rate and therefore, ensuing hyper-aminoacidemia that differed between milk and soy.
If leucine content and overall nitrogen balance is in a deficit, it would make intuitive sense that muscle protein synthesis rates cannot occur for a longer duration during recovery from a bout of RT. Such is the case in Bos et al., 2003, who assessed the protein kinetics in a group of men and women who ingested either milk (N=8) or soy (N=8), with the former group having greater nitrogen retention in the muscle, compared to the latter, in the 8-hour post-prandial period, thus allowing MPS to be elevated. The authors concluded that soy and milk-based protein have different kinetics and could be due to the AA profile of the sources. Similar findings are observed in Luiking and colleagues (2005), that had a similar study design and protein doses (0.42g/kg) but compared casein (N=12) vs soy protein (N=10), measuring splanchnic extraction and urea production rates in the 8-hour post-prandial period, with significantly greater absolute splanchnic extraction of leucine in the casein group compared to soy (P=0.01) and close to significant results in greater urea synthesis rates in the soy protein group (P=0.07). This would allow casein protein to be used as a substrate to stimulate skeletal MPS. It should be noted that consumption and subsequent assessment of protein kinetics was done at rest and not post-RT in both studies.
It appears from the literature that when comparing animal protein sources (whey and casein) to plant-based protein sources (soy) the former is more favourable for the stimulation of MPS in a resting and post exercised state in elderly and young populations.
Next week in part 2 of the blog, I will review the scientific literature to see the differences between animal and plant-based protein on our ability to build muscle over a longer term (8-weeks).