The Optimum Dietary Protein Source
An ideal protein source to maximise hypertrophy will therefore consist of comparable essential amino acid levels to that of human muscle, with leucine levels near 100% of that found in human body protein, and inclusion of non-essential amino acids to support metabolism and promote homeostasis in the muscles. To compare two common protein sources, whey and soy, soy protein offers the closest match to whole body protein, but has lower levels of leucine. This could go some way to explaining the individual MPS profiles of each protein. MPS following whey consumption was 18% higher than that of soy in one paper and the high leucine content of whey is thought to be the reason   [68-70].
Interestingly, whey has close to whole body protein levels of leucine, but it has low levels of threonine, valine and histidine, all essential amino acids which could be part of the reason why some studies report a faster decline in MPS with whey than with other dietary proteins .
Understanding the biological factors behind maximum muscle protein synthesis allows us to identify the qualities required for an optimum protein source. One product, hydrolysed whole salmon protein, closely matches these parameters and may prove to be the best tool for maximising muscle protein synthesis.
Bearing in mind all we know about MPS, we can identify the qualities of the ideal protein source. It would consist of free amino acids and short-chained polypeptides, making it rapidly digestible allowing free amino acids to reach the bloodstream within the first 30 minutes of the anabolic window, the point at which blood flow to the muscles and maximum amino acid transport is at its maximum. This would allow the rate of MPS to achieve its full potential. Until recently, aside from the intravenous injection of amino acids, this has not been achievable. However, the arrival of enzymatically hydrolysed whole salmon protein to the sports nutrition market may address this problem with its profile suggesting it is capable of achieving rapid absorption – faster than whey, casein or any other whole protein source.
Hydrolysed whole salmon protein is a source of liquid protein derived from the Atlantic salmon that has been pre-digested and hydrolysed into short chain polypeptides. Analysis of the product shows that 20% of the protein present is below 200Da in size indicating that these may be free amino acids ready for direct transport through the intestinal lumen. A further 20% of the protein is below 1,000Da, most likely consisting of short chain amino acids of the approximate size permitted for direct transport across the villi of the jejunum. The remaining peptides are also short, and therefore able to be rapidly digested by the enzymes of the duodenum and jejunum. This is in direct contrast to whey protein isolate which, due to the process of manufacturing, is invariably over 20,000Da in size taking vital minutes to digest. In a direct comparison, over 96% of the hydrolysed salmon protein peptides are shorter than the smallest peptide in whey protein isolate.
|Hydrolysed Salmon Protein – Molecular Weight Distribution|
|(Nofima BioLab 25/02/15)
|Below 10,000 Dalton||87.9%|
|Below 6,000 Dalton||74.5%|
|Below 1,000 Dalton||35.0%|
Figure 1: Low molecular size is vital to bioavailability
It should also be noted that the 100ml volume of this new protein source is less than the maximum volume of the small intestine, meaning that there is no lost time when useful protein remains outside the small intestine in the stomach where it cannot be absorbed. The physiology of the human digestive system means that when athletes consume large volumes of liquid protein, it takes several hours to process in full, meaning much of the protein completely misses the window of anabolic potential.
Because the hydrolysed salmon protein’s amino acids are already bioavailable, athletes can expect to see increases of amino acid in the blood within 30 minutes after exercise, at the point at which blood flow and oxygen levels in the muscle are still elevated. This takes advantage of the optimum conditions for rapid amino acid uptake into the muscle tissue, something not possible through other supplements and previously only achieved via intravenous injection. By delivering amino acid sooner to the MPS window, a greater maximum MPS rate can be achieved. In addition, the salmon has close to human muscle levels of leucine, as well as an amino acid profile highly similar to human muscle. This high leucine content allows it to activate mTOR rapidly, driving the maximum response.
Whey protein is arguably the best commonly available protein for promoting hypertrophy. However, its slower absorption speed compared to hydrolysed salmon protein is just one disadvantage. Whey protein also has low levels of several essential amino acids and therefore it cannot sustain MPS   , a problem shared by branched-chain amino acid supplements. Hydrolysed salmon protein with a human-like essential amino acid profile, plus supporting non-essential amino acids, provides the optimum amino acid formulation to support MPS. This form of dietary protein is the closest match to the desired biological requirements of elite athletes looking to optimise recovery and compete at the highest level.