Fishing for Muscle: Cod Protein Promotes Muscle Repair After Injury More than Casein or Peanut Protein

Image 1: There are obviously more nutritionally valuable parts to cod than just its liver.

On Wednesday, you have learned that diet-deoptimization with rice instead of casein protein is a possible way to gain less weight. Today, we are going to tackle what appears to be a way more promising alternative to the dairy-based top-dogs among the protein supplements: Cod protein! Within the health and fitness community, the cold(er) water fish is hitherto, above all, known for its vitamin-laden liver and the oil humans have been producing from it and consuming for centuries, now. That the arginine-, glycine- and taurine-rich protein of its tasty white flesh could soon replace - or at least complement - dairy proteins (casein, whey) as the physical culturists' go-to protein for muscle building and regeneration will yet probably be news to most of you, right?

COD - Canned or dried? Probably doesn't matter as long as you eat it.

In a recently published paper on yet another rodent protein feeding trial (Dort. 2012), Junio Dort and his colleagues from the Laval University and the Research Center of CHUQ, CHUL in Quebec, Canada, report that the artificially injured tibialis muscle of rodents that were kept on cod-protein based diets for 21-days healed significantly faster than the skeletal muscle of the peanut or casein protein control groups.

Figure 1: Amino acid profile of casein, peanut and cod protein source on which the otherwise identical rodent diets were based (based on Dort. 2012)

For the smart SuppVersity student you are, it should not take more than just a brief glance at the amino acid profiles of the three protein sources to identify cod protein and casein as superior and peanut (as it was to be expected) inferior protein source. With -24% and -30% less branched-chain (BCAA) and total essential amino acids (EAA), peanut protein would certainly not be the first choice of any non-vegan physical culturist, let alone bodybuilder, who is interested in opti- and not deoptimizing his his/her diet (on an unrelated not: Don't you Americans never refer to the ladies, first? I always read "his/her" - that would not exactly be gentleman-like here, in Germany!).

118 neutrophils and still counting: Cod protein (not oil, in this case) tames the inflammation

In order to assess how peanut, casein and cod-based diets would modulate the rodents' response to muscular injury the animals were treated with bupivacaine, a substance that is myotoxic ("kills" muscle cells, but - and this is a specialty of bupicacaine - not satellite cells) at higher doses (here 100µL). The drug was injected into one of the animals' tibialis muscles, while the contra-lateral side was sham-injected (saline injection) to serve as a control. At days 3, 14, and 24 post-injury, both the injured and sham-injected tibialis muscles were "collected" (8 animals per dietary group) and the neutrophil count, and macrophage infiltration - both measures of ongoing inflammation and thusly incomplete healing subsequent to prior muscle damage - were assessed.

Figure 2: Neutrophil count and EDI+ macrophage count in bupivacaine injected tibialis muscle 3 and 14 days and 14 and 24 days after the injection; data expressed relative to sham control (data calculated based on Dort. 2012)

As the data in figure 2 goes to show, the cod protein group showed a markedly faster reduction in neutrophil and EDI+ macrophage count than the casein group, which - in a separate experiment - had already been found to sustain the healing process better than the nutritionally inferior peanut proteins, which also exhibited a -19% lower feeding efficacy (meaning that similar to the rice protein in Wednesday's newspost, it lead reduced weight gain; again, not necessarily desirable, specifically in injured rats) and, "in results previously published, [...] lower skeletal muscle mass than those fed casein [even] before injury" (Dort. 2012).

The anti-inflammatory effects of cod protein reach beyond skeletal muscle

Though muscle is, as my friend Carl Lanore likes to say, "metabolic currency" and it's protection and repair should be on everyone's, man and women top list of health priorities, the benefits of cod protein extend beyond skeletal muscle. A brief review of the literature revealed among others ...

• increases in HDL, decreasse in VLDL with cod over casein and soy (Jacques. 1995)
• restoration of GLUT-4 activity in skeletal muscle of HFD obese rodents (Trembley. 2003)
• lower hepatic triglyceride production vs. beef or casein (Demonti. 2003)
• lowest insulin / glucose ratio (vs. soy or casein), when given as part of complex test meal (Post-Skagegard. 2006)
• improvements in insulin sensitivity and reductions in C-reactive protein vs. diet containing beef, pork, veil, eggs and dairy in insulin resistant men and women (Ouellet. 2007; Ouellet. 2008)

Just as the improved healing of the muscoskeletal injury in the rodent study at hand, most of the aforementioned effects are probably attributable to the modulatory the homemade cod protein (the scientists simply used frozen cod fillets to prepare their protein powder) exerts on the immune system. In this context, it is particularly important to mention that

[...] an impairment of insulin-stimulated glucose uptake and a reduction of protein synthesis, combined with an increase of muscle protein degradation, are the main adverse metabolic changes induced by injuries in skeletal muscle.

In previous studies, the researchers were also able to show that the profound impairment of the AKT /PKB pathway, which is one of the key mechanisms behind the nutrient induced increase of protein synthesis, is protected from the impairments of "high fat diets" (the researcher variety, which is more akin to the standard American than to "low carb" diet), if the latter contains cod, instead of soy- or casein-protein (Tremblay. 2003).

Arginine for repair, EAA for growth: It may be of interest that Dort et al. attribute the muscle building and muscle repairing effects of cod protein to different amino acid in the cod protein. While they believe that its high arginine content suffices as NO precursor to drive and accelerate the repair process, they hold the high essential amino acid (EAA) content responsible for its pro-anabolic effects which are comparable to those of casein (and probably even whey) proteins.

Image 2: Fish is not for you? Maybe you just don't know how to prepare it properly? It's not really difficult to grill a fillet, trust me - even I can do that.

It stands to reason, that both the restoration and / or maintenance of skeletal muscle mass and insulin sensitivity, as well as the general anti-inflammatory properties of cod protein (remember: the protein in the study was derived directly from frozen fillets and contained almost no fat!) come handy for everyone who wants to live a healthy and active live into the old age. In this regard the study result do not only underline the importance and multifaceted benefits of regular fish consumption (fatty or not) as part of a healthy diet, they also support my repeatedly proffered believe that the latter should not be defined by macronutrient ratios, let alone calories, but must be build around concrete meal and food suggestions, as well as general and flexible recommendations regarding the frequency and combinations in which these can be consumed.