Bodybuilding for Pekin Ducks: L-Arginine Supplementation Gets Poultry Stage Ready. More Muscle, Less Fat.

Image 1: Not your usual exercise and
nutrition science magazine:
The Journal of British Poultry Science
(Taylor Francis Group. 2011)

Those of you who have followed the Amino Acids for Super Human Series on Carl Lenore's Super Human Radio will be familiar with the manifold benefits supplementation with the conditionally essential amino acid l-arginine has on blood pressure, glucose metabolism, endothelial health, etc. If you also listened to the last installment of the series (Amino Acids for Super Humans III: The Sulfur Amino Acids), you will know about my special affiliation with chicken, with chicken. Taken together, this may in parts explain, why today's SuppVersity newsitem is about a study from the Chinese Hubei Key Laboratory of Animal Nutrition and Feed Science in Wuhan (Wu. 2011).

In their study that has been published in the latest issue of the "famous" Journal of British Poultry Science (52;2) Wu et al. report the effects of the addition of 10g/kg l-arginine to the standard-feed of 80 twenty-one-day-old male and female White Pekin ducks over a feeding period of 3 weeks:

[...] the addition of L-Arg had no significant effect on feed intake, but significantly increased body weight gain by 5·2 %, breast muscle weight relative to live body weight by 9·9%, carcase crude protein content by 9·2%, ether extract content in breast muscle by 11·9%. Arg supplementation significantly decreased skin with fat and abdominal fat pad contents by 7·6% and 4·9% respectively and the ether extract content of carcase by 7·2%.

For the poultry farmer, this statistically significant increase in lean mass and a decrease in fat mass compared to the 80 ducks on standard feed means more bang for just a little more bucks. For the average gymrat it would mean building muscle without getting fat via supplemtal l-arginine, if the results from adolescent poultry would translate 1:1 to adult human beings. That this may not be as far fetched, as the biological differences between ducks and men may suggest, is highlighted by a 2009 study of Tan et al. (Tan. 2009) who observerd similar effects in swine, i.e. omnivores, which - believe it or not - are a very good model of human metabolism.

Figure 1: Weight of breast muscle, leg muscle, skin and abdominal fat relative to total body weight
(data adapted from Wu. 2011).

In 2006, already Jobgen et al. had suspected that the underlying mechanism of the repartitioning effect of l-arginine may be related to its modulation of the metabolism of energy substrates (fat, carbs, protein). The decreased adipocyte sizes observed in both studies, suggest an overall decrease in triglyceride deposition (not a reduction in adipocyte differentiation, which would result in a lower number of adipocytes) to be the "mechanistic" reason for the "anti-obesity effects" of l-arginine. Wu et al. speculate that this may be related to a decrease in NADPH activity and, consequently, reduced fatty acid synthase (FAS) in the liver of the ducks. With the latter being the major site of for lipogenesis in avian species, specifically, this still leaves the previously raised question, whether, or not, these results may be transfered to human beings, open. This is especially true in view of the fact that, for most of you, supplementation would be initiated years after adolescence (remember the Pekin ducks and the pigs in the Tan study were still growing). 

Image 2: Reduced skin fat is something,
the arginine fed ducks and IFBB Pro
Dexter Jackson certainly have in common ;-)
(photo by: LocalFitness.com.au)

With appropriate training, one may however argue that you are in a "state of growth", as well... so, after all this could turn out to be another good reason to give the purported nitric oxide booster a(-nother?) try. But how much would you have to take? Well, it would be wise to take the swine from the Tan study (Tan. 2009) as a reference, because pigs are certainly more "human", i.e. a better model of human metabolism, than Pekin ducks. Tan et al. fed their pigs an additional 1% of arginine to their basal diet, which - considering body weight, food intake and nutrient composition of the diet - would translate to roughly 0.6g/kg body weight in swine. Taking into account the respective conversion factor of K_m = 10.31 (data adopted from calculations in Wollison. 1999), this would translate into a human equivalent dose of roughly 0.17g/kg or 13.4g for an 80kg human being [notice: there will be a short article on how to calculate this dosages available in the course of the weekend, so stay tuned]. This is not only way more than what was used in many of the studies that report no effects of arginine supplementation in athletic populations (e.g. Greer. 2011), it is also an issue of permanent vs. singular supplementation, with the latter being the (cost-efficient) method of choice in most published studies. So if you did not notice your small dose of arginine taken on workout days, only, it could be worth trying to take larger amounts on a daily basis.