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Stack CLA and L-arginine: more muscle, less fat

If you combine CLA and L-arginine supplements [structural formula shown below] with each other, it could be a quicker way of building up muscle. We're treading carefully here because the research we refer to, which was performed at Texas A&M University, was done on rats, not people. But we wanted to share it with you nevertheless.

Let's refresh our memory: CLA, or conjugated linoleic acid, is a mix of two unsaturated fatty acids found in animal products. CLA increases fat burning in muscles. Cell studies have also shown that CLA blocks the 'fat sensor' PPAR-gamma. The slimming and muscle-building effect of CLA has been confirmed in long-running human trials. But although the effects are statistically significant, they are clinically not so convincing. Taking supplements for a year only makes a couple of kilograms difference.

L-Arginine is an amino acid that plays a key role in fat burning processes. When taken as a supplement the muscle cells become more sensitive to anabolic stimuli. The androgen receptor for example works better if sufficient amounts of the arginine metabolite NO are present in the muscle cells.

In the study that will soon be published in the Journal of Nutrition the researchers set out to find out whether the slimming effects of CLA and L-arginine reinforce each other. They gave rats a diet enriched with 1.25 percent L-arginine or another non-active amino acid for five weeks. Both groups of rats were divided again into sub-groups. One got feed containing 1.5 percent CLA and the other group got feed containing non-active fat from canola oil. So altogether there were four sub-groups.

The table below shows the changes in the test animals after five weeks.

Stack CLA and L-arginine: more muscle, less fat

The slimming effects of CLA and L-arginine complemented each other but did not strengthen each other. In other words, on the fat level there was no synergy between the two substances. In that respect the trial was disappointing.

But the researchers did notice that the rats' muscle mass increased considerably. You don't see this if you look at the effect on the calf muscles in the table, but you do if you look at the effect on the weight of the carcass. The latter increased in the group that was given both CLA and L-arginine, although the fat mass decreased at the same time. "We conclude that arginine plus CLA increased axial muscle mass", the researchers write.

The glutamine [structure left] production decreased in the rats' muscle tissue. According to the researchers, this is an indication of the mechanism through which the CLA-L-arginine cocktail leads to muscle growth: the combination of CLA and L-arginine helps muscles to use amino acids more sparingly. In experiments L-arginine activates the anabolic key molecule mTOR in muscle cells. CLA does the same in fat cells. Maybe, the researchers reason, the two substances together reinforce each other's effect on mTOR. So it could be that on the muscular level CLA and L-arginine work synergistically after all.

J Nutr. 2009 May 13. [Epub ahead of print].

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