In recent years I've tried a few different supplements & found pretty well all the claims to be bull. But I've just started taking a protein mix daily (a generic style powder from the supermarket with negligible fat & no carbo or sugar content) and feel this might actually be worthwhile. The mix has 16% glutamic acid as a component. I can definitely feel a benefit in reduced muscle fatigue & better recovery. What I'm not sure about is why - I've done nothing else differently & am not combining the protein mix with anything else. I've attempted to research the benefits but, as always, have found some fairly contrasting studies/claims and I haven't been able to clearly establish the relationship/comparison between the 'Glutamic acid' in this protein mix & pure L-Glutamine supplements. I'm thinking that the protein mix is, apart from the minor fluid gain it apparently generates, a completely safe and good thing but would additional L-Glutamine supplementation have benefits for my weary 50 y/o legs ? I try to do about 250-300km a week including raceday & sometimes lately have struggled with recovery. If I continue with the protein would L-Glutamine supplementation require a different protein mix without the 'Glutamic acid' component ? Any positive or negative experiences out there ? Any alternative suggestions ? Thanks... I'm always very wary of anything you put in your mouth !