Additionally, some companies inflate their amino acid counts by adding low-grade amino acids like taurine and glycine, which are not effective in stimulating muscle protein synthesis.

Source: https://www.kuwaittimes.com/safety-of-gym-supplements/

Glutathione is basically an antioxidant and is made up of three amino acids, namely cysteine, glycine and glutamate.

Source: https://indianexpress.com/article/health-wellness/made-in-heaven-season-2-glutathione-skin-whitening-treatment-8892166/

Studies suggest that collagen proteins can be a good source of glycine However, homemade bone broth is not a reliable source of collagen or amino acids.

Source: https://www.healthcanal.com/nutrition/diet/carnivore-diet-meal-plan