A capsule of cosmo skin contains the following (according to cosmo-skin.com):
Alpha lipoic Acid 100mg
Ascorbic Acid 100mg
A capsule of met contains the following (please check on the label to verify):
Alpha Lipoic Acid 100mg
Vitamin C 250mg
Reduced glutathione alone is useless as it is not absorbed by the body. Vitamin C or Ascorbic Acis is needed to better absorb glutathione, it also acts as a precursor of glutathione. So I guess, the more vit c the better. But overdosage is dangerous.
I have also read that it is best to take l-glutathione with empty stomach to optmize absorption. If you're full, there are still other substances that your body has to absorb.
I have never tried using any other two brands or any l-glutathione food supplements so I can't make a judgment based on experienced. I just presented you with some info I researched. Ill use l-glutathione in the near future.
And yeah, mas mura nga yong cosmo. Local siguro yung gumagawa tapos yung met is imported kaya ganun, I guess.