Reduced glutathione supplements such as NOW Foods' Glutathione have only become available recently, and are legitimate liver-support substances such as milk thistle extracts to help your skin, n-acetyl-cysteine and al lipoic acid. Taking glutathione precursors like cysteine has been shown to do that; if any glutathione is broken down during digestion, it will be broken down into glutathione precursors, which can then be used to make more glutathione.