The relevance here is evidential, not procedural: because delivery and stability vary so much, comparing results across products and studies is genuinely difficult, and that heterogeneity is one reason a clean answer to the title question has been so slow to emerge
Int J Mol Sci 2021
Sulfation helps eliminate hormones, neurotransmitters, and environmental toxins
Glutathione is a strong antioxidant with additional anti-melanogenic properties, making this the most popular systemic skin lightening molecule
Galactomyces Ferment Filtrate, Glycerin, 1,2-Hexanediol, Niacinamide, Water, Methylpropanediol, 2,3-Butanediol, Diphenyl Dimethicone, Bis-PEG-18 Methyl Ether Dimethyl Silane, Triethylhexanoin, C12-14 Alketh-12, Hydroxyacetophenone, Hydrogenated Lecithin, Polyglyceryl-10 Oleate, Sodium Citrate, Ethylhexylglycerin, Butylene Glycol, Citric Acid, Adenosine, Disodium EDTA, Oryza Sativa (Rice) Bran Extract, Caprylyl Glycol, Glutathione, 3-O-Ethyl Ascorbic Acid, Tocopherol, Portulaca Oleracea Extract, Betaine, Hydrolyzed Hyaluronic Acid, Ulmus Davidiana Root Extract, Amaranthus Caudatus Seed Extract, Oryza Sativa (Rice) Bran Oil, Propanediol, Ceramide NP, Phytosphingosine, Saccharomyces/Rice Ferment Filtrate, Acetyl Hexapeptide-1