glutathione growth hormone alters methionine and metabolism in Ames dwarf mice Growth hormone and cognitive function

Factors such as your metabolism, genetic predisposition, lifestyle habits (like diet, exercise, and sleep), and individual response to B12 can all influence the timeline for experiencing improvements

McGowan, Catherine White et al

Vitamin B12 5,000mcg | Methylcobalamin | 2 Pack | 120 Vegan Capsules

Free radicals generate, and Glutathione kicks into high gear to render those free radicals harmless

The less active this enzyme is, the less melanin is produced

Additional factors include excessive alcohol consumption, smoking, stress, gastric hyperacidity, diet, genetics, and radiotherapy (Sostres, Gargallo, and Lanas 2013 )