New England Journal of Medicine , 390(8), 701-714
This is for several reasons: Abundant subcutaneous tissue: The abdomen typically has sufficient subcutaneous fat tissue, even in lean individuals
Children presenting neurological signs or symptoms, those unable to take oral medication, individuals with known malabsorption syndromes, infants under 6 months old, and patients using medications that may interfere with vitamin B12 absorption are typically treated with a parenteral protocol (1)
Other nutrients, such as B vitamins, vitamin C, vitamin E, selenium, and omega-3 fatty acids have also been shown to support glutathione levels, so eating foods that are high in these nutrients may also be helpful [14]