Its a self-regulating system
were used for the induction of colitis
Administration Routes: Choosing the Right Method Vitamin B12 injections can be given in different ways
Nadeem A, Al-Harbi NO, Ahmad SF et al (2018) Glucose-6-phosphate dehydrogenase inhibition attenuates acute lung injury through reduction in NADPH oxidase-derived reactive oxygen species
Vidal-Casariego 2013 meta-analysis: Four RCTs with 284 type 2 diabetes patients showed 23 g/day L-carnitine for 1252 weeks reduced fasting glucose, total cholesterol, LDL cholesterol, and apolipoproteins B100 and A1 but NOT triglycerides, lipoprotein(a), or HbA1c [3][43]
I do think there's a lack of really good solid evidence in humans, but that might only be because it's just not studied enough, and that's usually the case