Vitamin B12 Foods: Animal and Plant-Based Sources of Vitamin B12 Self-production in the body Vitamin B12 is not produced in plants but in bacteria (microorganisms), which can be found in the earth as well as in the gut of humans and other animals
Also, sadly enough, there also are many types of (chronic) diseases that require B12 injections, such as Pernicious Anemia, people with Crohns, celiac, and people with intestinal imbalances, such as intestinal tapeworms and excessive bacterial growth
Journal of the American Geriatrics Society
Higher Dosages : In some treatment protocols, larger doses of B12 may be required, ranging from 1 ml to 3 ml
For an effect size of .25 SD, we would need to analyse 676 infants to achieve a statistical power of 90% (p values of 0.05)