Vitamin B12 deficiency can be cause by a number of things but its most commonly the result of a digestive system that cannot adequately absorb the vitamin from regular foods. For a normally functioning human, vitamin b12 is hard to break down and absorb via the intestines, which is why so many healthy adults (with good diets) still have low levels of vitamin b12. Some people have conditions that make the absorbtion of vitamin b12 especially difficult which results in more serious deficiencies that can have long-lasting effects.
This can be caused by:
- Pernicious anemia which is a condition in where there is a lack of a protein called Intrinsic Factor which is made in the stomach and necessary for vitamin b12 absorption.
- Atrophic gastritis which is a thinning of the stomach lining (affecting up to 30% of people aged 50 and older) that makes absorption of b12 more difficult.
- Conditions such as Crohns disease, celiac disease, bacterial growth, or a parasite in which the small intestine (where most of b12 is absorbed) is impacted.
- Excessive alcohol consumption.
- Autoimmune disorders, such as Graves disease
Because some of the best sources of b12 are animal products, vitamin B12 deficiency is not uncommon in vegetarians and vegans, especially, are at the greatest risk.