“Vitamin B12 is combined with a protein called intrinsic factor in your stomach. This mix of vitamin B12 and intrinsic factor is then absorbed into the body in part of the gut called the distal ileum.
“Pernicious anaemia causes your immune system to attack the cells in your stomach that produce the intrinsic factor, which means your body is unable to absorb vitamin B12.”
Some people may develop vitamin B12 deficiency as a result of not getting enough B12 from their diet.
The health body continues: “A diet that includes meat, fish and dairy products usually provides enough vitamin B12, but people who do not regularly eat these foods, such as those following a vegan diet or who have a generally very poor diet, can become deficient.”