Vitamin B12 is a water soluble vitamin involved in the metabolism of every cell in the body, but particularly in the development and normal function of the brain and central nervous system, and in the production of red blood cells. Vitamin B12 is found naturally in foods on animal origin, such as fish, meat, poultry, eggs and dairy. It is also added to certain breads and breakfast cereals that are usually called ‘fortified’. Vitamin B12 is normally absorbed in the intestine after binding with a protein produced in the stomach called ‘intrinsic factor’. Vitamin B12 deficiency is more common in people who follow a plant based or vegetarian diet, in people who do not produce intrinsic factor, or those where the intrinsic factor is not able to mix with the food such as after bariatric surgery. Acid suppression medications and metformin also reduce vitamin B12 absorption and so increase the risk of deficiency.
People with vitamin B12 deficiency may develop anaemia, tingling in the hands and feet, inflammation of the tongue, fatigue, palpitations and pale skin. Vitamin B12 deficiency during pregnancy can cause serious developmental problems in children. Although we regularly measure B12 levels after bariatric surgery by blood tests, these do a poor job of estimating low total body B12 levels, or identifying deficiency. We therefore have a low threshold to supplement additional vitamin B12.
Although most bariatric specific multivitamins contain additional vitamin B12, because absorption is reduced after bariatric surgery, vitamin B12 deficiency can still occur. Vitamin B12 deficiency is more common in people who have had a gastric bypass than people who have had a sleeve gastrectomy. When we detect low B12 levels these can be treated either by vitamin B12 injections in to the muscle (similar to a vaccination, different from insulin or clexane) or high dose oral capsules. Injections are usually started monthly for 3 months and then will need to be continued every three months for life. These can usually be given by your GP’s practice nurse. Oral capsules need to be of at least 1000mcg strength, and while these can be purchased from pharmacies most of the vitamin B12 capsules are of much lower strength so it is important to check this. Oral vitamin B12 is not subsidised on prescription. Evidence comparing these different routes of supplementation show them to be equally effective so people can choose whichever they find most convenient.