Introducing Vitamin B12

Discovered in 1926

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Vitamin B12, also known as cobalamin, works with many other B vitamins to carry out key roles in functions of the human body. Together with folate and vitamin B6, cobalamin helps to maintain normal blood homocysteine levels which is important as raised homocysteine is a risk factor for cardiovascular disease.

In addition, vitamin B12 serves as a co-factor for enzymes involved in the normal function of the nervous system, the formation of red blood cells, and for the metabolism of folate. It is also involved in energy production.

The Primary Sources of Vitamin B12

Vitamin B12 is found only in foods of animal origin. One exception is when plant-based foods are fortified. Rich sources of vitamin B12 include shellfish, liver, and game meat such as venison and rabbit. It can also be found in milk and milk products as well as some fish such as herring, sardines, salmon, and trout.

Bioavailability of Vitamin B12

While there is insufficient data on the absorption of vitamin B12, experts assume that about 50% of vitamin B12 is absorbed by adults with a healthy digestive tract. Inadequate absorption occurs when there is not enough acid in the stomach, or when a protein called intrinsic factor is not produced in the stomach. Conventional cooking methods involving high heat (e.g. microwave) and long cooking times may result in some vitamin B12 losses.

Risks Related to Inadequate or Excess Intake of Vitamin B12

About 10–30% of older adults are estimated to have chronic inflammation of the stomach, a condition that impairs the absorption of vitamin B12. It is advised that older adults consume fortified foods or supplements to meet their vitamin B12 requirements. Vegans (individuals who do not consume animal-source foods), who do not take fortified foods or supplements, will develop vitamin B12 deficiency. However, it can take several years to develop a vitamin B12 deficiency because the body recycles much of its vitamin B12 by reabsorbing it over and over again. Infants born to vegan mothers are also at risk for deficiency if their mother’s vitamin B12 status was low during pregnancy. Vitamin B12 requirements are increased for individuals who are HIV-positive with chronic diarrhea. Symptoms of vitamin B12 deficiency include anemia, general fatigue, loss of appetite, gastric atrophy, neuromuscular pain, neurological problems (gait, memory loss). No adverse effects with excessive intakes of vitamin B12 have been reported.

Find more information on vitamins and micronutrient deficiencies though our partner, Vitamin Angels or download our complete vitamin and mineral guide here

Incorporate vitamin B12 into your next meal with this delicious recipe below. 

Venison Sausage and Chestnut Casserole*


Venison Sausage casserole

2 tbsp sunflower oil 
16 venison sausages
2 medium onions, thinly sliced
3 celery sticks, trimmed and thinly sliced
200g chestnut mushrooms, halved (or quartered if large)
300ml red wine
1 beef stock cube
200g pack vacuum-packed cooked  chestnuts
2 tbsp tomato purée
1 bay leaf
2 tbsp cornflour

For the mustard mash
1½ kg medium  potatoes cut into even chunks
75g butter
150ml tub double cream
2 tbsp wholegrain mustard


Begin by heating 1 tbsp of the oil in a large non-stick frying pan and fry the sausages in two batches over a medium heat for 15 mins, turning regularly, until nicely browned. Transfer the sausages to a large flameproof casserole dish. Next, tip the onions and celery into the frying pan and cook over a medium-high heat for 5 mins or until beginning to soften and lightly colour, stirring regularly. Add a splash more oil if needed. Tip the vegetables into the casserole dish.

Put the remaining oil in the pan, cook the mushrooms over a high heat for 4-5 mins until lightly browned, then add to the casserole. Pour the wine and 300ml water into the dish and crumble the stock cube over the top. Stir in the chestnuts, tomato purée and bay leaf. Bring to a boil, then reduce the heat, cover loosely with a lid and simmer gently for 30 mins, stirring occasionally. 

Meanwhile, make the mustard mash. Put the potatoes in a large pan of water, bring to the boil, then reduce the heat and simmer for 15-20 mins or until the potatoes are soft but not falling apart. Drain well in a colander, then return to the pan and mash with the butter and cream until smooth.Beat in the mustard, season to taste, and set aside.

Mix the cornflour with 2 tbsp cold water until smooth. Stir into the casserole and cook for 2-3 mins, stirring regularly, until the sauce has thickened. Remove the dish from the heat, season and sprinkle with chopped parsley, if using. Serve with the mustard mash.

*This recipe is adapted from BBC food.