If you live a vegetarian or vegan lifestyle, chances are you do not get enough Vitamin B12 from your foods…a few questions you may have are why not, and which food sources can I get this essential vitamin from?
Vitamin B12 helps to make DNA, nerve and blood cells, and is important for the neurological (brain), and immune system (1, 2) functions. Vitamin B12 is only found in animal products such as eggs, meat, shellfish and dairy. It is a water soluble vitamin containing the mineral cobalt (2), and exists in several different forms. It is bound to protein in food, and is released by the activity of stomach acid and gastric protease (1). The free form of vitamin B12 combines with intrinsic factor (a glycoprotein secreted by the stomach's parietal cells) and then this complex is absorbed in the distal ileum.
Vitamin B12 deficiency can occur if the diet is inadequate, or if the body does not absorb enough through the digestive tract. Common causes for vitamin B12 deficiency include impaired gastric absorption (i.e. people with pernicious anemia or gastrectomy/bariatric patients), impaired intestinal absorption (i.e. ileal resection, Crohn’s, or parasites), pancreatic insufficiency, decreased intake (i.e. malnutrition,reduced intake of animal products, strict vegan diet), congenital/ inherited disorders, increased requirements (i.e. HIV), and certain drugs which impair absorption (i.e. alcohol, nitrous oxide, proton pump inhibitors, Metformin)(1,3).
Symptoms of vitamin B12 deficiency may include: anemia, loss of peripheral nerve function (peripheral neuropathy), vision disturbance, memory loss, psychiatric abnormalities, temporary infertility (women), increased heart rate, high homocysteine levels, and exhaustion (1, 2, 4). Some people are unaware that they have a deficiency until a blood test is conducted to prove this.
After a confirmed diagnosis of vitamin B12 deficiency, the current UK clinical practice is to offer treatment with intramuscular injections of1000 micrograms on alternate days for 2 weeks (for people without neurological impairment). Oral treatment may also be considered in certain situations or some new nasal preparations. The Institute of Medicine has not established an upper limit of vitamin B12 due to its low risk of toxicity, and no adverse effects have been associated with excess vitamin B12 from food or supplements(1).
Recommended intakes of Vitamin B12 are 2.4 micrograms daily forhealthy adults (2.6 micrograms for pregnancy and 2.8 micrograms during lactation) (1). The American Dietetic Association recommends daily vitamin B12 supplementation and consumption of vitamin B12 fortified foods for vegans and lacto-ovo-vegetarians. This is especially so during both pregnancy and lactation to ensure adequate vitamin B12 istransferred to the foetus and infant (5). The synthetic supplements are derived from bacteria not animals, and are therefore ethically reasonable to consume. The bacteria Propionibacterium shermanii and Pseudomonas denitrificans are the ones commonly used. Yeasts and fermented products also contain bacteria and contribute small amounts of vitamin B12.
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