<h2>Practice points</h2><ul><li>Those at greatest risk of B12 deficiency include vegetarians and vegans, the elderly, those with malabsorption syndromes, breastfed babies of vegan mothers and alcoholics</li><li>Medications that reduce gastric acidity increase the risk of deficiency due to reduced B12 absorption in the stomach</li><li>Folic acid supplementation may mask an underlying B12 deficiency, leading to the progression of neurological symptoms. Check folic acid status</li><li>Some people are unable to easily absorb B12 from the intestine and may require intramuscular injections, although evidence suggests that oral forms may be as effective</li><li>Serum B12 levels are not an accurate guide to B12 status. Elevated serum or plasma homocysteine in conjunction with methylmalonic acid (MMA) testing is considered to be a more accurate measure</li></ul><h2>Key functions &amp; indications</h2>DNA synthesis: In conjunction with folate.Red blood cell production: In bone marrow.Nervous system function: Synthesis of protein structures in myelin sheath and nerve cells plus normal neurological function.Cognitive health: There is an association between low B12 and folate levels, elevated homocysteine and dementia.Pregnancy: B12 is required to cleave folate, without which folate is not effective. There may be an increased risk of neural tube defects with B12 deficiency.Homocysteine metabolism: B12 in conjunction with B6 and folic acid reduces elevated homocysteine levels. Elevated homocysteine levels in the blood have been associated with increased risk of cardiovascular disease. Methylcobalamin is required for conversion of homocysteine to methionine which is then converted to S-adenosylmethionine (SAMe). SAMe is important for methylation reactions and protein synthesis. <h2>Risk factors for deficiency/insufficiency</h2>Vitamin B12 absorption is complex and requires optimum gastric function. There are a number of population groups at risk:<ul><li>Vegans and vegetarians (plus babies breastfed from vegan mothers)</li><li>Patients taking medications such as proton pump inhibitors and metformin which can reduce B12 absorption</li><li>Elderly: 10-15% of people over the age of 60 are B12 deficient</li><li>Patients with pernicious anaemia</li><li>Atrophic gastritis (inflammation of the stomach lining): affects 10-30% of elderly who appear to have higher rates of B12 deficiency which responds to B12 supplementation</li><li>Patients with malabsorptive conditions such as Crohn’s disease or coeliac disease</li><li>Patients with gastric atrophy, achlorhydria or those who have had gastric or intestinal resection </li><li>Patients with conditions of parasitic or bacterial overgrowth such as SIBO (Small Intestinal Bowel Overgrowth)

</li></ul><img src="https://images.contentstack.io/v3/assets/blt948bd74310fc0ad0/blt7b62468db2b0bfcb/69f29a70700ea20a8f58bb40/vit_b12_wheel.jpg" alt="vit_b12_wheel.jpg" class="embedded-asset" /><h2>Sources</h2>Plants do not contain B12 but microorganisms including bacteria and algae can make it. Sources include meat, fish, eggs, sardines and liver.Red meat: 100 g of beef contains 5 μg of B12Fish: 100 g of bream contains 2.2 μg of B12Eggs (hard-boiled): 100 g contains 3.7 μg of B12Yeast spreads: 100 g contains 10 μg of B12Canned tuna in water: 85 mg contains 2.5 μg of B12Beef liver, cooked: 85 g contains 71 μg of B12<a href="http://www.foodstandards.gov.au/science/monitoringnutrients/afcd/Pages/default.aspx" target="_blank">Search for nutrient content of foods here</a><h2>B12, B6 and folic acid are commonly combined for homocysteine metabolism</h2>

<h2>Contraindications/cautions</h2><ul><li>B12 supplements are well tolerated</li></ul>

Cautions

<h2>Possible interactions</h2><ul><li>Proton pump inhibitors: concern that resulting reduction in stomach acid may reduce B12 absorption. Observe with long term PPI use</li><li>Metformin: clinical evidence suggests reduced absorption in up to 30% of medication users</li></ul>For more information visit: <a href="~/link.aspx?_id=4471DACF65C148EA8FD82B23FD6712D4&_z=z">https://www.blackmoresinstitute.org/interactions</a>

Interactions

<h2>Dosage range</h2><ul><li>Adults (13 + years): 2.4 μg/day</li><li>Pregnancy/lactation: 2.4-2.8 μg/day</li><li>Requirements may be higher for elderly with impaired absorption or digestion</li><li>Sublingual cyanocobalamin: 1000-2000 μg/day taken 30 mins before breakfast</li><li>Pernicious anaemia: Vitamin B12 1000 μg intramuscularly 2-4 times weekly until haematological abnormalities are corrected, then once monthly</li><li>Hyperhomocysteinaemia: 500 μg/day (in combination with B12 and folic acid)</li></ul>Nutrient Reference Values: <a href="https://www.nrv.gov.au/nutrients/vitamin-b12" target="_blank">https://www.nrv.gov.au/nutrients/vitamin-b12</a>

Dosage

<h2>Supplements</h2><ul><li>Found in multivitamins and B complex formulae as cyanocobalamin or methylcobalamin</li><li>Stand-alone supplements are available in strengths from 50 to 2,000 μg</li><li>Sublingual and ‘melt’ forms of vitamin B12 are also available</li><li> A coenzymatically active form, methylcobalamin, may be more readily utilised in the body</li><li>Certain populations are unable to easily absorb B12 from the intestine and may require intramuscular injections, although evidence suggests that oral forms may be as effective</li></ul><h2>Are oral forms of B12 supplementation effective?</h2>There is now considerable evidence that oral B12 supplements are comparable to parenteral therapy for improving haematological and neurologic responses in vitamin B12-deficient patients. Oral therapy is considered a safer option, with improved compliance. 1000-2000 μg/day may be required initially.

Supplements

1. Braun L, Cohen M. Herbs and Natural supplements. 4th edition. Chatswood: Elsevier 2015 2. Natural Medicines 2016 Professional Monographs https://naturalmedicines.therapeuticresearch.com/databases/food,-herbs-supplements.aspx 3. Oregon State University; Linus Pauling Institute; Micronutrient Information Centre 2016 http://lpi.oregonstate.edu/mic 4. Australian Government, National health and Medical Research Council and Ministry of Health New Zealand. Nutrient Reference Values for Australia and New Zealand https://www.nrv.gov.au/nutrients 5. National Institutes of Health. Office of Dietary Supplements https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/

B12 (Cobalamin)

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