Vitamin B12

Vitamin B12, also known as cobalamin, is a water-soluble <a href="/facts/Vitamin/SnW0LYBL">vitamin</a> involved in <a href="/facts/Metabolism/WxDrm8k5">metabolism</a>. One of eight <a href="/facts/B_vitamins/m6ekXy6A">B vitamins</a>, it serves as a vital <a href="/facts/Cofactor_(biochemistry)/AGo0PCUU">cofactor</a> in <a href="/facts/DNA_synthesis/ywV1plto">DNA synthesis</a> and both <a href="/facts/Fatty_acid_metabolism/Se3rnCT8">fatty acid</a> and <a href="/facts/Amino_acid_metabolism/o5IuYIcR">amino acid metabolism</a>. It plays an essential role in the <a href="/facts/Nervous_system/CDxRKU2U">nervous system</a> by supporting <a href="/facts/Myelinogenesis/6xbzyRvW">myelin synthesis</a> and is critical for the maturation of <a href="/facts/Red_blood_cell/Kggpq8Jh">red blood cells</a> in the <a href="/facts/Bone_marrow/4dfudk0H">bone marrow</a>. While animals require B12, plants do not, relying instead on alternative enzymatic pathways.
Vitamin B12 is the most chemically complex of all vitamins, and is synthesized exclusively by certain <a href="/facts/Archaea/Adxh0aHw">archaea</a> and <a href="/facts/Bacteria/wC8xSCsU">bacteria</a>. Natural food sources include <a href="/facts/Meat/DUHTTM1d">meat</a>, <a href="/facts/Shellfish/JjTSlMgw">shellfish</a>, <a href="/facts/Liver/Rtp4Fk2b">liver</a>, <a href="/facts/Fish/fln4gH9V">fish</a>, <a href="/facts/Poultry/u8hUQ64j">poultry</a>, <a href="/facts/Egg_as_food/dRLxAGev">eggs</a>, and <a href="/facts/Dairy_product/rGVJUHVb">dairy products</a>. It is also added to many <a href="/facts/Breakfast_cereal/UoB6gfz3">breakfast cereals</a> through <a href="/facts/Food_fortification/Yr96v3Jj">food fortification</a> and is available in <a href="/facts/Dietary_supplement/SHXNNxaS">dietary supplement</a> and pharmaceutical forms. Supplements are commonly taken orally but may be administered via <a href="/facts/Intramuscular_injection/PPNwW2wB">intramuscular injection</a> to treat deficiencies.
<a href="/facts/Vitamin_B12_deficiency/WeChf6H3">Vitamin B12 deficiency</a> is prevalent worldwide, particularly among individuals with low or no intake of animal products, such as those following <a href="/facts/Veganism/ENrKFBzz">vegan</a> or <a href="/facts/Vegetarianism/ryP05yWa">vegetarian</a> diets, or those with low socioeconomic status. The most common cause in developed countries is impaired absorption due to loss of <a href="/facts/Intrinsic_factor/m8rE46ps">gastric intrinsic factor</a> (IF), required for absorption. A related cause is reduced <a href="/facts/Gastric_acid/btVCyhYH">stomach acid</a> production with age or from long-term use of <a href="/facts/Proton-pump_inhibitors/JIpwabbk">proton-pump inhibitors</a>, <a href="/facts/H2_blocker/Ra6UHBGy">H2 blockers</a>, or other antacids.
Deficiency is especially harmful in <a href="/facts/Pregnancy/vEKYGpep">pregnancy</a>, <a href="/facts/Childhood/GGe19I8d">childhood</a>, and older adults. It can lead to <a href="/facts/Neuropathy/2KjA7nyD">neuropathy</a>, <a href="/facts/Megaloblastic_anemia/Ru2zwG6C">megaloblastic anemia</a>, and <a href="/facts/Pernicious_anemia/6WVBYjso">pernicious anemia</a>, causing symptoms such as <a href="/facts/Fatigue/C2oo4Hvg">fatigue</a>, <a href="/facts/Paresthesia/hRBAxluk">paresthesia</a>, cognitive decline, <a href="/facts/Ataxia/suENWGS6">ataxia</a>, and even irreversible nerve damage. In infants, untreated deficiency may result in neurological impairment and anemia. Maternal deficiency increases the risk of miscarriage, <a href="/facts/Neural_tube_defect/3bK6SC0W">neural tube defects</a>, and developmental delays in offspring. <a href="/facts/Folate/8Eb7An6D">Folate</a> levels may modify the presentation of symptoms and disease course.

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Vitamin B12