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| For other uses, see B12 (disambiguation).Protein binding
Very high to specific transcobalamins plasma proteins
Binding of hydroxocobalamin is slightly higher than cyanocobalamin.CN) which they pick up in the process of activated charcoal purification of the vitamin after it is made by bacteria in the commercial process.It is normally involved in the metabolism of every cell of the body, especially affecting the DNA synthesis and regulation but also fatty acid synthesis and energy production.DNA when the body does not have a proper supply of folic acid for the production of thymine.SAMe) and substrates (methylmalonic acid, MMA).Terminology
2 Structure
3 Synthesis
4 Functions
5 Human absorption and distribution
6 History as a treatment for anemia
7 Symptoms and damage from deficiency
8 Sources
9 Allergies
10 Side effects, contraindications, and warnings
11 Pregnancy and breastfeeding
12 Other medical uses
13 Interactions
13.Interactions with drugs
13.Aerobacter, Agrobacterium, Alcaligenes, Azotobacter, Bacillus, Clostridium, Corynebacterium, Flavobacterium, Micromonospora, Mycobacterium, Nocardia, Propionibacterium, Protaminobacter, Proteus, Pseudomonas, Rhizobium, Salmonella, Serratia, Streptomyces, Streptococcus and Xanthomonas.The most used species are Pseudomonas denitrificans and Propionibacterium shermanii, often genetically engineered and grown under special conditions to enhance yield.Rearrangements in which a hydrogen atom is directly transferred between two adjacent atoms with concomitant exchange of the second substituent, X, which may be a carbon atom with substituents, an oxygen atom of an alcohol, or an amine.CH3) group transfers between two molecules.DNA, as well as elevated homocysteine levels (see below) can often be corrected with supplementation with the vitamin folic acid.Failure of this second reaction to occur results in elevated levels of methylmalonic acid.If this abnormal fatty acid subsequently is incorporated into myelin or if the methylation of the myelin sheath phospholipids fails to occur, the resulting myelin will be too fragile, and demyelination will occur.The result is subacute combinded degeneration of central nervous system and spinal cord.Stomach proteolysis of these proteins requires an acid pH, and also requires proper pancreatic release of proteolytic enzymes.B12), which serves as the plasma transporter of the vitamin.The cure was discovered by accident.For this, the three men shared the 1934 Nobel Prize in Medicine.The chemical structure of the molecule was determined by Dorothy Crowfoot Hodgkin and her team in 1956, based on crystallographic data.At levels only slightly lower than normal, a range of symptoms such as fatigue, depression, and poor memory may be felt.Eggs are often mentioned as a good source, but they also contain a factor that blocks absorption.However, it is rare to eat unwashed vegetables in the West, so vegans need to take special care to supplement their diets accordingly.Injection is sometimes used in cases where digestive absorption is impaired, but there is some evidence that it may not necessary with modern high potency oral supplements (such as 500 to 1000 mcg or more).Even pernicious anemia can be treated entirely by the oral route.Cyanocobalamin is also sometimes added to beverages including Diet Coke Plus and many energy drinks, in some cases with over 80 times the recommended intake.However, direct allergy to a vitamin or nutrient is extremely rare, and if reported, other causes should be sought.Some studies have found reduced serum levels in oral contraceptive users, but others have found no effect despite use of oral contraceptives for up to 6 months.Blood counts should be monitored closely if this combination cannot be avoided.Colchicine: Colchicine in doses of 1.In a group of children treated with cholestyramine for up to 2.Routine supplements are not necessary.H2 blockers for prolonged periods.Supplements are not usually needed with normal doses.This may contribute to the megaloblastic anemia, primarily caused by folate deficiency, associated with these drugs.This effect has been reported with potassium chloride and, to a lesser extent, with potassium citrate.See especially discussion on activated charcoal column purification for the origin of this compound.Bauman WA, Shaw S, Jayatilleke E, Spungen AM, Herbert V.Medline Plus (National Library of Medicine).Vital Nutrient for Good Health at the Weston A.This page was last modified 07:50, 9 January 2008.All text is available under the terms of the GNU Free Documentation License.See Copyrights for details.Cyanocobalamin is an especially common "vitamer" (that is, member of a family of vitamins, all of which have some particular nutritional activity in preventing some vitamin deficiency disease).See Copyrights for details.This monograph is intended for informational purposes only, and should not be interpreted as specific medical advice.Vitamin B12 is an essential water soluble vitamin that is commonly found in a variety of foods such as fish, shellfish, meats, and dairy products.Vitamin B12 is frequently used in combination with other B vitamins in a vitamin B complex formulation.It helps maintain healthy nerve cells and red blood cells, and is also needed to make DNA, the genetic material in all cells.Vitamin B12 is bound to the protein in food.Hydrochloric acid in the stomach releases B12 from protein during digestion.Once released, B12 combines with a substance called intrinsic factor (IF) before it is absorbed into the bloodstream.The human body stores several years' worth of vitamin B12, so nutritional deficiency of this vitamin is extremely rare.Elderly are the most at risk.However, deficiency can result from being unable to use vitamin B12.Inability to absorb vitamin B12 from the intestinal tract can be caused by a disease known as pernicious anemia.Additionally, strict vegetarians or vegans who are not taking in proper amounts of B12 are also prone to a deficiency state.B12 can be obtained by eating 1 chicken breast (0.Uses based on scientific evidenceGrade* Vitamin B12 deficiency Studies have shown that a deficiency of vitamin B12 can lead to abnormal neurologic and psychiatric symptoms.Researchers report that these symptoms may occur when vitamin B12 levels are just slightly lower than normal and are considerably above the levels normally associated with anemia.People at risk for vitamin B12 deficiency include strict vegetarians, elderly people, and people with increased vitamin B12 requirements associated with pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, liver or kidney disease.Administering vitamin B12 orally, intramuscularly, or intranasally is effective for preventing and treating dietary vitamin B12 deficiency.Oral preparations should not be used in patients with diarrhea, vomiting, severe neurologic involvement, or in patients likely to be noncompliant to therapy.Vitamin B12 deficiency is a cause of megaloblastic anemia.In this type of anemia, red blood cells are larger than normal, and the ratio of nucleus size to cell cytoplasm is increased.There are other potential causes of megaloblastic anemia, including folate deficiency or various inborn metabolic disorders.If the cause is B12 deficiency, then treatment with B12 is the standard approach.Patients with anemia should be evaluated by a physician in order to diagnose and address the underlying cause.Pernicious anemia (blood abnormality) is a form of anemia that occurs when there is an absence of intrinsic factor, a substance normally present in the stomach.Vitamin B12 binds with intrinsic factor before it is absorbed and used by the body.An absence of intrinsic factor prevents normal absorption of B12 and may result in pernicious anemia.Pernicious anemia treatment is usually lifelong supplemental vitamin B12 given either intramuscularly, intranasally, or by mouth.Some patients diagnosed with Alzheimer's disease have been found to have abnormally low vitamin B12 levels in their blood.However, vitamin B12 deficiency itself often causes disorientation and confusion and thus mimics some of the prominent symptoms of Alzheimer's disease.Well designed clinical trials are needed before a recommendation can be made.Some evidence suggests that folic acid 1mg plus vitamin B12 400mcg and pyridoxine 10mg daily can decrease the rate of restenosis in patients treated with balloon angioplasty.But this combination does not seem to be as effective for reducing restenosis in patients after coronary stenting.An intravenous loading dose of folic acid, vitamin B6 and vitamin B12 followed by oral administration of folic acid 1.B6 48mg and vitamin B12 60mcg taken daily after coronary stenting also does not seem to reduce restenosis and might actually increase restenosis.Due to the lack of evidence of benefit and potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents.Researchers at Johns Hopkins University report that women with breast cancer tend to have lower vitamin B12 levels in their blood serum than do women without breast cancer.In a subsequent review of these findings, it was hypothesized that vitamin B12 deficiency may lead to breast cancer because it could result in less folate being available to ensure proper DNA replication and repair.The risk may be further reduced in women who also consume high amounts of dietary vitamin B12 in combination with dietary pyridoxine (vitamin B6) and methionine.However, there is no evidence that dietary vitamin B12 alone reduces the risk of breast cancer.However, it is not clear if lowering homocysteine levels results in reduced cardiovascular morbidity and mortality.Folic acid, pyridoxine (vitamin B6), and vitamin B12 supplementation can reduce total homocysteine levels, however, this reduction doesn't seem to help with secondary prevention of death or cardiovascular events such as stroke or myocardial infarction in people with prior stroke.More evidence is needed to fully explain the association of total homocysteine levels with vascular risk and the potential use of vitamin supplementation.There is some evidence that intramuscular injections of 5mg of vitamin B12 given twice per week might improve the general well being and happiness of patients complaining of tiredness or fatigue.Well designed clinical trials are needed before a recommendation can be made.B12 in combination with 5 grams of fish oil might be superior to fish oil alone when used daily to reduce total serum cholesterol and triglycerides.Well designed clinical trials of vitamin B12 supplementation alone are needed before a conclusion can be drawn.Further research is needed to confirm these results.Sickle cell disease One study suggests that a practical daily combination may be 1mg folic acid, 6mcg vitamin B12, and 6mg vitamin B6.This combination may be a simple and relatively inexpensive way to reduce these patients' inherently high risk of endothelial damage.Circadian rhythm sleep disorders Taking vitamin B12 orally, in methylcobalamin form, does not seem to be effective for treating delayed sleep phase syndrome.Preliminary evidence suggests that there is no relationship between vitamin B12 status and lung cancer.In people with a history of stroke, neither high dose vitamin B12 combinations containing 25mg of pyridoxine, 0.B12, and 20mcg of folic acid seem to affect risk of recurring stroke.Vitamin B12 is contraindicated in early Leber's disease, which is hereditary optic nerve atrophy.Vitamin B12 can cause severe and swift optic atrophy.Uses based on tradition or theoryThe below uses are based on tradition or scientific theories.The below doses are based on scientific research, publications, traditional use, or expert opinion.The below doses may not apply to all products.Recommended daily allowances (RDAs) :2.B12 efficiently, those over 50 years of age should meet the RDA by eating foods fortified with B12 or by taking a vitamin B12 supplement.B12 levels in older people.For malabsorption of vitamin B12 from food or pernicious anemia, cyanocobalamin doses of 300 to 2000mcg daily have been used.For hyperhomocysteinemia , vitamin B12 in a dose of 500mcg in combination with 0.To decrease the rate of restenosis after coronary angioplasty, a combination of vitamin B12 400mcg plus pyridoxine (vitamin B6) 10mg and folic acid 1mg taken daily has been used, however unproven.For reducing increased homocysteine concentrations associated with nitrous oxide general anesthesia, a supplement containing vitamin B12 500mcg with pyridoxine (vitamin B6) 25mg and folic acid 2.For sickle cell disease , o ne study suggests that a practical daily combination may be 1mg folic acid, 6mcg vitamin B12, and 6mg vitamin B6.B12 in combination with 5 grams of fish oil might be superior to fish oil alone when used daily to reduce total serum cholesterol and triglycerides .Both cyanocobalamin and hydroxocobalamin forms are used.For familial selective vitamin B12 malabsorption , cyanocobalamin 1000mcg weekly for 3 weeks, followed by 250mcg monthly has been used.B12 daily for two weeks, then weekly for two months, and once a month thereafter has been used.For decreasing homocysteine levels and normalizing B12 levels in adult vegetarians, cyanocobalamin 1000mcg has been used.There is some evidence that intramuscular injections of 5mg of vitamin B12 given twice per week might improve the general well being and happiness of patients complaining of tiredness or fatigue , although unproven.There is no guarantee of strength, purity or safety of products, and effects may vary.If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.Vitamin B12 supplements should be avoided in people sensitive or allergic to cobalamin, cobalt or any other product ingredients.Side Effects, Contraindications and Warnings Cardiovascular : Caution should be used in patients undergoing angioplasty since an intravenous loading dose of folic acid, vitamin B6 and vitamin B12 followed by oral administration of folic acid 1.B6 48mg and vitamin B12 60mcg taken daily after coronary stenting might actually increase restenosis rates.Symptoms may persist for up to 4 months after the supplement is stopped, and may require treatment with systemic corticosteroids and topical therapy.Gastrointestinal : Diarrhea has been reported.Hematologic : Peripheral vascular thrombosis has been reported.Treatment of vitamin B12 deficiency can unmask polycythemia vera, which is characterized by an increase in blood volume and the number of red blood cells.The correction of megaloblastic anemia with vitamin B12 can result in fatal hypokalemia and gout in susceptible individuals, and it can obscure folate deficiency in megaloblastic anemia.Leber's disease : Vitamin B12 is contraindicated in early Leber's disease, which is hereditary optic nerve atrophy.Vitamin B12 can cause severe and swift optic atrophy.Pregnancy and Breastfeeding Vitamin B12 is likely safe when used orally in amounts that do not exceed the recommended dietary allowance (RDA).The RDA for vitamin B12 in pregnant women is 2.There is insufficient reliable information available about the safety of larger amounts of vitamin B12 during pregnancy.Andres E, Kurtz JE, Perrin AE, et al.Badner NH, Freeman D, Spence JD.Bauman WA, Shaw S, Jayatilleke E, et al.Increased intake of calcium reverses vitamin B12 malabsorption induced by metformin.Gastin I, De Korwin JD, et al.Preventive health care, 2000 update: screening and management of hyperhomocysteinemia for the prevention of coronary artery disease events.The Canadian Task Force on Preventive Health Care.Bostom AG, Gohh RY, Beaulieu AJ, et al.Effects of folic acid and combinations of folic acid and vitamin B12 on plasma homocysteine concentrations in healthy young women.Megaloblastic anemia due to vitamin B12 malabsorption associated with longterm metformin treatment.Vitamin B12 deficiency: a new risk factor for breast cancer?Oral or parenteral therapy for B12 deficiency.Study of the role of vitamin B12 and folinic acid supplementation in preventing hematologic toxicity of zidovudine.Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (2000).Effect of histamine H2 receptor antagonists on vitamin B12 absorption.Force RW, Meeker AD, Cady PS, et al.Increased vitamin B12 requirement associated with chronic acid suppression therapy.Oral contraceptives can cause falsely lower vitamin B12 levels.Gharakhanian S, Navarette MS, Cardon B, Rozenbaum W.Vitamin B12 injections in patients treated with zidovudine.The challenge of stroke prevention.B6), B12, and folate with lung cancer risk in older men.Houston DK, Johnson MA, Nozza RJ, et al.Lindenbaum J, Healton EB, Savage DG, et al.Neuropsychiatric disorders caused by cobalamin deficiency in the absence of anemia or macrocytosis.Signs of impaired cognitive function in adolescents with marginal cobalamin status.Manns B, Hyndman E, Burgess E, et al.Omeprazole therapy causes malabsorption of cyanocobalamin.Effects of vitamin B12 on performance and circadian rhythm in normal subjects.Familial Alzheimer's disease and vitamin B12 deficiency.Serum folate, vitamin B12, and homocysteine in major depressive disorder, Part 2: predictors of relapse during the continuation phase of pharmacotherapy.Penninx BW, Guralnik JM, Ferrucci L, et al.Ruscin JM, Page RL, Valuck RJ.Salom IL, Silvis SE, Doscherholmen A.Effect of cimetidine on the absorption of vitamin B12.B12, and vitamin B6 on clinical outcome after percutaneous coronary intervention.Seal EC, Metz J, Flicker L, Melny J.B12 supplementation in older patients with subnormal or borderline serum vitamin B12 concentrations.Toole JF, Malinow MR, Chambless LE, et al.Lowering homocysteine in patients with ischemic stroke to prevent recurrent stroke, myocardial infarction, and death: the Vitamin Intervention for Stroke Prevention (VISP) randomized controlled trial.Tremblay R, Bonnardeaux A, Geadah D, et al.Optimization of folic acid, vitamin B12, and vitamin B6 supplements in pediatric patients with sickle cell disease.Webb DI, Chodos RB, Mahar CQ, et al.Mechanism of vitamin B12 malabsorption in patients receiving colchicine.Yamadera H, Takahashi K, Okawa M.B12, bright light therapy, chronotherapy and hypnotics.Mayo Foundation for Medical Education and Research (MFMER).LEGAL CONDITIONS AND TERMS OF USE APPLICABLE TO ALL USERS OF THIS SITE.ANY USE OF THIS SITE CONSTITUTES YOUR AGREEMENT TO THESE TERMS AND CONDITIONS OF USE.Get your free trial issue of Health Letter now!More titles from MayoClinic.B12
By Hans R.Alzheimer's actually suffer from a vitamin B12 deficiency.Clearly, it is very important to maintain adequate body stores of this crucial vitamin.B12 are liver, especially lamb's liver, and kidneys.Fortunately, oral supplementation with vitamin B12 is safe, efficient and inexpensive.Many older people suffer from a deficiency of vitamin B12 (cobalamin).B12 for at least six months.Annals of Pharmacotherapy, Vol.Glucophage) for five years.B12) for two months reversed the deficiency.Archives of Internal Medicine, Vol.Is it a novel causative agent in vitamin B12 deficiency?B12 levels in their blood serum than do women without breast cancer.B12 had a 2.Vitamin B12 deficiency: a new risk factor for breast cancer?B12 level is low.Cobalamin has no known toxic effects.To B12 or not to B12?Their study involved 368 men and women aged 75 years or older.By the fifth injection his mental status had vastly improved and his lethargy had completely vanished.United States may be too low and should be reassessed.Prevalence and diagnosis of cobalamin deficiency in older people.American Geriatrics Society, Vol.Vitamin B12 deficiency common among elderly people
NEW YORK, NY.B12 deficiency versus only 17.American Journal of Clinical Nutrition, Vol.Vitamin B deficiencies are common in elderly people
LEUVEN, BELGIUM.B12 deficiency requires high supplement doses
WAGENINGEN, THE NETHERLANDS.Vitamin B12 deficiency is fairly common among older people and can cause anemia, pain and depression.Supplementation with cobalamin may reverse the deficiency, however, the ideal dose when given orally is yet to be determined.University of Wageningen undertook a study in which 120 participants were given either 2.These doses cover the full range from recommended dietary allowance in the Netherlands to the normal dose
used in injections for B12 deficiency.They were all mildly deficient in vitamin B12, with
serum concentrations of 100 to 300 picomoles per liter.Their levels of methylmalonic acid (MMA, a marker for vitamin B12 deficiency) were above 0.Compliance with the medication was very high, at 98 per cent.Overall, levels of MMA and serum vitamin B12 improved with increasing doses of cobalamin.The percentages of participants whose MMA reduced to below 0.However, they add that diagnosing vitamin B12 deficiency is complicated
due to the limitations of current techniques.The authors conclude that the lowest dose needed to normalize vitamin B12 deficiency is more
than 200 times higher than the recommended dietary allowance.They add that the relevance of treating vitamin B12 deficiency in older people
could be substantial, were further trials able to show benefits to cognitive functioning and depression.Oral cyanocobalamin supplementation in older people with vitamin B12 deficiency.This deficiency is mostly related to an inability to absorb cobalamin bound to food.CFS but also impair the healing process.CFS patients have been inconclusive so far Dr.Nutritional strategies for treating chronic fatigue syndrome.Is oral supplementation effective?Oral or parenteral therapy for B12 deficiency.American Geriatrics Society, Vol.Journal of the American Geriatrics Society, Vol.Journal of Nutrition, Vol.Effects of vitamin B12 on cognitive function in older people
WAGENINGEN, NETHERLANDS.Deficiency of vitamin B12 is common among older people.However, randomized trial results have so far been inconclusive.They investigated the effects of daily oral supplementation
with vitamin B12 at a high dose (1,000ug) on adults aged 70 years or above with a mild deficiency.B12 supplements are considered to be safe
and no upper safety level has been set in the US or Europe.After 24 weeks, vitamin B12 status and cognitive function were assessed.This may be because a longer course of vitamin B12 is necessary to repair any existing cognitive damage.Individuals who have had mild cognitive impairment for less than six months may also be more likely to respond to treatment with vitamin B12.An antibiotic to treat Alzheimer's?Alzheimer's disease thus explaining the association between low vitamin B12 levels and Alzheimer's.B12 has been found to slow this progression.Alzheimer's disease (AD) and dementia; other studies have found no such correlation.B12 or folic acid (folate) is associated with an increased risk of AD and dementia.B12 and folate levels.B12 and folate the participants with low levels of at least one of the vitamins had a 2.Vitamin B12 and folate in relation to the development of Alzheimer's disease.Vitamin B12 deficiency implicated in Alzheimer's disease
CLWYD, NORTH WALES.B12 levels in their blood.Familial Alzheimer's disease and vitamin B12 deficiency.Grain fortification with vitamin B12?Importance of both folic acid and vitamin B12 in reduction of risk of vascular disease.The participants were then given 5 mg of folic acid, 100 mg of vitamin B6, and 0.At the end of the five weeks their average homocysteine level had decreased to 5.B6 per day and 500 micrograms of vitamin B12.Homocysteine and coronary artery disease.Homocysteine: A new risk factor for atherosclerosis.The average age of the patients was 35 years and 93 per cent of them were women.SLE patients with elevated homocysteine levels have a 2.They found that folic acid is very effective in lowering homocysteine levels.United States were to supplement with 400 micrograms per day of folic acid.B12 (cobalamin) is substantially higher than the normal upper limit.However, careful enquiry very frequently demonstrates that no external human intervention explains the finding of high vitamin B12 levels.Indeed, the perfusion of tritiated PABA, a classic precursor substrate for the bacterial folate synthesis, led to the identification of bacterially synthesized (as marked) folates aspirated from in the small intestine.B1, B2, B5, B8 and B9) supposedly absorbed by the small intestine may be assimilated by the colonocytes, while several compounds (vitamins B9 and B12) supposedly synthesized by colonic bacteria may actually be generated in the small intestine!Unfortunately, if we wanted to explain the high vitamin B12 blood levels by some colonic absorption, we must underline that absolutely nothing has been published about this and what seems true for other vitamins B would not be so for cobalamin.B12 is absorbed in the small intestine, where most of the assimilation process of other B vitamins takes place.SMVT) taking care of biotin (vitamin B8) and of pantothenic acid (vitamin B5).The term vitamin B12 or cobalamin actually refers to four different forms found in the diet and mostly bound to proteins: methylcobalamin, hydroxocobalamin, cyanocobalamin, and deoxyadenosylcobalamin.The cobalamins are released from their protein complexes through the action of acid or pepsin in the stomach.The brush border membrane of the terminal ileum enterocytes contains a specific receptor for the dimeric complex and its importance in the process is shown by a congenital vitamin B12 malabsorption syndrome due to a defect in this receptor.Under normal physiological conditions, bacterial growth in the small intestine is inhibited by the acidic environment caused by the presence of hydrochloric acid.Indeed, the unexplained increase of blood levels that we are describing about vitamin B12 may also occur with folic acid.Celiac disease had been ruled out, but he showed an increase of specific urinary organic metabolites corresponding to a bacterial overgrowth, typically from Clostridium.However, the young woman was not complaining about her digestive system, even if she occasionally
mentioned some severe but transitory abdominal cramps.Baker, Vitamin B12 synthesis by human small intestinal bacteria.Eur J Cancer Prev, 1997.JPEN J Parenter Enteral Nutr, 1997.Am J Physiol Gastrointest Liver Physiol, 2001.Am J Physiol Cell Physiol, 2000.Cellular uptake of biotin: mechanisms and regulation.Chaia, Assessing survival of dairy propionibacteria in gastrointestinal conditions and adherence to intestinal epithelia.Am J Physiol Gastrointest Liver Physiol, 2003.Synthesis of riboflavin by intestinal bacteria.THTR2) in epithelial cells.Prog Nucleic Acid Res Mol Biol, 2001.Said, Folate uptake in the human intestine: promoter activity and effect of folate deficiency.Said, Mechanism and regulation of human intestinal niacin uptake.Intrinsic factor secretion and cobalamin absorption.Scand J Gastroenterol Suppl, 1991.Brown, Vitamin B12 deficiency.Update on cobalamin, folate, and homocysteine.Hematology (Am Soc Hematol Educ Program), 2003: p.Gastroenterol Clin North Am, 1998.Aliment Pharmacol Ther, 1998.L) and a Schilling test demonstrated malabsorption of vitamin B12.B12 injections were responsible for resolving it.LEVEL CONTENT CATEGORY
hbx.CAMPAIGN ID IN QUERY
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hbx.American Academy of Family Physicians.DNA synthesis and neurologic function.B12 deficiency before initiating folic acid therapy.B12 or folic acid may lead to increased homocysteine levels.B12 that is bound to food.B12 in the duodenum.B12 in the terminal ileum.Vitamin B12 absorption and transport.There are, however, a few caveats to keep in mind.Information from Stabler SP.Geriatr Soc 1995:43:1295, and Snow CF.B12 and folate deficiency.B12 deficiency by this mechanism.B12 deficiency has been intramuscular injections.B12 in doses of 500 mcg or less.The authors thank Linda L.Internal Medicine, Walter Reed Army Medical Center, Washington, D.Madigan Army Medical Center, Fort Lewis, Wash.Address correspondence to Robert C.High prevalence of cobalamin deficiency in elderly outpatients.Oral or parenteral therapy for B12 deficiency.B12 deficiency after gastric surgery.Lindenbaum J, Savage DG, Stabler SP, Allen RH.Oral cobalamin for pernicious anemia.Adachi S, Kawamoto T, Otsuka M, Fukao K.B12 supplements reverse postgastrectomy B12 deficiency.B12 and folate are B complex vitamins that are necessary for normal red blood cell formation, tissue and cellular repair, and DNA synthesis.Over time, a deficiency in either B12 or folate can lead to macrocytic anemia, a condition characterized by the production of fewer, but larger red blood cells and a decreased ability to carry oxygen.Patients who have this condition may tire easily, be weak, and be short of breath.Pregnant women need increased amounts of folate for proper fetal development.B12 deficiency anemia is a drop in the number of red blood cells due to a lack of vitamin B12.Vitamin B12 is essential for normal nervous system function and blood cell production.The main sources of vitamin B12 include meat, eggs, and dairy products.For vitamin B12 to be absorbed by the body, it must bind to intrinsic factor, a protein secreted by cells in the stomach.The risk factors are related to the causes.Treatment depends on the specific cause of B12 deficiency anemia.Pernicious anemia requires lifelong vitamin B12 injections.Those with anemia due to a lack of vitamin B12 may be told to take vitamin supplements and to follow a more balanced diet.It may be treated initially with vitamin B12 injections.Anemia caused by malabsorption is treated with vitamin B12 injections until the condition improves.The signs and symptoms related to the central nervous system may be irreversible if treatment is not begun within 6 months of when these symptoms begin.Vitamin B12 affects epithelial cells (cells that form the outer surface of the body and line inner passageways).B12 injections can prevent anemia after surgeries known to cause vitamin B12 deficiency.Early diagnosis and prompt treatment can limit the severity and complications of this anemia.Nutritional disorders in the elderly.Textbook of Family Practice.Philadelphia, Pa: WB Saunders; 2005:1232.The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.Call 911 for all medical emergencies.Support a child from Uganda, East Africa.Norman Clinical Laboratory, Inc.NCL) provides a means to test individuals through the mail for cobalamin (vitamin B12 ) deficiency.This test is often used by physicians wishing to make a conclusive diagnosis of vitamin B12 deficiency with a single test, individuals desiring to be tested by mail from the privacy of their home, and investigators seeking to conduct the most valid research study.Vitamin B12 deficiency can cause dementia identical to early stage Alzheimer's disease (AD).In addition, vitamin B12 deficiency has been implicated as a risk factor for developing AD.Early detection and treatment usually with vitamin B12 injections can reverse disability.Strict vegetarians and breast fed infants of vegans are at risk of having B12 deficiency.Vitamin B12 is found only in animal sources such as meat, fish, eggs and milk.Unless a person is a vegetarian, vitamin B12 deficiency is usually caused from malabsorption due to lack of the stomach protein, intrinsic factor, resulting in pernicious anemia.B12 deficiency is found in some elderly individuals affected with atrophic gastritis.B12 deficiency in this population 1,2 but yearly uMMA screening is still warranted.It is important to accurately diagnose vitamin B12 deficiency since treatment may be extensive.For example, individuals with neurologic manifestations, the recommendation is for a B12 injection intramuscular (IM) of 1,000 micrograms daily for 2 weeks, then every two weeks for 6 months, and then monthly for life.Some physicians may treat using high amounts of oral B124, intranasal B12 4A, or sublingual B12.However, adequate response to serious neurologic symptoms to oral therapy has not been conclusively proven.Follow up uMMA levels on individuals receiving oral, intranasal B12, or sublingual B12 will assess compliance as well as B12 absorption and assimilation for correction of B12 deficiency at the tissue level.Hematology Division of the University of Cincinnati College of Medicine, USA.Identify high prevalence of neurologic disease in vitamin B12 deficient patients without anemia.Identify high prevalence of metabolic B12 deficiency in older populations.Identify high prevalence of metabolic B12 deficiency in individuals with a normal serum vitamin B12.Validate the urinary MMA test as a screening tool for identifying tissue B12 deficiency in older populations.Vitamin B12
Vitamin B12 has the largest and most complex chemical structure of all
the vitamins.For this reason cobalamin
is the term used to refer to compounds having vitamin B12 activity.B12 used in the human body (1).Methylation of DNA may be important in cancer prevention.This biochemical reaction plays an
important role in the production of energy from fats and proteins.CoA is also required for the synthesis of hemoglobin,
the oxygen carrying pigment in red blood cells (3).Stomach acid and enzymes free vitamin B12 from
food, allowing it to bind to other proteins called R proteins (3).B12 to bind to intrinsic factor (IF), a protein
secreted by specialized cells in the stomach.B12 complex only in the
presence of calcium, which is supplied by the pancreas (5).B12 dose is absorbed passively (2).B12 complex, further inhibiting vitamin B12
absorption.B12 absorption is diminished.B12 malabsorption do not have an increased requirement
for vitamin B12; they simply need it in the crystalline form found in fortified foods and dietary supplements.B12 deficiency is presently an area of
active research (4).Alcoholics may experience reduced intestinal absorption of vitamin B12 (2).B12 deficiency (see Drug interactions).CoA called methylmalonic acid (MMA).MMA may be elevated (12).Thus, in both folate and vitamin B12 deficiencies,
folate is unavailable to participate in DNA synthesis.However, if vitamin B12 deficiency is the cause,
it will persist despite the resolution of the anemia.B12 deficiency, especially if they have been present
for a long time.Tongue soreness, appetite loss, and constipation have also been associated
with vitamin B12 deficiency.Some evidence indicates that vitamin B12 deficiency is a major
cause of elevated homocysteine levels in people over the age of 60.B12 deficiency or a combined B12
and folate deficiency (16).Although increased intake of folic acid and vitamin B12 has been found to decrease homocysteine levels, it is not presently known whether increasing intake of these vitamins will translate to reductions in risk for cardiovascular diseases.Nevertheless, the completion of ongoing clinical trials should help to answer whether or not supplemental B vitamins lower risk for cardiovascular diseases.B12 traps folate in a form that is unusable by the body for
DNA synthesis.DNA damage and altered methylation of DNA, both of which are important
risk factors for cancer.B12 daily in cereal for two months (18).Stratification of the data revealed that the inverse association between dietary vitamin B12 intake and breast cancer risk was stronger in postmenopausal women compared to premenopausal women, though both associations were statistically significant.B12 or low dietary vitamin B12 intakes
were a cause or a result of breast cancer.However, high dietary folate intakes have been associated with reduced risk for breast cancer in several studies, and some studies have reported that vitamin B12 intake may modify this association (21, 22).NTD cases when women consumed folic acid supplements in addition to
a varied diet during the month before and the month after conception.B12 for effective functioning of the methionine synthase enzyme.B12 intake in addition to
folic acid may be beneficial in the prevention of NTD.Alzheimer's disease often have low blood levels of vitamin B12.B12 did not differ (25).The reason for the association of low vitamin B12 status with
Alzheimer's disease is not clear.Some but not all studies have associated elevated homocysteine concentrations or decreased serum levels of vitamin B12 with an increased risk of Alzheimer's disease.Alzheimer's disease was confirmed by examination
of brain cells after death (26).Alzheimer's disease in 370 elderly
men and women followed over three years (27).Alzheimer's disease and other types of dementia (28).L) had a significantly higher risk of developing Alzheimer's disease or dementia, but vitamin B12 status was not related to risk of Alzheimer's disease or dementia in this study (30).Similarly, another prospective study in 965 older adults found that vitamin B12 status was not related to the risk of Alzheimer's disease (31).Further, a prospective study in 1,041 older adults, followed for a median of 3.B12 dietary intake was not associated with risk of developing Alzheimer's disease (32).B12, and 10 mg vitamin B6) for two years did not affect measures of cognitive performance despite an average 4.B12 supplementation (1 mg daily) for six months had no effect on measures of cognitive function (34).B12 deficiency plays a causal role
in depression.B12 deficiency as part of a medical evaluation for
depression.In the United
States, the average intake of vitamin B12 is about 4.B12 content in
micrograms (mcg).USDA food composition database.Cyanocobalamin is the principal form of vitamin B12
used in supplements but methylcobalamin is also available as a supplement.No toxic or adverse effects have been associated with large intakes of
vitamin B12 from food or supplements in healthy people.B12 are given orally, only a small percentage can
be absorbed, which may explain the low toxicity.B12 deficiency does not generally develop until after at least
three years of continuous therapy (44).B12 in the form of a supplement because gastric
acid is not required for its absorption.B12 deficiency, leaving the
individual at risk of developing irreversible neurologic damage (6).B12 in a form that is easily absorbed.Higher doses of vitamin B12 supplements are recommended for patients taking medications that interfere with its absorption (see Drug interactions).Written in March 2003 by:
Jane Higdon, Ph.Updated in August 2007 by:
Victoria J.Micronutrient Information Center provides scientific information on health aspects
of micronutrients and phytochemicals for the general public.The information should not be used in place of a consultation with a competent
health care or nutrition professional. |
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![Sister Machine Gun : [R]evolution](/covers/10/10747/alb_72171_th.jpg "Sister Machine Gun : [R]evolution")
