Nutrients - Vitamin B12

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Vitamin B12
OverviewAll B vitamins are water-soluble,meaning that the body does not store them. Vitamin B12, also calledcobalamin, is one of 8 B vitamins. It is important to know that allB vitamins help the body convert food (carbohydrates) into fuel(glucose), which is used to produce energy. These B vitamins,commonly referred to as B complex vitamins, also help the body usefats and protein. B complex vitamins are also used for healthy skin,hair, eyes, and liver. They help the nervous system functionproperly.
Vitamin B12 is an especially importantvitamin for maintaining healthy nerve cells, and it helps in theproduction of DNA and RNA, the body's genetic material. Vitamin B12also works closely with vitamin B9, also called folate or folic acid,to help make red blood cells and to help iron work better in thebody. Folate and B12 work together to produce S-adenosylmethionine(SAMe), a compound involved in immune function and mood.
Vitamins B12, B6, and B9 work togetherto control blood levels of the amino acid homocysteine. High levelsof homocysteine are associated with heart disease. However,researchers aren't sure whether homocysteine is a cause of heartdisease or just a marker that indicates someone may have heartdisease.
It' s rare for young people to bedeficient in vitamin B12, but it' s not uncommon for older people tobe mildly deficient. That may be because their diets are not ashealthy or because they have less stomach acid, which the body needsto absorb B12. Low levels of B12 can cause a range of symptomsincluding fatigue, shortness of breath, diarrhea, nervousness,numbness, or tingling sensation in the fingers and toes. Severedeficiency of B12 causes nerve damage.
Others at risk for B12 deficiencyinclude:1. Vegans, vegetarians who also don't eat dairy or eggs -- vitaminB12 is found only in animal products2. People with problems absorbing nutrients, due to conditions suchas Crohn's disease, pancreatic disease, and people who have hadweight loss surgery3. People who are infected with Helicobacter pylori, an organism inthe intestines that can cause an ulcer. H. pylori damages stomachcells that make intrinsic factor, a substance the body needs toabsorb B124. People with an eating disorder5. People with HIV6. The elderly
Folic acid (vitamin B9), especiallywhen taken in high doses, can mask the symptoms of a vitamin B12deficiency. The danger is that without symptoms, someone with avitamin B12 deficiency may not know it, and could run the risk ofdeveloping nerve damage. Anyone planning to take more than 800 mcg offolic acid should talk to their doctor first, to make sure they donot have a B12 deficiency.
Vitamin B12
Vitamin B12 isbound to protein in food. The activity of hydrochloric acid andgastric protease in the stomach releases vitamin B12 from itsprotein.  Once it is released, vitamin B12 begins to workquickly. It is important for the formation of red blood cells,neurological function, and DNA synthesis. It also supports thedigestive system in keeping glucose levels stable. A simple blood test can determine thelevel of B12 in the body. Adults who have a value below 170 to 250pg/ml are considered deficient in the vitamin. An elevated bloodhomocysteine level or elevated methylmalconic acid level may alsosuggest a B12 deficiency.
TestsVitamin B12 and folate are ordered todetect deficiencies and to help diagnose the cause of certainanemias. One type of associated anemia is pernicious anemia, anautoimmune disease that affects the absorption of B12. Thismegaloblastic anemia occurs when the body produces antibodies againstthe gastric parietal cells or the intrinsic factor, resulting in B12malabsorption.
Folate, B12, and an assortment of othertests may be ordered to help evaluate the general health andnutritional status of a person with signs of significant malnutritionor dietary malabsorption. This may include people with alcoholism,other liver diseases, gastric cancer, and those with malabsorptionconditions such as celiac disease, tropical sprue, Crohn’s disease,inflammatory bowel disease, and cystic fibrosis.
B12 and folate may also be ordered toaid in diagnosis when an individual presents with an altered mentalstate or other behavioral changes, especially in the elderly. B12 maybe ordered with folate, by itself, or with other screening laboratorytests (antinuclear antibody, CRP, rheumatoid factor, CBC andchemistry blood tests) to help establish reasons why a person showssymptoms of neuropathy.
In those treated for known B12 andfolate deficiencies, these tests will be ordered occasionally tomonitor the effectiveness of treatment. This is especially true inthose who cannot properly absorb B12 and/or folate and must havelifelong treatment.
Recommended Daily AllowanceIf you are considering taking a B12supplement, ask your health care provider to help you determine theright dose for you.Daily recommendations for dietaryvitamin B12 are listed below.Pediatric Newborns - 6 months: 0.4 mcg(adequate intake) Infants 6 months - 1 year: 0.5mcg (adequate intake) Children 1 - 3 years: 0.9 mcg(RDA) Children 4 - 8 years: 1.2 mcg(RDA) Children 9 - 13 years: 1.8 mcg(RDA) Teens 14 - 18 years: 2.4 mcg(RDA)Adult 19 years and older: 2.4 mcg(RDA)* Pregnant women: 2.6 mcg (RDA) Breastfeeding women: 2.8 mcg(RDA)*Because 10 - 30% of older people maynot absorb B12 from food very well, people over 50 should meet theirdaily requirement through either foods fortified with vitamin B12 ora supplement containing B12.
CautionsIf the B12 deficiency is not remedied,permanent nerve damage can occur. Neuropathy is a common problem forpeople with diabetes, who experience pain, tingling, and numbness intheir arms, hands, legs, and feet, resulting in sores.
Vitamin B12 is an especially importantvitamin for maintaining healthy nerve cells, and it helps in theproduction of DNA and RNA, the body's genetic material. Vitamin B12also works closely with vitamin B9, also called folate or folic acid,to help make red blood cells and to help iron work better in thebody.
Food SourcesVitamin B12 is found only in animalfoods. Liver, sardines, and salmon rank highest, with liver runningaway with it. Kidney, eggs, beef, and pork are also good sources.There are no vegetarian sources. Supplements include -Methylcobalamin is probably the best.
PrecautionsOne large study found that women whotook 1,000 mcg of vitamin B12 along with 2500 mcg of folic acid and500 mg of vitamin B6 daily reduced their risk of developing AMD, aneye disease that can cause loss of vision.
Fatigue is one of the symptoms of avitamin B12 deficiency. One preliminary study indicated that peoplewith chronic fatigue syndrome might benefit from B12 injections,although more research is needed to know for sure.
Although there is no evidence thatvitamin B12 alone reduces the risk of breast cancer, populationstudies have shown that women who get more folate in their diet havelower risk of breast cancer. Vitamin B12 works with folate in thebody, so it may help contribute to a lesser risk. Another preliminarystudy suggested that postmenopausal women who had the lowest amountsof B12 in their diet had an increased risk for breast cancer.
Studies suggest that vitamin B12supplements may improve sperm counts and sperm mobility. However, thestudies were of poor quality. Better studies are needed to seewhether B12 has any real effect.
Possible InteractionsIf you are currently being treated withany of the following medications, you should not use vitamin B12supplements without first talking to your health care provider.Medications that reduce levels of B12in the body include:Anti-seizure medications -- includingphenytoin (Dilantin), phenobarbital, primidone (Mysoline)Chemotherapy medications --particularly methotrexateColchicine -- used to treat goutBile acid sequestrants -- used to lowercholesterol; include colestipol (Colestid), cholestyramine(Questran), and colsevelam (Welchol)H2 blockers -- used to reduce stomachacid; include cimetidine (Tagamet), famotidine (Pepcid AC),ranitidine (Zantac)Metformin (Glucophage) -- medicationtaken for diabetesProton pump inhibitors -- used toreduce stomach acid; include esomeprazole (Nexium), lansprazole(Prevacid), omeprazole (Prilosec), and rabeprazole (Aciphex)
Antibiotics, Tetracycline -- VitaminB12 should not be taken at the same time as tetracycline because itinterferes with the absorption and effectiveness of this medication.Vitamin B12 should be taken at different times of the day fromtetracycline. All vitamin B complex supplements act in this way andshould be taken at different times from tetracycline. In addition,long-term use of antibiotics can lower vitamin B levels in the body,particularly B2, B9, B12, and vitamin H (biotin), which is consideredpart of the B complex vitamins.