Guest guest Posted January 10, 2005 Report Share Posted January 10, 2005 Cyanocobalamin (vitamin B12) JoAnn Guest Jan 09, 2005 18:21 PST ======================================================================= Cyanocobalamin (vitamin B12) Cyanocobalamin is the technical term for vitamin B-12. The bacteria that grows in the intestinal tract may be a source of vitamin B12 and the reason why most vegans are not clinically deficient. Lessons from history B12 is an exceptional vitamin. It is required in smaller amounts than any other known vitamin. Ten micrograms of§ B12 spread over a day appears to supply as much as the body can use. Individuals with pernicious anemia or with gastrointestinal disorders may benefit from or require a vitamin B12 supplement. Older adults may benefit from a vitamin B12 supplement or an increased intake of foods fortified with vitamin B12. Some medications may decrease absorption of vitamin B12. Chronic use of those medications may result in a need for supplemental B12. When is a deficiency of vitamin B12 likely to occur? Results of two national surveys, the National Health and Nutrition Examination Survey (NHANES III-1988-94) and the Continuing Survey of Food Intakes by Individuals (CSFII 1994-96) found that most children and adults in the United States (U.S.) consume recommended amounts of vitamin B12. A deficiency may occur as a result of an inability to absorb B12 from food. As a general rule, most individuals who develop a vitamin B12 deficiency have an underlying stomach or intestinal disorder that limits the absorption of vitamin B12. Sometimes the only symptom of these intestinal disorders is subtly reduced cognitive function resulting from early B12 deficiency. Anemia and dementia follow later. Anemia is a condition that occurs when there is insufficient hemoglobin in red blood cells to carry oxygen to cells and tissues. Common signs and symptoms of anemia include fatigue and weakness. Anemia can result from a variety of medical problems, including deficiencies of vitamin B12, vitamin B6, folate and iron. Pernicious anemia is the name given more than a century ago to describe the then-fatal vitamin B12 deficiency anemia that results from severe gastric atrophy, a condition that prevents gastric cells from secreting intrinsic factor. Intrinsic factor is a substance normally present in the stomach. Vitamin B12 must bind with intrinsic factor before it can be absorbed and used by your body. An absence of intrinsic factor prevents normal absorption of B12 and results in pernicious anemia. Most individuals with pernicious anemia need parenteral (deep subcutaneous) injections (shots) of vitamin B12 as initial therapy to replenish depleted body B12 stores. Body stores of vitamin B12 can then be managed by a daily oral supplement of B12. A physician will manage the treatment required to maintain the vitamin B12 status of individuals with pernicious anemia. Individuals with gastrointestinal disorders Individuals with stomach and small intestinal disorders may be unable to absorb enough vitamin B12 from food to maintain healthy body stores. Intestinal disorders that may result in malabsorption of vitamin B12 include: Sprue, often referred to as Celiac Disease (CD), is a genetic disorder. People with CD are intolerant to a protein called gluten. In CD, gluten can trigger damage to the small intestines, where most nutrient absorption occurs. People with CD often experience nutrient malabsorption. They need to follow a gluten free diet to avoid malabsorption and other symptoms of CD. Crohn's Disease is an inflammatory bowel disease that affects the small intestines. People with Crohn's disease often experience diarrhea and nutrient malabsorption. Surgical procedures in the gastrointestinal tract, such as surgery to remove all or part of the stomach, often result in a loss of cells that secrete stomach acid and intrinsic factor .. Surgical removal of the distal ileum, a section of the intestines, also can result in the inability to absorb vitamin B12. Anyone who has had either of these surgeries usually requires lifelong supplemental B12 to prevent a deficiency. These individuals would be under the routine care of a physician, who would periodically evaluate vitamin B12 status and recommend appropriate treatment. Older adults Gastric acid helps release vitamin B12 from food. This must occur before B12 binds with intrinsic factor and is absorbed in your intestines. Atrophic gastritis, which is an inflammation of the stomach, decreases gastric secretion. Less gastric acid decreases the amount of B12 separated from proteins in foods and can result in poor absorption of vitamin B12. Decreased gastric secretion also " results " in overgrowth of normal " bacterial flora " in the small intestines. The bacteria may take up vitamin B12 for their own use, further " contributing " to a vitamin B12 deficiency. Up to 30 percent of adults 50 years and older may have atrophic gastritis, an overgrowth of intestinal flora, and be unable to normally absorb vitamin B12 in food. They are, however, able to absorb the synthetic B12 added to fortified foods and dietary supplements. Vitamin supplements and fortified foods may be the best sources of vitamin B12 for adults over the age of 50. Researchers have long been interested in the potential connection between vitamin B12 deficiency and dementia. A recent review examined correlations between cognitive skills, homocysteine levels, and blood levels of folate, vitamin B12 and vitamin B6. The authors suggested that vitamin B12 deficiency may decrease levels of substances needed for the metabolism of neurotransmitters . Neurotransmitters are chemicals that transmit nerve signals. Reduced levels of neurotransmitters may result in cognitive impairment. In 142 individuals considered at risk for dementia, researchers found that a daily supplement providing 2 milligrams (mg) folic acid and 1 mg B12, taken for 12 weeks, lowered homocysteine levels by 30%. They also demonstrated that cognitive impairment was significantly associated with elevated plasma total homocysteine. However, the decrease in homocysteine levels seen with vitamin supplementation did not improve cognition. It is too soon to make any recommendations, but is an intriguing area of research. Drug : Nutrient Interactions Table 4 summarizes several drugs that potentially influence vitamin B12 absorption. Table 4: Important vitamin B12/drug interactions Drug Potential Interaction Proton Pump Inhibitors (PPIs) are used to treat gastroesophageal reflux disease (GERD) and peptic ulcer disease. Examples of PPIs are Omeprazole (Prilosec©) and Lansoprazole (Prevacid©) PPI medications can interfere with vitamin B12 absorption from food by slowing the release of gastric acid into the stomach [31-33]. This is a concern because acid is needed to release vitamin B12 from food prior to absorption. So far, however, there is no evidence that these medications promote vitamin B12 deficiency, even after long-term use [34]. H2 receptor antagonists are used to treat peptic ulcer disease. Examples are Tagament©, Pepsid©, and Zantac© H2 receptor antagonists can interfere with vitamin B12 absorption from food by slowing the release of gastric acid into the stomach. This is a concern because acid is needed to release vitamin B12 from food prior to absorption. Metformin© is a drug used to treat diabetes. Metformin© may interfere with calcium metabolism [35]. This may indirectly reduce vitamin B12 absorption because vitamin B12 absorption requires calcium [35]. Surveys suggest that from 10% to 30% of patients taking Metformin© have evidence of reduced vitamin B12 absorption [35]. In a study involving 21 subjects with type 2 diabetes, researchers found that 17 who were prescribed Metformin© experienced a decrease in vitamin B12 absorption. Researchers also found that supplementation with calcium carbonate (1200 milligrams per day) helped limit the effect of Metformin© on vitamin B12 absorption in these individuals [35]. It is important to consult with a physician and registered dietitian to discuss the best way to maintain vitamin B12 status when taking these medications. Vitamin B12, folate, and vitamin B6 are involved in homocysteine metabolism. In fact, a deficiency of vitamin B12, folate, or vitamin B6 may increase blood levels of homocysteine. Recent studies found that supplemental vitamin B12 and folic acid decreased homocysteine levels in subjects with vascular disease and in young adult women. The most significant drop in homocysteine level was seen when folic acid was taken alone [48-49]. A significant decrease in homocysteine levels also occurred in older men and women who took a multivitamin/ multimineral supplement for 56 days [50]. The supplement taken provided 100% of Daily Values (DVs) for nutrients in the supplement. Evidence supports a role for supplemental folic acid and vitamin B12 for lowering homocysteine levels, however this does not mean that these supplements will decrease the risk of cardiovascular disease. Clinical intervention trials are underway to determine whether supplementation with folic acid, vitamin B12, and vitamin B6 can lower risk of coronary heart disease. It is premature to recommend vitamin B12 supplements for the prevention of heart disease until results of ongoing randomized, controlled clinical trials positively link increased vitamin B12 intake from supplements with decreased homocysteine levels AND decreased risk of cardiovascular disease. What is the health risk of too much vitamin B12? The Institute of Medicine of the National Academy of Sciences did not establish a Tolerable Upper Intake Level for this vitamin because Vitamin B12 has a very low potential for toxicity. The Institute of Medicine states that " no adverse effects have been associated with excess vitamin B12 intake from food and supplements in healthy individuals " [7]. In fact, the Institute recommends that adults over 50 years of age get most of their vitamin B12 from vitamin supplements or fortified food because of the high incidence of impaired absorption of B12 from animal foods in this age group. Getting an adequate amount of B12 National recommendations for B12 intakes vary significantly from country to country. The US recommended intake is 2.4 µgs a day for ordinary adults rising to 2.8 µgs for nursing mothers. The German recommendation is 3 µgs a day.§ Recommended intakes are usually based on 50% absorption, as this is typical for small amounts from foods. To meet the US and German recommendations you need to obtain sufficient B12 to absorb 1.5 µgs per day on average. This amount should be sufficient to avoid even the initial signs of inadequate B12 intake, such as slightly elevated homocysteine and MMA levels. Achieving an adequate B12 intake is easy and there are several methods to suit individual preferences. Absorption of B12 varies from about 50%, if about 1 µg or less is consumed, to about 0.5% for doses of 1000 µgs (1 mg) or above. So the less frequently you consume B12, the higher the total amount needs to be to give the desired absorbed amount. Frequent use of foods fortified with B12 so that about one microgram of B12 is consumed three times a day with a few hours in between will provide an adequate amount. Availability of fortified foods varies from country to country and amounts of B12 vary from brand to brand, so ensuring an adequate B12 supply from fortified foods requires some label reading and thought to work out an adequate pattern to suit individual tastes and local products. Taking a B12 supplement containing ten µgs or more daily provides a similar absorbed amount to consuming one µg on three occasions through the day. This may be the most economical method as a single high potency tablet can be consumed bit by bit. 2000 µgs of B12 consumed once a week would also provide an adequate intake.§ Any B12 supplement tablet should be chewed or allowed to dissolve in the mouth to enhance absorption. Tablets should be kept in an opaque container. As with any supplement it is prudent not to take more than is required for maximum benefit, so intakes above 5000 µg per week should be avoided despite lack of evidence for toxicity from higher amounts. All three options above should meet the needs of the vast majority of people with normal B12 metabolism. Individuals with impaired B12 absorption may find that the third method, 2000µg once a week, works best as it does not rely on normal intrinsic factor in the gut. There are other, very rare, metabolic defects that require completely different approaches to meeting B12 requirements. If you have any reason to suspect a serious health problem seek medical advice promptly. In the absence of any apparent dietary supply, deficiency symptoms usually take five years or more to develop in adults. References Herbert V. Vitamin B12 in Present Knowledge in Nutrition. 17th ed. Washington, D.C.: International Life Sciences Institute Press, 1996. Herbert V and Das K. 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