VITAMIN B-12 (Cobalamin, Cyanocobalamin)

General - water-soluble; anti-pernicious anaemia factor;

• Most complex vitamin;
• Resembles plant pigment chlorophyll & blood pigment heme, but contains cobalt instead of magnesium (plant) or iron (blood);
• Only vitamin that contains a metal;
• For absorption, requires intrinsic factor, a mucoprotein present in gastric juice of normal individuals, but absent in individuals with defective gastric secretion or genetic condition;
• Supplementation with intrinsic factor helps those unable to produce their own, but does not significantly increase B-12 absorption in normal individuals;
• History: found that raw liver cures pernicious anaemia in 1926 (Nobel Prize awarded in 1934); isolated in 1948; synthesized in 1973;

Nutrition

• Sources: best: fish, dairy, organ meats (esp. liver & kidney); good: eggs, meats; poor: small (insufficient) quantities are present in spirulina, sea vegetables, fermented soy products (tempeh), & other vegetarian sources;
• Supplements: B-12, B-complex, multi-vitamin, multi-mineral-vitamin formulations; intramuscular injections;
• Absorption: of conjugated cobalamin occurs in illeum of small intestine, where intrinsic factor is released; 60 - 80% of low intake absorbed; 5 - 10% of high intake absorbed; increased during pregnancy; many small doses absorbed better than few large ones;
• Improved by: presence of intrinsic factor; calcium, presence of vitamin C, B-6, other B-complex vitamins & hydrochloric acid;
• Antagonized by: alcohol, lack of HCl & intrinsic factor (hereditary or age-related); deficiency of iron, B-6 & calcium; potassium blocks absorption;
• Transport: to liver and through the bloodstream by several different globulin proteins;
• Stability: destroyed by light & alkali; over 50% is in unstable form, destroyed in processing & food preparation; remainder is in stable form; stable to acid & oxidation;
• Storage: mainly in liver, bone marrow, kidneys, heart, pancreas & brain; high levels in blood of healthy individuals; depleted by laxatives;
• Excretion: in bile, urine, saliva;
• Metabolism: works in conjunction with folic acid; conversion to active form of B-12 requires B-2, B-3 & manganese;
• Interactions: anti-gout medications & anticoagulants may block absorption; aspirin & its substitutes, codeine, antibiotics, laxatives, oral contraceptives interfere with functions;

Functions of B-12

• Participates in physiological activities basic to growth & division of all healthy cells; especially important in rapidly dividing cells;
• Involved in synthesis of nucleic acid (DNA);
• Essential for function of several enzymes involved in amino acid & fatty acid metabolism;
• Involved in fat & carbohydrate metabolism;
• Involved in metabolism of liver, kidneys, nervous system, heart, skin, muscle & bone;
• Maintains healthy nervous tissue; keeps anti-oxidant glutathione - involved in several enzymes of carbohydrate (brain energy) metabolism - in active (reduced -SH form);
• Necessary for metabolism of iron, folic acid & glucose; helps turn folic acid into active form; aids in formation of folic acid; produces single-carbon units which folic acid transfers from one substance to another; releases folacin from methyl folacin stored in liver (B-12 deficiency produces folacin deficiency); helps folic acid to make choline;
• Together with folic acid, B-12 regulates formation of healthy red blood cells, providing methyl (CH3) groups for DNA of dividing cells; lack of CH3 prevents cell division & produces undivided giant red blood cells (megaloblasts);
• Promotes nitrogen retention & raises biological value of proteins, leading to more rapid growth per unit of food (animals); antibiotics in feeds may speed animal growth by killing bacteria that destroy B-12;
• Growth factor in underweight children, along with improvement in diet;
• Maintains fertility, normal growth & development;
• Closely related to functions of 4 amino acids (methionine-homocysteine, glycine, serine, glutamic acid), & vitamins B-5 & C; improves iron function;
• Helps bring vitamin A into tissues; helps absorb & convert carotene to vitamin A;

Quantities

• Measurement: micrograms (mcg);
• Optimum: (SONA) average 2 to 3 μg/day;
• Individual optimum must be established for each individual;
• Minimum: (DRI) set at 2.4μg/day;
• Less than RDA: 30%, according to a U.S. government survey;
• Deficiency: micrograms quantities of B-12 can be difficult to obtain, due to dietary deficiency; impaired absorption; lack of intrinsic factor, transfer proteins (trans-cobalamin I & II), stomach hydrochloric acid (HCl), or calcium, all of which are essential for absorption; tapeworm or bacteria in stomach & intestines; increased requirement;
• At risk: vegan diets provide insufficient vitamin B-12 & need to be supplemented; deficiency develops slowly in vegan adults (10+ years); vegan children (small stores of B-12 to draw on) may show deficiency 2 - 3 years after birth; HCl production decreases with age & elderly individuals require more cobalamin;
• Symptoms include: pernicious anaemia, characterized by inability of bone marrow to produce normal, healthy red blood cells;
• Prolonged pernicious anaemia can result in brain damage &/or severe neuritis, including degeneration of nerves & spinal cord;
• Sub-clinical deficiency may include: tenderness in legs; slow reflexes; memory loss; irritability & mood swings; red-tipped sore tongue (like B-3 deficiency, without white coating); impaired sensory perception; anaemia; fatigue, loss of appetite & constipation; laboured breathing; palpitation; headache; difficulty walking; stammering & jerking;
• Toxicity: injections of more than 1,000 μg/day cause no ill effects; low absorption rate suggests that oral intake of 10 times that amount will produce no adverse effects;

Therapy with cobalamin

• Usual therapeutic doses range from 3 to 1,000 μg/day;
• Injected B-12, or large oral doses, reverse clinical & sub-clinical symptoms;
• Powerful rejuvenating & energizing effects; especially useful during periods of stress, fatigue, recovery from illness (even when B-12 normal by standard measures;
• Improves memory, reasoning ability, concentration; dispels mental disturbances, prevents mental deterioration;
• Restores appetite & vigour; helps patients recover from viral & bacterial infections;
• Effective for treating osteoarthritis, osteoporosis, bursitis & asthma;
• Protects against smoking-induced cancer (smokers have abnormally low levels of B-12 & folic acid ); smoke reduces levels of B-12 & folate in lung tissue;
• 2,000 - 4,000 mcg sublingually protects against toxins & allergens, especially sulphites (food & wine additives);
• Massive oral doses or injections help people lacking intrinsic factor;
• Keeps those eating vegan or macrobiotic diets from deteriorating due to B-12 deficiency;
• Intrinsic factor can also be supplemented together with B-12;