Vitamin B12, a water-soluble vitamin, is unique in being the first cobalt-containing substance found to be essential for longevity, and it is the only vitamin that contains essential mineral elements. It cannot be made synthetically but must be grown, like penicillin, in bacteria or molds. Animal protein is almost the only source in which B12 occurs naturally in foods in substantial amounts. Liver is the best source; kidney, muscle meats, fish, and dairy products are other good sources.
Vitamin B12 is necessary for normal metabolism of nerve tissue and is involved in protein, fat, and carbohydrate metabolism. B12 is closely related to the actions of four amino acids, pantothenic acid, and vitamin C. It also helps iron function better in the body and aids folic acid in the synthesis of choline. B12 helps the placement of vitamin A into body tissues by aiding carotene absorption or vitamin A conversion. It also aids in the production of DNA and RNA, the body's genetic material.
Vitamin B12 is prepared for absorption by two gastric secretions. It is poorly absorbed from the gastrointestinal tract unless the "intrinsic factor," a mucoprotein enzyme, is present. Autoimmune reactions in the body can bind the intrinsic factor, preventing B12 absorption. The intrinsic factor itself may not even be made because autoimmune reactions prevent the cells' ability to produce it. A defect in the molecule that transports B12 from the blood to the tissues can cause a deficiency even when a normal serum B12 level is read.
B12 needs to be combined with calcium during absorption to benefit the body properly. The presence of hydrochloric acid aids in the absorption of B12 given orally, and a properly functioning thyroid gland also helps B12 to be better absorbed.
After absorption, B12 is bound to serum protein (globulins) and is transported in the bloodstream to various tissues. The highest concentrations of B12 are found in the liver, kidneys, heart, pancreas, testes, brain, blood, and bone marrow. These body members are all related to red blood cell formation.
People deficient in B12 usually lack one or more gastric secretions necessary for its absorption. Many people lack the ability to absorb it at all.
The actual amount of B12 absorbed is regulated by the intrinsic factor. When intake is low, 60 to 80 percent of the vitamin is absorbed. When high amounts are taken, the absorption decreases to 5 to 10 percent. Absorption of B12 is better when it is taken with several meals instead of one. Absorption of B12 appears to decrease with age and with iron, calcium, and B6 deficiencies; absorption increases during pregnancy. The use of laxatives depletes the storage of B12.
Because of its close relationship with folic acid, both vitamins taken together could be of benefit in many cases.
Human requirements are minute but essential. The Recommended Dietary Allowance of vitamin B12 is 3 micrograms for adults and 4 micrograms for pregnant and lactating women. Infants require a daily intake of 3 micrograms, and growing children need 1 to 2 micrograms. A vegetarian diet frequently is low in vitamin B12 and high in folic acid, which may mask a vitamin B12 deficiency. No cases of vitamin B12 toxicity have been reported, even with large doses.
Deficiency Effects and Symptoms
Symptoms of a vitamin B12 deficiency may take 5 or 6 years to appear, after the body's supply from natural sources has been restricted.15 A deficiency of vitamin B12 is usually due to an absorption problem caused by a lack of the intrinsic factor. It can also be the result offish tapeworm infestation or excessive bacteria in the stomach and intestines. Symptoms of a deficiency begin with changes in the nervous system such as soreness and weakness in the legs and arms, diminished reflex response and sensory perception, difficulty in walking and speaking (stammering), and jerking of limbs.
Lack of B12 has been found to cause a type of brain damage resembling schizophrenia. This brain damage may be detected by the following symptoms: sore mouth, numbness or stiffness, a feeling of deadness, shooting pains, needles-and-pins, or hot-and-cold sensations. The British Medical Journal (March 26, 1966) stated editorially, "It is true that vitamin B12 deficiency may cause severe psychotic symptoms which may vary in severity from mild disorders of mood, mental slowness, and memory defect to severe psychotic symptoms . . . occasionally, these mental disturbances may be the first manifestations of B12 deficiency. ..."
Vitamin B12 deficiency also manifests itself in nervousness, neuritis, unpleasant body odor, menstrual disturbances, and difficulty in walking.
If a deficiency is not detected in early stages, it may result in permanent mental deterioration and paralysis. When symptoms become serious, do not try to treat them yourself. Consult a doctor.
Beneficial Effect on Ailments
Injections of B12 can be used to treat patients suffering from pernicious anemia, an ailment characterized by insufficient red blood cells in the bone marrow. Injections rather than oral doses of B12 are used to bypass the absorption defect in pernicious anemic patients. B12 helps the red blood cells to mature up to a certain point, and after that, protein, iron, vitamin C, and folic acid help to finish the development of the cells so that they can mature. Like folic acid, vitamin B12 has been effective in the treatment of the intestinal syndrome sprue.
The Medical Press reported remarkable results in the treatment of osteoarthritis, a degenerative joint disease, and osteroporosis, a softening of the bone, with vitamin B12 (see Human Tests). The condition known as "tobacco amblyopia," a dimness of vision or a loss of vision due to poisoning by tobacco, has been improved with injections of vitamin B12 whether or not the patient stopped smoking. Symptoms are blackouts, headaches, and farsightedness.
B12 has provided relief of the following symptoms: fatigue, increased nervous irritability, mild impairment in memory, inability to concentrate, mental depression, insomnia, and lack of balance. B12 also has been used successfully in the treatment of hepatitis, bursitis, and asthma.
Studies have confirmed that B12 improves the growth rate of children. In animal experiments, pregnant females' resistance to infection was considerably enhanced when given more-than-normal amounts of the vitamin. Vitamin B12 is important in reproduction and lactation. It helps to reduce the effects of bruising and black eyes. It has been successfully used for hangovers, leg paralysis, and atrophy of the brain's cerebellum. Under certain circumstances, B12 can protect the liver from injury caused by toxic substances.