Vitamin B12 deficiency

Vitamin B12 deficiency, also known as cobalamin deficiency, is the medical condition in which the blood and tissues have a lower than normal level of vitamin B12. Mild deficiencies may have few or absent symptoms. In moderate deficiencies, feeling tired, feeling faint, mouth ulcers, rapid breathing, upset stomach, pallor, hair loss, decreased ability to think and joint pain and the beginning of neurological symptoms, including abnormal sensations such as, numbness and tingling, and tinnitus may occur. Severe deficiencies may include symptoms of reduced heart function, suppression of bone marrow, as well as more various severe neurological symptoms possibly including sensory loss, abnormal balance and reflexes, memory and consciousness impairment, smell and taste problems, depression, irritability, confusion, and psychosis. If left untreated, some of these changes can become permanent. Onset of deficiency may take years to develop. In exclusively breastfed infants of vegan mothers, undetected and untreated deficiency can lead to poor growth, poor development, and difficulties with movement. In healthy adults, vitamin B12 deficiency is not common, mainly because body stores of the vitamin are substantial and turnover is slow, with relatively low dietary requirements. Risk factors may occur possibly more in elderly people due to impaired intestinal absorption, and in children, premenopausal women, and pregnant women, whose diets are low in animal foods. Causes are usually related to conditions that give rise to malabsorption of vitamin B12, particularly autoimmune gastritis in pernicious anemia. Other conditions giving rise to malabsorption include surgical removal of the stomach, chronic inflammation of the pancreas, intestinal parasites, certain medications such as long-term use of proton pump inhibitors, H2-receptor blockers, and metformin, and some genetic disorders. Deficiency can also be caused by inadequate dietary intake such as with the diets of vegetarians, and vegans, and in the malnourished. Elevated methylmalonic acid levels may also indicate a deficiency. Treatment is by vitamin B12 supplementation, either by mouth or by injection. If no reversible cause is found, or when found it cannot be eliminated, lifelong vitamin B12 administration is usually recommended. Vitamin B12 deficiency is preventable with supplements, which are recommended for pregnant vegetarians and vegans, and not harmful in others. Vitamin B12 deficiency in the US and the UK is estimated to occur in about 6 percent of those under the age of 60, and 20 percent of those over the age of 60. In Latin America, about 40 percent are estimated to be affected, and this may be as high as 80 percent in parts of Africa and Asia. Marginal deficiency is much more common and may occur in up to 40% of Western populations.

Signs, symptoms and complications

Vitamin B12 deficiency appears slowly and worsens over time, and can often be confused with other conditions. It may often go unrecognized, as the body becomes used to feeling unwell. Vitamin B12 deficiency can lead to anemia, neurologic, and digestive dysfunctions. A mild deficiency may not cause any discernible symptoms, but moderate deficiency can cause various symptoms, such as feeling tired, lightheadedness, cold intolerance, pale skin, sore tongue, upset stomach, loss of appetite, numbness or tingling (pins and needles) of the fingers and toes, and vision, cognitive or psychological problems. Severe vitamin B12 deficiency can damage nerve cells. If this happens, vitamin B12 deficiency may result in sense loss, loss of sensation in the feet, difficulty walking, poor balance, blurred vision, changes in reflexes, muscle weakness, decreased smell and taste, decreased level of consciousness, mood changes, memory loss, depression, irritability, clumsiness, disorientation, dementia and, in severe cases, psychosis. Tissue deficiencies may negatively affect nerve cells, bone marrow, and the skin. Clinical manifestations, such as low blood pressure, and low-grade fevers, and dark circles around the eyes, may occur. A further complication of severe deficiency is the neurological complex known as subacute combined degeneration of spinal cord. also myelosis funicularis, or funicular myelosis. This complex consists of the following symptoms:

Impaired perception of deep touch, pressure and vibration, loss of sense of touch, very annoying and persistent paresthesias Ataxia of dorsal column type Decrease or loss of deep muscle-tendon reflexes Pathological reflexes – Babinski, Rossolimo and others, also severe paresis. The presence of peripheral sensory-motor symptoms or subacute combined degeneration of the spinal cord strongly suggests the presence of a B12 deficiency instead of folate deficiency. Methylmalonic acid, if not properly handled by B12, remains in the myelin sheath, causing fragility. Dementia and depression have been associated with this deficiency as well, possibly from the under-production of methionine because of the inability to convert homocysteine into this product. Methionine is a necessary cofactor in the production of several neurotransmitters. Each of those symptoms can occur either alone or with others. Vitamin B12 is essential for the development of the brain. Its deficiency can cause neurodevelopmental problems, which can be partly reversible with early treatment. Only a small subset of dementia cases are reversible with vitamin B12 therapy. Tinnitus may be associated with vitamin B12 deficiency. Vitamin B12 deficiency may accompany certain eating disorders or restrictive diets.

Pernicious anemia Pernicious anemia is a disease caused by an autoimmune response that produces antibodies that attack the parietal cells in the stomach lining, preventing them from creating intrinsic factor needed for the absorption of vitamin B12. It occurs in only about 2-3% of the population over the age of 65. It is the main and most common cause of vitamin B12 deficiency anemia in developed countries, and is characterized by a triad of symptoms:

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