COBALAMIN (ALSO KNOWN AS VITAMIN B12)

Cobalamin, also known as vitamin B12, is one of the eight B-complex vitamins. Cobalamin cannot be manufactured by humans and is thus a true vitamin, obtained exclusively from the diet.

Cobalamin is an enzyme cofactor for only two human enzymes, yet they are in critical pathways: energy metabolism and methylation/folate metabolism. Among many other functions, some of the more critical requirements for cobalamin are in the function of the nervous system, including via the synthesis of myelin (white matter), and in the formation of red blood cells.

Cobalamin deficiency is fairly common, especially in individuals with diets poor in animal products, gastrointestinal conditions, and/or autoimmune disease. Deficiency might first present as a megaloblastic (large red blood cells) anemia. Functional symptoms are common, including fatigue, weakness, lightheadedness, constipation, diarrhea, loss of appetite, heart palpitations with shortness of breath. Neurological features are also common, and may in part be irreversible, including numbness or tingling, problems walking, loss of vision or taste, anxiety, depression, mania, psychosis, memory loss, or behavioral changes.

Multiple studies support the role of cobalamin in the treatment of autism and related brain disorders. Cobalamin, often along with folate and pyridoxine, is sometimes used to treat elevated levels of blood homocysteine, which is a risk factor for cardiovascular disease. Although used, its use in cognitive function and dementia have not been substantiated. Cobalamin is a common ingredient in “energy drinks”.

Methylcobalamin and 5-deoxyadenosylcobalamin are the active forms of cobalamin used in human enzymes. The form of cobalamin used in most nutritional supplements is cyanocobalamin. Methylcobalamin, the substrate for methionine synthtase, is also available as a supplement, and is preferred due to the lack of need to detoxify the cyanide component, however small, of cyanocobalamin. The body’s ability to absorb cobalamin from the gut is limited by the availability of intrinsic factor, which is the reason that injectable forms of cobalamin are employed in many studies related to autism.

Cobalamin is water-soluble and excessive amounts are excreted by the kidneys, so toxicity is unlikely. Far higher dosages are frequently provided by injection in children with ASD. Side effects are rare at usual doses used in oral supplementation.

Laboratory testing can reveal the presence of a deficiency of this nutrient, but this test often fails to reveal deficiencies that are mild. The preferred test is to measure blood methylmalonate and homocysteine levels, which are elevated even in mild cobalamin deficiency. Decreased brain and/or spinal cord myelination is another sign of potential cobalamin deficiency.