What do we know about vitamin B12 deficiency?

Victoria, British Columbia by night. (Dr. Noorali Bharwani)
Victoria, British Columbia by night. (Dr. Noorali Bharwani)

Even after more than 100 years, vitamin B12 (cobalamin) is still the subject of intense research.

Vitamin B12 plays an important role in red blood cell formation, cell metabolism, nerve function and the production of DNA. As we know, the function of DNA is to store all of the genetic information that a person needs to develop, function, and reproduce.

Vitamin B12 is also necessary for normal bone marrow and central nervous system function. The vitamin is absorbed in the distal ileum (where the small bowel joins the large bowel). Its absorption in the distal ileum requires intrinsic factor.

Where can you find intrinsic factor?

Intrinsic factor is a natural substance normally found in the stomach. Lack of intrinsic factor leads to vitamin B12 deficiency and pernicious anemia, and can cause brain and nervous system problems. There may be cognitive decline. There may be peripheral neuropathy. Quite often the presentation can be very suttle and potentially serious.

Vitamin B-12 deficiency is associated with dementia and low cognitive function, but it’s not clear whether vitamin B-12 supplements might help prevent or treat dementia.

The discovery of vitamin B12

“The discovery of vitamin B12, the elucidation of its role in metabolism, and the effects and treatment of its deficiency occurred in distinct phases over more than 100 years, and it was the subject of two separate Nobel Prizes,” says an article in Ann Nutr Metab 2012 (The discovery of vitamin B12 – authors Scott and Molloy).

The next advance was made with the discovery that a gastric component, which was named intrinsic factor, was missing in pernicious anemia. Many years later, intrinsic factor was found to be a glycoprotein that formed a complex with vitamin B12, promoting its absorption through ileal receptors.

The article says vitamin B12 is still the subject of intense research and, in particular, its role in preventing some irreversible neurological lesions remains unclear.

The incidence of vitamin B12 deficiency increases with age. The condition affects five to 20 per cent of adults older than 60 years.

The main source of vitamin B12 is animal-based foods such as meat, fish, eggs, and dairy products. In addition, some vegetable-based foods have been fortified with vitamin B12.

Individuals who do not consume these foods are more susceptible to vitamin B12 deficiency.

Other common causes include autoimmune gastritis (which causes pernicious anemia), malabsorptive states (e.g., pos-gastrointestinal surgery), and certain medications like metformin, proton pump inhibitors and histamine-2 receptor antagonists.

Managing B12 deficiency

The recommended daily amount of vitamin B12 for adults is 2.4 micrograms. Most people get enough of it from a balanced diet.

But it is important to recognize that certain segment of the population is vulnerable to be B12 deficient. If left untreated, vitamin B12 deficiency can lead to anemia, fatigue, muscle weakness, intestinal problems, nerve damage and mood disturbances.

All people over 65 years of age who are malnourished, all people in institutions or psychiatric hospitals, and all people with hematological or neuropsychiatric symptom should have their serum B12 levels measured.

Older adults, vegetarians, vegans and people who have conditions that affect their ability to absorb vitamin B12 from foods might benefit from the use of oral supplements.

Vitamin B12 supplements also are recommended for women who are pregnant or breastfeeding. Vitamin B12 is transferred through the placenta to the fetus during pregnancy and through breast milk after birth. Infants who drink breast milk from a mother who consumes adequate amounts of vitamin B12 or infants who drink infant formula, will receive enough vitamin B12.

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