Vitamin B12 Benefits & Side Effects

vitamin pills falling from the bottle
Pills of soluble vitamin B-12 spill out from a container onto a white counter.. (Image: Sergej Petrakov/iStock/Getty Images)

Vitamin B-12 is an essential water-soluble vitamin involved in a variety of bodily functions. Foods rich in vitamin B-12 include fish, meat, poultry, eggs and fortified cereals. in addition to food sources, the vitamin is available as a prescription medication and a dietary supplement. Adequate intake of vitamin B-12 offers many health benefits, but deficiencies can lead to side effects such as anemia or memory loss. Toxicity is rare, as the body easily expels excess amounts of water-soluble vitamins.

Blood and Nerve Cells

Vitamin B-12 plays a major role in red blood cell formation and nerve cell maintenance, according to the Office of Dietary Supplements. The body requires B-12 during DNA synthesis, particularly rapid synthesis, such as during blood cell formation in the bone marrow. In the nervous system, vitamin B-12 functions in the metabolism of fatty acids involved in the formation of the myelin sheath around nerve cells. Myelin insulates nerve cells and increases the speed of electrical impulses between nerve cells. The breakdown of myelin, due to a lack of vitamin B-12, can be detrimental, leading to a variety of neurological and neuromuscular disorders.

Homocysteine and Cardiovascular Health

High levels of homocysteine – a naturally occurring amino acid in the blood – link to an increased risk of cardiovascular disease. Elevated levels promote blood clot formation, narrowing and hardening of the arteries, and nerve cell damage, according to the Office of Dietary Supplements. Vitamin B-12 plays a major role in the conversion of homocysteine to methionine, an essential compound in the body. Thus, vitamin B-12 is beneficial in the breakdown of homocysteine and prevention of diseases associated with homocysteine damage.

Vitamin B-12 Deficiency

Vitamin B-12 deficiency is rare in healthy children and adults, but affects approximately 10 to 15 percent of individuals over age 60, according to an article in the a 1999 issue of "Annual Reviews in Nutrition." The deficiency is most often due to intestinal absorption problems of the vitamin and not dietary intake. Anemia, or lack of red blood cells, is a common side effect of vitamin B-12 deficiency, leading to fatigue and shortness of breath. Neurological problems associated with B-12 deficiency include peripheral neuropathy, nerve damage and paresthesia – a feeling of numbness or tingling of the skin. Psychiatric conditions linked to deficiencies include dementia, depression, personality changes and memory impairments, according to an article in a 2003 issue of "American Family Physician."

Side Effects and Interactions

Although rare, side effects from vitamin B-12 can occur. It may cause mild diarrhea, heart palpitations and chest pain, anxiety and breathing problems. Sleep may also be disturbed leading to insomnia. Vitamin B-12 may potentially interact with certain medications, so it is important to speak with a doctor before starting any new medications or dietary supplements. Medications that may interact with vitamin B-12 include certain antibiotics, proton pump inhibitors, H2 receptor antagonists to treat peptic ulcers, and certain glucose-controlling medications used in the treatment of diabetes, according to the Office of Dietary Supplements.

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