Vitamin B12 is an essential water-soluble vitamin that plays several roles in your body. It is the only water-soluble vitamin that can be stored in the body in small amounts for years. Since your body does have some B12 on hand at all times, it may take a while to notice the effects of a deficiency. Having a vitamin B12 deficiency can lead to several neuropsychiatric disorders, but your doctor needs to check your B12 levels to determine if a deficiency is the cause.
How B12 Functions
Vitamin B12 has a more complex structure than other vitamins. It is the only vitamin that attaches to a mineral, cobalt, to function. Methylcobalamin and 5-deoxyadenosyl are the two forms of B12 that have biological activity in the human body. B12 helps your body use amino acids that power your brain. Not only is it essential for normal neurological function, it also works to synthesize DNA and RNA, the genetic material found in all cells. Without adequate amounts of B12 in your system, certain neurological disorders may occur, as well as damage to DNA and RNA. For normal health, you need 2.4 mcg of B12 daily, but your doctor may suggest larger doses to recover from a deficiency.
Neuropsychiatric features of disorders are abnormalities in specific areas of higher brain function, including the limbic system, which controls feelings and emotions. Disorders can include attention deficit disorder, or ADD, dementia, epilepsy or some sort of head trauma. These disorders can have features such as depression, anxiety, irritability, memory impairment and psychosis. While genetics can play a role in each of these, having a B12 deficiency may also be a cause.
Consequences of Low B12 Levels
Vitamin B12 helps protect nerve cells by maintaining the myelin sheath, which is the protective coating surrounding nerves. If the myelin sheath sheath breaks down, neurological dysfunction occurs. Low B12 levels result in dramatic cognitive decline, causing neuropsychiatric features associated with certain disorders. In particular, B12 reduces accumulation of beta-amyloid plaque. This harmful compound stems from iron, copper and zinc buildup in the brain, turning into hydrogen peroxide that attacks and kills brain cells. Since these effects progress slowly over time, they may not be reversible. Research published in the "The American Journal of Clinical Nutrition" in 2007 showed that low levels of B12 in the body are associated with cognitive decline. Vitamin B12 helps maintain normal homocysteine levels. This amino acid is elevated in patients with dementia, particularly in Alzheimer's. Certain populations have a greater risk for B12 deficiency and should take proper measures to ensure adequate B12 levels are maintained.
Causes of a B12 Deficiency
Vitamin B12 is attached to protein in animal foods and is released by acids in the stomach for absorption. Once it is released, it binds with a glycoprotein called "intrinsic factor" in the duodenum, and is sent to the ileum of the small intestine for absorption. According to research published in the "American Family Physician" in 2003, having inadequate intrinsic factor can cause a B12 deficiency since your body is not able to absorb the vitamin. Suffering from a gastrointestinal disorder, such as irritable bowel syndrome or Crohn's disease, limits absorption of nutrients and may increase your risk of deficiency. Additionally, since B12 comes primarily from animal foods, vegetarians or vegans have a high risk for deficiency. Senior citizens are another population at risk, since diet is often limited and digestion slows down with age.
- "American Family Physician": Vitamin B12 Deficiency; Robert C. Oh and David L. Brown; March 2003
- Linus Pauling Institute: Vitamin B12; August 2007
- Pacific Neuropsychiatric Institute: What Is Neuropsychiatry and Behavioral Neurology?
- "The American Journal of Clinical Nutrition"; Low Vitamin B12 Status and Risk of Cognitive Decline in Older Adults; Robert Clarke, et al; November 2007
- "Neurology"; Homocysteine and Holotranscobalamin and the Risk of Alzheimer Disease; Dr. B. Hooshmand; October 2010