What Is It
Also known as cobalamin, vitamin B12 was the last vitamin
to be discovered. In the late 1940s it was identified as the
substance in calf's liver that cured pernicious anemia, a
potentially fatal disease primarily affecting older adults.
Vitamin B12 is the only B vitamin the body stores in large
amounts, mostly in the liver. The body absorbs B12 through
a very complicated process: Digestive enzymes in the presence
of enough stomach acid separate B12 from the protein in foods.
The vitamin then binds with a substance called intrinsic factor
(a protein produced by cells in the stomach lining) before
being carried to the small intestine, where it is absorbed.
Low levels of stomach acid or an inadequate amount of intrinsic
factor-both of which occur with age-can lead to deficiencies.
However, because the body has good reserves of B12, it can
take several years for a shortfall to develop.
What Does It Do
Vitamin B12 is essential for cell replication and is particularly
important for red blood cell production. It maintains the
protective sheath around nerves (myelin), assist in converting
food to energy, and plays a critical role in the production
of DNA and RNA, the genetic material in cells.
Common Uses
• Prevents a form of anemia.
• Helps reduce depression.
• Thwarts nerve pain, numbness, and tingling.
• Lowers the risk of heart disease.
• May improve multiple sclerosis and tinnitus.
Prevention
Moderately high blood levels of homocysteine, an amino acid-like
substance, have been linked to an increased risk of heart
disease. Working with folic acid, vitamin B12 helps the body
process homocysteine and so may lower that risk. Because of
its beneficial effects on the nerves, vitamin B12 may help
prevent a number of neurological disorders, as well as the
numbness and tingling often associated with diabetes. It may
also play a part in treating depression.
Additional Benefits
Research shows that low levels of vitamin B12 are common in
people with Alzheimer's disease. Whether this deficiency is
a contributing factor to the disease or simply a result of
it is unknown. The nutrient does, however, keep the immune
system healthy. Some studies suggest that it lengthens the
amount of time between infection with the HIV virus and the
development of AIDS. Other research indicates adequate B12
intake improves immune responses in older people. With its
beneficial effect on nerves, vitamin B12 may lessen ringing
in the ears (tinnitus). As a component of myelin, it is valuable
in treating multiple sclerosis, a disease that involves the
destruction of this nerve covering. And through its role in
cell replication, B12 may improves symptoms of rosacea.
How Much You Need
The RDA for vitamin B12 is 2.4 mcg a day for adults. But,
many experts recommend that you get 100 to 400 mcg. Supplements
of vitamin B12 are very important for older people and vegans
(who eat no meat products).
If You Get Too Little: Symptoms of a vitamin
B12 deficiency include fatigue, depression, numbness and tingling
in the extremities caused by nerve damage, muscle weakness,
confusion, and memory loss. Dementia and pernicious anemia
can develop; both are reversible if caught early.
The level of B12 in the blood decreases with age. People with
ulcers, Crohn's disease, or other gastrointestinal disorders
are at risk, as are those taking prescription medication for
epilepsy (seizures), chronic heartburn, or gout. Excessive
alcohol also hinders absorption of vitamin B12.
If You Get Too Much: Excess vitamin B12 is
readily excreted in urine; there are no known adverse side
effects from a high intake of vitamin B12.
How To Take It
Dosage: A general dose of 1,000 mcg of vitamins B12
a day is useful for heart disease prevention, pernicious anemia,
numbness and tingling, tinnitus, multiple sclerosis, and roseacea.
If you’re deficient in B12, higher doses may be needed.
Or if you do not produce enough intrinsic factor, B12 shots
or a prescription nasal spray may be necessary; ask your doctor.
Guidelines For Use: Take vitamin B12 once
a day, preferably in the morning, along with at least 400
mcg of folic acid. Most multivitamins contain at least the
RDA of vitamin B12 and folic acid; B-complex supplements have
higher amounts. For larger therapeutic amounts, look for a
supplement with just vitamin B12 or B12 with folic acid. Using
a sublingual (under-the-tongue) form enhances absorption.
Other Sources
Animal foods are the primary source of B12. These include
organ meats, brewer's yeast, oysters, sardines and other fish,
eggs, meat, and cheese. Some breakfast cereals are fortified
with this vitamin as well.
Caution!
If you take a vitamin B12 supplement, you must also have a
folic acid supplement: A high intake of one can mask a deficiency
of the other.
Latest Findings
• Having a sufficient amount of vitamin B12 in the body
may slow the progression of HIV infection to AIDS, according
to a study of 310 HIV-positive men. On average, those with
low B12 levels developed AIDS within four years of the start
of the study, versus eight years in men who had higher B12
levels.
• Older people who have mildly low vitamin B12 levels
may not get the full protection from a pneumonia vaccine.
In a study of 30 elderly people, those with inadequate B12
stores produced fewer antibodies to the virus that causes
pneumonia after vaccination than those with sufficient levels
of B12. This low response would reduce their ability to fight
off the disease.
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