Vitamin B12

Vitamin B12

DEFINITION
Vitamin B12 or Cobalamin is a member of the B group vitamins
that are essential for the growth and replication of cells in the
body.
DESCRIPTION
Vitamin B12 is a water-soluble vitamin that is stored in the
liver. Vitamin B12 is absorbed from the stomach using a special
‘carrier’-like substance called intrinsic factor. Intrinsic factor
is secreted by the stomach lining and it tightly binds Vitamin B12
and helps it pass through the intestinal lining and into the blood.
Any abnormal production of this intrinsic factor can result in
Vitamin B12 deficiency. Vitamin B12 is important for the activity
of certain enzymes within calls that control fat, amino acid and
carbohydrate metabolism (enzymes are special substances that speed
up reactions in the body). Both Vitamin B12 and the vitamin folate
are essential for the production of genetic material in the body
(DNA and RNA). Vitamin B12 deficiency prevents the body from using
folate properly, which causes abnormal red blood cells to be
produced that are too large, few in number and unable to carry
oxygen very effectively. There is little evidence that very large
doses of Vitamin B12 cause any ill health effects (i.e. Vitamin B12
toxicity), as some people are given very high doses of Vitamin B12
on a monthly basis because they cannot absorb this vitamin from the
food they eat.
MEDICAL USE
Always consult your Health Professional to advise you on
dosages and any possible medical interactions. Vitamin B12 is used
medically both as oral supplements and in injection form to treat a
number of diseases and conditions. Oral supplements may sometimes
be given to people who do not eat animal products (e.g. vegans) or
those whose dietary intake is inadequate (e.g. alcoholics) to
prevent or treat Vitamin B12 deficiency. People who have had part
of their intestines removed during a surgical procedure may also be
at risk of Vitamin B12 deficiency because they cannot absorb this
nutrient. Certain people do not produce adequate amounts of the
intrinsic factor that is essential for absorption of Vitamin B12.
These people may be given Vitamin B12 injections to prevent
deficiency and anaemia. Poor dietary intake in some older people
may result in mild deficiency of Vitamin B12 that may be managed
using injection of this vitamin. Certain medications, such as the
proton pump inhibitor drug omeprazole, can reduce the amount of
Vitamin B12 absorbed by the body. People taking these medications
may also require Vitamin B12 injections.
DEFICIENCY
Vitamin B12 deficiency can take some time to appear after a
person stops receiving adequate amounts of this nutrient, because
the liver stores a supply of about 5 years worth of Vitamin B12.
Vitamin B12 deficiency affects the blood and the nervous system.
The cells in the blood divide rapidly and need to copy their
genetic material frequently, but Vitamin B12 deficiency prevents
them from doing this normally. This causes abnormally large red
blood cells to be produced, a condition called macrocytic (or
megaloblastic) anaemia. Vitamin B12 deficiency also causes
irreversible damage to the nervous system. A thick, protective
sheath surrounds the nerves in the brain and body that helps the
nerves to conduct messages. Vitamin B12 deficiency causes damage to
this thick sheath as well as the death of nerve cells. This results
in numbness and loss of feeling in the hands and feet, unsteadiness
and uncoordination, confusion, moodiness, loss of memory and even
loss of central vision. Vitamin B12 deficiencies in pregnant women
increases the risks of their developing child having a
malformations called neural tube defect. The neural tube is a
foetal structure that develops into the spine and spinal cord. One
type of neural tube defect is spina bifida.
SOURCES
Vitamin B12 is found only in animal products. High levels are
found in foods such as organ meats (liver, kidney etc.), bivalve
molluscs such as clams and oysters, and at moderate levels in egg
yolks, muscle meat, poultry, fish, fermented cheeses and dry
milk.
DOSAGE
The recommended dietary intake for Vitamin B12 is 2 micrograms
per day for adults, but women who are pregnant require 3 micrograms
per day and who are lactating require 2.5 micrograms per day. Much
larger dosages may be recommended by a Doctor to prevent or treat
Vitamin B12 deficiency.