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| Vitamin B |
| The vitamin B group consists of a number of chemically
different substances. They are grouped together because they
have similar functions and they are often found together in
the same foods. The B complex group includes thiamine, or vitamin
B2, nicotinic acid, pyridoxine or vitamin B6, pantothenic acid,
biotin, folic acid and cyanocobalamin or vitamin B12. |
| The main function of most of the vitamin B group
is to act as co-enzymes in metabolic processes which are complex
chains of chemical reactions. For example, certain B vitamins
regulate the rate at which the chemical reactions leading to
the release of energy proceed. |
| Some B group vitamins, particularly folic acid
and vitamin B12, are required for building red blood cells and
for maintaining a healthy blood system. B group vitamins are
also needed for the transfer of impulses along nerves, and like
all other vitamins, they are essential for the growth of young
children. |
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| Dietary sources |
Thiamine - bread and flour, cereal foods, meat
potatoes, liver
Riboflavin - liquid milk, meat, liver, eggs
Nicotinic acid - meat and meat products, bread, flour and cereals,
vegetables and milk
Vitamin B12 - liver, fatty fish, meat, cheese, eggs, milk.
Yeast extract and wheatgerm are rich sources of B vitamins. |
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| Deficiency effects |
Milk deficiency may occur among some old people
causing mental confusion, sore tongue and cracks at the sides
of the mouth.
Thiamine deficiency may also be found among alcoholics. Some
people cannot absorb vitamin B12 even though their food supplies
adequate amounts of this vitamin. If untreated, such people
develop pernicious anaemia. |
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| Excessive intakes |
Being water-soluble vitamins, any dietary intake
in excess of requirement is soon excreted from the body. Some
B vitamins are also prescribed in very large doses as drugs.
For example, nicotinic acid is used in some treatment of schizophrenia.
These mega-doses have proved harmful in certain cases by causing
liver damage.
Stability of B group vitamins. |
| Of all the vitamins in this group, thiamine is
most easily destroyed. It is vulnerable to heat and is destroyed
during cooking. Riboflavin is also unstable in alkaline solutions
and is destroyed by sunlight. Nicotinic acid is a stable nutrient
and is lost only through its solubility in water. |
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- VITAMIN C |
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