Vitamins
Vitamins
are a group of organic substances
that mammals and humans are not able to produce consequently they are necessary
for life. They regulate our metabolism through enzyme system. A
single
deficiency can endanger the whole body.Vitamins can be easly supplied through a
varied andbalanced diet as they are needed only in small amounts. They can be
divided into two main groups:fat-soluble vitamins (A, D, E, and K) and
water-soluble vitamins (the B group of vitamins and vitamin
C). Unlike fat-soluble vitamins , water soluble-vitamins are not stored by the
body and can be lost from food through the processes of storing, preparation and
cooking ( they can also be temperature-dependent). It is therefore necessary
that adequate amounts of the water-soluble vitamins are included in the daily
diet .The exact requirement of most vitamins for an adult of average size is
known, althoughmore may be required
during lactation, pregnancy, illness and strenous work. Growing children need
more than in proportion to body weight. There are a variety of
factors that influence vitamin deficiency other than diet intake:
Physiologic
factor |
Vitamin
affected |
Comments |
Endogenus
synthesis |
D,
K, B6, Biotin |
|
Enteroepatic
circulation |
A,
polar metabolites of vitamin D, folic acid, cobalamin |
|
Dietary
intake |
All
except K, B6, biotin |
K,
B6, and biotin are probably
produced by
enteric bacteria |
Decreased
storage capacity |
Cobalamin,
A |
Stored
in liver |
Increased
utilization |
Folic
Acid |
Used
in increased amounts
during pregnancy,
hemolysis |
Increased
loss from body |
All |
During
malabsorption |
Nowdays
is very difficult to found in developed countries an absolute inadequacy of any
vitamins, although it is possible to find any partial deficiency. Vitamin are
classed in micro-nutrients since weneed only very small amounts of them in our
diet. Historically vitamins have been classified in simple alfabetic order (although
vitamin B is actually a group of vitamins rather than a single vitamin).
Vitamin |
Major
causes of deficiency |
Manifestation
of deficiency |
Sources |
A |
Fat
malabsorption, alcoholism |
Poor dark
adaptation, xerophthalmia,
bryness of skin |
cod liver oil,
spinach, carrot, cheese, butter,
eggs, margarine
fortified |
B1 thiamin |
Inadequate
intake, alcholism |
Cardiac failure,
peripheral neurophaty,
Wernicke's encephalopathy |
Brazil nouts,
brown rice, wholemeal bread,
peas, beans, and other pulses |
B2 riboflavin |
Inadequate
intake |
Angular
stomatitis, sore lips, cheilosis,
geographic tongue,
seborrheic dermatitis |
Milk, cheese,
yogurt, eggs, meat and offal
such as liver, green leafy
vegetables. Richest source yeast
extract |
Niacin |
Inadequate
intake, alcoholism, carcinoid
syndrome |
Dermatitis (photosensitive), dementia,
diarrhea |
Meat, poultry,
oily fish, cheese, milk, bread,
fortified breakfast cereals. Richest
sources: yeast extract, and
brewer's yeast |
B6 pyridoxine |
Inadequate
intake, old age, alcoholism |
Glossitis,
cheilosis, peripheral neuritis,
seborrheic dermatitis |
Wholemeal bread,
wheatbran, liver, bananas,
fish and nuts. Richest sources
dried brewers'yeast and yeast
extract |
B12 cobalamin |
Malabsorption,
pernicious anemia,
vegetarian diet |
Fatigue, anemia,
sore tongue, paresthesias |
Animal foods:
offal, meat, poultry, fish, eggs |
Biotin |
Total parenteral
nutrition |
Scaly dermatitis,
alopecia |
Dried brewer's
yeast, offal, yeast extract,
wheatgerm, wholemeal bread, milk,
brown rice, cheese, yogurth |
Folic acid |
Inadequate
intake, alcoholism, malabsorption,
hemolysis, pregnancy, drugs
such as anticonvulsivants,
methotrexate,
sulfasalazine |
Anemia, sore
tongue, diarrhea |
Liver, broccoli
and green cabbage, wheatgerm,
pulses, nuts, and yeast extract |
Panthotenic acid |
Spontaneous
human deficiency is
not clearly recognized |
Loss of
appetite, abdominal pain, tenderness
in the feet |
Dried brewer's
yeast, yeast extract, kidney,
nuts, soya flour, wheatgerm, eggs,
pulses, dried fruit |
C ascorbic acid |
Alcoholism,
inadequate intake (destroies
through poor handling,
cooking, processing) |
Fatigue,
ecchymoses, bleeding gums,
anemia |
Citrus fruits,
blackcurrants, kiwi strawberries,
broccoli, raw cabbage, peas,
potatoes |
D |
Fat
malabsorbtion, lack of sunlight, breast
milk-fed newborn |
Osteomalacia,
rickets, vertebral
fractures, muscle weakness |
Cod liver oil,
kippers, mackerel, canned salmon,
eggs and milk. Sunlight on
uncovered skin |
E |
Premature
infants, cystic fibrosis, fat
malabsorbtion, chronic biliary
obstruction |
Areflexia,
anemia, ophthalmoplegia |
Wheatgerm, nuts,
vegetable oils, eggs, green
leafy vegetables, wholemeal bread |
K |
Fat
malabsorbtion, excessive warfarin dose |
Bleeding |
Cauliflower,
brussels sprouts, broccoli,
spinach, liver, lean meat, potatoes, cow's milk |
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