VITAMIN B
ture, for night vision, and for protecting
the linings of the respiratory, digestive,
and urinary tracts against infection.
Vitamin A is absorbed by the body in
the form of retinol.This is found in liver,
fish-liver oils, egg yolk, dairy produce,
and is added to margarines.
C a ro te n e
,
which the body converts into retinol, is
found in various vegetables and fruits.
DEFICIENCY
Vitamin A deficiency is rare in deve-
loped countries. In most cases, it is due
to
m a la b s o r p t io n
.
Vitamin A deficiency
may also result from long-term treat-
ment w ith certain
lip id - lo w e r in g d r u g s
.
Deficiency is common in some devel-
oping countries due to poor diet.
The first symptom of deficiency is night
blindness, followed by dryness and eye
inflammation (see
x e ro p h t h a lm ia ), k e ra -
to m a la c ia
(damage to the cornea), and
eventually blindness. Deficiency also caus-
es reduced resistance to infection, dry
skin, and, in children, stunted growth.
EXCESS
Prolonged excessive intake of vitamin A
can
cause
headache,
nausea,
loss
of
appetite, skin peeling, hair loss, and
irregular menstruation. In severe cases,
the liver and spleen become enlarged.
Excess vitamin A, especially in the form
of retinol, has been linked with an
increased risk of bone fractures. Exces-
sive intake during pregnancy may cause
birth defects. In infants, excessive intake
may
cause
skull
deformities,
w hich
disappear if the diet is corrected.
MEDICAL USES
The drug
t re tin o in
(a derivative of vita-
m in A) is used to treat severe
a c n e
.
v ita m in B
See
v ita m in B 12; v ita m in B c o m p le x .
v ita m in B 12
A water-soluble
v ita m in
that plays a vital
role in the activities of several
e n z y m e s
in the body. Vitamin B12 is important in
the production of the genetic material
of cells (and thus in growth and devel-
opment),
in the
production
of red
REFERENCE NUTRIENT INTAKE (RNI) FOR SELECTED VITAMINS
The table (below) gives the reference nutrient intake (RNI)
RNI for males and females, when they are different, are
of vitamins for which amounts have been established; the
denoted by the letters M and F.
Vitamin
Birth
- 6
6
months
1-3
4-6
7-10
11-14
15-18
19-50
51+
Extra needed:
months
-1 year
years
years
years
years
years
years
years
Pregnancy
Breast-feeding
Folic acid
(mcg/day)
50
50
70
100
150
200
200
200
200
+100
+60
Niacin
(mg/day)
3
5
8
11
12
m 15
F12
M 18
F14
M 17
F13
M 16
F 12
0
+2
Vitamin B6
(mg/day)
0.2
0.4
0.7
0.9
1.0
M 1.2
F 1.0
M 1.5
F 1.2
M 1.4
F 1.2
M 1.4
F 1.2
0
0
Riboflavin
(mg/day)
0.4
0.4
0.6
0.8
1.0
M 1.2
F 1.1
M 1.3
F 1.1
M 1.3
F 1.1
M 1.3
F 1.1
+0.3
+0.5
Thiamine
(mg/day)
0.2
0.2
0.5
0.7
0.7
M 0.9
F 0.7
M 1.1
F 0.8
M 1.0
F 0.8
M 0.9
F 0.8
+0.3
+0.2
Vitamin A
(mcg/day)
350
350
350
400
500
M 600
F 600
M 700
F 600
M 700
F 600
M 700
F 600
+100
+350
Vitamin B12
(mcg/day)
0.3
0.4
0.5
0.8
1.0
1.2
1.5
1.5
1.5
0
+0.5
Vitamin C
(mg/day)
25
25
30
30
30
35
40
40
40
+10*
+30
Vitamin D **
(mcg/day)
8.5
7
7
0
0
0
0
0
10f
+10
+10
V
Vitamin E
There is no recommended intake for vitamin E. The
amount that is needed depends on the amount of
polyunsaturated fatty acids in the diet. There is some
evidence that high levels ofvitamin E protect against
cancer and heartdisease, although intake of high levels
are not yet recommended. The safe daily intake is up to
4 mg for males and up to 3 mg for females.
Units
* For last trimester only
mg = milligrams
** Vitamin D
is derived from sunlight. Certain
(thousandths of a gram)
individuals or at-risk groups may require dietary
mcg = micrograms
vitamin D
(millionths of a gram)
* For people aged 65 years or more only
794
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