Evening star., 1940-04-27
Of Sturs, Men
And Atoms y.
Notebook Of Science Progress
In Field. Laboratory
And Study

In Field. Laboratory
And Study
"a By Thomas R.> Henry.
A veritable chemical Cinderella Is vita
min A.
Ten years ago 1t was recognized only as
preventive Of night blindness, an in
ability to see in dim light, which was so
extremely rare in the United States and
Western Europe that few physicians ever
had seen case Of 1t.
Today the substance is known as an
absolute essential to human and animal
life. Most Of the inner surfaces OF the
body are lined with askind Of Skin"
known as epithelial tissue. 1t lines, for
example, the digestive tract and separates
the living parts of the body from food
which has not yet been thoroughly di-
gested and from waste products which
are to be excreted.
With a total deficiency Of vitamin A, 1t
has been found, this epitheiium degener-
ates and its function as protective lay
er is largely destroyed. Life becomes i'm
possible.
One sees by chemical process brought
about when light falls on a substance
known as visual purple in the retina Of
the eye. This process sets up nerve i'm
pulses to the brain. The visual purple is
altered and must be regenerated. One OF
the chemical constituents of visual pur-
pie is vitamin A. Unless there is suffi-
cient supply Of it on hand the vital "see-
ing stuff" becomes diluted to the point
where it cannot function. In the end
there may be total blindness from which
there Is unlikely to be any recovery
There is no question, Department of
Agriculture specialists say, that def
cheney of vitamin A is very bad for the
eyes. Whether a more than adequate
supply is of any great benefit to the eyes
is more debatable. Folks tell marvellous
stories of failing eyesight restored by eat
ing carrots. but few of these are suscep-
tible to scientific proof
The vitamin demonstrably plays some
part in-normal bone development. Chill
dren with deficiency of it in their diets
grow defective teeth. Some authorities
claim it is the most serious Of all def
ciencies in the young. OF late the vita
min has received much publicity as
preventive Of infections, especially colds.
AS for this say Drs. Leila E. Booher and
Elizabeth c. Callison of the Department
of Agriculture, recent medical reports in
dicate that the substance has no specific
anti-lnfection properties, although there
may be some indirect relation.
when the body contains goodly store
OF vitamin A. they say, no further re-
sistance to infection can be secured by
the administration of increased amounts.
However, when the body Is suffering from
a moderate or severe deficiency most au-
thorities are agreed that there would be a
lowered resistance. 1t is important to
provide fairly liberal stores to bridge over
periods Of Illness. or emergencies attended
with low vitamin A intake"
In animals there is accumulating evi-
dence lack Of vitamin A may cause
sterility. This has not been demonstrated
for human beings.
Vitamin A, per Sc, exists only in ami
mails, or animal products, such as milk
and eggs. Animals make it In their own
bodies-so, Of course, do human beings
out of a lovely orange-yellow pigment.
1t is carotene, the stuff that makes car
rots yellow. There are three chemically
distinguishing forms Of carotene. One
leaves. 1t always accompanies the green
coloring matter of vegetation, chlorophyll,
which is the cornerstone of all life on
earth. 1t apparently is made in the same
way and is one of natures devices for
trapping the energy of sunlight. The
animal body changes these carotenes
into something which can be obtained in
the form of pale yellow crystals and is
the actual vitamin A.
1t now is recognized that there are at
least two and perhaps three or four
vitamin A forms, depending on which
kind of carotene is used as a starting
point. Each may eventually be consid-
cred separate vitamin. So far as known
the functions are very similar. 1t makes
very little difference whether one eats
the vitamin A itself or the things out of
which it can be manufactured, except in
cases of illness when the conversion may
be slow and inadequate.
The substance is contained in fish liver
oils, milk, butter, cheese and egg yolks.
The amounts in dairy products and eggs,
however, are quite variable, depending on
the amounts of carotene in the feed of the
cows and poultry.
Most leafy green and yellow vegetables
contain one or more Of the carotenes.
Red and yellow carrots yellow sweet po-
tatoes and ripe tomatoes are excellent
sources
The average adult human being, the
Department of Agriculture's specialists
calculate, should have about IL milli-
grams of vitamin A in the diet every day.
A milligram is about one thirty-thou-
sandth of an ounce. In a recent expert
ment there three subjects volunteered to
eat diets without any vitamin A. AS soon
as that which was stored in their own
livers was exhausted they soon reached
the point where they required ten times
as much light to see as when they were