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Beta
Carotene Is The Safe Form Of Vitamin A
Author: ©Darrell Miller
The fact that beta carotene is stated to be a safe form of vitamin
A suggests that vitamin A is in some way unsafe. In fact an overdose
of vitamin A can lead to any one of a number of conditions, including
nausea, jaundice, vomiting, abdominal pain and headaches. This
vitamin is fat soluble, and so any excess is not easily washed
out of the body but can build up in the tissues.
Toxicity in the liver can occur at fairly low concentrations,
and the toxicity of the vitamin is increased by excessive alcohol
intake. However, toxicity only occurs with vitamin A already formed
such as that obtained from liver.
There are several forms of vitamin A, including the retinoid form
originating from animal sources and the carotenoid forms that
have a vegetable origin. Carotenoids are converted to vitamin
A in the liver, but the higher the concentration of beta carotene
in the body, the smaller the percentage that is converted to vitamin
A, so beta carotene is a safer source of vitamin A than retinoids.
It is only the finished form of vitamin A that is toxic, and beta
carotene is therefore self-regulating in its production.
This vitamin is stored in the body in the form of the alcohol
(retinol) and of retinyl esters. Studies have indicated that as
much as 95% if the stored vitamin is in the form of the ester.
The liver is responsible for releasing vitamin A to the body as
it is required. One of its better known effects is on vision,
and the old wives tale that carrots help you to see in the dark
has an element of truth in it.
In order for it to aid vision, retinol is oxidized to the aldehyde,
retinal, that forms a complex with a molecule of opsin, a light
sensitive protein found in the retina. Rhodopsin, as the complex
is called, is an essential component of the biochemical chain
of events that lead to the perception of light. It is extremely
sensitive, and enables you see in very low levels of light. In
other words it is essential for good night vision, so carrots
do help you to see in the dark! When a photon of light hits a
molecule of rhodopsin, it leads eventually to an impulse being
sent up the optic nerve to the brain.
One of its properties is its reaction to white light. When rhodopsin
is exposed to white light it loses its pigmentation, and hence
its photoreceptor properties and can take 30 minutes to regenerate.
That is why you lose your night sight if your retina is exposed
to bright light. The more rhodopsin you can generate the quicker
you develop night sight.
The other biochemical processes of the vitamin include the synthesis
of some glycoproteins and maintenance of normal bone density.
Without vitamin A, calcium is not properly absorbed by the body
and glycoproteins are involved in this process. A deficiency of
vitamin A can lead to the abnormal development of bone and other
health problems, so there are limits between the levels of vitamin
A in the body that must be maintained: above or below these limits
will lead to health problems, some of which can be extremely serious.
Most of the biochemistry of vitamin A in the liver is initiated
by the presence of alcohol, and otherwise it is though to passively
store the vitamin until needed when it is released into the blood.
There are several ways in which the presence of alcohol allows
the liver to deplete its store of retinol, but generally there
are a number of enzymes that, in the presence of ethanol, can
render vitamin A into a water soluble form that is excreted by
the urine.
The benefits of vitamin A other than its effect on night sight
and the healthy development of bone tissue, includes a powerful
antioxidant effect that neutralizes free radicals that can destroy
body cells. These free radicals are generated by the body's metabolism
in generating energy from blood glucose, and are also created
through exposure to pollutants such as cigarette smoke and traffic
fumes. They are electron deficient, so when they are generated
they grab an electron from tissue close by which destroys the
cells involved. This can lead not only to the appearance of premature
aging as the skin cells are damaged but also to serious health
problems such as atherosclerosis and some forms of cancer. Vitamin
A helps to protect against these by destroying the free radicals
before they can do damage. It also helps build up resistance against
infections by supporting the immune system.
Beta carotene is converted to vitamin A either by cleaving at
the center of the molecule, or by breaking it down from one of
the ends. This latter process is carried out in the small intestine,
and the resultant vitamin stored in the liver in the ester form.
Only a proportion of what you eat is converted to retinol ester
in this way, and the more beta carotene you consume, the less
is converted, so you can never suffer from an overdose of beta
carotene-derived vitamin A. It might turn you yellow, but you
won't suffer from excess vitamin A since the excess beta carotene
is stored in your body fat, including the subcutaneous fat reserves.
Alpha carotene can also be used in the synthesis of vitamin A,
but not as actively as beta carotene. The best natural sources
are fruits and vegetables, especially the red, yellow and orange
varieties such as carrots and apricots, and also the leafy green
vegetables, although supplements are also a convenient way of
maintaining your beta carotene uptake. It is a much safer supplement
than straight vitamin A for the reasons explained earlier. The
supplement is not useful just for its antioxidant effect, but
also for its ability to protect you from excessive exposure to
the sun. While not as effective as a good sun blocker, beta carotene
does provide some protection.
There is no doubt that beta carotene is a safer way to maintain
an adequate vitamin A uptake due to the fact that you cannot take
an overdose, since an overdose of beta carotene does not translate
into the same dose of vitamin A, and the change is self-regulating.
It is therefore safer to obtain your vitamin A needs from colored
fruits and vegetables or beta carotene supplements than from eating
liver, from which the retinol is in a form that can cause damage
in the event of consuming an excess.
The old adage that you should never eat polar bear livers is a
true one, and certainly has a provable scientific basis, so use
beta carotene as your main vitamin A source for maximum health
benefits in the safest possible way.
About
the Author: More information on beta carotene vitamin
A can protect and heal the body at VitaNet ®, LLC Health
Food Store. http://vitanetonline.com/
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