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L-ornithine
DESCRIPTION
In adults, L-arginine and L-ornithine are "non-essential"
Amino Acids which means the body can make its own supply of
them. However a dietary supply of L-arginine is thought to
be essential for children because not enough can be made by
the juvenile body for the requirements of growth.
Like most other Amino Acids,
L-arginine is a component of body proteins. However, L-ornithine
is unusual in that it is not incorporated into proteins.
FUNCTIONS
Detoxification
L-arginine and L-ornithine both play an important part in
the urea cycle, which detoxifies ammonia (1). The liver, which
contains all the relevant enzymes in proper proportions, is
by far the most important site of urea cycle reactions.
Growth Hormone
L-arginine and L-ornithine also have the physiological role
of stimulating the pituitary gland to release growth hormone
(2). Growth hormone is very important in the growth and development
of children and in the addition of muscle in adults. It also
has the effect of improving the immune function of the thymus
gland and stimulating Wound healing.
Sperm
L-arginine is the precursor of two substances found in sperm
called spemidine and spermine. The amino acid is an extremely
rich component of seminal fluid, making up 80% of this substance.
SUPPLEMENTAL USES
Fertility
Several studies have reported the treatment of male Infertility
with arginine supplements. L-arginine may help to alleviate
male infertility, improving sperm production and motility
(2).
Wound Healing
Wound healing may also be speeded up by supplementing with
L-arginine and/or L-ornithine (3,4). It appears that these
two Amino Acids stimulate the formation of collagen - the
important connective tissue in Skin.
Muscle Tone
The theory that oral supplements of L-arginine and L-ornithine
can help to "slenderise" the body through burning
fat and stimulating muscle formation is not borne out by research
(2). For any effect in this area, high levels of
L-arginine and L-ornithine would be needed intravenously.
Cardiovascular Health
L-arginine improves the bioavailability of nitric oxide (a
powerful vasodilator) and therefore has a potential role in
heart health and circulation (5).
SAFETY
Up to 6g daily of L-ornithine
or L-arginine has been used safely on a short-term basis,
and up to 40g has been administered as a one-off without side
effects. However 500-2000 mg is the normally accepted level
for safe self-administration.
INTERACTIONS AND CONTRA-INDICATIONS
Herpes Simplex
L-arginine supplements should be avoided by those that have
a tendency to suffer from herpes simplex (cold sores), as
this amino acid can exacerbate the condition. (Consumption
of L-arginine rich foods such as chocolate, milk, meat, cheese,
nuts, popcorn and peas should be reduced as well).
L-ornithine does not have
the same stimulating effect on herpes simplex.
Schizophrenics
Neither L-ornithine nor L-arginine should be taken by schizophrenics.
N.B. L-ornithine is an unstable
nutrient and has to be present in the form of L-ornithine
hydrochlorida (HCl) in supplements.
REFERENCES
1. Gebhardt R, et al. Treatment
of cirrhotic rats with L-ornithine-L-aspartate enhances urea
synthesis and lowers serum ammonia levels. .J Pharmacol Exp
Ther, 283;1:1-6 1997.
2. The Healing Nutrients Within, E R Braverman & C C Pfeiffer,
Keats, 1987.
3. Ulland AE, et al. Altered Wound arginine metabolism by
corticosterone and retinoic acid. J Surg Res, 70;1:84-88 1997.
4. Albina JE, Abate JA, Mastrofrancesco B. Role of ornithine
as a proline precursor in healing Wounds. J Surg Res, 55;1:97-102
1993.
5. Chowienczyk P, Ritter J. Arginine: NO more than a simple
aminoacid? The Lancet, 350;9082:901-902 1997.
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