Arginine
The amino acid arginine is considered
semi-essential, since adults manufacture sufficient quantities of Arginine;
however during periods of growth, a dietary source of arginine is required.
Therefore, arginine is necessary for growth, but not for maintenance, of the
body.
Arginine helps remove ammonium from the body,
facilitates immune function, and promotes the secretion of several hormones,
including glucagon, insulin and growth hormone.* Arginine is also a
precursor to nitric oxide, which aids blood vessel dilation.*
Carnitine
The body is able to synthesize carnitine from
the amino acids lysine and methionine, therefore Carnitine is considered
non-essential. Carnitine is utilized in the complex process which releases
energy from fat.* Rare genetic limitations can interfere with the body’s
production of carnitine and result in a deficiency of this amino acid.*
Glutamine
The amino acid glutamine can be synthesized
from glutamate and glutamic acid and so is non-essential. Glutamine serves
as a source of fuel for cells lining the intestines.* Glutamine is the
dominant amino acid in blood and cerebrospinal fluid. It is necessary for
the synthesis of other non-essential amino acids.
Lysine
As an essential amino acid, Lysine plays
several roles in the body, including the regulation of nitrogen balance and
the absorption of calcium.* Lysine is also important in the formation of
collagen.* Research suggests that lysine may play a role in blood pressure
maintenance, cholesterol levels, and the body’s susceptibility to certain
viruses.*
Cysteine and N-acetyl Cysteine (NAC)
Cysteine, another non-essential amino acid,
is one of the few amino acids which contains sulfur. The functions of
cysteine and NAC include being a component of the important antioxidant
glutathione and helping to produce the amino acid taurine. In addition,
cysteine strengthens the protective lining of the stomach and intestines,
has a role in the proper function of the immune system and can be converted
into glucose to be used as a source of energy.*
Histidine
Histidine is another semi-essential amino
acid, since adults generally produce adequate amounts, while production may
not be adequate during periods of growth. Histidine is also a precursor of
histamine, a compound released by immune system cells during an allergic
reaction, auto-immune response or trauma. Research reports that histidine
levels may be low in some individuals with arthritic conditions.*
Methionine
Methionine, an essential amino acid,
supplies sulfur and other compounds required by the body for normal
metabolism and growth. Methionine also belongs to a group of compounds
called lipotropics (the others in this group include choline, inositol, and
betaine). As a lipotropic, methionine helps the liver to metabolize fats.*1
Methionine, along with lysine, is also used by
the body to produce carnitine.* Excessive methionine intake, particularly if
B-vitamin intake is inadequate, can increase the conversion of methionine to
homocysteine—which in turn may cause high homocysteine levels, adversely
affecting the heart.*
Ornithine
Ornithine is manufactured by the body when
another amino acid (arginine) is metabolized during the production of urea.*
Some research suggests that ornithine promotes muscle building activity in
the body, but other research does not support this claim.*
Phenylalanine
This essential amino acid can be converted to
tyrosine, which in turn, is used to manufacture L-dopa, epinephrine and
norepinephrine.* Phenylalanine can also be converted (through a separate
pathway) to phenylethylamine, a naturally-occurring substance in the brain
which may play a role in mood.*1 DL-phenylalanine is a mixture of
the L-phenylalanine form of the amino acid and its mirror image D-phenylalanine.
It has similar functions as the L-phenylalanine form.*,
Tyrosine
Non-essential tyrosine can be synthesized
from phenylalanine. Tyrosine is the precursor of several neurotransmitters,
including L-dopa, dopamine, norepinephrine, and epinephrine.* Tyrosine is
formed by skin cells into melanin.* Thyroid hormones also contain tyrosine
as part of their structure.*
Taurine
Non-essential Taurine can be manufactured
from methionine (with the exception of infants). Taurine serves as a
constituent of bile acids, which in turn are needed in the absorption of
fats and fat-soluble vitamins.* Other important functions of taurine may
include the regulation of calcium and potassium levels in the heart.*
Diabetics have been found to have lower blood levels of taurine since it has
an influence upon blood sugar levels.*
