Also
referenced as: Carnitine and
carnitor.
L-carnitine should
not be confused with
Acetyl-L-Carnitine or Propionyl-L
Carnitine; as they are completely
different substances.
L-carnitine is
a key nutrient in the body's production of
cellular energy. It is
necessary for the body to utilize a
chief energy source, fatty acids.
L-carnitine also allows for
fatty acids to undergo
beta-oxidation in the mitochondria
of the cells. In order for a
fatty acid (which are typically very
long molecules) to enter the cell,
it must be bound to a specific
enzyme (coenzyme A) to form a
complex known as fatty acyl-Coenzyme
A. L-carnitine serves as a
"gatekeeper," and is responsible for
moving the fatty acyl-Coenzyme A
molecule into the cell for
utilization in the energy
processes. [1]
Carnitine has many
applications in the areas of health and well-being. However, carnitine has been marketed
for many other purposes that while
not fully validated, do have
interesting theoretical applications
based on the actions of this
nutrient in the body.
L-carnitine
is, technically, an amino acid.
It is found in the highest quantities in
protein-based food sources (e.g. meats), with less in
dairy products and comparatively
little or none found in fruits,
vegetables, or cereals
(as evidenced by their low overall
protein content). [2] Carnitine is synthesized in the body
from two primary amino acids: methionine and lysine;
both of which are
available components of most
protein sources. The kidney plays a
role in maintaining levels of carnitine in the body by preventing
its loss through urination. Typically, the large majority of carnitine is reabsorbed in the
kidneys rather than lost. Reabsorbtion of carnitine becomes
even more efficient if the body is
low in this amino acid. [3]
Because of the
widespread implication of
carnitine's mechanism of action within the body,
there are several applications for
its use. Primarily, L-carnitine
is used to supplement people
suffering from specific genetic
conditions or 'inborn errors of
metabolism'; in which they are
unable to synthesis or retain this
amino acid. L-carnitine
is also widely employed as an adjunctive
nutritional nutrient for those
undergoing hemodialysis (artificial
blood filtration due to kidney
damage). Supplementation with
L-carnitine in this circumstance
has been shown to augment red blood cell and
hemoglobin numbers. [4]
Additionally, the use of L-carnitine in end
stage renal disease (and subsequent
hemodialysis) is sanctioned by the
Food and Drug Administration. [5]
L-carnitine
can also be used to treat overdose
of valproate (an anticonvulsant
drug) and muscle diseases resulting
as a side
effect from the administration of zidovudine and
isotretinoin. L-carnitine is
especially useful in strict
vegetarians, as their levels of this
amino (as well as levels of L-carnitine
precursor amino acids) may be
suboptimal.
Other uses of
L-carnitine include;
supplementation following heart
attack, stable angina, and
congestive heart failure. L-carnitine
is also commonly utilized in
premature infants. It may also be
supplemented in those with
chronic fatigue syndrome, leg ulcers,
and persons wishing to enhance exercise
performance. The intravenous
administration of L-carnitine has
been used to bolster CD-4 cell
levels in people with HIV/AIDS and
in patients receiving TPN (total
parenteral nutrition).
Typically,
L-carnitine is dosed at one to two
grams, twice per day. Higher end
doses have been reported and may
reach up to 6
grams per day. [6]
|
L-Carnitine
Deficiencies and
Toxicities |
L-Carnitine
Deficiencies
Frank deficiency of
L-carnitine is relatively rare, with
the exception of those born with
metabolic errors in which carnitine
becomes deficient. L-carnitine
deficiency may occur at some level
in long-term vegetarians, vegans, or
those on protein-restrictive
diets. As mentioned earlier,
a
deficiency of L-carnitine will
occur in those with kidney failure
who are undergoing hemodialysis; as
this artificial blood filtration
mechanism cannot retain L-carnitine
as efficiently as the kidneys. Deficiency
may also arise from taking certain
pharmaceutical drugs such as zidovudine (for treatment of HIV)
and isotretinoin (for severe acne
and other skin conditions).
L-Carnitine
Toxicities
Side effects
reported when taking L-carnitine
(either orally or intravenously) include;
nausea, vomiting, diarrhea,
seizures, heartburn, body odor, and
gastrointestinal (GI) distress. [7] Some people may have the presence of
an L-carnitine metabolite that may
lead to foul smelling urine, breath,
and sweat. [8] A certain mixture of L-carnitine and
its isomer D-carnitine have been
administered together with negative
results. This included
symptoms of muscle wasting,
weakness, and discolored urine (due
to myoglobinuria). The compound,
DL-carnitine is thought to allow
D-carnitine to competitively inhibit
the action of L-carnitine in the
body, leading to a L-carnitine
deficiency state. [9]
L-Carnitine
Interactions:
-
Herbs/Supplements:
D-carnitine may interfere with
L-carnitine in the body; high doses
may lead to L-carnitine deficiency
symptoms. [9,
10]
-
Laboratory tests:
L-carnitine may elevate CD4
and CD8 cell counts in people with
HIV/AIDS. [11,
12] L-carnitine may elevate HDL
cholesterol and decrease
triglyceride levels in children
with type IV hyperlipoproteinemia. [13]
-
Disease conditions:
L-carnitine may negatively
affect thyroid hormone activity in
some susceptible people; it should
be avoided in people with
hypothryoidism. [14] Some people with a medical history
of seizures may experience an
increase in number or severity of
seizures when taking L-carnitine; the mechanism of this is
action remains unknown.
-
Drugs:
Several
pharmaceutical medications can
lower endogenous levels of
carnitine; supplementing with carnitine
may be considered when taking
these drugs: Carbamazepine,
cefditoren pivoxil
pivampicillin, phenobarbital,
phenytoin,
valproic acid,
and zidovudine. [15,
19]
The following table lists various
products that contain a safe and
reliable source of L-Carnitine:
|
Manufacturer |
Ingredient |
Amount |
US RDA |
Learn More |
|
NSI |
L-Carnitine (Fumerate) |
--
|
500mg |
Click Here
 |
|
GNC |
L-Carnitine (L-Tartrate) |
-- |
500mg |
Click Here
 |
|
Natrol |
L-Carnitine
(Free Form) |
-- |
500mg |
Click Here
 |
