Nutritional Support for Brain, Heart & Skeletal Muscle Health
L-carnitine is sometimes referred to
as Vitamin Bt because of its vitamin-like roles. The body needs lysine,
methionine, Vitamin C, iron, niacin, and Vitamin B-6 to produce limited
quantities of L-carnitine, mainly in the liver and the kidneys.
L-carnitine
is found in small amounts in the diet, primarily in red meat. Mutton
and lamb are the richest sources, whereas chicken and turkey contain
much less; dairy products contain only small amounts of L-carnitine.
The
typical daily diet of a non-vegetarian supplies approximately 50 mg of
L-carnitine. However, some researchers argue that human beings consumed
500 mg or more of this nutrient throughout most of pre-history. Stone
Age humans ate a diet that was very high in hunted meat.
In the human body, L-carnitine is
concentrated in the heart and the skeletal muscles, and also in the
brain and in the sperm. Research into L-carnitine supplements has found
that different forms of L-carnitine may be better suited for enhancing
brain and nervous tissues, on the one hand, and muscle tissues, on the
other hand.
For
instance, forms with attached acetyl-groups cross the blood-brain
barrier and therefore fall into the first category, whereas forms with
attached Krebs Cycle intermediates fall into the second category.
Carnitine - Essential for Energy
Although L-carnitine is usually referred to as an amino acid, this is technically incorrect since there is no amino (NH2)
group present in the molecule. The primary role of L-carnitine in the
body is as a biocatalyst or coenzyme. One of its most important
functions is in the oxidation of long chain fatty acids, a process that
takes place inside the mitochondria, the "energy factories" of the
cells. This process is known as beta-oxidation (the rate at which fats are oxidized/burned to supply energy).
L-carnitine converts into an enzyme,
acetyl-carnitine transferase that shuttles fatty acids into the
mitochondria and removes waste afterwards. Fats are the preferred
source of fuel for the skeletal muscles, and even more so for the heart
muscle. As much as 70% of the energy generated in muscle tissues comes
from the oxidation of fats!
L-carnitine also increases the rate of
oxidation of fats in the liver. This suggests that L-carnitine plays a
role in improving energy generation, as well. Some authors argue that
in proper amounts, L-carnitine supplementation during dieting helps to
reduce the negative effects of ketosis (the accumulation of waste
products of fat metabolism) in those who are susceptible to this
problem.
Similarly,
there is evidence that some forms of obesity may be related to a
genetic propensity to produce less L-carnitine. Liver and kidney
problems will reduce the body's production since some four fifths of
our total L-carnitine is produced internally by these organs.
L-Carnitine for Sports and Protection
L-carnitine has a definite place in
the supplements taken by the amateur and weekend athlete. Research
shows that individuals who supplement with L-carnitine while engaging
in an exercise regimen are less likely to experience muscle soreness.
Moreover,
L-carnitine has been given to people with chronic sub-optimal lung
function in trials investigating how the body responds to exercise. In
these double blind reports, 2 grams of L-Carnitine taken twice per day
for two to four weeks led to positive changes in breathing response
during exercise.
However, the belief that L-carnitine's
effect on energy release will help to build muscle or to improve
athletic performance requires qualification. The experiences of healthy
athletes with supplementation have been mixed up. Of course, the
results with well-trained athletes likely are not appropriate for
comparisons with those of individuals suffering from excess weight or
related difficulties.
Current
findings indicated that the mixed results came about because many
researchers did not know what to look for or did not employ the
appropriate dosage levels. As indicated above, L-carnitine
supplementation in an experimental study reduced at least some of the
after-effects of strenuous exercise.
One way in which L-carnitine may aid
the athlete is by acting locally in the muscle tissues as an
antioxidant. L-carnitine penetrates into the mitochondria themselves,
where most of the free radicals of our tissues are generated through
the oxidation of food for energy.
There
is some evidence that L-carnitine serves to spare antioxidants, such as
Vitamin C, although the mechanism by which this is done has not yet
been uncovered. This protection would be in addition to the antioxidant
protection given to neurons by protecting against the superoxide
radical.
The Krebs Cycle Carnitines: L-Carnitine Fumarate and Ester Carnitine
The Krebs Cycle is a major component
in the body's energy pathways. Various intermediate products of the
Krebs Cycle have their own special roles in physiology, but also can be
used as additional materials for energy production.
The
heart, in particular, may benefit. The effects upon the heart include
improvements in energy production and other parameters. Supplemental
L-carnitine was associated with significantly higher concentrations of
pyruvate, ATP and creatine phosphate (crucial components in energy
production) in portions of the heart muscle during conditions of
extreme stress. Similarly, in tests upon peripheral circulation,
L-carnitine was found to be quite useful for improving blood flow.
L-carnitine Fumarate is L-carnitine
that has been stabilized by the addition of fumaric acid to the
molecule. L-carnitine Fumarate is a stable and bio-available carnitine
salt supplying 58% carnitine and 42% fumarate.
Fumarate
is an intermediate in energy production in the Krebs Cycle. It also
helps to maintain the production of other intermediates via a process
known as anaplerosis (filling up or replenishing Krebs Cycle
intermediates). As such, it is an active complement to carnitine.
The champion in the area of Krebs
Cycle carnitines, however, is Ester Carnitine. Ester Carnitine is
glycine propionyl-L-carnitine. This is a new and patented L-carnitine.
Ester Carnitine (GPLC) is the first and only Muscle Specific Carnitne.
The focus of this form of L-carnitine is on the muscles, such as the
heart, and the vascular system. Compared with at least one other form
of L-carnitine, propionyl-L-carnitine appears to produce greater
increases in cellular L-carnitine concentrations.
Researchers
believe that it is transported more easily into muscle fibers and may
better support muscle-cell energy production, perhaps because it
increases the flow of pyruvate into the Krebs Cycle.
Propionyl-L-carnitine also exhibits significant free radical scavenging
activity and helps to reduce blood from coagulating too readily.
Athletes
in particular may be pleased with the benefits of GPLC. In addition to
the benefits from propionyl-L-carnitine, GPLC includes the amino acid
glycine. Glycine may improve the uptake of carnitine from the intestine
and also support Phase 2 detoxification in the liver.
Brain Health, Acetyl-L-Carnitine
Many authorities point out that
acetyl-L-carnitine more readily crosses the blood-brain barrier than do
other forms of L-carnitine. Moreover, in the human brain, the
acetylation of L-carnitine is a normal event. This is one explanation
sometimes given for the greater activity found with acetyl-L-carnitine
than with other forms of L-carnitine in conditions involving the brain.
Acetyl-L-carnitine influences neuronal
levels of acetylcholine, a major neurotransmitter responsible for
memory and proper brain function, but supporting its synthesis and
functions. Acetyl-L-carnitine also enhances the release of dopamine
from neurons and helps it bind to dopamine receptors.
As
the brain ages, the ability to synthesize and utilize acetylcholine and
dopamine declines. Researchers have discovered that acetyl-L-carnitine
further acts as an antioxidant within the brain, that is stabilizes
cell membranes, and enhances energy production within brain cells. Source: Jarrow Formulas
View our Selection of Products
Scientific References
Brass EP, Scarrow AM, Ruff LJ, Masterson KA, Van Lunteren E. Carnitine delays rat skeletal muscle fatigue in vitro. J Appl Physiol. 1993 Oct;75(4): 1595-600.
Brevetti G, Fanin M,
De Amicis V, Carrozzo R, Di Lello F, Martone VD, Angelini C, Changes in
skeletal muscle histology and metabolism in patients undergoing
exercise deconditioning: effect of propionyl-L-carnitine. Muscle Nerve. 1997 Sep;20(9): 1115-20.
Carta A et al. Acetyl-L-carnitine and Alzheimer's disease: Pharmacological considerations beyond the cholinergic sphere. Ann N Y Acad Sci. 1993;695: 324-326.
Costell M, O'Connor JE, Grinsolia S. Age-dependent decrease of carnitine content in muscle of mice and humans. Biochem BioPhys Res Commun 1989;161(3): 1135-1143.
Fiori L, Rampello L.
L-acetylcarnitine attenuates the age-dependent decrease of
NMDA-sensitive glutarnate receptors in rat hyppocampus. Acta Neurol (Napoli) 1989;11(5): 346-350.
Hiatt WR, Regensteiner
JG, Creager MA, Hirsch AT, Cooke JP, Olin JW, Gorbunov GN, Isner J,
Lukjanov YV, Tsitsiashvili MS, Zabelskaya TF, Amato A.
Propionyl-L-carnitine improves exercise performance and functional
status in patients with claudication. Am J Med. 2001 Jun 1;110(8): 616-22.
Huertas R et al. Respiratory chain enzymes in muscle of endurance athletes: Effect of L-carnitine. Biochem BioPhys Res Commun 1992;188:102-106.
Marconi C. Effects of L-carnitine loading on the aerobic and anaerobic performance of endurance athletes. Eur J Appl Physiol 1985;54(2):131-135.
Ruggiero FM et al. Effect of aging and acetyl-L-carnitine on the lipid composition of rat plasma and erythrocytes. Biochem BioPhys Res Commun 1990;170(2):621-626.
Schonekess BO, Allard
MF, Lopaschuk GD. Propionyl-L-carnitine improvement of hypertrophied
heart function is accompanied by an increase in carbohydrate oxidation.
Circ Res. 1995 Oct;77(4):726-34.
Swart I et al.
The effects of L-carnitine supplementation on plasmea carnitine levels
and various performance parameters of male marathon athletes. Nutrition Research 1997;17:405-414.
Taglialatela G, Navarra D, Olivi A, et al. Neurite outgrowth in PC12 cells stimulated by acetyl-L-carnitine arginine amide. Neurochem Res 1995 Jan;20(1):1-9.
Vermeulen RCW, Scholte
HR. Exploratory Open Label, Randomized Study of Acetyl- and
Propionylcarnitine in Chronic Fatigue Syndrome. Psychosomatic Medicine. 2004;66:276-282.
Wutzke KD, Lorenz H.
The effect of L-carnitine on fat oxidation, protein turnover, and body
composition in slightly overweight subjects. Metabolism. 2004
Aug;53(8):1002-6.
Zhi-Quan He et al. Body weight reduction in adolescents by a combination of measures including using L-carnitine. Acta Nutrimenta Sinica 1997;19(2): 146-151.
| 
