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L-CARNITINE
Physiology
and Clinical Effects
L-carnitine is made in the body from the amino acids lysine and methionine.
It is needed to release energy from fat. Its actions appear to be
particularly important in the heart. For congestive heart failure, much of
the research has used a modified form of carnitine called
propionyl-L-carnitine (PC). In one double-blind trial, using 500 mg PC per
day led to a 26% increase in exercise capacity after six months.1
Research shows
that individuals who supplement with carnitine while engaging in an
exercise regimen are less likely to experience muscle soreness.2
However, the belief that carnitine’s effect on energy release will help
build muscle or improve athletic performance has, so far, not been
supported by most research.3 4
However,
carnitine has been given to people with chronic lung disease in trials
investigating how the body responds to exercise.5 6
In these double-blind reports, 2 grams of carnitine BID for two to four
weeks led to positive changes in breathing response to exercise.
Food
Sources
Dairy and red meat contain the greatest amounts of carnitine. Therefore,
people who have a limited intake of meat and dairy products tend to have
lower carnitine intakes.
Deficiency
Risk and Symptoms
Carnitine deficiencies are rare, even in strict vegetarians, because the
body produces carnitine relatively easily.
Rare genetic
diseases can cause a carnitine deficiency. Also, deficiencies are
occasionally associated with other diseases, such as diabetes and
cirrhosis.7 8 A carnitine deficiency can also result from
oxygen deprivation which can occur in some heart conditions. In Italy,
carnitine is prescribed for heart failure, heart arrhythmias, angina
pectoris, and lack of oxygen to the heart.9
Recommended
Dosage
Most people do not need carnitine supplements. For therapeutic use,
typical amounts are 1–3 grams per day.
It remains
unclear whether the propionyl-L-carnitine form of carnitine used in
congestive heart failure research has greater benefits than the L-carnitine
form, since limited research in both animals and humans with the more
common L-carnitine has also shown very promising effects.10
Contraindications
L-carnitine has not been consistently linked with any toxicity.
The body needs
lysine, methionine, vitamin C, iron, niacin, and vitamin B6 to produce
carnitine.
References:
1. Mancini M,
Rengo F, Lingetti M, Sorrentino GP, Nolfe G. Controlled study on the
therapeutic efficacy of propionyl-L-carnitine in patients with congestive
heart failure. Arzneimittelforschung 1992;42:1101–4.
2. Giamberardino MA et al. Effects of prolonged L-carnitine administration
on delayed muscle pain and CK release after eccentric effort. Int J
Sports Med 1996;17:320–4.
3. Green RE, Levine AM, Gunning MJ. The effect of L-carnitine
supplementation on lean body mass in male amateur body builders. J Am
Dietet Assoc 1997;(suppl):A-72.
4. Murray MT. The many benefits of carnitine. Am J Natural Med
1996;3:6–14 [review].
5. Dal Negro R, Pomari G, et al. L-carnitine and rehabilitative
respiratory physiokinesitherapy: metabolic and ventilatory response in
chronic respiratory insufficiency. Int J Clin Pharmacol Ther Toxicol
1986;24:453–6.
6. Dal Negro R, Turco P, Pomari C, De Conti F. Effects of L-carnitine on
physical performance in chronic respiratory insufficiency. Int J Clin
Pharmacol Ther Toxicol 1988;26:269–72.
7. Dipalma JR. Carnitine deficiency. Am Family Phys
1988;38:243–51.
8. Kendler BS. Carnitine: an overview of its role in preventive medicine. Prev
Med 1986;15:373–90.
9. Del Favero A. Carnitine and gangliosides. Lancet 1988;ii:337
[letter].
10. Kobayashi A, Masumura Y, Yamazaki N. L-carnitine treatment for
congestive heart failure--experimental and clinical study. Jpn Circ J
1992;56:86–94.
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