L-carnitine is a nutritional supplement that has been touted by body builders and other athletes as a safe and helpful way to create bigger and more efficient muscles. Some physicians and researchers have looked at L-carnitine to prevent muscle wasting in people who need kidney dialysis; alternative medicine purveyors suggest that L-carnitine may stop cellular aging. In order for you to make a healthy decision about using L-carnitine, we've put together some information any potential buyer should have.
What is L-carnitine, anyways?
L-carnitine is a modified amino acid, produced in the liver. Most amino acids form the building blocks of proteins, which in turn provide much of the structure and function of the body. L-carnitine is different than amino acids in that it doesn't form a part of a protein; instead it serves as a delivery van, moving fats into specialized parts of our cells, where they can be used for energy.
Several conditions can result in lowered L-carnitine levels, including:
-rare genetic (hereditary) conditions
-loss of L-carnitine during dialysis (the mechanical process used to clean the blood in patients whose kidneys can't manage it)
-certain persons (for example, premature babies) who may not get enough L-carnitine in their diets and cannot make adequate amounts in their livers
Where can I get some?
Most people synthesize (make) enough L-carnitine for their needs in the liver. You can also get significant amounts in your diet from:
Even strict vegetarians generally make enough that they don't need to eat meat to have the needed L-carnitine ; they can also get small amounts from sources like avocado, whole wheat bread and asparagus.
Should I be taking L-carnitine supplements?
People who have a liver condition that doesn't allow L-carnitine to be synthesized need to take L-carnitine supplements in order to survive; this is also the case for people who are born with kidneys that excrete L-carnitine in large amounts.
Because L-carnitine is so important in creating energy, many people swear by it to enhance their athletic activity. They feel that this is particularly important in their muscles, which often need lots of energy in order to increase in size (as in body building) and to function over long periods of time (in marathon runners).
Unfortunately, studies to date have not shown conclusively that supplementation improves athletic performance or muscle bulk. Some research suggests though that larger studies need to be done to see if there is an effect on certain types of exercise or certain sub-groups of athletes.
There is a little more evidence that L-carnitine may be useful for people with conditions that lead to loss of L-carnitine, for example:
*Aging. Some studies suggest that energy and memory losses may in part be due to decreased levels of L-carnitine in older rats and mice; L-carnitine has been shown to partially reverse these changes. Large studies are planned to see if L-carnitine has this effect on aging humans
*Heart damage. Several studies in humans suggest that L-carnitine supplementation after myocardial infarction (heart attack) may help the heart repair damaged cells and help it function better. L-carnitine even seems to help people who are having angina - the pain that sometimes precedes heart attack.
*Muscle loss from kidney disease. The Food and Drug Administration (FDA) has approved the use of L-carnitine in dialysis patients to prevent and treat carnitine deficiency that is caused by kidney disease and dialysis. While it does not work for all patients who experience muscle weakness and loss, it is available as an alternative if standard treatments aren't working.
The Short Answer...
Unless you have one of a few specific conditions, it's not yet clear whether L-carnitine will help you with your goals. Since for some people (including those with seizure disorders, who have Alzheimer's disease, or who are pregnant and nursing) L-carnitine supplements may be dangerous, your best bet might be to wait until more information is available.
Brass E., "Supplemental carnitine and exercise," American Journal of Clinical Nutrition, Volume 72, issue supplement 2, p 618S-623S, 2002
Davini P, et al "Controlled study on L-carnitine therapeutic efficacy in post-infarction," Drugs Under Experimental and Clinical Research, Volume 18, issue 8, p 355-365, 1992
Hagen T., et al. "Feeding acetyl-L-carnitine and lipoic acid to old rats significantly improves metabolic function while decreasing oxidative stress," Proceeds of the National Academy of Science, Volume 99, issue 4, p1870-1875, 2002
National Kidney Foundation, "Adult Guidelines for Maintenance Dialysis: L-carnitine," update 2000
Sakurauchi Y, et al., "Effects of L-carnitine supplementation on muscular symptoms in hemodialyzed patients," American Journal of Kidney Disease, Volume 32, p258-264, 1998.
Sein, H., "Carnitine and its precursor, gamma-butyrobetaine," In: Kramer K, et al, eds. Nutraceuticals in Health and Disease Prevention, New York: Marcel Dekker, Inc, p 217-256, 2001
Wachter, S. et al, "Long-term administration of L-carnitine to humans: effect on skeletal muscle carnitine content and physical performance," Clinica Chimica Acta, Volume 318, issues 1-2, p. 51-61, 2002
Copyright (C) Shoppe.MD and Ian Mason, 2004-2005
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