L-Carnitine

L-Carnitine

17-06-2015
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What you can achieve by taking it
Faster recovery after workout
It promotes recovery after weight training by easing injuries in the muscle tissues. As a consequence, there will be more receptors available for responding to anabolic hormones than there would be without L-Carnitine.
Fat burning
If you exercise regularly, taking L-Carnitine can help you burn fat by transporting acyl-CoA (acyl-coenzyme-A)-bound activated fatty acids into the mitochondria, which will then “burn” them (use them up).

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Review

L-Carnitine (formerly called Vitamin BT; but since the human body is capable of producing it, it is not considered a vitamin) is a nitrogen-containing hydroxy-amino acid, which cannot be found in proteins. Its biosynthesis starts with the methylation of lysine. A lot of vitamins and minerals are required to ensure sufficient L-Carnitine synthesis; (especially iron, vitamin C, B12, betaine [a choline-derivative], niacin, magnesium and many other agents including methionine). L-Carnitine is synthesized in the livers, kidneys and brains of mammals in a proportion of approx. 0.16 to 0.48 mg/kilogram of bodyweight per day. The total carnitine reserves of a healthy human body make about 20 grams. L-Carnitine facilitates fat burning by transporting acyl-CoA (acyl-coenzyme-A)-bound activated fatty acids into the mitochondria. About 60 per cent of the heart’s energy consumption comes from fats. But remarkable fatty acid oxidation (breaking down of fats) is going on in other parts of the body, too, like in the skeletal muscles or the liver, especially at rest. In physically fit people, it goes on for most of the time during physical activity as well. Carnitine is indispensable for the transportation of long-chain fatty acids. In the outer membrane of the mitochondrion, carnitine will be connected to acyl-CoA (coenzyme A, which forms one complex with a fatty acid) by the enzyme carnitine acyltransferase I. The carnitine transport system will take the long-chain fatty acid to the energy-producing “organ” of the cell, where the enzyme carnitine acyltransferase II will separate the acyl-CoA from the transferring agent in the inner mitochondrial membrane. Thus the transferring agent (L-Carnitine) can get back to transporting more fatty acids. The process of breaking down fatty acids in the mitochondrion continues with beta-oxidation.

Experiments have been conducted on overweight people, and these have shown that the group in which the subjects received 1000 mg of L-carnitine daily for 3 months, have lost significantly more weight than the other group, which received no supplementation. However, other studies haven’t shown any positive effect on weight loss. The joint application of aspartate, asparagine and carnitine slowed down glycogen consumption in the muscles, while fatty acid consumption increased significantly (because both aspartate and asparagine are oxaloacetate precursors), which had an apparently positive impact on performance. Carnitine supplementation has clearly had positive effects in cases of venous disorders, cardiac decompensation, chronic fatigue and high triglyceride or high cholesterol levels (i.e. in case of deficiency). In case of an overactive thyroid, it can prevent the symptoms. (This is quite unusual for a fat burning supplement to influence the thyroid in this way.) And since it has little or no side effects, it can be applied successfully in treatment. L-Carnitine can also protect you from the undesirable consequences of a high-protein diet, i.e. the neurotoxic effects of higher ammonium levels. The exact mechanism has not been revealed yet. It might have something to do with the antioxidant properties of ALC. Experiments have shown that L-Carnitine has no measurable side effects in doses up to a few grams. Acetyl-L-Carnitine is one of the carnitine esters. Carnitine and its esters prevent the toxic accumulation of fatty acids and acetyl-CoA, and provide free coenzyme A for the cells, when needed. The effect of L-Carnitine on athletes has been examined a lot, and the results are quite controversial. There were scientists who have not experienced any improvement in performance during L-Carnitine supplementation of 1-2 grams per day. It is assumed that L-Carnitine supplementation is only effective in the case of insufficient synthesis (deficiency). Workout will make the carnitine concentration in the muscles drop, but there are no reliable data that could show, to what extent supplementation can influence it. Short-term application (like a few weeks) is not likely to bring about any significant change in the concentration of carnitine in the muscles. Furthermore, it may improve nitrogen balance, too (even though not to a remarkable extent). This means, it enhances protein absorption into the muscles, i.e. it has a slightly anabolic effect. It promotes recovery after weight training by easing injuries in the muscle tissues. As a consequence, there will be more receptors available for binding anabolic hormones than there would be without L-Carnitine. L-carnitine usage can also affect erectile dysfunction and/or infertility positively. So, whether you wish to recover completely from a steroid cycle or cure your symptoms that appear with age, L-Carnitine can help you. As scientific evidence, let us cite an experiment: the effects of testosterone undecanoate, propionyl-L-carnitine, acetyl-L-carnitine (ALC) and placebo were compared in the treatment of aging male symptoms. Scientists found that carnitine derivatives proved to be significantly more effective in improving nighttime erections and the International Index of Erectile Function than testosterone, and all this without undesirable side effects. Both L-carnitine and acetyl-L-carnitine (ALC) can be found in high concentrations in the epididymides and play critical roles in spermatozoa metabolism and spermatogenesis. They both affect sperm motility (the agility of spermatozoa) and have antioxidant properties as well. Reviewing literature, you can find several studies which prove that a daily dosage of 2-3 grams of L-carnitine and/or ALC significantly improves the quality and concentration of sperm, as well as the total number of spermatozoa.

Carnitine can be found in meat in significant amounts. This means about 30 to 90 mg per 100 grams of meat. Following from this, the serum carnitine levels of vegetarians are lower. However, deficiencies occur rarely, thanks to endogenic carnitine synthesis. But in the case of kidney or liver malfunction, a serious illness or high physical activity, this can easily happen. Carnitine is absorbed by the intestines, competing with other amino acids. This means, better absorption ratio can be achieved when taken on an empty stomach. Still this ratio is not too high: only 55 to 85 % or less will be absorbed in the digestive system. The carnitine produced by the liver and the kidneys will be stored in the skeletal muscles and discharge with urine. A study has shown that the intestines cannot absorb more than 2 grams of L-Carnitine daily. Anyhow, it is advisable to take it in several smaller portions throughout the day. Doing so, the systems that processes it won’t get oversaturated. In the case of carnitine supplementation from external sources, the renal excretion of carnitine will be increased in the urine (and reabsorption will be decreased). In other words, they compensate. This often happens in the case of other supplements as well.

Why it is worth using

  • It promotes recovery after weight training by easing injuries in the muscle tissues. As a consequence, there will be more receptors available for binding anabolic hormones than there would be without L-Carnitine.
  • It can diminish erectile dysfunction and improve overall well-being, especially in elderly people. A daily dosage of 2-3 grams of L-carnitine and/or ALC significantly improves the quality and concentration of sperm, as well as the total number of spermatozoa.

Further benefits

  • In the case of dialysis patients, L-Carnitine, applied under medical supervision, can also be used to treat the common side effects of dialysis like fatigue, muscular fatigue or anemia, if it doesn’t respond (well) to EPO treatment.
  • Furthermore, some research projects (even though still in the initial phase) seem to indicate that carnitine might be successfully applied as an auxiliary therapy for HIV patients, too.

How to use it

A study has shown that the intestines cannot absorb more than 2 grams of L-Carnitine daily. Anyhow, it is advisable to take it in several smaller portions throughout the day. Doing so, the systems that processes it won’t get oversaturated. L-Carnitine should be applied in quite large doses (500-1000 mg). Consuming more than 1 gram may cause fish odor because of the by-products produced by the intestinal bacteria that break down L-Carnitine. In this case, reduce the amount. Take it on a empty stomach, 30-60 minutes before workout, and apply it for a longer period of time (several months). Also it is advisable to combine it with fat burners that contain choline. And, if you don’t have any cardiovascular disorders (since excessive caffeine intake might even cause a heart attack), you may take caffeine supplements, too, in moderate amounts throughout the day. It is not recommended to take L-carnitine in itself, since poor absorption, insufficient amount and/or duration of dosage, insufficient training or a too high calorie intake can all neutralize its positive effects. On the other hand, it will prove much more potent when combined with other substances (e.g. green tea).

Interactions and synergies

Choline supplementation can help you reduce urinary carnitine excretion and increase the carnitine reserves of your muscles.

Drugs used in HIV treatment (e.g. AZT) may cause L-Carnitine deficiency, just like many other medicines like chemotherapeutic agents or antibiotics containing pivalic acid (i.a. pivampicillin, pivmecillinam or pivcephalexin). If you are on medication, ask your physician whether L-Carnitine supplementation is necessary and safe. Another proven drug interactions: Allopurinol, anticonvulsants, Doxorubicin, Gabapentin, Phenobarbital, Valproic acid.

Natural sources

Carnitine can be found in meat in significant amounts. This means about 30 to 90 mg per 100 grams of meat.

Carnitine content of ingredients (mg/100g)

Whole milk 3.5 mg
Chicken breast 3.5 mg
Pork 28 mg
Beef 95 mg

Possible side effects

Consuming more than 1 gram (or 3, based on other data) may cause fish odor because of the by-products produced by the intestinal bacteria that break down L-Carnitine. In this case, reduce the amount. There isn’t any known toxicity. However, it may cause gastrointestinal problems, vomiting or diarrhea when applied in excessive amounts. Consult your physician if you are pregnant or nursing. Furthermore, L-carnitine is also contraindicated if you have a liver, kidney or thyroid disorder or diabetes. In any of these cases, consult your physician under any circumstances.

Contraindication: None.

The history of L-Carnitine

L-Carnitine was first isolated from meat in 1905. This is where the name is coming from (carnus, carn- ~meat). It was named Vitamin BT based on animal testing. But since higher life forms, including humans, can synthesize it, it should not be called a vitamin.

Q & A on L-Carnitine

As a bodybuilder, can I profit from taking L-Carnitine supplements?

Most probably, you can, since there aren’t any known negative effects on healthy individuals. If you exercise regularly, taking L-Carnitine can help you burn fat by transporting acyl-CoA (acyl-coenzyme-A)-bound activated fatty acids into the mitochondria, which will then “burn” them (use them up). It has a slightly anabolic effect, i.e. it helps the muscles build in more protein. It promotes recovery after weight training by easing injuries in the muscle tissues. As a consequence, there will be more receptors available for binding anabolic hormones than there would be without L-Carnitine. Due to its proven effect of improving the quality and concentration of sperm and the total number of spermatozoa, it can promote recovery after steroid courses (but please keep in mind that no human experiments have been conducted on this matter yet).

Bibliography

Ahmad S. L-carnitine in dialysis patients. Semin Dial. 2001;14(3):209-217.

Cavallini G, Caracciolo S, Vitali G, Modenini F, Biagiotti G. Carnitine versus androgen administration in the treatment of sexual dysfunction, depressed mood, and fatigue associated with male aging. Urology. 2004 Apr;63(4):641-6.

Caviglia D, Scarabelli L, Palmero S. Effects of carnitines on rat sertoli cell protein metabolism. Horm Metab Res. 2004 Apr;36(4):221-5.

Clinical practice guidelines for nutrition in chronic renal failure. K/DOQI, National Kidney Foundation. Am J Kidney Dis. 2000;35(6 Suppl 2):S1-140.

Guarnieri G, Situlin R, Biolo G. Carnitine metabolism in uremia. Am J Kidney Dis. 2001;38(4 Suppl 1):S63-67. Hurot JM, Cucherat M, Haugh M, Fouque D. Effects of L-carnitine supplementation in maintenance hemodialysis patients: a systematic review. J Am Soc Nephrol. 2002;13(3):708-714. Kraemer WJ, Volek JS, French DN, Rubin MR, Sharman MJ, Gomez AL, Ratamess NA, Newton RU, Jemiolo B, Craig BW, Hakkinen K The effects of L-carnitine L-tartrate supplementation on hormonal responses to resistance exercise and recovery. J Strength Cond Res. 2003 Aug;17(3):455-62.

Vesela E, Racek J, Trefil L, Jankovy'ch V, Pojer M. Effect of L-carnitine supplementation in hemodialysis patients. Nephron. 2001;88(3):218-223.

Volek JS, Kraemer WJ, Rubin MR, Gomez AL, Ratamess NA, Gaynor P. L-Carnitine L-tartrate supplementation favorably affects markers of recovery from exercise stress. Am J Physiol Endocrinol Metab. 2002 Feb;282(2):E474-82.



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