Carnitine supplement health benefit and side effects, helps improve energy and useful for heart tissue by Ray Sahelian, M.D.
Does this nutrient help with weight loss? What is the right daily dosage, is it 100 mg, 200, 250, 500, or 1000 mg
Research studies with propionyl l carnitine, and other forms such as tartrate and fumarate
Feb 5 2014

L-carnitine is a naturally occurring substance found in most cells of the body, particularly the brain, neural tissue, muscle, and heart. Carnitine, whose structure is similar to choline, is widely available in animal foods (meat, poultry, fish and dairy products), whereas plants have very small amounts. Most non-vegetarians consume about 100 to 300 mg of carnitine a day, and the body is able to synthesize this nutrient if dietary intake is inadequate. Ninety-five percent of the body carnitine pool resides in skeletal muscle where it plays a vital role in fuel metabolism. However, vegetarians obtain negligible amounts from their diet.
   When ingested as a pill, carnitine is not able to cross the blood-brain barrier as well as its activated form acetylcarnitine which has a more noticeable mental effect and usually enhances mental clarity and focus, along with slight mood elevation. The effects of carnitine tend to be more physical than mental, in the sense that it provides enhanced physical energy.  Both nutrients are wonderful antioxidants.

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Carnitine is sold by itself as a single nutrient in a bottle. It can be found in vitamin stores, on the internet, and many pharmacies or drug store chains. A number of natural products promoted for improving energy may contain it along with other vitamins and herbs.

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What's the right dosage?
Since each person has a unique biochemistry, dosage recommendations vary. A range of 50 to 500 mg daily works for most people. Take a day or two off each week. The effects of carnitine accumulate over time, therefore your dosage may need to be reduced or you may wish to take breaks more often. Much depends on whether you are taking other medications and supplements. If you are already taking natural products that increase energy, your required dosage of this nutrient would be less since taking too many energy enhancing natural pills can cause restlessness and insomnia. A carnitine supplement is particularly helpful for vegetarians since it is found in only small amounts in vegetables, fruits, and legumes.

L carnitine benefits studies
This supplement has potential as a treatment in several conditions, but more research is needed to determine the appropriate dosage and interactions with various other supplements and medications.
    

ADHD
Treatment with carnitine decreased attention problems and aggressive behavior in boys with ADHD.

Carnitine and acetyl l carnitine as anti-aging supplements?
In addition to producing energy, these two nutrients remove toxic accumulations of fatty acids from mitochondria, keeping these organelles healthy and functioning at their best. Energy production in mitochondria is not a perfect process and toxic metabolites do accumulate. Accumulation of these toxic metabolites and the resulting oxidative damage is likely to contribute to aging of cells. A waste substance called lipofuscin accumulates in cells as we age and perhaps adequate acetyl-l carnitine intake can help minimize this accumulation. A study in rats providing acetyl-l carnitine from youth showed this nutrient to decrease lipofuscin levels in their brain as they got old. Therefore, it is theoretically possible that supplementation with either can slow the aging process.

Brain health research
Comparison of the effects of L-carnitine and acetyl-L carnitine on carnitine levels, ambulatory activity, and oxidative stress biomarkers in the brain of old rats.
Ann N Y Acad Sci. 2004.
Aged rats were given each at 0.15% in drinking water for 4 weeks. Both were similar in elevating carnitine levels in plasma and brain. Both increased ambulatory activity similarly. However, acetyl-L carnitine decreased the lipid peroxidation in the old rat brain, while L-carnitine did not which indicates the former may be a better supplement for brain health.


For diabetic patients
Oral administration reduces oxidized LDL cholesterol levels in patients with type 2 diabetes.

L-Carnitine supplementation reduces oxidized LDL cholesterol in patients with diabetes.
American Journal of Clinical Nutrition, 2009.
Eighty-one patients with diabetes were randomly assigned to 1 of 2 treatment groups for 3 months. The 2 groups received either 2 grams once daily or placebo. At the end of the study period, the L-carnitine-treated patients showed significant improvements compared with the placebo group in the following markers: oxidized LDL levels decreased; LDL cholesterol decreased; triglycerides decreased; apolipoprotein A1 concentrations decreased; apolipoprotein B-100 concentrations decreased. Our study indicates that oral administration reduces oxidized LDL cholesterol levels in patients with type 2 diabetes.

Energy increase
I get the most wonderful 'feel good' and energy when I take SAM-e 100mg and 150 mg of L-carnitine.

Exercise
Carnitine improves recovery after heavy exercise and may be of use in improving exercise capacity of people with peripheral arterial disease. It moderately improves the duration of exercise and time to recovery in patients with chronic stable angina.

Fat metabolism
I live with chronic fatigue syndrome, hypothyroidism, and depression. I would like to improve fat metabolism by supplementing with L carnitine. However, acetyl l carnitine could also be very useful for energy production. Will acetyl l carnitine improve fat metabolism as well, or would I need to supplement with both to get the benefits they both offer?
   Both have some overlapping functions. It is difficult to predict which one will be more effective and in what dosage. A good option is to try each one by itself in varying dosages and you can have a better understanding which one works for you better. Then you can decide whether you wish to combine them.


Fatigue benefit
Carnitine may improve fatigue in certain conditions, including cancer patients receiving chemotherapy. It decreases the severity and type of fatigue induced by interferon-alpha in the treatment of patients with hepatitis C.
Older individuals may benefit from the use of this nutrient to enhance energy levels and wellbeing.
Supplements may benefit certain patients with fatigue if there are no obvious causes, such iron deficiency anemia, a serious medical condition, etc.

At 2 grams a day, it did not improve symptoms of fatigue in cancer patients compared to placebo. Journal of Clinical Oncology, online September 17, 2012. At least a quarter of the participants did not complete their follow-up assessment so it is not clear if this influenced the results. It is possible dosages above 500 mg could cause insomnia and thus the 2 grams that was given to the patients may have caused sleep disturbances and thus had a negative impact on energy levels. I would be interested to see a study using 250 mg or 500 mg.

Neurometabolic diseases
Gene. January 10 2014. L-carnitine supplementation as a potential antioxidant therapy for inherited neurometabolic disorders.

Seniors and the elderly
Italian researchers at the University of Catania gave sixty-six centenarians 2 grams l carnitine daily for six months. At the end of the study period, the treated centenarians showed significant improvements in total fat mass and total muscle mass. They were also less likely to have physical and mental fatigue. LDL-cholesterol levels fell among the individuals taking the supplement. L-carnitine takers gained 3.8 kilograms (8 pounds) of muscle mass, on average, and lost 1.8 kg (4 pounds) of fat mass. They were also able to walk 4 meters  further during a 6-minute walking test after treatment than those given placebo.
   Comments: This study shows how much we still can learn about the benefits of supplements in the aged. My preference would be to use a lower amount, such as 250 mg or 500 mg. Sometimes when high dosages of energy enhancing pills are taken for prolonged periods, they can accumulate and interfere with sleep.

L-Carnitine treatment reduces severity of physical and mental fatigue and increases cognitive functions in centenarians: a randomized and controlled clinical trial
American Journal of Clinical Nutrition, 2007. Mariano Malaguarnera, Lisa Cammalleri, Maria Pia Gargante,. From the Department of Senescence, Urological, and Neurological Sciences, University of Catania, Catania, Italy
Sixty-six centenarians with onset of fatigue after even slight physical activity were recruited to the study. The 2 groups received either 2 grams l carnitine once daily or placebo. The l carnitine treated centenarians, compared with the placebo group, showed significant improvements in total fat mass, total muscle mass, and plasma concentrations of total carnitine. Significant differences were also found in physical fatigue and mental fatigue. Our study indicates that oral administration of l carnitine produces a reduction of total fat mass, increases total muscular mass, and facilitates an increased capacity for physical and cognitive activity by reducing fatigue and improving cognitive functions.

L carnitine administration in elderly subjects with rapid muscle fatigue: effect on body composition, lipid profile and fatigue.
Drugs Aging. 2003.
Eighty-four elderly subjects with onset of fatigue following slight physical activity were recruited to the study. One group received carnitine 2g twice daily and the other placebo. The treated patients showed significant improvements in the following parameters: total fat mass, total muscle mass, total cholesterol, LDL-C, HDL-C, triglycerides, apoA1, and apoB. There was improvement in physical fatigue and mental fatigue. Administration of carnitine to healthy elderly subjects resulted in a reduction of total fat mass, an increase of total muscle mass, and appeared to exert a favourable effect on fatigue and serum lipids.

Fertility and sperm health
Carnitine and acetyl carnitine therapy are effective in increasing fertility and sperm-semen quality. Several studies have shown improved sperm motility with supplementation. Also consider the herb maca from South America.

Combined treatment with L-carnitine, a popular dietary supplement, and acetyl-carnitine, a related chemical, appears to improve sperm motility in men with fertility problems. In the study, 60 infertile men between the ages of 20 and 40 years were randomly selected to take a combination of L-carnitine and L-acetyl-carnitine or an inactive "placebo" for 6 months. In the medical journal Fertility and Sterility, researchers at the University of Rome led by Dr. Andrea Lenzi report that 2 months after the completion of therapy, men who took these pills had increases in sperm concentration, forward movement, and total movement. The most significant improvements in sperm motility, both forward and total, were observed in men who had the lowest levels of moving sperm when the study began. The researchers note that four spontaneous pregnancies were achieved during the study by men who had taken the combination therapy.

Placebo-controlled double-blind randomized trial on the use of L-carnitine, L-acetyl carnitine, or treatment in men with idiopathic asthenozoospermia.
Fertility & Sterility 2005.
Sixty infertile men, ages 20 to 40 years, with the following baseline sperm selection criteria: concentration > 20 x 10(6)/mL, sperm forward motility < 50%, and normal sperm morphology > 30%. Patients underwent a double-blind therapy of carnitine 3 grams a day, acetyl carntine 3 grams a day, a combination of carnitine 2 g/d and acetyl carnitine 1 g/d, or placebo for a period of six months. Sperm cell motility increased in patients to whom acetyl carnitine was administered both alone or in combination with carnitine; combined  therapy led to a significant improvement of straight progressive velocity. The combined administration is effective in increasing sperm kinetic features in patients affected by idiopathic asthenozoospemia and improves the total antioxidant status of the seminal fluid.

Heart health
Those with heart failure may benefit from carnitine supplements. However there have been some recent concerns that meat eaters may form an undesirable substance called TMAO from intake of high levels. There's a lot to investigate in the TMAO formation from carnitine use before knowing if there are any risks involved.

I take L-Carnitine for my heart. Would the acetyl version be of more benefit or should I stick with the former?
   It is not possible to know in any individual person without knowing the full medical history and exam. There are many other natural option for heart health which are reviewed on the heart disease page.

Hormonal effect
Does it have any hormonal effects such as gynecomastia or testicular atrophy in males?
   We're not aware of any obvious hormonal effects with this supplement, but we have not seen any specific studies addressing this issue in humans for any length of time.

Hyperthyroidism
Carnitine is effective in both reversing and preventing symptoms of hyperthyroidism and has a beneficial effect on bone mineralization.
Because hyperthyroidism depletes the body deposits of carnitine and since this supplement has little toxicity, teratogenicity, contraindications and few interactions with drugs, carnitine can be of clinical use.

Kidney dialysis
Intravenous administration is an accepted pharmaceutical treatment for carnitine deficiency in end-stage renal disease in patients undergoing dialysis.

Liver cirrhosis
Treatment of patients with liver cirrhosis with signs of liver insufficiency is complex and seldom satisfactory. Carnitine is involved in liver lipid metabolism and thus might be a potentially effective nutrient. One study shows L carnitine lowers serum ammonia concentration and improves lipid metabolism in patients with liver cirrhosis. Carnitine may also play a beneficial role in the treatment of mild or moderate hepatic encephalopathy, and perhaps liver cancer.

Liver cancer
L-carnitine inhibits hepatocarcinogenesis via protection of mitochondria.
Int J Cancer. 2004.
Recently, we reported that mitochondrial dysfunction plays an important role in liver cancer via the production of free radicals. Furthermore, we proved that L-carnitine effectively protects mitochondrial function in vivo. Therefore, we investigated whether long-term administration of L carnitine could prevent hepatitis and subsequent hepatocellular carcinoma in Long-Evans Cinnamon rats that are often analyzed as a model of hepatocarcinogenesis. The results indicated that oxidative stress elicited from abnormally accumulated copper increased the amount of free fatty acids, thereby inducing mitochondrial dysfunction, resulting in cell death and enhanced secondary generation of reactive oxygen species, which were significantly inhibited by carnitine treatment. Mitochondrial injury plays an essential role in the development of liver cancer and the clinical use of carnitine may have therapeutic potential in individuals with chronic hepatitis.

Sexual health
Apparently l carnitine is helpful in sexual enhancement. Acetyl-l-carnitine is also helpful in this regard. There are many herbs that are much more potent, including tribulus terrestris, mucuna pruriens, maca, catuaba, yohimbe, and tongkat ali.

W
eight loss
L carnitine may be an effective supplement for weight loss by itself, but when combined with other nutrients it is even more effective.

The effect of l-carnitine on fat oxidation, protein turnover, and body composition in slightly overweight subjects.
Metabolism. 2004.
We used a combined tracer technique with the stable isotopes (13)C and (15)N to gain further insight into the metabolic changes that accompany supplementation of l-carnitine. The aim of the present study was to investigate whether l-carnitine supplementation can influence fat oxidation, protein turnover, body composition, and weight development in slightly overweight subjects. Twelve volunteers received an individual regular diet either without or with l-carnitine supplementation of 3 grams a day for 10 days. Body fat mass, total body water, and lean body mass were calculated by using bioelectric impedance analysis. L-carnitine supplementation led to a significant increase in protein synthesis indicating that the increased dietary fat oxidation in slightly overweight subjects was not accompanied by protein catabolism.

Caffeine, carnitine and choline supplementation of rats decreases body fat and serum leptin concentration as does exercise. J Nutr 2000.

Thalassemia blood disorder
Effect of L-carnitine on the physical fitness of thalassemic patients.
Ann Hematol. 2007. El-Beshlawy A, El Accaoui R, Abd El-Sattar M, Gamal El-Deen MH, Youssry I, Shaheen N. Department of Pediatrics, New Children Hospital, Cairo University, Cairo, Egypt.
The main objective of this study is to assess the effect of the administration of oral L-carnitine on exercise tolerance and physical fitness in patients with thalassemia major. Thirty patients followed up at the New Cairo University Children Hospital were included in this study. Clinical, laboratory, and cardiopulmonary exercise testing were performed before and after 6 months of oral L-carnitine therapy (50 mg per kg per day). The oxygen consumption, cardiac output, and oxygen pulse at maximal exercise significantly increased after L-carnitine therapy. However, there was no significant change in minute ventilation and ventilatory equivalent of carbon dioxide. There was also significant increase in the blood transfusion intervals after L-carnitine administration. However, there was no significant change in hemoglobin concentration. L-Carnitine seems to be a safe and effective adjunctive therapeutic approach in thalassemic patients. It improves their cardiac performance and physical fitness. The younger the patients are, the higher is the degree of improvement in their exercise parameters.

   Comments: For long term use we suggest using a much lower dosage of 5 to 10 mg per kilogram body weight.

Thyroid medication
Is it safe to use these pills with thyroid therapy? I take l carnitine before I exercise and as a recovery, but now that I'm on Synthroid have read that it might affect the thyroid. I've also thought about trying Armour thyroid but I want to continue my carnitine so am wondering if there is any interactions with it and thryoid replacement therapies.
    I have not seen specific studies with the combination of this nutrient and thyroid hormone therapy. As a general rule, it is best to begin with low dosages and be monitored with routine tests to see if there are any effects. The response of different individuals may vary even if the same combination is used so it is difficult to predict what would happen in any individual.

L carnitine side effects, safety, danger, caution, risks
It seems l carnitine is a relatively safe nutrient in doses ranging from 50 to 500 mg. Higher doses may lead to excess energy, restlessness, perhaps insomnia. Long term side effects of high dose carnitine use are not fully known.

How does it work?
Carnitine and acetyl-l carnitine play several important roles in the human body, particularly in energy metabolism. These nutrients shuttle acetyl groups and fatty acids into mitochondria for energy production. Without carnitine, fatty acids cannot easily enter into mitochondria. The acetyl group of acetyl-l carnitine is used to form acetyl-CoA, the most important intermediary in the generation of energy from amino acids, fats, and carbohydrates. Therefore, acetyl-l carnitine serves as an energy reservoir of acetyl groups and both help improve energy production. Those who take carnitine pills often notice an increase in energy levels.   

Deficiency
Carnitine is comprised of two amino acids, lysne and methionine. Its role is to transport long-chain fatty acids across the cell's inner mitochrondial membrane. Mitochrondia use fatty acids and glucose to produce energy. Secondary carnitine deficiency is a rare metabolic disorder usually diagnosed at birth. However, primary carnitine deficiency, which is due to decreased synthesis of carnitine in the body or altered transport of carnitine across the cellular membrane, can occur in people of all ages. Carnitine levels decrease with age.

Metabolism
Carnitine, the L-beta-hydroxy-gamma-N-trimethylaminobutyric acid, is synthesized primarily in the liver and kidneys from lysine and methionine. Carnitine covers an important role in lipid metabolism, acting as an obligatory cofactor for beta-oxidation of fatty acids by facilitating the transport of long-chain fatty acids across the mitochondrial membrane as acylcarnitine esters. Furthermore, since carnitine behaves as a shuttle for acetyl groups from inside to outside the mitochondrial membrane, it covers a key role in glucose metabolism and assists in fuel-sensing. A reduction of the fatty acid transport inside the mitochondria results in the cytosolic accumulation of triglycerides, which is implicated in the pathogenesis of insulin resistance.

Various forms are available:
Raw material suppliers, such as Sigma Tau, have a wide variety of products, including:
L-Carnitine Fumarate
Base USP, FCC, EP
Hydrochloride
Creatine Dihydrogen Phosphate
Hydrogen Fumarate Creatinate
Lysine L-Carnitine Fumarate Hydrochloride
Glycine Propionyl L-Carnitine Hydrochloride
L carnitine L tartrate
   There has not been enough research with each of these forms to determine which is best for long term human consumption.

Free and total carnitine concentrations in pig plasma after oral ingestion of various L carnitine compounds.
Int J Vitamin Nutrition Research. 2005.
This study was undertaken to investigate the bioavailability of various L carnitine esters (acetyl L carnitine and lauroyl L carnitine) and salts (L carnitine L tartrate, L carnitine fumarate, L carnitine magnesium citrate) relative to base of free L carnitine. Six groups of five or six piglets each were administered orally a single dose of 40 mg L carnitine equivalents/kg body weight of each of those L carnitine compounds. AUC values, calculated for the time interval between 0 and 32 hours, for both free and total carnitine were similar for base of free L carnitine and the three L carnitine salts (L carnitine L tartrate, L carnitine fumarate, L carnitine magnesium citrate) while those of the two esters (acetyl L carnitine, lauroyl L carnitine) were lower. Administration of Lcarnitine L tartrate yielded a higher plasma free carnitine AUC value for the time interval between 0 and 3.5 hours than administration of the other compounds. The data of this study suggest that L carnitine salts have a similar bioavailability to that of free L carnitine while L carnitine esters have a lower one. The study also suggests that L carnitine L tartrate is absorbed faster than the other L carnitine compounds.

Propionyl l carnitine research studies
Evaluation of the efficacy of propionyl-L-carnitine versus pulsed muscular compressions in diabetic and non-diabetic patients affected by obliterating arteriopathy Leriche stage II.
Int Angiol. 2008 June. Riccioni C, Sarcinella R, Palermo G, Izzo A, Liguori M, Koverech A, Messano M, Virmani A. Complex Unit of Angiology, Nuovo Regina Margherita Hospital, Rome, Italy.
The effectiveness of propionyl L carnitine (PLC) monotherapy regimen alone or in association with pulsed muscular compression was compared to the physical therapy by itself against obliterant arteriopathy Leriche Fontaine stage II. PLC is involved in cellular metabolism and is transformed into two active substances, free L-carnitine and propionyl-coenzyme A in the mitochondria, which take part in fatty acid transfer and in the citric acid cycle, respectively. Forty-two patients with arterial disease were selected (22 males and 20 females; mean age: 62+/-8 years; 21 type 2 diabetic [DB] and 21 non-DB [NDB]). Patients were randomized in three groups, each of them composed by 14 patients (7 DB and 7 NDB): the first group was submitted to infusional propionyl L carnitine therapy at a dosage of 4 fl (total: 1,200 mg PLC) in 250 cc of physiological solution for 5 days a week for 4 weeks; the second group was treated with PLC in association with pulsed muscular compression therapy by Vascupump; the third group was submitted only to Vascupump. From a subjective point of view, patients referred benefits both in clinical terms, i.e. increased walking distance and of decreased intensity of the calf pain. The instrumental parameters showed a trend towards normality. Combined pharmaco- and physical therapy was most efficient treatment regime and best results were seen in NDB compared to the DB patients.

Levo-propionyl-carnitine improves the effectiveness of supervised physical training on the absolute claudication distance in patients with intermittent claudication.
Angiology. 2008; Andreozzi GM, Leone A, Laudani R, Martin R, Deinit G, Cataldi V. Angiology Care Unit of University Hospital of Padua, Italy.
Levo-propionylcarnitine increases the walking ability in claudicants, providing an additional energy to the ischemic muscle. Therefore, the current study was carried out to ascertain whether the combined treatment has a synergistic effect. The results confirm the effectiveness of supervised physical training in patients with IC, and we recommend the use of LPC during the exercise training program, at least in patients with severe claudication.

Effect of glycine propionyl-L-carnitine on aerobic and anaerobic exercise performance.
Int J Sport Nutr Exerc Metab. 2008; Smith WA, Fry AC, Tschume LC, Bloomer RJ. Dept. of Health and Sport Sciences, University of Memphis, Memphis, TN, USA.
The purpose of this study was to evaluate the effect of glycine propionyl-L-carnitine (GPLC) supplementation and endurance training for 8 wk on aerobic- and anaerobic-exercise performance in healthy men and women (age 18-44 yr). Participants were randomly assigned to 1 of 3 groups: placebo, 1 g/d GPLC, or 3 g/d GPLC, in a double-blind fashion. Muscle carnitine (vastus lateralis), VO(2peak), exercise time to fatigue, anaerobic threshold, anaerobic power, and total work were measured at baseline and after an 8-wk aerobic-training program. There were no statistical differences between or within the 3 groups for any performance-related variable or muscle carnitine concentrations after 8 wk of supplementation and training. These results suggest that up to 3 g/d GPLC for 8 wk in conjunction with aerobic-exercise training is ineffective for increasing muscle carnitine content and has no significant effects on aerobic- or anaerobic-exercise performance.

Testimonials
I am a 48 yr. female registered nurse from New Zealand. I have been taking L- Carnitine 300mg for 7 days to assist in weight loss after doing on-line research. Most of my 30 yr career in nursing has been as an operating theatre nurse because of this I suffer from plantar fascitis, first in my left foot resulting in a bony spur then in my right foot - no bony spur. This has been very painful, I have received many forms of treatment from orthopaedic surgeon i.e.: steroid injection to podiatrist etc. It has been very interesting to note that from Day 4 of taking L- carnitine that the usual level of daily pain has lessened considerably to zero even.