L-carnitine - what it is, properties, effects on weight loss + opinions

There are flakes stuck to certain substances. And just as caffeine stimulates and magnesium is for cramps, L-carnitine... slims you down. It's just that these and other substances offer many more interesting properties.

What if I told you that L-carnitine is more effective at supporting your liver and sugar-insulin metabolism than it is at shedding 5 kilos for you? Together with nutritionist and trainer Marta Kaczorek, we're ripping off the fat burner patch of L-carnitine - it can do so much more.

See also:

• Citrulline
• BCAA - does it work or not?
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• Creatine
• Caffeine
• NAC
• Protein nutrient
• Omega-3 in an athlete's diet
• Collagen for athletes
• Collagen for runners

L-carnitine - what is it?

L-carnitine is the biologically active form of carnitine used by the body. Over 95% of L-carnitine stores are found in the muscles, with trace amounts in the blood, liver, heart and kidneys. It plays an important role in energy production by transporting fatty acids into the mitochondria of cellsand.

The process of transporting fatty acids into the mitochondria of cells is important because in the mitochondria fatty acids are converted into energy .

Are carnitine and L-carnitine the same thing?

Carnitine and L-carnitine are essentially the same thing - the terms are often used interchangeably. Carnitine is an amino acid that is naturally produced in the body and taken in from food. L-carnitine, on the other hand, is the biologically active form of carnitine, i.e. the one that is used by your bodyand.

What does the 'L' next to carnitine stand for?

Marta Kaczorek explains:

Carnitine can exist in the body in two forms that mirror each other - one form is D-carnitine and the other is L-carnitine. But only one of these - L-carnitine - is active and actually useful to your body.

How does L-carnitine work?

Research to date suggests that its beneficial effects on the body may be due to supporting cellular energy production, increasing antioxidant capacity, protecting cell membranes from oxidative stress, reducing inflammation and increasing nitric oxide levelsand.

Carnitine types

There are four forms of carnitine. Below you will read how they differ and how they workand.

It is the most effective form of carnitine.

L-carnitine - properties

Many people choose to supplement with L-carnitine because of its health benefits. Previous research suggests that this amino acid potentiallyand:

Promotes weight loss

L-carnitine is a common ingredient present in diet supplements for weight loss. A comprehensive review of 2020 studies involving 37 studies with 2292 participants suggests that L-carnitine supplementation for weight lossand:

• produced the best results at a dose of 2000 mg per day,
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• reduced body weight by an average of 1.21 kg,
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• reduced BMI by 0.24 kg/m2,
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• reduced body fat mass by an average of 2.08 kg,
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• had no effect on abdominal fat content.
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Are these good results? Yes, weight and fat loss (especially in overweight people) is always desirable, but a calorie deficit (you eat less than your energy requirements)and is key.

Does L-carnitine work without exercise?

No, L-carnitine doesn't work without exercise. Just taking capsules (even high doses like 4,000 mg) or L-carnitine injections alone will not reduce body weight. For this, you need a reduction diet preferably combined with physical activityand. L-carnitine can only help the weight loss process.

Improves exercise performance

Several scientific studies suggest that L-carnitine can help athletes in several ways. Its effects onand:

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• extending performance and efficiency during training,
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• muscle regeneration,
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• delaying the feeling of fatigue,
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• increasing oxygen supply to muscles,
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• improving blood flow and nitric oxide production,
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• reducing muscle soreness,
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• production of red blood cells (transport oxygen in the body and muscles).
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L-carnitine will be a helpful dietary supplement for active people, and is best taken approximately 30-60 minutes before training in a serving of 2000 mg.

Promotes the treatment of type II diabetes

L-carnitine may be a helpful dietary supplement for patients with type 2 diabetes.

A review of 41 studies involving 2,900 people was published in 2023, suggesting that L-carnitine supplementation mayand:

• lower fasting blood sugar and haemoglobin levels,
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• reduce the HOMA-IR insulin resistance index,
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• improve insulin sensitivity in people with diabetes, overweight or obesity,
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• help improve the function of pancreatic cells responsible for insulin production,
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The beneficial effects of L-carnitine may be due to its effect on altering insulin receptors and the expression of specific genes that regulate sugar metabolismand.

Improves semen quality

A comprehensive review of 2023 studies suggests that L-carnitine may improve fertility in menand.

The review included 69 scientific papers involving 4,000 adult men with confirmed infertility or subfertility. Nutritional therapies or the use of dietary supplements to improve fertility were studied.

L-carnitine supplementation increased sperm motility and improved pregnancy rates. However, it had no effect on sperm concentration or semen volumeand. For improving fertility parameters, the combination of L-carnitine and selenium  had the best effect.

Improves female fertility

A review of 2018 research suggests a promising role for L-carnitine in improving female fertility. L-carnitine and acetyl-L-carnitine have tremendous potential to regulate oxidative stress and metabolic regulation of the female reproductive systemand.

Both of these forms, alone or in combination with other nutrients, as well as antioxidants, have potent effects in improving or restoring female reproductive functionand.

Promotes liver health

In research studies, L-carnitine supplementation has been shown to have a protective effect on the liver, particularly in patients with NAFLD - non-alcoholic fatty liver diseaseand.

A 2023 meta-analysis that included eight studies involving 544 participants with NAFLD found that L-carnitine reduced (improved) liver enzymes ALT, AST and triglycerides compared to placebo. Daily portions ranged from 500 to 2250 mg of L-carnitine.

Despite promising research, L-carnitine is not a popular active ingredient in liver supplements. Manufacturers of supplements rely on curcumin, glutathione, silymarin or artichoke extracts.

Promotes the treatment of PCOS

Polycystic ovary syndrome (PCOS) polycystic ovary syndrome) is an endocrine disorder affecting women of reproductive age. It affects, among other things, menstrual disorders and fertility problemsand. The problem can affect 8-20% of women of reproductive age worldwide .

The 2019 study included 74 female patients with PCOS. They took 3,000 mg of L-carnitine per day for 12 weeks.

After this time, the subjects observedand:

• significant improvement in insulin sensitivity,
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• increase in blood levels of HDL (so-called good cholesterol),
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• reduction of LDL (so-called bad cholesterol) levels in the blood,
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• reduction of BMI,
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• more regular menstrual cycles,
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• reduction of hirsutism (excessive hair in typically male areas),
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May support brain health

A 2020 research analysis suggests that acetyl-L-carnitine supplementation (ALCAR) may prevent age-related mental impairment and improve learning parametersand.

In a 2018 study involving people with dementia, 1,500 milligrams (mg) of ALCAR daily for 28 weeks significantly improved brain function.

Other studies in healthy individuals, however, have yielded mixed resultsand. Remember, dementia is best prevented and the nervous system is looked after from a young age.

L-carnitine and depression

Scientists are very cautious about the use of dietary supplements in the course of depression, as drug treatment combined with therapy has the best results. Several studies have examined whether L-carnitine affects the course of this illness when used as addition to therapy.

In a 2018 review, researchers analysed 12 studies involving a total of 791 patients with depression. It suggests that acetyl-L-carnitine supplementation reduced depressive symptoms compared to placeboand.

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Interestingly, in some cases it was noted that supplementation with this amino acid caused fewer side effects than antidepressants .

If you suffer from depression or other disorders, remember to first and foremost consult your treatment with your doctor, and consider supplementation as a supplement.

L-carnitine and autism

Polish researchers have addressed the interesting topic of the effects of L-carnitine on the autism spectrum in Journal of Clinical Medicine the 2021and. The pooled trial data suggest that L-carnitine improves neurological and neuropsychiatric function in patients on the autism spectrum. 

L-carnitine therapy shows positive correlations between an increase in serum L-carnitine and a reduction in specific autistic symptoms.

Daily requirements for L-carnitine

There is no set daily requirement for L-carnitine. In 1989. The Food and Nutrition Board (FNB) of the National Academy of Sciences, Engineering and Medicine concluded that carnitine is not an essential nutrientand.

Hence, healthy children and adults do not need to consume carnitine from food or supplements, as the liver and kidneys synthesise sufficient amounts to meet daily requirements .

The body produces approximately 15-20 mg of carnitine per day. Its natural production takes place in the kidneys and liver. There is approximately  20 g of carnitine in your body.

Carnitine deficiency

Carnitine deficiency is rare and most often results from genetic problems associated with disorders of the carnitine transport mechanism or due to disease (e.g. chronic renal failure)and. Carnitine deficiency manifests as weakness, skeletal muscle atrophy, muscle failure, fatigue .

Carnitine excess

Over-supplementation of L-carnitine most commonly occurs as a result of taking too many dietary supplements with the compound - typically more than 4,000 mg per day. Excessive supplementation can cause nausea, vomiting, abdominal cramps, diarrhoea, fishy skin, muscle weakness in people with uremia and seizure disorders in people with seizure disordersand.

Best sources of L-carnitine

Most L-carnitine can be found in red meat - beef, pork, mutton, horse meat and kangaroo meat, poultry, and in smaller amounts in other animal products such as eggs, milk, cheeseand.

The content of this amino acid in food products depends on the conditions under which the animal was raised, the heat treatment and can vary considerably. However, it is not difficult to obtain L-carnitine from food.

Products rich in L-carnitine

It is estimated that the average person consumes 20-200 mg of carnitine dailyand.

Food-derived carnitine has a relatively high absorbability of approximately 54-76%. The bioavailability of carnitine from dietary supplements is much lower at around 14-18%.

How to use L-carnitine?

A wide range of dosages have been used in studies on the potential benefits of L-carnitine. Typically, 500-4000 mg per day consumed on an empty stomach or 0.5-1 hour before physical activityand.

Daily intake may vary depending on the manufacturer, form of carnitine and purpose of supplementation, but efficacy has been shown in research studies for use:

• L-carnitine-L-tartrate: to improve exercise performance and support fat burning, 1,000 to 4,000 mg per day is usedand.
• Acetyl-L-carnitine: to improve brain function, 500 to 3000 mg per day is used .
• Propionyl-L-carnitine: for cardiovascular support, 500-2000 mg per day is used .
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L-carnitine before or after a meal?

To increase the absorption of L-carnitine, it is best taken on an empty stomach or approximately 0.5-1 hour before a meal. Remember that the bioavailability of carnitine from dietary supplements is low at only 14-18%and.

Adequate amounts of vitamin C and of iron in the diet promote natural carnitine production and absorption from dietary supplementsand.

What not to combine L-carnitine with

L-carnitine should not be combined with medicines that affect blood clotting (e.g. warfarin, acenocoumarol) and should not be taken at the same time as medicines containing thyroid hormones. L-carnitine exacerbates or weakens the effect of these preparations.

L-carnitine - is it worth it?

Yes, it is worth supplementing with L-carnitine, especially if you don't eat meat, which is a natural, well-absorbed source of it (the body absorbs about 54-76%). It can be helpful during weight loss and can also be used to support diabetes, PCOS or to improve sperm quality.

Remember that supplementation alone will not help with the ailments mentioned above, and you should consult your doctor for intake. Treat L-carnitine supplements as a supplement and support, not as the main source of treatment or weight loss.

Contraindications to the use of L-carnitine

Contraindications to the use of L-carnitine includeand:

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• pregnancy (the effect of supplementation on the health of the baby and mother is not known),
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• breastfeeding,
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• use of medications affecting blood clotting, medications containing thyroid hormones,
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• diagnosed kidney disease or epilepsy,
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Before starting supplementation, consult your doctor to determine the appropriate daily dose, avoid interactions with medications and adjust the time of intake so that L-carnitine helps - not hurts.

L-carnitine - side effects

L-carnitine side effects usually occur at doses above 4,000 mg and cause: nausea, vomiting, abdominal cramps, diarrhoea and a fishy smell to sweat or breath. It can also cause muscle weakness in people with uremia and convulsions in people with seizure disordersand.

See also:

• Berberine -  properties
.
• Berberine for weight loss
• Protein before or after training?
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• Whey protein concentrate (WPC)
.
• Whey protein isolate (WPI)
.
• Whey protein hydrolysate (WPH)
• Vegetable protein
• Casein
• Protein
• Citrulline
• Arginine

Summary