L-carnitine: what is it, health benefits and side effects

11/10/2022
woman athlete runs in autumn forest

Among the most well-known and well-studied substances for increasing energy levels, is carnitine. Scientists classify it as one of the most important fat burners. Carnitine supplements are often used in athletes, people with low energy levels and even in the treatment of pathological conditions.

But what is true and how can we benefit from taking carnitine?

Carnitine: What it is

Let’s start from the basics! Carnitine is naturally formed from the essential amino acids lysine and methionine and is excreted in the liver and kidneys. Its main role is to mediate various metabolic pathways and mainly energy production in the mitochondria of cells. [1]

Carnitine has the ability to be stored in muscles, brain, heart and even sperm.

 

Carnitine: Sources

Foods containing carnitine are usually products of animal origin. Specifically:[1][2]

  • Dairy products
  • Poultry
  • Meat (mainly red)

As for vegan foods, those with a high carnitine content include:

  • the asparagus
  • wholemeal bread
  • the beans
  • the avocado

It is noted that vegans tend to get less carnitine from food.

 

Carnitine: In which forms do we find it?

L-carnitine is the biologically active form of carnitine, which is found in the body, in food and in most nutritional supplements.

There is no such thing as “the best form of carnitine”, only “the right form”. Therefore, the additional forms of carnitine and their respective actions are as follows: [2]

  • D-Carnitine: This is an inactive form which can cause carnitine deficiency in your body, inhibiting the absorption of other, more useful forms.
  • Acetyl-L-Carnitine: Often called ALCAR, this is probably the most effective form for your brain. Studies show that it can benefit people with neurodegenerative diseases.
  • Propionyl-L-carnitine: This form is suitable for circulatory problems such as peripheral vascular disease and high blood pressure. In particular, it can boost the production of nitric oxide, which improves blood flow.
  • L-carnitine L-tartrate: Commonly added to sports nutrition supplements due to its fast absorption rate. Contributes to the reduction of muscle pain and recovery after exercise.

For most people, acetyl-L-carnitine and L-carnitine seem to be the most effective forms for general use. However, you should always choose the format that is best for your personal needs and goals.

Carnitine: Properties and benefits

Carnitine for weight loss

Many researchers include carnitine among fat burners for rapid weight loss and “fat burning”. A systematic review and meta-analysis of 37 randomized controlled clinical trials with dose-response analysis concluded that carnitine supplementation:[3]

  • achieved a modest reduction in body weight, improving Body Mass Index (BMI) and reducing adipose tissue.

Results were seen in overweight/obese people.

Carnitine and fertility

Regarding male infertility, the administration of 3 gr L-Carnitine has been shown to be effective in men with fertility problems in terms of increasing sperm: [4][5]

  • quality and 
  • quantity

Of course, further studies are needed to strengthen the above claim.

Regarding female infertility, taking carnitine alone or in combination with other antioxidants has been shown to improve female reproductive function.

How?

  • Directly: by increasing oocyte energy production and effectively by providing protection against oxidative damage to reproductive cells.
  • Indirectly: by improving serum hormone levels.

fake red heart and a stethoscope

Carnitine and heart

Some studies show potential to reduce blood pressure and the inflammatory process associated with heart disease. A 12-month study observed a reduction in heart failure among participants who received L-carnitine supplements.

In particular, L-Carnitine through: [6]

  • of increasing carbohydrate metabolism
  • of increased glucose oxidation
  • promoting balanced blood flow,

manages to:

  • reduce cardiac arrhythmias
  • reduce the chance of an ischemic episode
  • reduce AV dysfunction

Carnitine and antioxidant activity

Carnitine is a powerful antioxidant molecule. It has the ability to interact with oxygen free radicals, thus protecting cells and DNA from oxidative damage.

Specifically, in a clinical study it was shown that the additional intake at a dose of 1000 mg/day: [7]

  • significantly reduced oxidative stress
  • increased the activity of antioxidant enzymes in patients with coronary artery disease.

Of course, further investigations in a healthy population are needed to ascertain the role of carnitine in reducing oxidative stress.

 

Carnitine and Type II Diabetes

Several human and animal studies have shown that L-carnitine supplementation: [8][9]

  • shows a beneficial effect on the use of glucose by the body,
  • improves many lipid parameters or markers of oxidative stress

In addition, low L-carnitine levels are associated with various diabetic complications.

In fact, clinical trials have shown that the administration of carnitine derivatives, such as acetyl-L-carnitine:

  • improved neurophysiological parameters,
  • reduce pain
  • reduced symptoms related to vascular degeneration in diabetic patients.

Therefore, it could be considered as a promising adjuvant in the treatment of diabetes and its complications.

A study in people with type 2 diabetes taking antidiabetic treatment showed that carnitine supplements were able to significantly lower blood sugar levels, compared to a placebo.[2]

Carnitine and metabolism

Carnitine has the ability to transport fatty acid molecules across cell membranes to the mitochondria, mainly in the heart and skeletal muscles, aiding in their further oxidation and use by the cells.

Specifically:[2]

  • helps in fat metabolism,
  • contributes to the protection of cells from fatty infiltration,
  • while favoring muscle recovery.

carnitine

Carnitine and athletic performance

Although carnitine has often been used to improve athletic performance, there are no studies that adequately support the benefit of taking it to enhance endurance and exercise performance.

The benefits of L-carnitine can be indirect and take weeks or months to show. This differs from nutritional supplements, such as caffeine or creatine, which can directly improve athletic performance.

L-carnitine may benefit:[2]

  • Recovery: Improves muscle recovery after intense training.
  • Muscle Oxygenation: It can increase the supply of oxygen to your muscles.
  • Endurance: Can increase blood flow and nitric oxide production, helping to delay discomfort and reduce fatigue.
  • Muscle pain: It can reduce muscle pain caused after vigorous physical activity.
  • Red Blood Cell Production: It manages to increase the production of red blood cells, which carry oxygen throughout your body.

Carnitine: dosage

A usual dose of L-carnitine is 500–2,000 mg per day. Although dosage varies from study to study, in a more general context up to 2,000 mg (2 grams)/day appears safe and effective in the long term.

We find it in oral form (ampoules, liquid form), as well as in food supplements in the form of capsules or tablets.

 

Carnitine: Side effects

In a review of studies on the safety of L-carnitine, doses of about 2 grams per day appeared to be safe even for long-term use. [2][10][11]

However, there were some mild side effects, including nausea and stomach upset. Less commonly, a “fishy” odor may be observed in the breath or sweat which is likely due to the formation of trimethylamine.

In addition:

  • epileptics,
  • people with thyroid problems (hypothyroidism)
  • and patients with kidney disease, can only take it after medical advice and under medical supervision.

 It is recommended to be avoided by pregnant and lactating women.

At Vita4you.gr you will find a wide variety of carnitine supplements

References

  1. Carnitine: What are the benefits and risks?
  2. L-Carnitine: Benefits, Side Effects, Sources and Dosage
  3. Effects of l-carnitine supplementation on weight loss and body composition: A systematic review and meta-analysis of 37 randomized controlled clinical trials with dose-response analysis
  4. Carnitines and male infertility
  5. Role of L-carnitine in female infertility
  6. l-Carnitine and heart disease
  7. Effects of L-carnitine supplementation on oxidative stress and antioxidant enzymes activities in patients with coronary artery disease: a randomized, placebo-controlled trial
  8. Role of carnitine and its derivatives in the development and management of type 2 diabetes
  9. Carnitine
  10. L-Carnitine
  11. L-Carnitine

Panagiotis Nevras

Pharmacist, graduate of School of Pharmacy, Aristotle University of Thessaloniki, specializing in Clinical Pharmacology, Pharmacognosy and Pharmaceutical Biotechnology, Gkatzouli Pharmacy head and member of the editorial team of vita4you.gr.

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The content of this blogspot is not and can not be considered as medical advice, diagnosis or treatment. All information is provided to readers solely for informational purposes. There is no intention to substitute this content for personalized medical advice, diagnosis, prognosis or treatment.

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