L-carnitine

What is l-carnitine?

L-carnitine is an amino acid that is naturally produced by the body and found in some foods. It is essential for the proper functioning of the heart and muscles and helps the body turn fat into energy.

How does it work?

L-carnitine is used for medicinal purposes to support heart and muscle function, improve athletic performance, and reduce fatigue and muscle damage. It works by transporting long-chain fatty acids into the mitochondria, where they are metabolized to produce energy. It also helps to remove waste products from the muscles, reducing muscle damage and promoting recovery.

What are the active ingredients that are important for its medicinal properties?

The active ingredient in l-carnitine is, of course, l-carnitine.

What forms does it come in?

L-carnitine is available in several forms, including capsule, tablet, liquid, and powder. Some popular forms include l-carnitine tartrate, acetyl-L-carnitine, and propionyl-L-carnitine.

What if there’s an imbalance or deficiency?

A deficiency in l-carnitine can lead to muscle weakness, heart problems, and decreased athletic performance. An imbalance or deficiency can also result from genetic disorders or certain health conditions, such as kidney disease.

When was it first used for medicinal purposes?

L-carnitine was first discovered in 1905 and has been used for medicinal purposes since the 1950s.

Summary:

L-carnitine is an amino acid that is naturally produced by the body and found in some foods. It is used for medicinal purposes to support heart and muscle function, improve athletic performance, and reduce fatigue and muscle damage. L-carnitine works by transporting long-chain fatty acids into the mitochondria to produce energy and by removing waste products from the muscles to promote recovery. The active ingredient in l-carnitine is l-carnitine. L-carnitine is available in several forms, including capsule, tablet, liquid, and powder. A deficiency in l-carnitine can lead to muscle weakness, heart problems, and decreased athletic performance, while an imbalance or deficiency can result from genetic disorders or certain health conditions. The most common side effects of l-carnitine supplementation include nausea, diarrhea, fishy body odor, and stomach upset. The recommended daily dose of l-carnitine is typically in the range of 500-2000 mg per day for adults. L-carnitine can be taken with or without food, at any time of day.

What does L-carnitine help with?

L-carnitine is a compound your body makes on its own. You also get it from meat and dairy. It is well established to help move fat into the part of the cell that burns fuel, which is basic biology rather than a trial result.

• Sore muscles and slow recovery after hard training
  Strong evidence — repeated human trials, mostly using the L-carnitine L-tartrate form. Trials with the tartrate form found less muscle damage after tough sessions. People also rated the same work as easier and bounced back faster. The library does not hold a single trial size or dose for this use.
  Evidence grade A · Traditional tier T0
• Trouble conceiving, with low sperm count or poor sperm movement
  Strong evidence — clinical trials in men, with the clearest gains in low sperm motility. Clinical trials found higher sperm counts, better sperm movement and better sperm shape. Men with low motility gained the most, as did men whose infertility was linked to varicocele, a swollen vein in the scrotum. Carnitine sits in high amounts in the tube where sperm mature.
  Evidence grade A · Traditional tier T0
• High blood sugar in type 2 diabetes
  Strong evidence — several randomised trials in people with type 2 diabetes. Several trials found lower fasting blood sugar and lower HbA1c with regular use. Insulin resistance scores fell too. Lab work ties this to less fat stored inside muscle cells, which can blunt insulin.
  Evidence grade A · Traditional tier T0
• Breathlessness and chest pain from a weak heart
  Good evidence — randomised trials, mostly with propionyl-L-carnitine, plus some pooled analyses. Trials found better exercise tolerance and less chest pain, mostly with propionyl-L-carnitine. Some pooled analyses after a heart attack found fewer deaths and fewer dangerous heart rhythms. Failing hearts often show low carnitine levels.
  Evidence grade B · Traditional tier T0
• Leg pain when walking from poor blood flow
  Good evidence — clinical trials of propionyl-L-carnitine in peripheral artery disease. In trials, people walked farther before leg pain began. They also reported better quality of life. The proposed route is that muscle pulls more energy from the blood it still gets.
  Evidence grade B · Traditional tier T0
• Memory slips and foggy thinking as you age
  Good evidence — trials of acetyl-L-carnitine in older adults and in mild Alzheimer's disease. Trials of acetyl-L-carnitine found modest gains in memory, attention and mood. The gains were real but small. This form crosses into the brain, and lab work links it to acetylcholine, a brain chemical tied to memory.
  Evidence grade B · Traditional tier T0
• Tiredness and cramps while on dialysis
  Early evidence — studies in dialysis patients, a small group with a measured shortage. Dialysis pulls carnitine out of the blood, so levels can drop very low. Doctors often prescribe it here to ease tiredness, muscle cramps and symptoms that look like anaemia. The studies are smaller and cover this one group only.
  Evidence grade C · Traditional tier T0
• Deep fatigue during cancer treatment
  Early evidence — several trials in people having chemo, with mixed results by carnitine level. Several trials found lower fatigue scores and more energy during chemo. Results were best where a carnitine shortage had been confirmed by testing. People with normal levels saw less change.
  Evidence grade C · Traditional tier T0
• Low mood, low drive and low energy in older men
  Evidence doesn't support this — a few trials with results that do not line up. Some trials in older men reported less tiredness, better mood and better sexual function. The suggested route is that carnitine makes muscle respond better to testosterone, an idea from early work only. Findings across trials do not agree, so nothing here is settled.
  Evidence grade D · Traditional tier T0

What L-carnitine has not been shown to do

• It has not been shown to burn fat on its own; pooled analyses found only small drops in weight and body fat, mainly alongside exercise.
• It has not been shown to raise testosterone levels in men.
• Trials in mild Alzheimer's disease found small changes in memory and mood; they did not show the disease was stopped or reversed.
• In cancer fatigue, it has not been shown to do much for people whose carnitine levels are already normal.

How to read this:

Each use gets its own grade, based on the studies behind that use. A means several matching human trials. B means at least one good human trial. C means small or mixed human studies. D means the human evidence is weak or conflicting. Insufficient means no human study at all. The overall grade on file for L-carnitine is A, but single uses sit lower. This page lists options, not advice, and it is not a promise of results. Talk with your own clinician before you start, above all if you take heart, blood sugar or kidney medicines.

What can L-carnitine help prevent?

• Carnitine deficiency in dialysis patients (well-established, medically recognized)
• Muscle damage from intense exercise (consistent evidence for reduced markers of exercise-induced injury)
• Progression of peripheral artery disease symptoms (propionyl-L-carnitine shown to preserve walking capacity)

Which foods are rich in it?

Foods that are rich in L-carnitine include:

• Beef and other red meats
• Chicken and turkey
• Dairy products
• Fish, such as salmon and cod
• Avocado
• Peanuts

What are possible side effects?

The most common side effects of L-carnitine supplementation include:

• Nausea
• Diarrhea
• Fishy body odor
• Stomach upset

What’s the recommended daily dose?

The recommended daily dose of L-carnitine varies depending on the individual and the condition being treated. It is typically in the range of 500-2000 mg per day for adults.

How many days does it take to work?

The time it takes for L-carnitine to work can vary depending on the individual and the condition being treated. In some cases, benefits may be seen within a few days, while in others, it may take several weeks to see significant results.

What time of day is best to take it?

There is no specific time of day that is best to take L-carnitine. It can be taken at any time of day, with or without food.

Is it best to take it with or without food?

L-carnitine can be taken with or without food. Some people prefer to take it with food to reduce the risk of stomach upset, while others find that it works best on an empty stomach. Ultimately, the best time to take L-carnitine will depend on the individual and their specific needs.