L-carnitine is an amino acid widely available in supplement form and often marketed as a weight loss aid. Produced naturally in the body, L-carnitine transports fat to cells in order to produce energy.
The mitochondria act as engines within your cells, burning these fats to create usable energy.
Your body can produce L-carnitine out of the amino acids lysine and methionine.
For your body to produce it in sufficient amounts, you also need plenty of vitamin C (4Trusted Source).
In addition to the L-carnitine produced in your body, you can also obtain small amounts by eating animal products like meat or fish (5Trusted Source).
The body creates carnitine from the amino acids lysine and methionine. Scientists first isolated it from meat. As a result, takes its name from the Latin word for meat.
There is some evidence to support the use of carnitine in medicine. It is a popular supplement among athletes, but more research is needed to confirm its effectiveness in improving performance.
While supplement manufacturers often claim that L-carnitine can “speed up” your metabolism, the evidence to support these claims are generally lacking.
Among the conditions that L-carnitine is believed to treat:1
- Brain disorders, including Alzheimer’s disease
- Alcohol and drug addiction
- Hypertension (high blood pressure)
It has also been suggested that L-carnitine can enhance sports performance, making it one of the more popular nutritional supplements used by athletes.
In theory, using L-carnitine as a weight loss supplement makes sense.
Since L-carnitine helps move more fatty acids into your cells to be burned for energy, you might think this would increase your ability to burn fat and lose weight.
Your body naturally creates L-Carnitine in the liver and kidneys, and most people have enough without supplementation. While this amino acid does assist in converting fat into energy, the University of Maryland Medical Center reports that no evidence links L-Carnitine supplements to weight loss. In addition, one study published in the “International Journal of Sport Nutrition and Exercise Metabolism” in 2000 found that L-Carnitine supplements had no weight-loss benefit among overweight women. However, it did sometimes cause nausea or diarrhea.
Carnitine is said to have many therapeutic properties that may be useful in treating a range of conditions and illnesses.
As an antioxidant, carnitine fights off harmful free radicals, which cause severe damage to cells.
Health conditions that carnitine may be used to treat include heart failure or heart attack, angina, and diabetic neuropathy.
One study found that ALC is as effective as a conventional treatment, methylcobalamin (MC), in treating diabetic peripheral neuropathy.
The most ambitious claim is that a type of L-carnitine, known as acetyl-L-carnitine (ALC), can improve memory, cognition, and attention in people with Alzheimer’s disease (AD).
A study conducted in 1991 found that while all participants experienced a decline in mental function after one year, the decline appeared to be slower in people prescribed ALC versus those given a placebo.
Other research suggests that ALC may help speed recovery from substance abuse by improving mental function and acuity. A 1990 study involving 55 people undergoing alcohol detox reported faster recovery in the group provided 2 grams of ALC after 30, 45, and 90 days versus those provided a placebo.
Some promising research has shown that carnitine supplementation could aid in maintaining normal blood sugar levels and fighting insulin resistance.
A study out of Rome published in the Journal of the American College of Nutrition showed that infusing people with diabetes with L-carnitine improved insulin sensitivity and increased the uptake of sugar from the bloodstream.
Another small study in 2010 conducted at Sapienza University’s Department of Clinical Medicine in Rome found that combining L-carnitine with caloric restriction helped reduce insulin resistance and increase sensitivity.
L-carnitine is LIKELY SAFE when taken by mouth for up to 12 months, and when used as an injection, with the approval of a healthcare provider.
People taking carnitine have reported a number of side effects, including:
- Diarrhea, nausea, stomach pain, and vomiting
- Trouble sleeping
- Higher blood pressure
- Lower blood sugar and higher triglycerides (in people with diabetes)
- Psychosis (in people with bipolar disorder)
In rare cases, L-Carnitine may cause dangerous side effects, such as depression, weakness, swelling, vision problems and dizziness. It may also rarely cause body odor or a tingling sensation. In addition, this supplement may not be safe for people with high blood pressure, diabetes, kidney disease or other medical conditions. Speak to your doctor before taking L-Carnitine or any other supplements.
Supplement makers suggest varying amounts of this supplement for different purposes. Common dosages range from 1 to 3 grams daily, divided into several doses. But optimal doses have not been established for any condition. Quality and active ingredients in supplements may vary widely from maker to maker. This makes it difficult to establish a standard dose.
Studies suggest varying doses for each form of L-carnitine for best results, the following is deemed optimal for each form of carnitine:5
- Acetyl-L-Carnitine: 600–2,500 mg per day.
- L-Carnitine L-Tartrate: 1,000–4,000 mg per day.
- Propionyl-L-Carnitine: 1,000–4,000 mg per day.