Carnitine (L-carnitine)

Also listed as: Acetyl-l-carnitine; L-carnitine

Overview

Carnitine is a nutrient responsible for the transport of long-chain fatty acids into the energy-producing centers of the cells (known as the mitochondria). In other words, carnitine helps the body convert fatty acids into energy, which is used primarily for muscular activities throughout the body. The body produces carnitine in the liver and kidneys and stores it in the skeletal muscles, heart, brain, and sperm.

Some people have dietary deficiencies of carnitine or cannot properly absorb this nutrient from foods that they eat. Carnitine deficiencies may be caused by genetic disorders, liver or kidney problems, high-fat diets, certain medications, and low dietary levels of the amino acids lysine and methionine (substances needed to make carnitine). Carnitine deficiencies may cause symptoms such as fatigue, chest pain, muscle pain, weakness, low blood pressure, and/or confusion. A healthcare provider may recommend use of the supplement levocarnitine (L-carnitine) for individuals who have a suspected or confirmed deficiency of this nutrient.

Uses

In addition to helping those with carnitine deficiencies, L-carnitine supplementation may benefit individuals with the following conditions:

Heart Disease心臟病

Congestive Heart Failure (CHF) 充血心衰竭

High Cholesterol 高的膽固醇 

Intermittent Claudication 

Athletic Performance 

Weight Loss 減肥

Eating Disorders 飲食失調

Alcohol-related Liver Disease 酒精性肝疾病

Dementia and Memory Impairment 智力衰退和記憶障礙

Down's Syndrome 

Kidney Disease and Hemodialysis 腎疾病

Male Infertility 男性不育

Chronic Fatigue Syndrome (CFS) 慢性疲勞

Some researchers speculate that chronic fatigue syndrome may be caused by deficiencies in a variety of nutrients, including carnitine. L-carnitine has been compared to a medication for fatigue in a study of 30 people with CFS. Those who took L-carnitine did much better than those who took the medication, particularly after receiving the supplement for 4 to 8 weeks.

Shock 

Peyronie's Disease 

Hyperthyroidism 甲狀腺機能亢進症

Dietary Sources 飲食的來源

Red meat (particularly lamb) and dairy products are the primary sources of carnitine. Carnitine can also be found in fish, poultry, tempeh (fermented soybeans), wheat, asparagus, avocados, and peanut butter. Cereals, fruits, and vegetables contain little or no carnitine.

How to Take It

A typical daily diet contains anywhere from 5 to 100 mg of carnitine, depending upon whether the diet is primarily plant-based or red meat-based.

Pediatric 

If laboratory tests reveal that a child has an amino acid imbalance requiring treatment, a healthcare provider may recommend a complete amino acid supplement containing carnitine. For children on valproate for epilepsy, which can lead to a deficiency of carnitine (see Interactions section), the doctor will likely prescribe a dose of 100 mg/kg of body weight per day, not to exceed 2,000 mg per day.

Adult 

Recommended doses of L-carnitine supplements vary depending on the health condition being treated. The following list provides guidelines for some of the most common uses, based largely on doses used in studies for these conditions:

• Fat metabolism (conversion of fat to energy) and muscular performance: 1,000 to 2,000 mg usually divided into two doses

• Heart disease: 600 to 1,200 mg three times daily, or 750 mg twice daily

• Alcohol-related carnitine deficiency: 300 mg three times daily

• Male infertility: 300 to 1,000 mg three times daily

• Chronic fatigue syndrome: 500 to 1,000 mg three to four times per day

• Overactive thyroid: 2,000 to 4,000 mg per day in two to four divided doses

Precautions

Because supplements may have side effects or interact with medications, they should be taken only under the supervision of a knowledgeable healthcare provider.

Although L-carnitine does not appear to cause significant side effects, high doses (5 or more grams per day) may cause diarrhea. Other rare side effects include increased appetite, body odor, and rash.

雖然 L –carnitine 沒有顯著的副作用，但劑量太高(每天5或更多克)可能引起腹瀉。其他可能的副作用包括食慾增加，產生體味和起疹子。 

D-carnitine supplements should be avoided as they interfere with the natural form of L-carnitine and may produce undesirable side effects.

Individuals taking L-carnitine as a sports supplement to improve fat metabolism and muscular performance should stop using it at least for one week each month.

Possible Interactions 可能的相互作用