Carnitine (L-carnitine)

Carnitine is a substance that helps the body turn fat into energy. Your body makes it in the liver and kidneys and stores it in the skeletal muscles, heart, brain, and sperm.

Usually, your body can make all the carnitine it needs. Some people, however, may not have enough carnitine because their bodies cannot make enough or cannot transport it into tissues so it can be used. Other conditions, such as angina or intermittent claudication, can also cause low levels of carnitine in the body, as can some medications.

Carnitine has been proposed as a treatment for many conditions because it acts as an antioxidant. Antioxidants fight harmful particles in the body known as free radicals, which damage cells and tamper with DNA. Antioxidants can neutralize free radicals and may reduce or help prevent some of the damage they cause.

Carnitine may help treat are certain conditions. Serious diseases require conventional medical treatment, and you should talk to your health care provider before taking carnitine. For other conditions, such as fatigue or improving athletic performance, carnitine seems safe but may not help much.

Heart Conditions

Peripheral Vascular Disease

Reduced blood flow to the legs from atherosclerosis or hardening of the arteries, where plaque builds up in the arteries, often causes an aching or cramping pain in the legs while walking or exercising. This pain is called intermittent claudication, and the reduced blood flow to the legs is called peripheral vascular disease (PVD). Several studies show that carnitine can help reduce symptoms and improve mobility among people with intermittent claudication. Most studies have used propionyl-L-carnitine. Scientists do not know whether L-carnitine would work the same.

Diabetic Neuropathy

Diabetic neuropathy happens when high blood sugar levels damage nerves in the body, especially the arms, legs, and feet, causing pain and numbness. Preliminary studies suggest acetyl-L-carnitine may help reduce pain and increase feeling in affected nerves. It is also possible that carnitine can help nerves regenerate. More research is needed.

Exercise Performance

Although carnitine is often taken to boost exercise performance, more research is needed.

Weight Loss

Although L-carnitine has been marketed as a weight loss supplement, scientific evidence is lacking. Some studies show that oral carnitine may help reduce fat mass, increase muscle mass, and reduce fatigue, which may contribute to weight loss in some people.

Alzheimer Disease and Memory Impairment

Evidence is mixed as to whether carnitine is useful in treating Alzheimer disease. Several early studies showed that acetyl-L-carnitine, might help slow down the progression of Alzheimer disease, relieve depression related to senility and other forms of dementia, and improve memory in the elderly. But larger and better-designed studies found it did not help at all. People should take carnitine for Alzheimer disease and other forms of dementia only under the supervision of their provider.

Kidney Disease and Dialysis

Because the kidneys make carnitine, kidney disease could lead to low levels of carnitine in the body. If you have kidney disease, your provider may prescribe carnitine. DO NOT take carnitine without medical supervision.

Male Infertility

Low sperm counts have been linked to low carnitine levels in men. Several studies suggest that L-carnitine supplements may increase sperm count and motility.

Erectile Dysfunction

Preliminary studies suggest propionyl-L-carnitine may help improve male sexual function. One study found that carnitine improved the effectiveness of sidenafil (Viagra) in men with diabetes who had not previously responded to Viagra. In another study, a combination of propionyl-L-carnitine and acetyl-L-carnitine improved the effectiveness of Viagra in men who had erectile dysfunction after prostate surgery. More studies are needed.

Peyronie Disease

Peyronie disease is characterized by a curvature of the penis that leads to pain during an erection. One promising study compared acetyl-L-carnitine to the medication tamoxifen in 48 men with this condition. Acetyl-L-carnitine worked better than tamoxifen at reducing pain during sex and reducing the curve of the penis. Acetyl-L-carnitine also had fewer side effects than tamoxifen. More research is needed.

Hyperthyroidism

Some research suggests that L-carnitine may help prevent or reduce symptoms of an overactive thyroid, such as insomnia, nervousness, heart palpitations, and tremors. In fact, in one study, a small group of people with hyperthyroidism saw these symptoms improve, and their body temperature become normal, when taking carnitine. But a larger, better-designed clinical trial is needed to see if carnitine really works. In addition, researchers think carnitine may work by blocking the action of thyroid hormone, which could be dangerous for people with low thyroid levels. DO NOT take carnitine for hyperthyroidism without your doctor's supervision.

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Review Date: 12/28/2014  

Reviewed By: Steven D. Ehrlich, NMD, Solutions Acupuncture, a private practice specializing in complementary and alternative medicine, Phoenix, AZ. Review provided by VeriMed Healthcare Network.

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