Acetyl-L Carnitine Overview

active brain
Acetyl-L-carnitine has shown some promise in enhancing quality of life for people with cognitive problems and nerve damage.
iStockphoto/Sebastian Kaulitzki

Better mental function and weight loss in the same bottle. It's an appealing proposition, and one that the proponents of acetyl-L-carnitine make regularly. Whether these claims hold any water is a murkier issue.

Let's start with what we do know. Acetyl-L-carnitine is one of several forms of carnitine at work in your body. Carnitines carry certain fatty acids to mitochondria to be burned as fuel. They also carry away the waste products of this process. In a healthy body, the kidneys regulate the level of carnitine -- if you have too much, they get rid of what you don't need. If your diet is low in carnitine, the kidneys hang on to what you have [source: NIH].


All carnitines are antioxidants, and because you can manufacture them yourself, they're classed as nonessential nutrients. Certain people do have carnitine deficiencies -- either genetic or induced by medication -- that stem from the inability to process certain dietary nutrients. Supplements can often help these patients. (You'll probably know if you are such a patient -- carnitine deficiency usually accompanies a more severe problem, such as kidney failure or cancer [source: NIH].)

The carnitines work in different but related ways. Some are more closely tied to cardiac health, some to metabolism and some to neurological health. Because some studies implicate mitochondrial decay as a cause of aging, some people speculate that using carnitine to maintain mitochondrial function could stave off symptoms of aging -- in particular, the frightening mental declines that accompany age-related illnesses such as Alzheimer's [source: NIH].

The way acetyl-L-carnitine works with your mitochondria helps your body metabolize fat. That makes it an appealing prospect for weight loss as well as for mental function, since the nervous system relies on certain fats. So far, though, claims about acetyl-L-carnitine and weight loss have had more style than substance.

This article will tell you a bit more about acetyl-L-carnitine including what we know and what we don't know. You'll also find out about the possible benefits and risks of taking it and its role in weight loss and cognitive function.


Acetyl-L Carnitine at Work in Your Body

Without acetyl-L-carnitine, the mitochondria can't absorb and metabolize fatty acids. This process has led to the claim that acetyl-L-carnitine can aid in weight loss.

There is little actual proof to support that claim, or the claim that acetyl-L-carnitine can lead to a better fat-to-muscle ratio. The supplement may improve the endurance of patients with emphysema (also known as COPD, or chronic obstructive pulmonary disease), and relieve the fatigue associated with fibromyalgia and celiac disease [source: NAT]. If you're already adhering to a substantial exercise program, though, there's no proof that acetyl-L carnitine will make a difference in your results.


It is somewhat more promising as a treatment for certain neural disorders. Acetyl-L-carnitine contains an acetyl group that is essential for the production of a key neurotransmitter [source: UMHS]. The nervous system depends on fat metabolism. Fat is a major component of the myelin sheath that coats each nerve cell. The chemical composition of the myelin sheath is what allows impulses to jump across synapses (the spaces between nerve cells) and travel through the body to turn into actions, sensations, ideas or feelings. The breakdown of the myelin sheath can prevent the nervous system from being able to communicate effectively with itself. That's what happens in diseases such as multiple sclerosis. A myelin sheath with a high fat content performs more effectively, insulating the nerve and allowing the impulse to travel faster [source: Nagel].

Because of the way acetyl-L-carnitine seems to aid in fat metabolism, some doctors believe it shows promise as a treatment for certain nervous and cognitive disorders. Among these disorders are dysthymia (mild depression), attention deficit and hyperactivity disorder (ADHD) Alzheimer's disease, the neural degeneration associated with cirrhosis and obsessive-compulsive disorder (OCD) [sources: Arnold, NAT]. Acetyl-L-carnitine has been studied as a way to reduce the hyperactivity associated with fragile X syndrome, a serious genetic disorder, but results are inconclusive [source: NAT].

Some complications of diabetes also impair the nerves. Certain doctors consider acetyl-L-carnitine a promising candidate for repairing the damage wrought by diabetic neuropathy, a harrowing complication that erodes nervous function in the arms and legs -- and sometimes in the heart -- leading to pain and numbness. But clinical proof is lacking, and at least one study indicates that carnitine supplements might actually hurt diabetics by increasing blood triglyceride levels (the amount of fat in the circulatory system) [source: NAT].

What do we definitely know about the benefits of acetyl-L-carnitine? Read on.


Acetyl-L Carnitine Benefits

Although much more study is needed, and several existing studies have been significantly flawed, acetyl-L-carnitine does seem to have promise in enhancing quality of life for people with cognitive problems and nerve damage, especially when those problems are the side effects of disease or other drug therapies [source: UMHS].

For example, some AIDS and HIV treatments cause muscular wasting and impair nervous function. There's a possibility that acetyl-L-carnitine could restore some of that function.


Likewise, alcohol abuse can gradually impair nervous function, partly because the liver loses its ability to process fat. In severe cases, it leads to a condition called hepatic encephalopathy. Acetyl-L-carnitine might help restore the balance. However, severe, long-term alcoholism has many cognitive effects that go beyond fat metabolism.

In a study, the drug also seemed to help a group of seniors with mild Alzheimer's disease, the progressive (and irreversible) neurological disorder that gradually destroys a person's memory, independence, motor functions and sense of self. Some patients who took supplements of acetyl-L-carnitine had reduced symptoms of dementia [source: NAT]. Later studies, though, were unable to duplicate this success [source: Hudson].

Another group of seniors with mild depression saw significant improvement following regular acetyl-L-carnitine supplements [source: NAT]. Some cases of depression are related to chemical imbalances in the brain and nervous system, so it's hypothesized that acetyl-L-carnitine would treat depression by improving the overall chemical function of the nervous system.

Of course, happy senior citizens and recovering alcoholics are not nearly as alluring as the image of you with bodybuilder muscles and increased sexual function, so those tend to be the aspects of acetyl-L-carnitine that the pill industry touts. Ironically, these are the claims with the least scientific evidence to back them up [source: UMMC]. Acetyl-L-carnitine may aid in the treatment of Peyronie's disease, which can affect male sexual function [source: NAT]. But it's probably not going to become the new Viagra any time soon.

What are the risks of taking acetyl-L carnitine? Read on.


Acetyl-L Carnitine Side Effects

Acetyl-L-carnitine seems to be safe in general. Clinical trials have included children, with no marked side effects [source: Arnold].

There is some evidence that its usage may lead to mild symptoms. Some of them are not surprising, given that the supplement may affect metabolic processes. They include nausea or vomiting, diarrhea, skin rash, agitation, increased appetite and altered or unpleasant body odor [sources: UMMC, UMHS]


One doctor has reported that a bipolar patient who began taking acetyl-L-carnitine had a psychotic episode that might have been triggered by the supplement [source: Evcimen]. Since acetyl-L-carnitine is often recommended for cognitive problems, which can be accompanied by mood disorders, patients with histories of mood imbalances should talk to their doctors before trying the supplement.

People taking certain drugs should probably avoid acetyl-L-carnitine. Some drugs reduce its effectiveness. Others can actually react with acetyl-L-carnitine to cause negative side effects. These drugs include:

  • Cisplatin (also called Platinol), a chemotherapy drug
  • The HIV drugs didanosine and stavudine
  • Paclitaxel or Taxol, a naturally derived cancer treatment [source: UMHS]

Acetyl-L-carnitine may be contraindicated for patients on dialysis or patients with high blood lipids. And although it may help patients with diabetes, heart disease, vascular disease and complications of alcoholism, it's especially critical that these patients talk to their doctors before beginning a course of acetyl-L-carnitine supplements. All these conditions affect the body's ability to handle waste products, so drugs may have unusual effects. Since acetyl-L-carnitine can alter the effects of other drugs, it may also interfere with the patients' existing therapies [source: UMMC].

Other drug regimens -- including AZT, Accutane and some anticonvulsants and cancer meds -- may inhibit your body's ability to produce its own acetyl-L-carnitine [source: UMMC]. The supplemental regimen may be a good counterpart to these therapies, but again, check with your doctor first.


Acetyl-L Carnitine and Weight Loss

Perhaps nothing reveals our collective longing for a weight-loss wonder drug so much as the ever-more-fantastic claims of the supplement industry, or the Photoshopped before-and-after pics of sagging guts and rock-hard abs.

Plenty of supplement sellers tout acetyl-L-carnitine's effects on fat metabolism. You'll actually start getting thinner at the mitochondrial level! Every cell in your body will get more efficient! You've never exercised like this before!


These claims might come from small, limited studies that link acetyl-L-carnitine to a balanced thyroid function, which certainly has an effect on your metabolism. But these studies dealt with the correction of an actual medical condition -- hyperthyroidism -- and results were not conclusive [source: UMMC].

The Atkins Diet listed acetyl-L-carnitine as a supplement that could help low-carb dieters with weight loss. Of course, the problem with that claim is that the Atkins plan, far from having widespread medical acceptance, is considered a fad diet that may actually have detrimental health effects (notably on blood lipids and cholesterol) [source: WebMD].

Unfortunately, there's just no proof that acetyl-L carnitine can help the Average Joe (or Jane) turn into Joe (or Jane) Six-Pack [sources: UMMC, NAT]. In fact, thanks to the kidneys' intervention, athletes who take acetyl-L carnitine supplements don't even show elevated levels of the chemical [source: NIH]. You're probably better off with the standard regimen of exercise, proper diet and sleep.

As for the necessity of taking a supplement, you're probably already getting enough acetyl-L-carnitine from dietary sources such as these:

  • Lamb and other red meat
  • Dairy products
  • Fish
  • Poultry
  • Peanuts
  • Tempeh
  • Wheat
  • Asparagus
  • Avocados [source: UMMC]

Acetyl-L-carnitine might actually help in treating some cognitive problems. We'll take a look at one on the next page.


Acetyl-L Carnitine and OCD

Obsessive-compulsive disorder, or OCD, can be a crippling cognitive impairment. It is classed as an anxiety disorder, akin to post-traumatic stress disorder and certain social phobias. Patients are often subject to irrational and uncontrollable impulses and tics, such as turning a light switch on and off 40 times before leaving a room. The tics may be tied to powerful senses of superstition -- "everyone in my family will die if I don't touch the doorknob three times." Patients may be aware of the irrational nature of the impulses, and humiliated by the public appearance of symptoms, but powerless to control the urges. The social consequences can be severe, and the rituals associated with OCD can destroy patients' productivity and focus, even threatening their ability to complete their studies or hold a job [source: NIMH].

Clearly, people suffering from OCD yearn for an effective therapy. Treatments include support groups and stress-management techniques, such as meditation. On the medical side, antianxiety drugs and antidepressants are both prescribed. Some of these have familiar names: Paxil, Zoloft and Prozac. They're called SSRIs, or selective serotonin reuptake inhibitors. They regulate the way the brain processes the mysterious neurotransmitter called serotonin [source: NIMH].


SSRIs have different effects depending on the patient. Some of these drugs can create heightened tolerance and dependence in the body, leading to withdrawal symptoms and other complications if the patient attempts to change therapies. The drugs' side effects, such as decreased libido, may themselves be sources of depression, as well as more severe medical problems such as blood clotting disorders [source: Harvard Health]. If acetyl-L-carnitine helps increase the effects of these drugs, it could allow patients to lower their dosages, reducing the incidence of some side effects.

The OCD Recovery Center lists acetyl-L-carnitine as a medicinal complement (that is, not a central therapy, but a treatment that may act to strengthen another therapy), citing a study that indicated acetyl-L-carnitine had benefits in improving visual memory and short-term memory. These effects could help patients with OCD regain some of their focus.

As with virtually every study involving acetyl-L-carnitine, more research is needed. Patients with OCD should check with their doctors before starting a regimen of acetyl-L-carnitine and those who do start a course of supplements should monitor their dosage and symptoms carefully.

What's the bottom line about acetyl-L-carnitine? It's probably more important for helping people with cognitive problems than for tweaking your weight-loss efforts.

To learn more, visit the links on the next page.


Lots More Information

Related HowStuffWorks Articles

  • Arnold, L. Eugene, Antonino Amato, Hernan Bozzolo, Jill Hollway, Amy Cook, Yaser Ramadan, Lindsay Crowl, Dan Zhang, Susan Thompson, Giussepe Testa, Vernon Kliewer, Timothy Wigal, Keith McBurnett, Michael Manos. "Acetyl-L Carnitine (ACL) in Attention Deficit/Hyperactivity Disorder." Journal of Child and Adolescent Psychopharmacology. December 2007. (Accessed 3/16/09)
  • Evcimen, Harun. "Psychosis Precipitated by Acetyl-L Carnitine in a Patient with Bipolar Disorder." Journal of Clinical Psychiatry, accessed through NIH PubMed. 2007. (Accessed 3/16/09)
  • Harvard Health. "SSRI Side Effects: Harvard Mental Health Letter discusses the real risks of antidepressants." May 2005. (Accessed 3/16/09)
  • Hitti, Miranda. "Antioxidants May Help Fight Fat." WebMD. November 2, 2007. (Accessed 3/16/09)
  • Hudson SA, Tibet N. Acetyl-l-carnitine for dementia. Cochrane Database of Systematic Reviews 2003, Issue 2. (Accessed 3/16/09)
  • Nagel, Sandra. "Myelin Sheath." Biological Psychology. Athabasca University. January 24, 2006. (Accessed 3/16/09)
  • National and Alternative Treatments Index. "Carnitine." (Accessed 3/16/09)
  • National Institutes of Health. "The Use of a Mitochondrial Enhancement Treatment in Bipolar Disorder." Clinical Trials. 2008. (Accessed 3/16/09)
  • National Institute of Mental Health. "Obsessive-Compulsive Disorder." 2009. (Accessed 3/16/09)
  • Nordkvist, Christian. "Stem Cells from Patient's Fat Used to Grow New Nerves." Medical News Today. October 21, 2007. (Accessed 3/16/09)
  • Office of Dietary Supplements. "Carnitine." National Institutes of Health. June 15, 2005. (Accessed 3/23/09)
  • University of Maryland Medical Center. "Carnitine (L-carnitine)." Medical Reference: Complementary Medicine. 2008. (Accessed 3/16/09)
  • University of MichiganHealth System. "Acetyl-L-Carnitine." Healthwise Knowledgebase. September 1, 2007. (Accessed 3/16/09) id=6&action=detail&AEProductID=hw_cam&AEArticleID=hn-2795007