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Acetyl-L-carnitine may lift your mood, sharpen your mind, and offset brain aging. It works by improving energy use in the body and boosting acetylcholine. However, most of its benefits lack stronger clinical evidence. Read on to find out if acetyl-L-carnitine is for you and how to use it for optimal results.
What is Acetyl-L-Carnitine?
Amino Acid Fuel
Acetyl-L-carnitine (ALC or ALCAR) is an amino acid that fuels energy production in your cells and supports nerve function. It supplies the acetyl group for burning fats in your mitochondria (fatty acid oxidation) and producing acetylcholine.
Your muscles and heart tissue stock different forms of carnitine as energy reserves.
Foods
Meat and other animal foods contain L-carnitine, but your liver and kidneys can also produce it from two amino acids: lysine and methionine. An enzyme called carnitine acetyltransferase (CRAT) then turns L-carnitine into acetyl-L-carnitine and vice versa.
Vegetarians consume less carnitine from the foods they eat, however, they maintain normal carnitine levels in the blood. How? The theory is that vegetarians are able to adapt to diets low in carnitine and absorb it more efficiently.
Snapshot
Proponents:
- • Combats depression
- • Helps with Alzheimer’s disease
- • May reverse brain and nerve damage
- • Improves fertility and sexual function
- • Reduces fatigue
Skeptics:
- • May cause stomach upset
- • May raise the risk of heart disease
- • May suppress thyroid hormones
Who Needs It?
Under normal conditions, your body will produce sufficient amounts of carnitine and acetyl-L-carnitine. However, the following may impair the process and raise your risk of carnitine deficiency:
- • Genetic disorders
- • Old age
- • Kidney and liver disorders
- • Antibiotics and drugs for seizures
- • Diabetes and obesity
- • Long-term fasting or calorie restriction
- • Premature birth
Do athletes and bodybuilders need more carnitine? Not quite. However, they might benefit from supplementation because higher levels of l-carnitine in the blood and muscles increase blood flow and oxygen supply, enhancing muscle recovery after exercise.
Most people use acetyl-L-carnitine to enhance their cognition and rev up energy levels. Clinical research confirms the benefits of acetyl-l-carnitine for the brain, especially in older people. We’ll cover the main ALCAR benefits below.
Your body makes enough acetyl-L-carnitine under normal conditions. Older people and kidney disease patients often lack L-carnitine and might thus require supplementation.
Acetyl-L-Carnitine vs. L-Carnitine
Both Acetyl-L-Carnitine (ALCAR) and L-carnitine combat fatigue and enhance fertility, but they also have some distinct benefits.
ALCAR boosts acetylcholine and has more pronounced effects on mental health and cognition. It also shields the brain against oxidative stress better than L-carnitine.
On the other hand, L-carnitine is a better-researched option for weight loss, physical performance, and heart health.
Acetyl-L-Carnitine Benefits
Possibly Effective:
1) Nerve Damage
Nerves are particularly sensitive to oxidative stress. Certain drugs and conditions such as diabetes can cause nerve damage (neuropathy), which manifests with pain, tingling, or numbness in legs and arms.
In two meta-analyses with more than 2,000 neuropathy patients, acetyl-L-carnitine (ALCAR) significantly reduced pain and improved nerve health.
Diabetic Neuropathy
Acetyl-L-carnitine seems to be an effective option for diabetic neuropathy. A review of six clinical trials (711 patients) suggested its ability to shield the nerves against toxic glucose levels and reduce pain in people with diabetes. However, the results are less convincing when it comes to nerve conduction speed.
Anti-HIV Treatment
Anti-HIV drugs can also cause nerve damage, antiretroviral toxic neuropathy (ATN), which is a major drawback of HIV treatment. Based on multiple reviews and clinical trials, ALCAR (2-3 g daily) can repair nerve damage and relieve pain and other symptoms in patients with ATN.
Other
According to animal trials and limited clinical evidence, acetyl-carnitine may also help with:
- • Carpal tunnel syndrome (hand and wrist nerve injury)
- • Spinal cord injury
- • Chronic pain due to nerve damage and inflammation
On the other hand, it may not help with nerve damage from chemotherapy (more details below).
A limitation for neuropathy benefits is that many studies used intravenous or intramuscular treatment; oral supplementation might not have the same effects.
Acetyl-L-carnitine can repair nerve damage and relieve pain caused by diabetes, anti-HIV treatment, and injuries. These conditions may require intravenous or intramuscular treatment.
2) Depression
Acetyl-L-carnitine (ALCAR) supplies the nerves with energy and enables the production of neurotransmitters crucial for mental health; these include acetylcholine, GABA, and glutamate.
It strengthens the myelin around the brain cells and stimulates their growth, helping to “regrow” your brain.
According to a meta-analysis of 11 clinical trials (791 patients), ALCAR is superior to placebo in reducing depressive symptoms. It seems to have effects comparable to standard antidepressants while causing fewer side effects.
Two clinical reviews came to a similar conclusion but also pointed out certain limitations that call for further research. According to one review, ALCAR is especially suitable for older patients and those struggling with side effects from antidepressants.
Rapid onset of action is another advantage of ALCAR when it comes to depression. Although patients used it for two months or more, most of them experienced improvement after one week.
Acetyl-L-carnitine may reduce depression by protecting the nerves and boosting neurotransmitters. In some studies, it had fewer side effects and acted faster than standard antidepressants.
3) Alzheimer’s Disease
No other neurotransmitter is more important for cognition and memory than acetylcholine; impaired cholinergic transmission is the hallmark of Alzheimer’s disease.
By boosting cholinergic activity in the brain, ALCAR may help prevent cognitive decline and Alzheimer’s disease.
It also increases brain levels of glutathione, shielding it against oxidative stress and amyloid beta plaques that destroy neurons in Alzheimer’s disease.
A meta-analysis summarized the data from 21 clinical trials with more than 1,200 Alzheimer’s disease patients. Long-term treatment with acetyl-L-carnitine (1.5-3g daily for 3+ months) was safe and significantly improved the patients’ mental condition.
Alzheimer’s patients receiving ALCAR had improved:
- • Attention and memory
- • Mental agility and focus (reaction time)
- • Speech and behavior
Another large review by came to a similar conclusion, though the authors emphasized most improvements were subjective. They also pointed to other statistical limitations and concluded that more research is needed to confirm the clinical effectiveness of ALCAR.
According to a study of 23 patients with drug-resistant Alzheimer’s disease, acetyl-carnitine may boost the effectiveness of standard drugs, such as donepezil (Aricept) and rivastigmine (Exelon).
Acetyl-L-carnitine may help with Alzheimer’s disease by boosting acetylcholine and reducing oxidative stress in the brain. It may also improve the effectiveness of drug treatment.
4) Fertility and Sexual Function
Men
In a meta-analysis of nine clinical trials with over 800 infertile men, a combination of L-carnitine and acetyl-L-carnitine (ALCAR) significantly improved sperm mobility. As a result, the chance of a successful pregnancy increased more than 4 times.
In 120 older patients, a combination of acetyl-carnitine and propionyl-carnitine (2 g daily each, for 6 months) was as effective as testosterone in improving sexual dysfunction. Carnitines showed even better effects on erectile function and, unlike testosterone, didn’t cause prostate enlargement.
Peyronie’s disease manifests with a curved penis during erection, due to the presence of scar tissue or plaque, which may lead to erectile dysfunction. In a study of 48 patients with this condition, ALCAR showed better results than a drug, tamoxifen. Unlike tamoxifen, ALCAR significantly reduced penile curvature while having fewer side effects.
Women
Women with hypothalamic amenorrhea have irregular cycles and fertility issues due to inadequate GnRH secretion. ALCAR increased sex hormones and improved the symptoms in three studies of 71 women.
Acetyl-L-carnitine may improve fertility and sexual function in both sexes, but the evidence for women is weaker. A combination with L-carnitine has shown the best results.
5) Cognitive Decline and Brain Damage
The brain-protective effects of acetyl-L-carnitine (ALCAR) aren’t limited to Alzheimer’s disease. It may also improve memory and reduce mental fatigue from different causes.
Studies in Older People
Maintaining good brain health is especially important for the aging brain. As cells age, they become senescent: less functional and more pro-inflammatory. As a result, they produce less acetylcholine.
Research suggests that ALCAR might offset senescence and thus improve mental health and cognition in the elderly.
In two studies with 576 older people, acetyl-L-carnitine enhanced cognition, improved mood and behavior, and reduced fatigue. In 56 older patients, it partially reversed dementia due to reduced blood flow in the brain.
Animal Studies
Many animal trials suggest that ALC may support learning, memory, and emotional health. Scientists observed its ability to shield the brain and improve cognition by:
- • Maximizing energy (ATP) production
- • Boosting mitochondrial health
- • Increasing acetylcholine
- • Scavenging free radicals
- • Preventing brain aging caused by lactate buildup in the brain
Based on these effects, acetyl-l-carnitine might also have nootropic effects (improve cognition) regardless of age, though studies haven’t researched this yet.
Alpha-Lipoic Acid Synergy
Alpha-lipoic acid is another potent antioxidant that protects the nerves against diabetes and other conditions with increased oxidative stress.
According to animal studies and limited clinical data, acetyl-L-carnitine and alpha-lipoic acid may have a synergistic effect on brain aging and oxidative damage, which makes them a potential combination for cognitive support.
Well-designed clinical trials should test the safety and efficacy of this combination.
Acetyl-L-carnitine combats brain aging and improves cognition, mood, and energy. A combination with alpha-lipoic acid may yield even better results, but the evidence is limited.
6) Hepatic Encephalopathy
Acetyl-L-carnitine was effective for brain damage due to liver disease (hepatic encephalopathy) in three clinical trials of over 250 patients. The treatment with ALCAR:
- • Reduced depression and improved cognitive function
- • Enhanced social function and general wellbeing
- • Lowered the levels of ammonia and improved other biomarkers
7) Fatigue
In 96 older people, supplementation with acetyl-L-carnitine (ALCAR) improved:
- • Fatigue after exercise, by 51%
- • Muscle pain, by 27%
- • Sleep disorders, by 28%
It also boosted mood and mental clarity while causing no side effects.
ALCAR (2 g daily) significantly improved mental fatigue and attention in 30 patients with chronic fatigue syndrome.
Patients with chronic fatigue due to multiple sclerosis may also benefit from acetyl-L-carnitine, but the available research doesn’t allow for a definite conclusion.
Acetyl-L-carnitine may boost energy production and combat fatigue. It’s particularly effective in older people who often lack carnitine.
8) Fibromyalgia Symptoms
Fibromyalgia is a complex syndrome that manifests with muscle pain, fatigue, and mood problems. Doctors are still looking for effective treatment options.
Acetyl-L-carnitine significantly reduced pain and depressive symptoms in 102 fibromyalgia patients. Researchers used a combination of oral (1000 mg/day) and intramuscular treatment.
In 65 women with fibromyalgia, ALCAR relieved pain and depression; it was equally effective as an antidepressant duloxetine.
9) Alcohol Addiction
In a study of 64 alcohol abusers, ALCAR (1g/day) provided some short-term benefits such as longer abstinence and reduced cravings. Further research should investigate the potential benefits for alcohol addiction and similar disorders in the long run.
Insufficient Evidence:
No valid clinical evidence supports the use of acetyl-L-carnitine for any of the conditions in this section. Below is a summary of up-to-date animal studies, cell-based research, or low-quality clinical trials which should spark further investigation. However, you shouldn’t interpret them as supportive of any health benefit.
Weight Loss and Bodybuilding
Acetyl-L-carnitine (ALC) is a popular supplement for boosting weight loss and physical performance, especially among bodybuilders. Most studies in this field have tested L-carnitine, and they showed mixed results.
A meta-analysis of nine clinical trials and 911 people suggested mild benefits of L-carnitine for weight loss. However, the effect tended to diminish over time, so it might be a good strategy to use it over short cutting cycles.
According to limited clinical evidence and animal trials, supplementation with L-carnitine may enhance physical performance, speed up recovery, and stimulate fat burning.
In theory, ALCAR might provide the same benefits by supplying L-carnitine, but no studies have confirmed this.
Also, comprehensive reviews have failed to confirm the above benefits of L-carnitine supplements in healthy people. Their effects may be limited to older or overweight people, kidney disease patients, and other groups with carnitine deficiency.
There’s no valid clinical evidence to support the use of ALCAR or L-carnitine for weight loss and physical performance.
Possibly Ineffective
Nerve Damage Due to Chemotherapy
Acetyl-carnitine has shown promising effects against chemotherapy-induced nerve damage in smaller clinical trials.
However, it provided no benefits in a study of 409 cancer patients. It even worsened the symptoms of nerve damage after 6 months of treatment.
Diabetes and Heart Health
Impaired fatty acid metabolism and oxidative stress contribute to diabetes. Acetyl-L-carnitine (ALCAR) may help prevent diabetes or reduce the symptoms by enhancing the breakdown of fats and scavenging free radicals.
In a small trial of 18 diabetic patients, intravenous ALCAR treatment improved glucose control.
However, a study of 229 diabetics with high blood pressure and lipids found no effects of ALCAR supplementation on glucose metabolism, lipid levels, or blood pressure.
ALCAR may not help reduce glucose and lipid levels and blood pressure.
Acetyl-L-Carnitine Dosage & Supplements
Supplements
Most products are sold as capsules with 500 mg of acetyl-L-carnitine HCl (hydrochloride). Some also contain alpha-lipoic acid.
You will also find products with different forms of carnitine combined. “Quadracarn” contains four of them, including L-carnitine and ALCAR.
Although meat and animal products are the main dietary source of carnitine, most ALCAR supplements are vegan-friendly.
Most supplements contain 500 mg of acetyl-L-carnitine per capsule. Combinations with other forms of carnitine and alpha-lipoic acid are also available.
Dosage
The below doses used in clinical trials may not apply to you personally. If your doctor suggests using ALCAR, work with them to find the optimal dosage according to your health condition and other factors.
The effective dosage of acetyl-L-carnitine for most conditions ranges from 1500 to 3000 mg, divided into two or three daily doses. Standard treatment duration is 2-3 months, though cognitive impairment and nerve damage may require 6-12 months.
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The Anti-Aging Effects of Acetyl-L-Carnitine
Acetyl-L-carnitine is the biologically active form of the amino acid L-carnitine and has been shown to protect cells throughout the body against age-related degeneration. Most clinical research has focused on the brain, where improved mood, memory and cognition has been observed in response to acetyl-L-carnitine administration. By facilitating the youthful transport of fatty acids into the cell's mitochondria, acetyl-L-carnitine better enables dietary fats to be converted to energy and muscle.
Carnitine is approved as a drug in the United States to protect against muscle wasting diseases, including heart muscle weakness and low energy levels. Despite FDA-approval, few conventional doctors prescribe carnitine to support those with cardiomyopathy, congestive heart failure, chronic fatigue, etc. The failure of doctors to prescribe this natural amino acid correlates directly with the lack of drug company advertising for the product. There is little economic motivation for drug companies to promote the benefits of carnitine to doctors when their patients can choose from hundreds of lower cost carnitine supplements available over the counter.
In addition to its "FDA-approved" indications, acetyl-L-carnitine has been shown to maintain immune competence and reduce the formation of a cell-clogging pigment called lipofuscin. The most important anti-aging effect of acetyl-L-carnitine, however, is to work with coenzyme Q10 and alpha lipoic acid to maintain the function of the mitochondria3. When the mitochondria function dwindles, degenerative disease becomes an inevitable consequence.
Foundation members use acetyl-L-carnitine as a multi-purpose anti-aging supplement. Newly published research shows this amino acid may be even more effective than previously shown.
THE ANTIAGING EFFECTS OF ACETYL-L-CARNITINE
In the early 1980s, acetyl-L-carnitine (ALC) was approved as a "drug" in Europe to treat heart and neurological disease. Americans had to wait until 1994 to legally buy acetyl-L-carnitine. Since this amino acid is sold as a "dietary supplement," it costs a lot less in the United States than its does overseas.
Reversing heart aging
The effects of aging were dramatically demonstrated when scientists measured cell energy activity and respiration rates in the heart mitochondria of rats. Both cellular energy and respiration was depressed around 40% in the older rats. When acetyl-L-carnitine was administered, their heart rates became almost completely restored to the metabolic function level of young control rats. This study showed that the heart mitochondrial content of cardiolipin, a key agent necessary for mitochondrial substrate transport, was markedly reduced in aged rats. Treatment of aged rats with acetyl-L-carnitine reversed the age-associated decline in cardiolipin content. This newly identified mechanism helps explain why acetyl-L-carnitine is so beneficial in treating congestive heart failure in humans.
Brain protection
Aging causes alterations in brain cell metabolism. Acetyl-L-carnitine has been shown to counteract several mechanisms of brain cell damage. A new study shows that acetyl-l-carnitine protects against temporary cerebral ischemia (no blood flow) by maintaining the cell's energy cycle5. Other recent studies show that acetyl-L-carnitine protects brain cells against glutamate-induced and ammonia-induced toxicity6. As people grow older, circulation to the brain diminishes, which sets off a cascade of pathological events that results in neurological impairment. Acetyl-L-carnitine appears to protect against some of the known negative effects that aging induces in the brain.
Emergency use of acetyl-L-carnitine
In animal stroke models, an 11-point neurologic deficit scoring system evaluated the treatment progression of acetyl-L-carnitine against a control vehicle. Acetyl-L-carnitine was shown to protect brain cells against ischemic injury and to improve neurological outcome with the treated animals being significantly improved over the controls. This study suggests that acetyl-L-carnitine might someday be used in hospital emergency rooms and stroke recovery centers to improve the prognosis of patients (with thrombotic or embolic stroke) who are often given little hope of full recovery.
Regenerating nerves
Acetyl-L-carnitine may facilitate nerve regeneration after nerve injury. Scientists surgically severed nerves and observed the typical motor-neuron degeneration that occurred at the site of the injury. Acetyl-L-carnitine was shown to have significant neuro-protective effect against the degeneration of traumatized motor-neurons. These observations prompted the scientists to postulate a better hypotheses concerning motor-neuron regeneration and even the possibility of inducing neuronal proliferation. These findings have practical applications in those who have suffered from loss of nerve function.
Another study showed that acetyl-L-carnitine prevented ethanol-induced brain cell alterations indicative of human fetal alcohol syndrome. The scientists who conducted this rat study stated that acetyl-L-carnitine might have an indirect anti-depressant benefit by protecting brain cells against the known neuro-toxicity effects of alcohol.
It is well known that many anti-viral HIV-drugs contribute to peripheral neuropathy. Doctors in London noted that treatment with acetyl-L-carnitine may assist in the treatment of drug-induced peripheral neuropathy.
In two related studies of diabetic nerve degeneration and neuropathy, acetyl-L-carnitine was shown to accelerate nerve regeneration after experimental injury. In the first study, doctors at the Hines VA Hospital in Illinois showed that diabetic rats treated with acetyl-L-carnitine maintained near normal nerve conduction velocity without any adverse effects on glucose, insulin or free fatty acid levels. These observations led the scientists to summarize that acetyl-L-carnitine can accelerate nerve regeneration after experimental injury. In another study, doctors at the Nagoya University School of Medicine in Japan showed that carnitine deficiency was closely related to the pathogenesis of diabetic neuropathy. The doctors concluded acetyl-L-carnitine has great potential for the treatment of this type of neuropathy.
Traditionally, some diabetics have suffered with peripheral neuropathy at various times throughout the course of their illness. Scientists now know that several mechanisms may produce this neuropathy in diabetics. In 1997, French doctors published a study stating that some of the most promising treatments for diabetic neuropathy may be gamma linolenic acid (GLA), antioxidants, aminoguanidine and, once again, acetyl-L-carnitine. It seems a particular enzyme in diabetics, which limits the availability of gamma linoleic acid, also decreases the endothelial synthesis of nitric oxide and of L-carnitine. The authors felt, though experimental, these treatments were a promising solution for diabetics.
Reports on acetyl-L-carnitine for the treatment of Alzheimer's disease have been contradictory. Some studies show encouraging degrees of efficacy, while other studies show no benefit. A placebo-controlled study at Stanford University School of Medicine in California showed that Alzheimer's disease patients under age 62 benefitted more from acetyl-L-carnitine than older patients. The doctors concluded that acetyl-L-carnitine slows the progression of Alzheimer's disease in younger subjects. Though this is an important study, Alzheimer's patients over 61 may want to still consider ALC for its other known neurological benefits, which were not evaluated in this study.
Acetyl-L-carnitine enhances energy production in every cell of the body. Two recent studies illustrate the unique ability of acetyl-L-carnitine to increase cellular respiration in aging models. A study from Berkeley examined liver parenchymal cells in old mice after feeding them a 1.5% solution of acetyl-L-carnitine for one month. The results show that acetyl-L-carnitine supplementation significantly reverses the age-associated decline of mitochondrial membrane function. A similar second study, also from Berkelely, again concluded the ability of acetyl-L-carnitine to reverse age-related mitochondrial decay.
Glycosylation and glycation are terms used to describe the binding of sugars to proteins that form non-functioning structures (crosslinks) in the body. Glycation-induced protein cross linking is most notable in the lense of the eye (cataract), the brain (senility) and the collagen of the skin. Protein glycation has been implicated in the development of cataracts. Scientists recently evaluated the effects of L-carnitine and acetyl-L-carnitine on the glycation of lens proteins. The results show that acetyl-L-carnitine suppresses glycation by 42%, but that l-carnitine has no effect. Additional evaluation shows that acetyl-L-carnitine produces a 70% reduction in one measurement of Advanced Glycation End products (AGEs). It is the formation of AGEs that makes cataract irreversible. This in-vitro study shows, for the first time, that acetyl-L-carnitine (but not L-carnitine) may prevent cataract by preventing glycation-mediated protein damage in the eye lense.
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