Given the limited amount of evidence of very low quality, we were not able to draw any conclusions about the effect of L-carnitine on cognitive function or its safety in healthy people.

Larger, better-quality studies conducted over a longer period of time are needed to answer our review question. Due to the limited number of included trials, short-term treatment, and inadequate reporting, we were unable to draw any conclusions about the efficacy or safety of L-carnitine for cognitive enhancement in healthy adults.

Well-designed, randomised, placebo-controlled trials of L-carnitine for cognition enhancement in cognitively healthy people, with large samples and relatively long-term follow-up, are still needed. Safe interventions to enhance cognitive function in cognitively healthy people would be very valuable for several reasons , including a better quality of life and professional success.

While L-carnitine has been reported to enhance cognitive function in some conditions, its efficacy is disputed. The evidence of its efficacy for cognitively healthy people has not previously been systematically reviewed. To assess the efficacy and safety of L-carnitine for the enhancement of cognitive function in people without cognitive impairment.

We searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group's Specialized Register, on 4 November We used the search terms 'L-carnitine' or 'acetyl-L-carnitine' or 'propionyl-L-carnitine' or 'ALC' or 'PLC' or 'ALCAR' or 'ALPAR'.

We ran additional separate searches in several other sources to ensure that we retrieved the most up-to-date results. We also reviewed the bibliographies of the randomised controlled trials identified and contacted the authors and known experts in the field and pharmaceutical companies to identify additional published or unpublished data.

Eligible trials were randomised controlled trials RCTs or quasi-RCTs, parallel-group or cross-over, that compared L-carnitine or its derivatives, acetyl-L-carnitine or propionyl-L-carnitine, at any dose and for any length of treatment, with placebo or no treatment in cognitively healthy people of any age and either gender.

We used standard methodological procedures expected by Cochrane. Two review authors independently selected trials and evaluated the methodological quality, then extracted and analysed data from the included trials. Only two RCTs were eligible. One was a cross-over trial with 18 participants. The other randomised participants to one of four treatments, of which two L-carnitine and placebo were relevant to this review, but the exact numbers of participants in these two treatment groups was not reported.

All participants were young adults. Methodological details were poorly reported, and we considered the risk of bias in both studies to be unclear. The trials assessed different cognitive outcomes. We could extract cognitive data on approximately participants from one trial.

We found no evidence that L-carnitine has any effect on reaction time, vigilance, immediate memory, or delayed recall after three days of treatment. This trial report stated that there was a small number of adverse effects, none of which were serious.

The small cross-over trial also reported no effect of L-carnitine on cognition, but did not provide data; no information was provided on adverse effects. We considered the available evidence to be of very low quality for all reported outcomes.

Language: English Deutsch Español فارسی 日本語 한국어 Polski Русский 简体中文. Background Cognition or cognitive function is a term used to describe thinking skills, including attention, memory, and reasoning. Results We found only two trials to include in the review.

Quality of the evidence It was difficult to properly assess the quality of the included trials because of poor reporting. In this cohort study, we found that 1 OLA monotherapy significantly decreased plasma levels of four L-carnitine metabolites in FES patients; 2 reduced plasma levels of 2-octenoylcarnitine and butyrylcarnitine were correlated with the cognitive improvement after treatment; and 3 baseline L-carnitine metabolite levels were not associated with cognitive improvement.

We found that OLA significantly decreased several L-carnitine metabolites levels in FES patients, including 2-octenoylcarnitine, 11z-octadecenylcarnitine, 9-decenoylcarnitine and L-palmitoylcarnitine.

All of these metabolites are known to be medium- or long-chain acylcarnitines with six or more carbons. More specifically, they are all acyl fatty acid derivative esters.

In the body, acylcarnitines can be divided into nine categories based on the size and type of acyl group: 1 short-chain ACs; 2 medium-chain ACs; 3 long-chain ACs; 4 very long-chain ACs; 5 hydroxy ACs; 6 branched chain ACs; 7 unsaturated ACs; 8 dicarboxylic ACs and 9 miscellaneous ACs.

Medium- and long-chain acylcarnitines are slightly less abundant in the body than short-chain acylcarnitines and are involved in the mitochondrial β-oxidation pathway in mitochondria. More specifically, 2-Octenoylcarnitine is an acylcarnitine having 2E -octenoyl as the acyl substituent.

L-palmitoylcarnitine is formed via palmitoyl-CoA reacts with L-carnitine, which is then moved into the mitochondrial intermembrane space. L-palmitoylcarnitine can react with the carnitine o-palmitoyltransferase 2 enzyme present in the mitochondrial inner membrane to once again form palmitoyl-CoA and L-carnitine.

Palmitoyl-CoA then enters into the β-oxidation pathway to form acyl coenzyme A aceytl-CoA. We found that levels of these three L-carnitine metabolites were decreased after treatment, which was in line with a previous study Cao et al.

However, given that no controls were recruited in this study, we do not know whether the decreased acylcarnitine levels normalized to those found in healthy controls, Acylcarnitine plays a fundamental role in the transfer of fatty acid to mitochondria for subsequent β-oxidation.

Consistent with our findings, some studies have also reported abnormal levels of acylcarnitine in various diseases. For example, 9-decenoylcarnitine has been shown to be increased the plasma of overweight individuals Kang et al.

Metabolite profiling of the British birth cohort also found a relationship between a module consisting of acylcarnitine and processing speed after controlling for life course, showing L-palmitoylcarnitine to be a hub Green et al.

Prior studies have also found acylcarnitines levels with abnormalities in the plasma of patients with schizophrenia and familial Mediterranean fever Kiykim et al. Moreover, the regulation of L-carnitine metabolites by antipsychotic drugs has been reported in clinical studies Lheureux and Hantson, ; Molina et al.

All these findings support our finding that the carnitine pathway can be regulated by OLA. The second finding was that cognitive improvement after OLA treatment was significantly associated with decreased levels of 2-octenoylcarnitine and butyrylcarnitine in schizophrenia.

And the lower the levels of 2-octenoylcarnitine and butyrylcarnitine, the better the cognitive improvement.

This finding is the first report in patients with schizophrenia, but is consistent with recent findings in AD patients. Studies in AD and preclinical AD have shown that some medium- or long-chain acylcarnitines involved in fatty acid transportation and metabolism were associated with cognitive decline Fiandaca et al.

For example, plasma acylcarnitines have been found to decrease aging and have been shown to predict conversion to mild cognitive impairment or AD. In addition, altered metabolism of medium-chain acylcarnitines and impaired ketogenesis may be metabolic features of AD Ciavardelli et al.

We cannot give an exact explanation for the close relationship between the two special acylcarnitines and cognitive improvement. However, it is known that the carnitine shuttle pathway is responsible for the transport of long-chain fatty acids from the cytoplasm into the mitochondria for subsequent β-oxidation, a process that requires aceytl-CoA and leads to the esterification of L-carnitine to form acylcarnitine derivatives Sharma and Black, It is possible that perturbation of the carnitine shuttle leads to compromised mitochondrial function, which could decrease cellular capacity to handle reactive oxygen species and increase the levels of the inflammatory cytokine, resulting in increased cellular dysfunction and cell death Mitchell et al.

The brain is highly dependent on oxidative metabolism. In the absence of carnitine, fatty acid metabolism and energy production in the brain are impaired, leading to cognitive impairment. A previous review has supported the critical role of acylcarnitine in fatty acid metabolism, ketosis and buffering the concentration ratio of acyl-CoA to free CoA in brain metabolism in neurological disorders Jones et al.

Considering the close relationship between metabolic disturbances and acylcarnitine, we further analyzed the relationship between acylcarnitine and cognitive impairment after controlling for weight gain and found that the association between decreased acylcarnitine levels and cognitive improvement remained significant.

Therefore, the association of cognitive improvement with acylcarnitine is reliable and robust, suggesting its role in schizophrenia. There were several limitations to note in this study.

First, only female patients were recruited in our study, as the majority of patients in our research center are female. Only female patients may limit generalizations to the broader population with FES schizophrenia.

Second, we did not collect data on the levels of L-carnitine metabolites in the cerebro-spinal fluid CSF. Further studies should include this data, which would lend consistency to the findings in this study. In summary, we found that OLA treatment significantly decreased L-carnitine metabolite levels and improved cognitive functions in patients with schizophrenia.

In addition, decreased carnitine metabolite levels were significantly associated with cognitive improvements after treatment. Our study provides new evidence for the involvement of L-carnitine metabolite levels in cognitive improvement after the treatment with OLA.

However, due to the small sample size and the short-term OLA monotherapy, our findings should be interpreted with great caution. Moreover, only female patients may limit generalizations to the broader population with DNFE schizophrenia. Further longitudinal studies using larger samples with longer antipsychotic treatment are warranted to understand the exact mechanism of L-carnitine metabolites in cognitive improvement in schizophrenia.

The raw data supporting the conclusion of this article will be made available by the authors, without undue reservation. The studies involving humans were approved by Ethics committee of Beijing huilongguan hospital.

The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.

No potentially identifiable images or data are presented in this study. MX: Writing—original draft. LZ: Conceptualization, data curation, investigation, writing—original draft. HL: Investigation, writing—original draft.

WW: Data curation, Investiagtion, Writing—original draft. YW: Data curation, Investiagtion, Writing—original draft. SL: Data curation, supervision, validation, writing—original draft. This study was funded by the Guangzhou Municipal Health Commission C-TS26 , Traditional Chinese Medicine Bureau of Guangdong Province No.

All funding had no role in study design, data analysis, paper submission and publication. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

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In the fight against chronic stress, depression, and age-related cognitive decline, acetyl-L-carnitine supports brain function and mental wellbeing.

For anyone looking to reduce the effects of stress on the brain, combat depression, and enhance overall brain performance, including mood and memory, the supplement acetyl-L-carnitine ALCAR should be at the top of your list. Further, ailing, poor-functioning mitochondria put a large amount of oxidative stress on the body, which can accelerate the aging process and lead to chronic inflammation.

Research has shown that ALCAR can improve cognitive function, particularly in people who are starting to experience age-related decline. In one study published in Molecular Psychiatry, researchers examined mice exposed to prolonged stress, finding structural changes in the amygdala, the part of the brain known to regulate emotions, including fear and anxiety.

During the study, mice endured 21 days of periodic confinement in a small space and then scientists tested to see how their behavior changed.

They also analyzed neurons within three regions of the amygdala. They found that neurons in the medial amygdala shrank. This kind of damage can lead to an inability to adapt to new experiences and contribute to feeling depressed.

They later repeated the chronic stress experiment, this time giving some mice ALCAR supplementation toward the end of the 21 days. These animals fared far better than the ones who did not receive ALCAR and their medial amygdalas showed more branching, or growth.

A meta-analysis found that ALCAR supplementation in humans significantly lowers depressive symptoms compared with placebo or no intervention, and does so with fewer adverse effects than established antidepressants, especially in older adults.

Further, several of the trials included in the review showed ALCAR to be as effective as prescription antidepressants in reducing depressive symptoms, with fewer side effects. The average dose was 3 grams per day. Doses ranging from 1. With its ability to easily cross the blood-brain barrier and support healthy mitochondria and energy production in the brain, in addition to reducing oxidative damage and inflammation, ALCAR is proving to be a valuable neuroprotective supplement.

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Browse Deals. Many supplements used to treat anxiety and depression also help improve focus. Creating a sense of calm can help eliminate distractions and improve concentration. When diet does not cover all of the necessary nutrients, supplements can step in. Speak with a pharmacist to learn more about supplements that can help to improve focus.

Prescription drugs can help manage chronic pain but come with the risk of side effects and addiction. A pharmacist can recommend effective natural OTC options. Many women need to continue taking medication during pregnancy. A pharmacist can help ensure the prescription is safe for mom and baby.

Medication effectiveness comes down to how drugs are used and the quality of the prescription. With adherence, patients can get the most out of the medication.

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Toggle Navigation COVID Testing COVID Booster Transfer Rx Articles Compounding Services Locations Contact Us Vaccination Clinic Inquiry. What Supplements Can I Take To Help Improve My Focus?

Neurotransmitters Neurotransmitters are the messengers of the brain. Supplements for concentration If a diet is lacking in one nutrient or another, supplements can be taken to fill in the nutritional deficit.

Gingko biloba Made from the leaf of the gingko tree, gingko biloba works by thinning the blood and increasing oxygen flow to the brain. Acetyl-L-carnitine Acetyl-L-carnitine is produced naturally in the body.

GABA GABA is an amino acid produced in the brain that blocks overactive nerve impulses. L-Theanine L-theanine is found in green tea and helps transmit nerve impulses within the brain. Inositol Inositol is found in fruits, legumes, nuts, and grains. Serotonin and dopamine imbalances will affect mood and concentration 5-HTP 5-HTP is naturally produced in the body and increases the production and synthesis of serotonin.

Mucuna pruriens Found in legumes native to Africa and Asia, Mucuna pruriens contains levodopa, a form of dopamine. Concentrate on the supplements Many supplements used to treat anxiety and depression also help improve focus.

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