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Met4.0
L-Methionine Research
Mostly mechanism / observational
38 peer-reviewed studies
What the evidence says
Mostly mechanism / observational
Most L-Methionine studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from high-quality meta-analyses and randomised trials published 2005–2026 with a typical study size of 132 participants.
Based on 38 studies · 12 meta-analyses · 13 RCTs · 65,251 total participants
Confidence
High confidence
What the studies found
2helped· 36 more without graded effect data
By outcome
Depression & mood
Mostly mechanism / observational18 studies
Therapeutic & clinical
Mostly mechanism / observational17 studies
Women's health
Mostly mechanism / observational5 studies
Liver health
Mostly mechanism / observational4 studies
Methylation & amino-acid metabolism
Mostly mechanism / observational4 studies
Glucose & metabolic
Mostly mechanism / observational3 studies
InflammationMethylation/detox precursor role; no trials show an anti-inflammatory benefit · 2-4 weeks
Mostly mechanism / observational3 studies
Cognitive function
Too few graded studies2 studies
Heart & blood pressure
Too few graded studies2 studies
Safety profile
Too few graded studies2 studies
Anxiety & stress
Too few graded studies1 study
Pain & analgesia
Too few graded studies1 study
Immune support
Too few graded studies1 study
By the numbers
Pulled from 20 studies with measurable effects
Likely real effects
67%
across studies
People studied
65k
typical study: 132 people
Strongest designs
25
12 pooled, 13 randomised
Showed benefit
100%
2/2 studies
How long studies ran
1–3 months
3
3+ months
1
Populations Studied
Patients with depression2
General population2
Patients with chronic liver disease1
Major depressive disorder patients1
Active research area
23 studies in the last 5 years · Latest meta-analysis: 2026
200520152026
1Depression symptoms reliefMeta-AnalysisCited 9×n=1,522 · large study2024
SAMe may provide relief of depression symptoms similar to imipramine or escitalopram.
Peng TR et al. · General hospital psychiatry (2024)
SAMe may provide relief of depression symptoms similar to imipramine or escitalopram.
However, the results of the comparisons should be interpreted with caution due to the small number of studies and the large range of SAMe doses that were used in the included trials.
Therefore, we recommend that patients discuss treatment options with their doctor before taking SAMe.
2Treatment of chronic liver diseaseMeta-AnalysisCited 41×n=705 · large study2015
However, SAMe also demonstrated limited clinical value in the treatment of certain chronic liver diseases.
Guo T et al. · PloS one (2015)
In a subgroup analysis of gravidas and children, several of the included data indicated that there was a significant difference in the pruritus score.
Furthermore, the results regarding ursodeoxycholic acid (UDCA) and stronger neo-minophagen C (SNMC) indicated that both treatments were more effective than SAMe was in certain chronic liver diseases.
These findings suggest that SAMe could be used as the basis of a medication regimen for liver function improvement because of its safety.
3Peripheral blood metabolites in major depressive disorderMeta-AnalysisCited 171×n=46 · small study2021
MDD patients were characterized by higher levels of asymmetric dimethylarginine, tyramine, 2-hydroxybutyric acid, phosphatidylcholine (32:1), and taurochenodesoxycholic acid and lower levels of L-acetylcarnitine, creatinine, L-asparagine, L-glutamine, linoleic acid... compared with controls.
Pu J et al. · Molecular psychiatry (2021)
Pathway and network analyses revealed altered amino acid metabolism and lipid metabolism, especially for the tryptophan-kynurenine pathway and fatty acid metabolism, in the peripheral system of MDD patients.
Our findings may facilitate biomarker development and the elucidation of the molecular mechanisms that underly MDD.
Currently the scientific evidence is insufficiently robust to establish definitive clinical practice guidelines, but processes could be established to track the impact of these ingredients.
Crawford C et al. · Pain medicine (Malden, Mass.) (2019)
Currently the scientific evidence is insufficiently robust to establish definitive clinical practice guidelines, but processes could be established to track the impact of these ingredients.
Until then, providers have the evidence needed to make informed decisions about the safe use of these dietary ingredients, and future research can address existing gaps.
No recommendations were made when the evidence was low quality or trade-offs were so closely balanced that any recommendation would be too speculative.
Crawford C et al. · Pain medicine (Malden, Mass.) (2019)
No recommendations were made when the evidence was low quality or trade-offs were so closely balanced that any recommendation would be too speculative.
Research recommendations are provided to enhance the quality and body of evidence for the most promising ingredients.
Clinicians and those with chronic pain can rely on evidence-based recommendations to inform their decisions.
However, there is currently a paucity of high-quality data regarding the use of add-on treatments in patients with MDD who are inadequate responders to antidepressants, with quetiapine XR presenting the most comprehensive evidence base to date.
Turner P et al. · Journal of psychopharmacology (Oxford, England) (2014)
Comparison of the different drug classes indicated that most interventions had similar efficacy.
The likelihood of response was significantly greater with SAMe versus placebo and lithium and with quetiapine XR versus placebo.
Most add-on interventions demonstrated comparable efficacy in patients with MDD and an inadequate response to initial antidepressants.
11Systematic ReviewCited 6×n=14 · very small study2021
The methodological shortcoming of existing studies and directions for future research are discussed to facilitate high-quality research in this evolving area of nutritional psychiatry.
Qureshi FM et al. · Aggressive behavior (2021)
Out of the 14 studies, 5 reported a beneficial effect of nutritional supplementation (omega-3 fatty acids, vitamins/minerals, S-adenosyl-l-methionine, or tryptophan).
The results overall indicated that research in this area is in its infancy: very few studies examined the same composition of nutritional supplementation and when they did so the results were contradictory.
The methodological shortcoming of existing studies and directions for future research are discussed to facilitate high-quality research in this evolving area of nutritional psychiatry.
Therefore, ursodeoxycholic acid, pirfenidone, S-adenosyl-L-methionine, and N-acetylcysteine could represent therapeutic strategies for the treatment of liver pathologies.
Muriel P et al. · International journal of molecular sciences (2026)
N-acetylcysteine (NAC) is a precursor to L-cysteine and GSH and is used in clinical settings to treat cancer, nephropathy, heart disease, pulmonary fibrosis, polycystic ovary syndrome, and influenza.
Regarding the liver, NAC is the most accepted treatment for DILI, especially after paracetamol overdose.
Owing to its antioxidant and anti-inflammatory actions, NAC has been successfully used to treat chronic liver injuries, including hepatosteatosis and fibrosis.
14Depression treatment outcomesMeta-AnalysisCited 40×n=185 · medium study2010
Participants in CAM trials were more likely to be female and to have a lower placebo-response rate compared to those in standard antidepressant trials for MDD.
Freeman MP et al. · The Journal of clinical psychiatry (2010)
Participants in CAM trials were more likely to be female and to have a lower placebo-response rate compared to those in standard antidepressant trials for MDD.
Trials of standard antidepressants and CAM therapies were composed of patients with similar depression severity.
15Antioxidant treatment effectiveness for ALSSystematic ReviewCited 66×n=23 · very small study2008
While there is no substantial clinical trial evidence to support their clinical use, there is no clear contraindication.
Orrell RW et al. · Amyotrophic lateral sclerosis : official publication of the World Federation of Neurology Research Group on Motor Neuron Diseases (2008)
Further well-designed trials of medications such as vitamin C and E are unlikely to be performed.
If future trials of antioxidant medications are performed, careful attention should be given to sample size, outcome measures, and duration of the trial.
The high tolerance and safety, and relatively low cost of vitamins C and E, and other considerations related to the lack of other effective treatments for amyotrophic lateral sclerosis, explain the continuing use of these vitamins by physicians and people with amyotrophic lateral sclerosis.
16Subclinical depression symptomsRCTCited 1×n=140 · medium study2023
Conclusions: The received results confirm the available evidence for the properties of SAMe in depression and complement them with evidence of the ef-fectiveness of the Deprilium® complex that contains SAMe and L-methylfolate with methylcobalamin, which together produce pharmacological and clinical synergy to reduce the severity of subclinical depressive manifestations in patients with NCD.
Results: After 60 days a statistically significant difference was observed in all clinical indicators between the intervention group and the control group.
When comparing the indicators of the intervention group on the 1st and on the 60th day of the study, statistically significant changes (p <0.000) were observed in all three indicators.
Further studies of the effectiveness of the use of the Deprilium® complex in patients with NCD are required.
17Liver fat content reductionRCTCited 18×n=140 · medium study2022
Our results showed that a new combination of bioactive molecules as nutraceutical was safe and effective in reducing liver fat content over 12 weeks in individuals with hepatic steatosis.
Ferro Y et al. · Journal of translational medicine (2022)
The CAP score reduction (%) was even greater in those with aged 60 or less, low baseline HDL-C, AST reduction as well as in men.
Our results showed that a new combination of bioactive molecules as nutraceutical was safe and effective in reducing liver fat content over 12 weeks in individuals with hepatic steatosis.
18Clinical parameters improvement in PCOSRCTCited 5×n=96 · small study2023
This study showed that the antioxidant combination might be a suitable therapy for patients with PCOS when oral contraceptive is not indicated, because in all groups clinical parameters, irregular menstruation as well as androstenedione and quality of life were significantly improved with no statistical difference between groups.
Pingarrón Santofímia C et al. · Gynecological endocrinology : the official journal of the International Society of Gynecological Endocrinology (2023)
Androstenedione was significantly reduced in all groups.
Clinical parameters that significantly improved in all groups were hirsutism, acne, irregular menstruation, and quality of life, with no statistical differences between the groups.