Month: December 2025

Human studies of ergothioneine

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Here are five 2025 human ergothioneine studies, starting with a clinical trial of healthy older adults:

“In this 16-week randomized, double-blind, placebo-controlled trial, 147 adults aged 55–79 with subjective memory complaints received ergothioneine (10 mg or 25 mg/day ErgoActive®) or placebo. Across all the groups, approximately 73% of participants in each group were female, with a median age of 69 years.

The primary outcome was the change in composite memory. Secondary outcomes included other cognitive domains, subjective memory and sleep quality, and blood biomarkers. At baseline, participants showed slightly above-average cognitive function (neurocognitive index median = 105), with plasma ergothioneine levels of median = 1154 nM.

Although not synthesized in the human body, ergothioneine is efficiently absorbed via the OCTN1 transporter (also known as the ergothioneine transporter, or ETT), which is expressed in many tissues, including the intestine, red blood cells, kidneys, bone marrow, immune cells, skin, and brain. This transporter enables ergothioneine to accumulate in high concentrations in organs vulnerable to oxidative stress and inflammation. Ergothioneine has multiple cellular protective functions, including scavenging reactive oxygen species, chelating redox-active metals, suppressing pro-inflammatory signaling, and protecting mitochondrial function.

Plasma ergothioneine increased by ~3- and ~6-fold for 10 mg, and ~6- and ~16-fold for 25 mg, at weeks 4 and 16, respectively.

While the primary outcome, composite memory, showed early improvement in the 25 mg group compared to baseline, this effect was not sustained and did not differ from placebo. Reaction time showed a significant treatment-by-time interaction favoring ergothioneine, yet the between-group differences were not significant, suggesting that any potential benefits were modest and require validation in larger or longer studies.

Other cognitive effects observed were primarily within-group and not consistently dose-responsive, highlighting the challenge of detecting objective cognitive changes over a relatively short study duration in high-functioning healthy populations. However, positive effects of ergothioneine supplementation were observed on subjective measures of prospective memory and sleep initiation that were not seen in the placebo group.

This trial adds to the growing body of evidence supporting the favorable safety profile of ergothioneine. No adverse events attributable to ergothioneine were reported. Additionally, we observed potential hepatoprotective effects, with significant reductions in the plasma AST and ALT levels, particularly among males in the ERG 25 mg group.”

https://www.mdpi.com/1661-3821/5/3/15 “The Effect of Ergothioneine Supplementation on Cognitive Function, Memory, and Sleep in Older Adults with Subjective Memory Complaints: A Randomized Placebo-Controlled Trial”

The third graphic for Ergothioneine dosing, Part 2 showed a human study where a 25 mg dosing stopped after Day 7, but the plasma ergothioneine level stayed significantly higher than baseline through Day 35.

The second graphic for Ergothioneine dosing, Part 2 was a male mouse experiment where plasma ergothioneine levels of a human equivalent 22 mg to 28 mg daily dose kept rising through 92 weeks.

This trial couldn’t explain the desirability of a 25 mg daily dose that was likely (per the second and third graphics for Ergothioneine dosing, Part 2) to sustain the subjects’ increased plasma ergothioneine levels well after the trial ended at Week 16. What effects can be expected from a sustained plasma ergothioneine level that’s 16 times higher than the subjects’ initial levels? Were these 16-fold sustained plasma ergothioneine levels better or worse than the 6-fold increases in the 10 mg group, both of which were likely to continue past the trial’s end?

A representative of the trial’s sponsoring company talked a little more about the trial in this interview:

Another clinical trial investigated ergothioneine’s effects on skin:

“We conducted an 8-week, randomized, double-blind, placebo-controlled clinical trial to evaluate effects of daily oral supplementation with 30 mg of ergothioneine (DR.ERGO®) on skin parameters in healthy adult women aged 35–59 years who reported subjective signs of skin aging. Objective measurements including melanin and erythema indices, skin glossiness, elasticity, and wrinkle and pigmentation counts were used to comprehensively evaluate changes in skin condition.

The OCTN1 transporter is preferentially expressed in basal and granular epidermal layers, where cellular renewal and barrier maintenance are most active. Once internalized, ergothioneine localizes to mitochondria, where it directly scavenges reactive oxygen species (ROS) and protects mitochondrial DNA from UV- and inflammation-induced damage.

At the signaling level, ergothioneine activates key protective pathways such as the Nrf2/ARE axis, enhancing expression of antioxidant enzymes including HO-1, NQO1, and γ-GCLC. These enzymes contribute to redox homeostasis and glutathione regeneration, reinforcing cellular defense systems against photoaging and environmental insult.

In parallel, ergothioneine modulates the PI3K/Akt/Nrf2 and SIRT1/Nrf2 pathways, which are implicated in collagen preservation, inflammation resolution, and mitochondrial maintenance. These pathways converge to reduce matrix metalloproteinase (MMP) activity, enhance collagen synthesis, and suppress pro-inflammatory cytokines (TNF-α, IL-6, IL-1β), all of which are central to maintaining skin structure and function.

Compared to placebo, the DR.ERGO® ergothioneine group showed significantly greater improvements in melanin and erythema reduction, skin glossiness, elasticity, and wrinkle and spot reduction. No adverse events were reported.

These findings corroborate and extend previous clinical evidence from (Hanayama et al., 2024), who investigated an ergothioneine-rich mushroom extract (Pleurotus sp., 25 mg ergothioneine/day) in a 12-week randomized double-blind trial, and (Chunyue Zhang, 2023), who examined pure ergothioneine supplementation (25 mg/day) in a 4-week open-label study. We contextualized our results within this existing literature by comparing key outcomes.

Several limitations should be acknowledged:

  1. The study cohort consisted solely of Japanese women aged 35–59 years, which may limit generalizability across sexes, ethnicities, and age groups.
  2. The 8-week intervention period, while sufficient to detect short-term effects, does not allow conclusions about the sustainability of benefits or the risk of relapse upon discontinuation.
  3. The placebo group also showed modest improvements in self-perception, highlighting the well-documented placebo response in beauty and wellness studies.
  4. This study focused on a single daily dosage (30 mg/day) without evaluating dose–response relationships, and hydration-specific endpoints such as corneometry or transepidermal water loss (TEWL) were not included.”

https://www.medrxiv.org/content/10.1101/2025.10.16.25337962v1.full-text “Effects of Continuous Oral Intake of DR.ERGO® Ergothioneine Capsules on Skin Status: A Randomized, Double-Blind, Placebo-Controlled Trial”

I read the compared 2024 trial, Effects of an ergothioneine-rich Pleurotus sp. on skin moisturizing functions and facial conditions: a randomized, double-blind, placebo-controlled trial. I’d guess there was a bit of cognitive dissonance in the women in the placebo group who disrupted their lives every day for 12 weeks to dutifully eat 21 tablets of what was glucose and caramel, not hiratake mushroom powder.

Two clinical trials investigated ergothioneine’s effects on sleep quality:

“A four-week administration of 20 mg/day ergothioneine (EGT), a strong antioxidant, improves sleep quality; however, its effect at lower doses remains unclear. This study estimated the lower effective doses of EGT using a physiologically based pharmacokinetic (PBPK) model in two clinical trials.

In Study 1, participants received 5 or 10 mg/day of EGT for 8 weeks, and their plasma and blood EGT concentrations were measured. An optimized PBPK model incorporating absorption, distribution, and excretion was assembled. Our results showed that 8 mg/day of EGT for 16 weeks was optimal for attaining an effective plasma EGT concentration.

In Study 2, a randomized, double-blind, placebo-controlled study, participants received 8 mg/day EGT or a placebo for 16 weeks. The subjective sleep quality was significantly improved in the EGT group than in the placebo group.

In mammals, EGT is not generated in the body but is acquired from the diet via the carnitine/organic cation transporter OCTN1/SLC22A4. Its plasma concentration after oral administration is quite stable and gradually increases after repeated dosing on a multi-day basis.

Blood concentrations of EGT increase after Day 8 when EGT intake is interrupted, and they continue to increase until Day 35. The delayed increase in EGT concentration in the blood, compared with that in the plasma, can be interpreted as its efficient uptake by undifferentiated blood cells, which express high levels of OCTN1/SLC22A4 in the bone marrow, and subsequent differentiation to mature blood cells that enter the circulation. This may imply the nonlinear absorption, distribution, and excretion of EGT owing to saturation of the transporter at higher concentrations, potentially leading to difficulty in model construction.

This is the first study to propose a strategy to estimate lower effective doses based on the PBPK model.”

https://onlinelibrary.wiley.com/doi/10.1002/fsn3.70382 “Estimation and Validation of an Effective Ergothioneine Dose for Improved Sleep Quality Using Physiologically Based Pharmacokinetic Model”

The bolded section above referenced a 2016 study / third graphic for Ergothioneine dosing, Part 2, where a 25 mg dosing stopped after Day 7, but the plasma ergothioneine level stayed high through Day 35. I didn’t see that the referenced 2004 and 2010 studies addressed this 2016 finding.

I also didn’t see that this study’s mathematical model accounted for saturation of the OCTN1 transporter or other effects, such as a very small ergothioneine clearance rate. Okay, lower the ergothioneine dose, and achieve a lower persistent plasma ergothioneine level, to what benefit?

The referenced 2004 paper, Expression of organic cation transporter OCTN1 in hematopoietic cells during erythroid differentiation, concluded:

“The present study demonstrated that OCTN1 is associated with myeloid cells rather than lymphoid cells, and especially with erythroid-lineage cells at the transition stage from immature erythroid cells to peripheral mature erythrocytes.”

Persistent high ergothioneine levels aren’t costless. Skewing bone marrow stem cells and progenitor cells toward a myeloid lineage is done at the expense of lymphocytes, T cells, B cells, and other lymphoid lineages.

Where are the studies that examine these tradeoffs? Subjective sleep quality in this study and sleep initiation in the first study above aren’t sufficiently explanatory.

A study investigated associations of plasma ergothioneine levels and cognitive changes in older adults over a two-year period:

“Observational studies have found that lower plasma levels of ergothioneine (ET) are significantly associated with higher risks of neurodegenerative diseases. However, several knowledge gaps remain:

  1. Most of the above studies were based on cross-sectional study design, and potential reverse causation cannot be excluded. It has been suggested that plasma ET declines concomitantly with the deterioration of cognitive function.
  2. Since the impact of a single dietary factor on health is mild, it is prone to be affected by the baseline characteristics of subjects (such as sex, educational level, disease status and gene polymorphism). However, no study has systematically evaluated potential effect modifiers on the association between ET levels and cognitive function.
  3. The dose-response distribution between ET and cognitive function remains undetermined.

In this prospective cohort study of 1,131 community-dwelling older adults (mean age 69 years), higher baseline plasma ET levels were significantly associated with slower cognitive decline, as assessed by Montreal Cognitive Assessment (MoCA) scores, during a 2-year follow-up period.

When the plasma concentration of ET exceeds 1,000 ng/mL, the decline in cognitive function significantly slows down. However, this association has only been observed in men.

Domain-specific analysis found that the observed ET-MoCA association was mainly driven by the temporary slowdown in the decline of visuospatial/executive and delayed recall. Impaired delayed recall represents one of the earliest and most sensitive cognitive markers of dementia progression, predictive of conversion from MCI to dementia. The preferential preservation of this function by ET suggests targeted neuroprotective effects within the hippocampus.

Visual inspection of the spline curves revealed a potential plateauing effect at ET concentrations ≥1,000 ng/mL in the total population.

Baseline ET concentrations differed between men and women. Most men (81.5%) had concentrations below 1,000 ng/mL (median 754.2, IQR 592.0–937.9 ng/mL). Women exhibited substantially higher median plasma ET concentrations than men, with 35.7% of women exceeded 1,000 ng/mL (median 890.1, IQR 709.7–1,095.6 ng/mL).

Our study included only participants with normal cognitive function, and the results remained robust even after excluding those with baseline cognitive function at the lower end of the normal range. Collectively, our findings support that low ET intake occurs prior to cognitive decline.

Our findings indicate that higher plasma ET levels are significantly associated with slower cognitive decline independent of confounders in non-demented community-dwelling elderly participants, with such association observed in men but not women. Dose-response curves indicated plateauing effects above 1000 ng/mL.”

https://www.medrxiv.org/content/10.1101/2025.07.16.25331363v2 “Associations of plasma ergothioneine levels with cognitive function change in non-demented older Chinese adults: A community-based longitudinal study”

The average age of this study and the first trial above were both 69 years. Since the first trial’s participants showed slightly above-average cognitive function (neurocognitive index median = 105), with plasma ergothioneine levels of median = 1154 nM at baseline, and this study showed plateauing effects above 1000 ng/mL, I wonder how raising plasma ergothioneine levels above 1000 ng/mL could possibly show a net benefit for older people? What are the trade-offs for older people between potentially increasing slightly above-average cognitive function with ergothioneine and its other effects from saturating their OCTN1 transporter?

This study is at its preprint stage. I’m interested to see if its peer review prompts these researchers to also investigate the common finding that people who are most deficient at baseline have the greatest improvements. If so, would these sex-specific associations still hold?

Wrapping up with a study that investigated associations of serum ergothioneine levels with the risk of developing dementia:

“1344 Japanese community-residents aged 65 years and over, comprising 765 women and 579 men, without dementia at baseline were followed prospectively for a median of 11.2 years.

During follow-up, 273 participants developed all-cause dementia. Among them, 201 had Alzheimer’s disease (AD) and 72 had non-Alzheimer’s disease (non-AD) dementia.

Age- and sex-adjusted hazard ratios (HRs) for all-cause dementia, AD, and non-AD dementia decreased progressively across increasing quartiles of serum ergothioneine. These associations remained significant after adjustment for a wide range of cardiovascular, lifestyle, and dietary factors, including daily vegetable intake.

In subgroup analysis, association between serum ergothioneine levels and the risk of dementia tended to be weaker in older participants and in women:

  • In older individuals, cumulative burden of multiple risk factors such as hypertension, diabetes mellitus, and smoking may contribute to both neurodegenerative and vascular pathology, potentially diminishing the relative influence of ergothioneine.
  • In women, postmenopausal hormonal changes, particularly the decline in estrogen, have been associated with increased oxidative stress and a higher vulnerability to neurodegenerative changes.

Several limitations should be noted:

  1. Since serum ergothioneine levels and other risk factors were measured only at baseline, we could not evaluate the changes of serum ergothioneine levels during the follow-up period. Lifestyle modifications during follow-up could have influenced serum ergothioneine levels and other risk factors. In addition, serum ergothioneine level was measured only once, and from a sample.
  2. We cannot rule out residual confounding factors, such as other nutrients in mushrooms and socioeconomic status.
  3. There is a possibility that dementia cases at the prodromal stage were included among participants with low serum ergothioneine levels at baseline.
  4. We are unable to specify which mushroom varieties were predominantly consumed by participants in the town of Hisayama.
  5. Given the limited discriminative ability of serum ergothioneine and potential degradation due to long-term sample storage, we were unable to explore a clinically meaningful threshold value of serum ergothioneine.
  6. Generalizability of findings was limited because participants of this study were recruited from one town in Japan.

These findings suggest that the potential benefit of ergothioneine may be attenuated in individuals with pre-existing, multifactorial risk profiles for dementia.

Our findings showed that higher serum ergothioneine levels were associated with a lower risk of developing all-cause dementia, AD, and non-AD dementia in an older Japanese population. Since ergothioneine cannot be synthesized in the human body, a diet rich in ergothioneine may be beneficial in reducing the risk of dementia.”

https://onlinelibrary.wiley.com/doi/10.1111/pcn.13893 “Serum ergothioneine and risk of dementia in a general older Japanese population: the Hisayama Study”

For five years I got most of my estimated 7 mg daily ergothioneine intake from mushrooms in AGE-less chicken vegetable soup per Ergothioneine dosing. The soup was always boring, but I got too bored this year and stopped making it. I haven’t replaced mushroom intake with supplements.

I still don’t eat fried or baked foods, preferring sous vide and braising cooking methods to avoid exogenous advanced glycation end products. I avoid buying foods that evoke a hyperglycemic response or otherwise form excessive endogenous AGEs per All about AGEs.

Eat broccoli sprouts for your heart, Part 2

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A 2025 rodent study investigated synergistic effects of sulforaphane (SFN) and nicotinamide mononucleotide (NMN) on diabetic cardiomyopathy:

“Diabetic cardiomyopathy (DCM) as a significant diabetes complication remains a major human challenge. In this study, we provide evidence that the fat mass and obesity-associated protein (FTO) plays a pivotal role in DCM pathogenesis.

Downregulation of FTO in DCM acts as a critical inducer of ferroptosis by increasing expression of acyl-CoA synthetase long-chain family 4 (ACSL4), a key positive mediator of ferroptosis. FTO-mediated mitigation of ferroptosis occurs in an ACSL4-dependent manner which leads to increased methylation of Acsl4 transcripts.

  1. Ferroptosis plays an essential role in the pathogenesis of DCM.
  2. As the most widespread mRNA modification, N6-methyladenosine (m6A) is globally downregulated and implicated in diabetes and its complications.
  3. FTO, which is an m6A demethylase, was found to be downregulated in diabetes and its cardiovascular complications.
  4. NAD+ enhances the demethylase activity of FTO. Dietary supplementation with NMN, a critical intermediate in the NAD+ biosynthetic pathway, has been shown to efficiently elevate endogenous NAD+ levels.

Enhancing the demethylase activity of FTO with NMN combined with SFN targeting NRF2 could synergistically reduce the level of lipid peroxides to inhibit ferroptosis, providing an effective avenue for alleviating DCM.

We found that NMN could alleviate ferroptosis and improve heart function through enhancing FTO. SFN could prevent ferroptosis and partly rescue heart function via AMPK-mediated NRF2 activation.

We demonstrated that SFN combined with NMN treatment could significantly inhibit lipid peroxidation and rescue cardiac function in DCM compared to SFN or NMN treatment alone.

Although the combined regimen further suppressed ferroptosis and improved cardiac performance, it fell short of complete remission, underscoring that additional pathways also contribute substantially to the pathogenesis of DCM.”

https://link.springer.com/article/10.1007/s12012-025-10080-w “FTO-Mediated Mitigation of Ferroptosis Occurs in an ACSL4-Dependent Manner in Diabetic Cardiomyopathy”

The epigenetic mechanism involved with this study’s dietary dissolved-in-water 100mM NMN dose was Non-CpG methylation. This study used the same very low sulforaphane dose intraperitoneally injected as Eat broccoli sprouts for your heart. Discussion of that study provided an example that if a person waited until a diabetes-related disease condition became a problem, capabilities to adequately address causes and prevent the problem may be lost.

Notice in the last bar of the second graphic above taken from Figure 7 that the combined treatment was also provided to non-diabetic mice. These researchers provided over a dozen other measurements in Figure 7 to show similar short-term non-effects of the combined treatment, i.e. that it neither benefited nor harmed non-diabetic subjects. Grok interpreted this study’s 3-month-long intervention to be a 1-to-5 year human equivalent, depending on the measured effect (shorter for metabolic effects like MDA, longer for structural cardiac changes like reduced ferroptosis.)

The male subjects began at 2-months old, a human-equivalent 15-20 years old. These researchers gave them diabetes by feeding them a “high-fat diet for 3 months to induce insulin resistance, followed by a single intraperitoneal injection of streptozotocin (STZ) (in 0.1 mol/L of citrate acid buffer, 60 mg/kg) to induce partial insulin deficiency.” A 5-months old mouse is a 25-30 years old human equivalent.

Grok considered this study’s NMN human equivalent dose to be extremely high if provided in drinking water, but not if injected, depending on volume. However, the study didn’t state that its NMN dose was injected, and there was no dose volume indicated.

A Nrf2 / NAD+ connection?

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Here are two 2025 papers, starting with a rodent study that investigated interactions between the Nrf2 and kynurenine pathways:

“Exposure to the tryptophan metabolite kynurenine and its electrophilic derivative kynurenine-carboxyketoalkene (Kyn-CKA) leads to an increase in the abundance of transcription factor Nrf2 and induction of Nrf2-target genes. The Keap1/Nrf2 system is the main orchestrator of cellular defence against environmental stress, most notably oxidative and inflammatory stress.

Nrf2 can be activated pharmacologically by small molecules, the majority of which are electrophiles and oxidants that modify specific cysteine-based sensors in Keap1. C151 in Keap1 is the target of the isothiocyanate sulforaphane, a classical Nrf2 activator that has been employed in ∼90 clinical trials, as well as for the two Nrf2 activators that are clinically in use: dimethyl fumarate, for relapsing remitting multiple sclerosis, and omaveloxolone, for Friedreich’s ataxia.

Kynurenine is an endogenous metabolite derived from the essential amino acid tryptophan. Kynurenine and its metabolites, such as the electrophilic kynurenine-carboxyketoalkene (Kyn-CKA), have been demonstrated to activate Nrf2 in other pathologies, including sickle cell disease, attenuating inflammation. Moreover, identification of the gene encoding the kynurenine-metabolising enzyme kynureninase as a gene transcriptionally upregulated by Nrf2, provides a plausible negative feedback regulatory mechanism.

Because kynurenine is not electrophilic, whereas its metabolite Kyn-CKA is, we considered the possibility that Kyn-CKA is the actual Nrf2 activator. Using biochemical and cell-based assays, we found that Kyn-CKA reacts with C151 in the BTB domain of Keap1 and increases the thermostability of Keap1, indicating target engagement. Consequently, Nrf2 accumulates and induces transcription of antioxidant/electrophile-responsive element (ARE/EpRE)-driven genes.

These findings demonstrate that Kyn-CKA targets C151 in Keap1 to derepress Nrf2, and reveal that Nrf2 is a main contributor to the anti-inflammatory activity of Kyn-CKA in macrophages.”

https://www.sciencedirect.com/science/article/pii/S2213231726000078 “The electrophilic metabolite of kynurenine, kynurenine-CKA, targets C151 in Keap1 to derepress Nrf2”

A review subject was targeting nicotinamide adenine dinucleotide, oxidized form (NAD+) for clinical use:

“Mammalian NAD+ biosynthesis includes four known pathways, primarily occurring in cytoplasm:

  • (a) the NRH pathway;
  • (b) the salvage pathway;
  • (c) the Preiss–Handler pathway; and
  • (d) the kynurenine pathway.

The de novo kynurenine pathway metabolizes tryptophan (Trp) to NAD+, producing various intermediates that serve as biomarkers for different diseases. These intermediates show alterations in various pathological conditions.

While kynurenine and its metabolic derivatives are intermediates in the de novo NAD+ biosynthesis pathway, these are also produced independently in various physiological contexts, particularly in immune cells, where they act as immunomodulatory compounds.”

https://www.nature.com/articles/s43587-025-00947-6 “Emerging strategies, applications and challenges of targeting NAD+ in the clinic” (not freely available) Thanks to Dr. Jianying Zhang for providing a copy.

This second paper above showed a graphic of the Nrf2 and kynurenine pathways together in a diagram showing relationships between NAD+ augmentation and the hallmarks of aging, but didn’t elaborate other than labeling their box Dysbiosis. So how these two pathways interact is better outlined in the first paper above with explaining how a kynurenine-metabolizing enzyme is one of the hundreds of Nrf2 target genes, creating a natural feedback loop between Nrf2 activation and the kynurenine pathway.

These reviewers also lumped SIRT1 in their Dysbiosis box, and into several other boxes, probably due to the penultimate coauthor’s influence:

However, repeating something over and over doesn’t make it scientifically valid regardless of the number of citations. Or, as a 2022 review Sirtuins are not conserved longevity genes concluded:

“A global pursuit of longevity phenotypes was driven by a mixture of framing bias, confirmation bias, and hype. Review articles that propagate these biases are so rampant that few investigators have considered how weak the case ever was for sirtuins as longevity genes.

Acknowledging that a few positive associations between sirtuins and longevity have been identified after thousands of person-years and billions of dollars of effort, we review the data and suggest rejection of the notions that sirtuins (i) have any specific connection to lifespan in animals and (ii) are primary mediators of the beneficial effects of NAD repletion.”

Discovering a new NAD+ precursor

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A 2025 rodent study investigated dynamics of organ and circulating nicotinamide:

“Liver-derived circulating nicotinamide from nicotinamide adenine dinucleotide (NAD+) catabolism primarily feeds systemic organs for NAD+ synthesis. We surprisingly found that, despite blunted hepatic NAD+ and nicotinamide production in liver-specific nicotinamide nucleotide adenylyltransferase 1 (NMNAT1) deletion mice (liver-specific knockout [LKO]), circulating nicotinamide and extra-hepatic organs’ NAD+ are unaffected.

Metabolomics reveals a massive accumulation of a novel molecule in the LKO liver, which we identify as nicotinic acid riboside (NaR). The liver releases NaR to the bloodstream, and kidneys take up NaR to synthesize NAD+ through nicotinamide riboside kinase 1 (NRK1) and replenish circulating nicotinamide.

Serum NaR levels decline with aging, whereas oral NaR supplementation in aged mice boosts serum nicotinamide and multi-organ NAD+, including kidneys, and reduces kidney inflammation and albuminuria. The liver-kidney axis maintains systemic NAD+ homeostasis via circulating NaR, and NaR supplement ameliorates aging-associated NAD+ decline and kidney dysfunction.

While this study provides evidence of hepatic production and renal consumption of NaR for NAD+ homeostasis in mice, future human works are warranted to confirm these findings. In addition, genetic studies will be necessary to fully understand NaR metabolism at cellular and organismal levels.

While this study shows the oral availability of NaR and its effect on systemic NAD+ metabolism in mice, human studies testing NaR safety, oral availability, pharmacokinetics, and pharmacodynamics should be performed to test potential clinical usage of NaR supplements. Additionally, future studies are needed to investigate physiological significance of NT5C2-mediated hepatic production of NaR in healthy mice and identify NaR transporter(s).”

https://www.cell.com/cell-metabolism/abstract/S1550-4131(25)00217-7 “Nicotinic acid riboside maintains NAD+ homeostasis and ameliorates aging-associated NAD+ decline” (not freely available) Thanks to Dr. Dorota Skowronska-Krawczyk for providing a copy.

An elaborating commentary was published along with this study:

“Nicotinamide (NAM), nicotinamide riboside (NR), nicotinic acid (NA), and NAR are the salvageable precursors that feed into production of nicotinamide mononucleotide (NMN) and nicotinic acid mononucleotide (NAMN) to regenerate NAD coenzymes. NAMN is at an interesting juncture in NAD metabolism because it is formed in de novo synthesis and in salvage synthesis from both NA and NAR.

Song and coworkers did not specifically set out to determine endogenous sources of NR and/or NAR. Rather, they wanted to see what would happen when they deleted the major Nmnat isozyme, Nmnat1, in liver.

With depression of hepatic NAD+, they saw elevation of liver NMN and NAMN and discovered a huge increase in hepatic and circulating NAR. By viral knockdown, the step of conversion of accumulated NAMN to NAR was found to be catalyzed by a 5′ – nucleotidase encoded by the Nt5c2 gene, and the major tissue receiving the NAR was found to be the kidney.

Further, they showed that levels of NAR decline in aging while provision of supplementary NAR supports a newfound ability of the mouse kidney to circulate NAM. Of potential translational significance, supplementary NAR also supported mouse kidney function in aging.”

https://www.brennerlab.net/curriculumvitae/ “The NARly side of whole-body NAD homeostasis” (*pdf at page bottom)

Human studies of astaxanthin – Part 2

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Continuing Part 1, here are four more 2025 human studies of the Nrf2 activator astaxanthin, starting with a randomized, double-blind, placebo-controlled trial of its effects on reducing oxidative stress and inflammatory responses following eccentric exercise:

“This study investigated effects of astaxanthin supplementation on plasma MDA and HMGB1 levels following acute eccentric exercise in recreationally active male students. Fifty-four students were assigned to receive either 12 mg/day of natural astaxanthin (AST, n = 27) or placebo (PLA, n = 27) for 14 days.

A key consequence of eccentric-induced muscle damage is overproduction of reactive oxygen species (ROS). When ROS production exceeds the capacity of endogenous antioxidant systems, lipid peroxidation can occur. Malondialdehyde (MDA) is a stable end-product of lipid peroxidation and serves as a widely recognized biomarker for oxidative stress and cell membrane damage.

In parallel, muscle cell damage results in release of damage-associated molecular patterns (DAMPs) into the extracellular space. Among these, High Mobility Group Box-1 (HMGB1) plays a central role in inflammation when passively released from the nucleus. HMGB1 acts as a potent pro-inflammatory signal by activating innate immune receptors, recruiting immune cells, and upregulating cytokines such as IL-6 and TNF-α.

This heightened immune activity contributes to delayed-onset muscle soreness, which typically peaks 24–72 hours post-exercise, and is associated with impaired recovery. Sustained elevations in oxidative and inflammatory biomarkers, including MDA and HMGB1, may further impair recovery and contribute to long-term muscle pathology.

Astaxanthin’s antioxidant effects are mediated through both direct and indirect mechanisms. Structurally, astaxanthin is a xanthophyll carotenoid with a unique polar–nonpolar–polar configuration that enables it to span the phospholipid bilayer of cell membranes. This positioning allows it to neutralize ROS both at the membrane surface and within the lipid bilayer.

In addition, astaxanthin enhances endogenous antioxidant defenses by upregulating enzymes such as superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx) through activation of the Nrf2–ARE signaling pathway. This dual mode of action provides both immediate and sustained protection against oxidative stress during and after exercise.

The placebo group showed substantial increases in MDA and HMGB1 after exercise, whereas the astaxanthin group experienced attenuated rises (~22% and ~27% smaller, respectively) and faster recovery toward baseline within 24 hours. These findings suggest that astaxanthin supplementation can be incorporated into recovery strategies for athletes and active individuals, especially during periods of heavy training or repeated bouts of intense eccentric exercise. By reducing oxidative damage and inflammation, astaxanthin may shorten recovery time, limit performance loss, and support overall training adaptations—benefits that are particularly valuable in sports requiring frequent high-intensity efforts.

Several limitations should be acknowledged in this study.

  1. Sample size was relatively small and limited to recreationally active young males, which may restrict generalizability of findings to other populations such as females, older adults, or elite athletes.
  2. Supplementation period was limited to 14 days; although this duration is sufficient to achieve plasma saturation of astaxanthin, longer interventions may produce different or more pronounced effects.
  3. Only two biomarkers were assessed (MDA and HMGB1), which provide important but incomplete insights into broader oxidative stress and inflammatory response. Including additional markers such as enzymatic antioxidants, cytokine profiles, and muscle damage indicators (e.g., creatine kinase) could yield a more comprehensive understanding.
  4. Dietary intake and physical activity outside the intervention were self-reported and not strictly controlled, which may have introduced variability in results.”

https://tmfv.com.ua/journal/article/view/3664/1922 “Taking Astaxanthin Supplementation Attenuates MDA and HMGB1 Following Eccentric Exercise: A Randomized Controlled Trial in Recreationally Active Students”

A clinical trial investigated astaxanthin’s effects with exercise in diabetic women:

“This study examined whether combined aerobic and resistance training (CT) and astaxanthin (AST) supplementation synergistically improve oxidant and inflammatory status as well as metabolic indices in T2DM, focusing on the mediatory role of Humanin (HN) and microRNAs (miRNA-122, miRNA-126-3p, and miRNA-146a).

Ninety women with T2DM were randomly assigned to six groups (n = 15 each):

  • Control (C), placebo (P), AST supplementation (S), combined training (CT), CT + placebo (CT + P), and CT + AST supplementation (CT + S).
  • CT, CT + P and CT + S groups underwent an 8-week training program (eight exercises, three sessions per week).
  • S and CT + S groups received 8 mg/day of AST.

This study only enrolled female participants age between 30 and 60 years old to minimize inter-individual biological variability arising from sex differences in hormone regulation, fat distribution, and gene expression related to inflammation and oxidative stress. Oxidative stress (OS) markers, inflammatory cytokines, HN levels, miRNAs expression, fasting blood glucose (FBG), insulin resistance (HOMA-IR), lipid profile, and hemoglobin A1c (HbA1c) were assessed.

HN is a member of a class of novel mitochondrial-derived peptides released during mitochondrial dysfunction. HN reduces ROS production, enhances antioxidant protein expression, maintains redox balance, and suppresses TNF-α, IL-1β, and IL-6 to inhibit inflammation. Furthermore, resistance and endurance training has shown to increase HN expression in patients with prediabetes. Exercise – aerobic and endurance – has been shown to increase circulating and skeletal muscle levels of HN, correlating with improved insulin sensitivity and mitochondrial function.

Our results showed:

  • CT and AST supplementation both improved antioxidant defense and reduced inflammation, and their combination was more effective than either intervention alone.
  • CT and AST supplementation increased blood concentration of HN, and their combination showed greater effects than AST supplementation, but not CT.
  • CT and AST supplementation increased blood levels of miRNAs-126-3p, and -146a and decreased miRNA-122, with their combination being slightly more effective in decreasing miRNA-122.
  • Both interventions improved lipid profile, with their combination being more effective in improving HDL and TG levels, although not total cholesterol.
  • FBG, HOMA-IR, and HbA1c were reduced by CT but not by AST supplementation.

Our data suggest that combining exercise with AST supplementation might improve oxidative status and inflammation through mechanisms involving HN and miRNAs 122, 126-3p, and 146a. Alleviating OS and inflammation could, in turn, lead to improvements in lipid profiles (e.g., TG, and HDL), IR, and reductions in HbA1c and FBG, as observed in our study. Furthermore, the combined approach seems to be more effective at improving cholesterol and TG levels.“

https://www.nature.com/articles/s41598-025-23914-y “Redox-sensitive miRNAs and Humanin could mediate effects of exercise and astaxanthin on oxidative stress and inflammation in type 2 diabetes”

A meta-analysis of randomized controlled trials reported until May 2025 assessed astaxanthin’s effects on lipid profiles. Neither of the two trials covered here nor the three trials covered in Part 1 were included in this meta-analysis.

“Astaxanthin, a xanthophyll carotenoid, has garnered significant interest due to its benefits with regard to dyslipidemia. This multifaceted functional food ingredient modulates several key enzymes associated with lipid regulation, including HMG-CoA reductase, CPT1, ACCβ, and acyl-CoA oxidase. It influences key antioxidant molecular pathways like Nrf2, limiting dyslipidemia occurrence and regulating liver cholesterol uptake through modulation of liver lipid receptors.

Astaxanthin daily doses and durations of analyzed studies: 12 mg for 8 weeks; 12 mg for 4 weeks; 20 mg for 12 weeks (two trials); 12 mg for 12 weeks; 8 mg for 8 weeks; 6 mg and 12 mg for 12 weeks; 6 mg, 12 mg, and 18 mg for 12 weeks.

This meta-analysis concludes positive effects of astaxanthin (6–20 mg/d) on HDL-C and triglyceride levels. Astaxanthin (6–20 mg/d) does not appear to significantly influence LDL-C and total cholesterol levels.

Regarding HDL-C, improvements were observed from 55 ± 8 mg/dL (pre-intervention) to 63 ± 8 mg/dL (post-intervention) (p < 0.01) in the 12 mg/d of astaxanthin groups. In triglyceride levels, results show a decrease from 151 ± 26 mg/dL (pre-intervention) to 112 ± 40 mg/dL (post-intervention) (p < 0.01) for 18 mg/d astaxanthin supplementation.

Further research is necessary to fully harness the potential of astaxanthin, which includes assessing astaxanthin in different subsets of patients, and in combination with other nutraceuticals to understand the compound’s effectiveness with regard to varying health conditions, genetic and epigenetic factors, and synergistic effects with other compounds.”

https://www.mdpi.com/1424-8247/18/8/1097 “Assessing the Effects of Moderate to High Dosage of Astaxanthin Supplementation on Lipid Profile Parameters—A Systematic Review and Meta-Analysis of Randomized Controlled Studies”

This same group of researchers assessed that in nine RCTs, astaxanthin had no effects on either body weight or BMI per https://www.mdpi.com/1424-8247/18/10/1482 “Therapeutic Potential of Astaxanthin for Body Weight Regulation: A Systematic Review and Meta-Analysis with Dose–Response Assessment”

Human studies of astaxanthin – Part 1

gettingwell4 4-5 stars Advanced knowledge, Epigenetics, Immune system, Stress , ,

Here are three 2025 clinical trials of the Nrf2 activator astaxanthin’s effects. Let’s start with a clinical trial of inflammation-related diabetic complications and insulin resistance:

“We investigated effects of 10 mg/day astaxanthin (ASX) supplementation for 12 weeks on microRNAs (miRNAs), lysophosphatidylcholine (LPC), and α-hydroxybutyrate (α-HB) as novel factors in development of a variety of diabetes-related complications.

  • LPC is believed to play a significant role in atherosclerosis and inflammatory diseases by modifying functions of multiple cell types, including smooth muscle cells, endothelial cells, monocytes, macrophages, and T cells. LPC can interfere with glucose-stimulated insulin secretion by impairing calcium homeostasis and other signaling pathways that are crucial for the proper functioning of beta cells. This impairment exacerbates hyperglycemia in diabetic patients. LPCs may impede insulin signaling pathways, thereby contributing to insulin resistance (IR).
  • α-HB is also an indicator of IR and impaired glucose regulation, both of which appear to result from excessive lipid oxidation and oxidative stress. The European population cohorts in 2016 identified α-HB as a selective biomarker for decreased glucose tolerance and prediabetes, which was independent of age, sex, BMI, and fasting glucose.
  • A number of studies have established a link between miR-21, miR-34a, and miR-155 and diabetic complications such as retinopathy and nephropathy.

In the ASX group, participants were divided into 2 subgroups according to the urinary albumin-to-creatinine ratio (ACR) (< 30 mg/g or ≥ 30 mg/g, an indicator of diabetic kidney disease).

  • The level of fasting plasma glucose before and after 12 weeks of treatment with ASX was 139.27 ± 21.18 vs. 126.43 ± 18.97 (p = 0.002), demonstrating a significant reduction compared to the placebo group.
  • In the ASX group, the mean HbA1c level at baseline was 7.89 ± 0.79 and declined to 7.05 ± 0.35 after the supplementation period, which was statistically significant.
  • Supplementation with ASX resulted in a statistically significant drop in HOMA-IR levels, whereas this parameter was not altered significantly in the placebo group.
  • The ASX group, in comparison with the placebo group, demonstrated marked changes in lipid profile factors such as TC, TG, and LDL (p = 0.011, p = 0.043, and p = 0.022, respectively).

Clinical studies indicate that rigorous diabetes management does not substantially diminish appearance of complications. Modifications in oxidative stress and IR markers, as well as miRNA expression, must be analyzed to identify biological markers with sufficient predictive power for development of complications in diabetic patients.

Supplementation with ASX substantially diminished the levels of α-HB, LPC, and inflammation-related miRNAs in diabetic patients with and without complications.”

https://onlinelibrary.wiley.com/doi/10.1155/ije/5878361 “Astaxanthin Modulates Inflammation in Type 2 Diabetes via Regulation of microRNAs, Lysophosphatidylcholine, and α-Hydroxybutyrate”

Another clinical trial investigated astaxanthin’s effects in heart failure patients:

“Chronic heart failure (HF) is often linked to increased oxidative stress and metabolic issues like high uric acid, which can worsen outcomes.This study aimed to investigate the effects of ASX supplementation on oxidative stress markers as the primary outcome and clinical symptoms in patients with HF.

80 patients with HF were enrolled and randomly assigned to receive either ASX (20 mg/day) or a placebo (20 mg/day of maltodextrin) for 8 weeks. Biomarkers including total antioxidant capacity (TAC), malondialdehyde (MDA), superoxide dismutase (SOD), serum uric acid (UA), and clinical symptoms (dyspnea, fatigue, appetite) were assessed pre-and post-intervention.

Daily supplementation with 20 mg of ASX for eight weeks in patients with HF resulted in significantly greater improvements in oxidative stress biomarkers compared to placebo group. This improvement included reductions in uric acid and MDA, along increases in TAC and SOD.

In our study, participants received the cis-isomer form of ASX. The cis-isomer of ASX demonstrates greater anti-inflammatory and antioxidant properties than the trans-isomer, along with enhanced bioavailability. Inconsistencies among studies may be attributed to differences in participants’ baseline antioxidant status, underlying medical conditions, dosage, isomeric form and formulation of ASX used, and the duration of intervention.

One of the strengths of this study is that it represents the first randomized clinical trial to evaluate the effects of ASX supplementation on oxidative stress markers, UA levels, and clinical symptoms in patients with HF. Additionally, potential confounding factors were controlled as much as possible. However, several limitations were identified, including the relatively short intervention duration, limited sample size, limited generalizability of the findings due to the single-center design, absence of blood ASX level measurements, and lack of long-term follow-up.”

https://link.springer.com/article/10.1186/s12872-025-05260-z “Impact of astaxanthin on oxidative markers, uric acid, and clinical symptoms in heart failure: a randomized clinical trial”

A third clinical trial evaluated astaxanthin’s effects as an adjunct to standard treatment of community-acquired pneumonia:

“Adult patients diagnosed with community-acquired pneumonia (CAP) were enrolled and assigned to receive either 12 mg/day ASX or a placebo in addition to standard antibiotic therapy for 7 days. Inflammatory markers, including interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interleukin-10 (IL-10), were measured at baseline and post-treatment. Secondary outcomes included Sequential Organ Failure Assessment (SOFA) and Acute Physiology and Chronic Health Evaluation II (APACHE II) scores.

A total of 80 patients (40 per group) completed the study. Patients receiving ASX exhibited significant reductions in pro-inflammatory cytokines compared to the placebo group. IL-6 and TNF-α levels were significantly lower in the ASX group at the end of the study (P < 0.05). Additionally, SOFA and APACHE II scores showed greater improvements in ASX-treated patients, suggesting a potential role in mitigating disease severity.

These findings suggest that ASX may help preserve organ function, limit the progression of inflammatory injury, and reduce overall disease severity in hospitalized patients with CAP.

ASX is widely regarded as the most potent carotenoid, owing to its unique molecular structure. Its polar-nonpolar-polar configuration enables it to span lipid bilayers and neutralize ROS both within and outside cellular membranes—an advantage not shared by other carotenoids that tend to localize at the membrane surface.

Despite the positive findings of this study, some limitations should nevertheless be considered.

  • The relatively small sample size may have limited the statistical power to detect differences in some outcomes and affects the generalizability of the findings.
  • Microbiological data on CAP pathogens were not collected. As different microorganisms can trigger distinct inflammatory responses, this limits our ability to assess pathogen-specific variations in ASX efficacy.
  • A notable limitation of this study is the short follow-up duration, with outcomes assessed only over a 7-day period. While this timeframe offers insight into the acute effects of ASX on inflammatory and OS markers, it does not clarify whether these benefits are sustained beyond the immediate treatment window.
  • The fixed dose of 12 mg once daily may not have maintained optimal therapeutic levels throughout the day. Dose-ranging studies and evaluations of alternative regimens are needed to determine the most effective strategy.”

https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2025.1621308/full “The anti-inflammatory and antioxidant effects of astaxanthin as an adjunctive therapy in community-acquired pneumonia: a randomized controlled trial”

Part 2 continues with four more 2025 human studies of astaxanthin.