The Science Behind NAD+ Cell Renewal

Nicotinamide mononucleotide (NMN) is a direct biosynthetic precursor of NAD+, the coenzyme that carries electrons through cellular energy metabolism and serves as substrate for the sirtuins and PARP enzymes. Massudi et al. (2012) measured NAD+ in human tissue and found a strong negative correlation with age in both men (r = -0.706, p = 0.001) and women (r = -0.537, p = 0.01), alongside rising DNA damage. That age-related decline is the rationale for supplementation.

That oral NMN raises NAD+ in humans is well established. Yi et al. (2023) ran a randomised, multicentre, double-blind, placebo-controlled, parallel-group, dose-ranging trial in 80 healthy middle-aged adults given 300, 600 or 900 mg NMN daily for 60 days. Blood NAD+ concentrations rose dose-dependently in all NMN arms versus placebo. Efficacy on blood NAD+ and on six-minute walk distance plateaued at 600 mg per day. Oral NMN was safe and well tolerated up to 900 mg daily.

Yoshino et al. (2021), in Science, randomised 25 postmenopausal women with prediabetes who were overweight or obese to 250 mg NMN daily or placebo for 10 weeks. Insulin-stimulated glucose disposal measured by hyperinsulinaemic-euglycaemic clamp, and skeletal muscle insulin signalling (AKT and mTOR phosphorylation), increased after NMN but not after placebo.

Irie et al. (2020) established single-dose safety and metabolism in healthy men at 100, 250 and 500 mg by mouth. Kim et al. (2022) examined sleep quality, fatigue and physical performance over 12 weeks in older Japanese adults, randomised, double-blind and placebo-controlled.

Raising blood NAD+ with oral NMN is established, dose-dependent and reproducible across independent trials.

Resveratrol is a stilbene polyphenol found in grape skin, red wine and Japanese knotweed, and one of the most intensively studied sirtuin activators in the literature.

Its human pharmacokinetics are unusually well characterised. Walle et al. (2004) gave six volunteers carbon-14 labelled resveratrol orally and intravenously. Absorption of a dietary-relevant 25 mg oral dose was at least 70 percent - high for a polyphenol. Peak plasma concentrations of resveratrol plus its metabolites reached about 2 micromolar (491 +/- 90 ng/mL), and the plasma half-life of total labelled material was 9.2 +/- 0.6 hours. Resveratrol is extensively conjugated to sulfates and glucuronides in the gut wall and liver on first pass, which is why unchanged resveratrol is present in plasma only in trace amounts after an oral dose. High absorption, very low bioavailability - that is the title of the paper and the central pharmacokinetic fact about the molecule.

The largest clinical trial is Turner et al. (2015) in Neurology: 119 patients with mild to moderate Alzheimer disease randomised to escalating oral resveratrol up to 1 g twice daily or placebo for 52 weeks. Cerebrospinal fluid and plasma amyloid-beta 40 declined more slowly in the resveratrol group than under placebo, and the compound was shown to cross the blood-brain barrier - a demanding test of any polyphenol's reach.

A meta-analysis of resveratrol bioavailability across clinical trial data, and a broad review of resveratrol clinical trials, both confirm that the compound is safe at gram doses.

N-acetylcysteine (NAC) is the acetylated form of the amino acid L-cysteine and the rate-limiting precursor for glutathione, the body's principal intracellular antioxidant. Unlike most ingredients in this category, NAC is a licensed medicine: it is the standard antidote for paracetamol (acetaminophen) overdose and is registered as a mucolytic. Its pharmacology, dosing and safety at gram quantities are therefore unusually well characterised, by the oral and intravenous routes.

In psychiatry and neurology, NAC has been tested extensively as an adjunctive treatment. Ooi, Green and Pak (2018) reviewed human clinical trials of NAC in psychiatric conditions published between 2007 and March 2018 and concluded that the evidence supports NAC as an adjunctive therapy alongside existing medication, at 2000 to 2400 mg per day by mouth. Zheng et al. (2018) meta-analysed randomised controlled trials of NAC across major mental disorders in Acta Psychiatrica Scandinavica, and Yolland et al. (2020) meta-analysed the schizophrenia trials specifically in the Australian and New Zealand Journal of Psychiatry.

The mechanistic chain is documented rather than inferred: oral NAC raises plasma cysteine, cysteine availability drives glutathione synthesis, and magnetic resonance spectroscopy studies have measured changes in brain glutathione and glutamate under NAC administration.

Few compounds in this field arrive with a pharmacological file of that depth behind them.

Lion's mane (Hericium erinaceus) is an edible mushroom whose extracts contain hericenones, found mainly in the fruiting body, and erinacines, found mainly in the mycelium. Both classes stimulate nerve growth factor synthesis in cell culture, which is the mechanistic basis for interest in the mushroom.

Mori et al. (2009) conducted the trial that established lion's mane in this field. Thirty Japanese men and women aged 50 to 80 with mild cognitive impairment were randomised, double-blind, to 250 mg tablets of Yamabushitake taken four tablets three times daily - 3 g per day of dried powder by mouth - or placebo, for 16 weeks, with 15 participants per arm. Scores on the Revised Hasegawa Dementia Scale increased significantly in the lion's mane group compared with placebo at weeks 8, 12 and 16. The difference disappeared four weeks after supplementation stopped, consistent with a reversible pharmacological effect that depends on continued intake.

A 2025 double-blind randomised placebo-controlled study of a standardised extract in healthy younger adults reported acute effects on some cognition and mood measures.

Lion's mane is a whole-mushroom extract rather than a single molecule, and its constituents span four orders of magnitude in size: erinacine A is a small molecule at 432.6 g/mol, while the beta-glucan polysaccharides that make up much of an extract's mass are polymers of tens to hundreds of kilodaltons.

Cordyceps preparations sold as supplements are almost never the wild fungus Ophiocordyceps sinensis. They are usually Cs-4, a fermentation product of a Cordyceps sinensis mycelial strain, or the cultivated species Cordyceps militaris. The trials below tested those preparations, taken orally.

Chen et al. (2010) randomised 20 healthy adults aged 50 to 75 to Cs-4 333 mg three times daily (about 1 g/day) or placebo for 12 weeks, double-blind. Maximal incremental cycle ergometer testing with breath-by-breath gas analysis showed that the metabolic threshold - the workload above which lactate begins to accumulate - rose 10.5 percent in the Cs-4 group, from 0.83 +/- 0.06 to 0.93 +/- 0.08 L/min. That is an instrumented physiological measurement rather than a questionnaire.

An earlier randomised, double-blind, placebo-controlled trial of Cs-4 in healthy elderly volunteers, published in the Chinese Journal of Integrative Medicine, likewise reported improvements in aerobic capacity and respiratory function.

A 2024 randomised controlled trial of a Cordyceps militaris beverage in healthy adults examined immune response endpoints.

Cordyceps is a whole-fungus extract rather than a single molecule. Its characterised nucleoside constituents are small - cordycepin (3-deoxyadenosine) at 251.2 g/mol and adenosine at 267.2 g/mol - while the polysaccharide fraction that makes up much of the extract mass is very much larger.