NAD Boosters (NMN, NR, NADH): Benefits, Forms, Dosing, and Side Effects

Nicotinamide adenine dinucleotide (NAD) is a coenzyme essential for energy production in mitochondria throughout the body. It exists in two interconvertible forms: NAD+ (the oxidized form) and NADH (the reduced form). NAD+ participates in hundreds of metabolic reactions, including cellular respiration, DNA repair, sirtuin-mediated deacetylation, and regulation of circadian rhythm [1][2]. Every living cell depends on NAD+ to convert nutrients into usable energy via the electron transport chain.

Interest in NAD-boosting supplements was sparked by preliminary laboratory research suggesting that NAD+ levels decline with age. A 2012 study found that NAD+ decreased in human skin tissue with advancing age [6], and a 2013 study in mice showed that raising NAD+ levels could reverse aspects of mitochondrial dysfunction [7]. However, a subsequent study in humans found no significant difference in NAD+ levels between older and younger people, casting doubt on the assumption that age-related NAD+ decline is universal [1][8].

The three main categories of NAD-boosting supplements are NADH (direct supplementation with the coenzyme), nicotinamide riboside (NR, a precursor converted to NMN then to NAD+), and nicotinamide mononucleotide (NMN, the immediate biosynthetic precursor to NAD+). If you already consume adequate vitamin B3 (14-16 mg daily for adults) from your diet and/or supplements, it is unclear whether any of these provide meaningful additional benefit [1].

Table of Contents

• Overview
• Forms and Bioavailability
• Evidence for Benefits
• Recommended Dosing
• Safety and Side Effects
• Drug Interactions
• Dietary Sources
• References

Overview

Nicotinamide adenine dinucleotide (NAD) is a coenzyme essential for energy production in mitochondria throughout the body. It exists in two interconvertible forms: NAD+ (the oxidized form, carrying a positive charge) and NADH (the reduced form, with a hydrogen atom attached, making it electrically neutral) [1][2]. NAD+ participates in hundreds of metabolic reactions, including cellular respiration, DNA repair, sirtuin-mediated deacetylation, and regulation of circadian rhythm [2][3]. Every living cell depends on NAD+ to convert nutrients into usable energy via the electron transport chain.

The body synthesizes NAD+ from dietary precursors — primarily niacin (vitamin B3) and its derivatives, including nicotinamide (niacinamide), nicotinamide riboside (NR), and nicotinamide mononucleotide (NMN) [1][4]. Some NAD+ is stored in red blood cells, while excess is broken down in the liver and excreted in urine [1]. The predominant route for NAD+ replenishment in mammalian cells is the salvage pathway, which recycles nicotinamide generated from NAD+-consuming enzymes such as sirtuins, PARPs (poly ADP-ribose polymerases), and CD38 [3][5]. This pathway accounts for over 85% of NAD+ production in most tissues [5].

Interest in NAD-boosting supplements was sparked by preliminary laboratory research suggesting that NAD+ levels decline with age. A 2012 study found that NAD+ decreased in human skin tissue with advancing age (Massudi et al., PLoS One, 2012) [6], and a 2013 study in mice showed that raising NAD+ levels could reverse aspects of mitochondrial dysfunction (Gomes et al., Cell, 2013) [7]. These findings raised the hope that boosting NAD+ could provide anti-aging benefits. However, a subsequent study in humans found no significant difference in NAD+ levels between older and younger people (Elhassan et al., bioRxiv, 2019 — preprint), casting doubt on the assumption that age-related NAD+ decline is universal or that supplementation would necessarily provide an anti-aging effect [1][8].

If you already consume adequate vitamin B3 (14-16 mg daily for adults) from your diet — which is not difficult, as B3 is present in many foods — and/or supplements, it is unclear whether any of the NAD-boosting supplements discussed in this article provide meaningful additional benefit [1].

The three main categories of NAD-boosting supplements are:

• NAD+/NADH — Direct supplementation with the coenzyme itself, usually in the reduced NADH form. NADH is 99.85% NAD by weight [1].
• Nicotinamide riboside (NR) — A precursor to NAD+ that is converted to NMN by nicotinamide riboside kinases (NRK1/NRK2), then to NAD+ by NMNATs [5][9]. Sold as Niagen (nicotinamide riboside chloride), nicotinamide riboside hydrogen malate, and crystalline nicotinamide riboside [1].
• Nicotinamide mononucleotide (NMN) — A nucleotide that sits one enzymatic step closer to NAD+ than NR in the salvage pathway. NMN is converted directly to NAD+ by NMNATs [3][5]. Typically marketed as NMN or beta-NMN (identical compounds) [1].

Forms and Bioavailability

NAD+ and NADH

NADH is the form used in clinical studies, as direct NAD+ exhibits poor cellular uptake when taken orally [3][10]. Stabilized NADH (such as the branded product ENADA) has been used at doses of 5-20 mg in clinical trials [1]. Oral NADH is absorbed in the small intestine, though bioavailability data in humans is limited. The primary advantage of NADH supplementation is that it provides the coenzyme directly without requiring conversion. However, because NADH is chemically unstable and sensitive to light, moisture, and stomach acid, stabilized or enteric-coated formulations are necessary for oral delivery [1][11].

Nicotinamide Riboside (NR)

NR is available in several commercial forms:

• Nicotinamide riboside chloride (Niagen) — The most extensively studied form in clinical trials. Manufactured by ChromaDex (now Niagen Bioscience) [1].
• Nicotinamide riboside hydrogen malate — An alternative salt form [1].
• Crystalline nicotinamide riboside — Used in Elysium Health's Basis product, combined with pterostilbene [1][12].

NR is orally bioavailable with high and consistent absorption, entering cells directly via equilibrative nucleoside transporters without significant gut degradation [3][10]. Once inside cells, NR is phosphorylated by nicotinamide riboside kinases (NRK1 and NRK2) to form NMN, which is then adenylated by NMNATs to form NAD+ [5][9]. A pharmacokinetic study among 11 healthy adults showed that single doses of 100 mg, 300 mg, or 1,000 mg of Niagen increased NAD+ levels in a dose-dependent fashion (Trammell et al., Nat Commun, 2016) [13]. In a longer trial, daily doses of 100 mg, 300 mg, and 1,000 mg of Niagen for 8 weeks increased whole blood NAD+ levels by 22%, 51%, and 142%, respectively, within two weeks (Conze et al., Sci Rep, 2019) [14].

Nicotinamide Mononucleotide (NMN)

NMN is a ribonucleotide consisting of a nicotinamide base linked to a ribose sugar with a phosphate group at the 5' position (molecular formula: C11H15N2O8P, molecular mass: 334.22 Da) [3]. It is water-soluble and functions as the immediate biosynthetic precursor to NAD+ in the salvage pathway [5].

NMN administered orally is rapidly absorbed from the small intestine, with peak plasma concentrations observed within 15-60 minutes of ingestion [3][15]. Human pharmacokinetic studies show that single doses of 100-900 mg elevate plasma NMN levels in a dose-dependent manner, alongside increases in NAD+ and its metabolites [3][15]. The bioavailability of oral NMN is characterized by rapid absorption followed by quick metabolism and clearance, with a half-life of approximately 1-2 hours. However, chronic supplementation at 250-900 mg daily for 4-12 weeks sustains elevated NAD+ levels in blood and tissues without accumulation of NMN itself [3][15][16].

The mechanism of NMN absorption remains debated. Evidence supports both direct cellular uptake via a specific transporter (Slc12a8) and extracellular dephosphorylation to NR by the enzyme CD73 before re-entry into cells [3][5][17]. Detection of intact NMN in plasma after oral dosing supports at least partial direct absorption [3][15].

Alternative delivery forms include sublingual (powders, lozenges) and liposomal encapsulation. Liposomal NMN has shown promise in small studies — one double-blind trial reported an 84% increase in blood NAD+ levels after four weeks with liposomal NMN, compared to lower elevations with standard capsules [3][18]. However, no peer-reviewed human studies have directly compared sublingual to oral administration, and claims of 2-3 times higher bioavailability remain unsubstantiated [3][19].

NR vs. NMN: Head-to-Head

Standard oral NR has historically shown higher effective bioavailability of the intact molecule compared to standard oral NMN, because NMN's phosphate group may require extracellular conversion to NR before cellular uptake [3][10]. However, NMN appears more stable in the bloodstream once absorbed, and both precursors are equally effective at elevating NAD+ levels in blood [3][10]. Head-to-head comparisons in 2026 trials demonstrated that NMN approximately doubles baseline NAD+ concentrations after 14 days of daily supplementation, comparable to NR [3]. The practical difference between the two precursors may be minimal for most users.

Quality Concerns

A 2021 analysis by ChromaDex of 22 top-selling NMN products on Amazon found that only 14% met or exceeded label claims, 23% were slightly below (88-99% of claimed NMN), and 64% contained less than 1% of claimed NMN, with 14% having none detectable [3]. This extreme variability underscores the importance of third-party testing when selecting NMN supplements.

Evidence for Benefits

Chronic Fatigue Syndrome (CFS) — NADH

Chronic fatigue syndrome has been associated with increased activity of enzymes that deplete ATP, the primary energy currency of cells. Since NADH is directly involved in ATP generation, there has been interest in using it to increase energy and reduce fatigue in CFS patients [1].

Crossover trial (n=26): A study among 26 people with CFS who received 10 mg of stabilized NADH (ENADA) or placebo daily for 4 weeks showed that 31% of NADH recipients experienced a clinically meaningful improvement in symptoms (defined as improvement of at least 10%), compared to only 8% on placebo. However, no formal between-group statistical comparison was performed. One participant reported feeling overly stimulated while taking NADH (Forsyth et al., Ann Allergy Asthma Immunol, 1999) [20].

Controlled trial with active comparator (n=20): A study of 20 CFS patients — 12 receiving 5 mg NADH daily (increased to 10 mg if symptoms did not improve) and 8 receiving nutritional supplements plus psychological therapy for up to 24 months — showed that both groups improved during the first 3 months compared to baseline, but there was no significant between-group difference (Santaella et al., P R Health Sci, 2004) [21].

NADH + CoQ10 combination (n=73, positive): A study among 73 CFS patients found that taking 20 mg NADH with 200 mg CoQ10 daily for 8 weeks modestly improved overall Fatigue Impact Scale (FIS-40) scores by approximately 7.5 points (out of 160), and this improvement was statistically significant compared to placebo (Castro-Marrero et al., Antioxid Redox Signal, 2015) [22].

NADH + CoQ10 combination (n=144, negative): A larger study among 144 CFS patients found the same combination taken daily for 8 weeks did NOT improve physical functioning, psychosocial symptoms, overall FIS-40 scores, or sleep quality compared to placebo (Castro-Marrero et al., Nutrients, 2021) [23].

Expert opinion: The European Network on Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (EUROMENE) has stated that NADH may be tried by people with CFS to relieve fatigue or cognitive dysfunction (Nacul et al., Medicina (Kaunas), 2021) [24].

Alzheimer's Disease and Cognitive Function — NADH

Dementia (n=19, uncontrolled): An uncontrolled study among 19 people with mild to moderate dementia found that 10 mg of NADH (ENADA) daily for 3 months did not improve measures of cognition compared to baseline (Rainer et al., J Neural Transm, 2000) [25].

Alzheimer's disease (n=24, controlled): A study among 24 people with probable Alzheimer's disease showed that those who took 10 mg NADH daily for 6 months experienced no cognitive decline and had higher scores on the Mattis Dementia Rating Scale compared to placebo. However, there was no between-group difference in attention, memory, or clinician-rated dementia severity (Demarin et al., Drugs Exp Clin Res, 2004) [26].

Parkinson's Disease — NADH

NADH is a coenzyme involved in the synthesis of L-DOPA, a precursor of dopamine — the neurotransmitter deficient in Parkinson's disease [1].

Open-label study (n=885): An open-label study among 885 Parkinson's patients found that 5 mg enteric-coated NADH by mouth or 12.5 mg NADH by infusion every other day for 2 weeks improved disability scores by approximately 20% (Birkmayer et al., Acta Neurol Scand Suppl, 1993) [27].

Open-label with levodopa: A study showed that 10 mg NADH by infusion for 7 days alongside 100 mg levodopa improved UPDRS scores by 9.3 points (out of 199) and slightly increased blood levels of levodopa (Kuhn et al., J Neural Transmission, 1996) [28].

Placebo-controlled trial (negative): Infusions of 25 mg NADH for 4 days, then intramuscular injections on days 20 and 35, did NOT improve UPDRS scores compared to placebo. Both groups improved versus baseline (Dizdar et al., Acta Neurol Scand, 1994) [29].

Depression — NADH

Open-label study (n=188): One open-label study among 188 people with depression found that 5 mg NADH by mouth or 12.5 mg by injection daily for up to approximately 10 months improved symptoms in 93% of participants, with 32% showing marked improvement. However, the lack of a control group prevents conclusions about causality (Birkmayer et al., New Trends Clin Neuropharmacol, 1991) [30].

Raising NAD+ Levels — Nicotinamide Riboside

Multiple studies confirm that NR reliably raises blood NAD+ levels, though translating this biochemical change into clinical benefit has proven difficult [1][13][14].

Dose-response (n=11): Single doses of Niagen at 100 mg, 300 mg, or 1,000 mg increased NAD+ levels without serious adverse events. Two people reported flushing at 300 mg and two reported "feeling hot" at 1,000 mg (Trammell et al., Nat Commun, 2016) [13].

Eight-week dose-response: Daily doses of 100 mg, 300 mg, and 1,000 mg of Niagen for 8 weeks increased whole blood NAD+ by 22%, 51%, and 142%, respectively, within two weeks. No flushing reported and no elevation of LDL cholesterol (Conze et al., Sci Rep, 2019) [14].

Older adults (n=24): Adults aged 55-79 taking 500 mg Niagen twice daily for six weeks had a 60% increase in blood NAD+ compared to placebo (Martens et al., Nat Commun, 2018) [31].

NR + pterostilbene (n=120): Basis (Elysium Health) — 250 mg NR plus 50 mg pterostilbene — among 120 older adults increased blood NAD+ by 40% (one capsule) and 55% (two capsules) over two months. A slight but significant increase in LDL cholesterol was observed with two capsules daily (Dellinger et al., NPJ Aging Mech Dis, 2017) [12].

Energy and Physical Performance — Nicotinamide Riboside

Due to NAD's role in cellular energy production, it was hoped that NR would improve functional energy levels. However, this has not been demonstrated in clinical studies [1]. The maker of Niagen (ChromaDex) previously claimed that Niagen increased energy but removed that claim in 2021 following a challenge by the Better Business Bureau. In March 2026, the NAD recommended that Niagen Bioscience discontinue several additional claims [1].

Physical performance review: A review of clinical studies evaluating NR for physical performance in older adults found small, short-term studies with mixed results (Cusodero et al., Exp Gerontol, 2020) [32].

Peripheral Artery Disease — Nicotinamide Riboside

Walking distance (n=89): A study among 89 adults (average age 71) with PAD found that 500 mg NR twice daily for 6 months increased 6-minute walking distance by 7 meters, while the placebo group decreased by 10.6 meters. This was statistically significant — although largely driven by the decline in the placebo group. NR did NOT improve maximum treadmill walking time or overall physical activity (McDermott et al., Nat Commun, 2024) [33].

Cognitive function in PAD (n=8): 1,000 mg NR daily for 4 weeks did NOT significantly improve executive function, attention, language, processing speed, or episodic memory (Szarvas et al., J Pharmacol Exp Ther, 2025) [34].

Alzheimer's Disease — Nicotinamide Riboside

Biomarker analysis (n=22): Blood analysis from 22 adults who took 500 mg Niagen twice daily for 6 weeks suggested NR raised NAD+ levels in the brain and reduced Alzheimer's biomarkers — but based on peripheral blood measurements, not direct evidence (Vreones et al., Aging Cell, 2023) [37].

Mild cognitive impairment (n=20): NR at titrated doses up to 1,000 mg daily did NOT significantly improve any cognitive measure compared to placebo in older adults with MCI. The placebo group showed greater improvements in physical function (Orr et al., Geroscience, 2024) [38].

Self-reported cognitive decline (n=37): 1 g NR daily for 8 weeks did NOT improve cognitive function scores compared to placebo. A small reduction in phosphorylated tau 217 (Alzheimer's biomarker) was observed, but no other biomarker differences (Wu et al., Alzheimers Dement (N Y), 2025) [39].

Blood Sugar and Insulin Resistance — Nicotinamide Riboside

Overweight men with insulin resistance (n=40): 1,000 mg NR twice daily for three months did NOT decrease fasting blood sugar, HbA1c, or improve insulin sensitivity or body composition compared to placebo (Dollerup et al., Am J Clin Nutr, 2018) [41].

Long COVID — Nicotinamide Riboside

Brain fog and fatigue (n=32): A 24-week study found that 1,000 mg NR twice daily increased NAD+ levels 2- to 3-fold, but there were NO significant improvements in cognitive function, fatigue severity, sleep quality, anxiety, or depression compared to placebo. Side effects included muscle cramps, nausea, bruising, headaches, flushing, rash, and vertigo (Wu et al., eClinicalMedicine, 2025) [42].

Raising NAD+ Levels — NMN

Like NR, NMN reliably raises blood NAD+ levels. Human clinical trials have consistently used daily oral doses ranging from 250 to 1,200 mg per day [3][43].

Postmenopausal women with prediabetes (n=25): 250 mg NMN daily for 10 weeks increased NAD+ in immune cells by approximately 43% compared to placebo. Skeletal muscle NAD+ was not increased (Yoshino et al., Science, 2021) [44].

Multicenter trial (n=80): 300 mg, 600 mg, or 900 mg NMN daily for 60 days significantly increased blood NAD+ in all groups (p ≤ 0.001). No significant changes in blood glucose, insulin sensitivity, lipids, or blood pressure. Six-minute walk distance improved (p < 0.01) [3][45].

Healthy Japanese adults (n=30): 250 mg/day NMN for 12 weeks raised whole-blood NAD+ at weeks 4, 8, and 12 (returning to baseline by week 16). No significant impacts on body composition, glucose metabolism, or lipid profiles [3][46].

Insulin Sensitivity — NMN

Postmenopausal women (n=25): 250 mg NMN daily for 10 weeks increased muscle insulin sensitivity by 25% compared to baseline (Yoshino et al., Science, 2021) [44]. However, this has been criticized because the placebo group had 2.35 times more liver fat at baseline — and liver fat is known to reduce muscle insulin sensitivity — making it unclear whether the difference was due to NMN or baseline imbalances (Brenner, Science, 2021) [47].

Exercise Performance — NMN

Recreational runners (n=48): 300 mg or 600 mg NMN twice daily for 6 weeks with training found dose-dependent improvements in ventilatory thresholds. However, neither dose increased maximum oxygen consumption. A lower dose (150 mg twice daily) did not improve any outcome (Liao et al., J Int Soc Sports Nutr, 2021) [48].

Systematic review of 10 RCTs: A 2024 review found non-significant overall improvements in physical strength and aerobic performance with NMN. Only 8.2% of 437 participants experienced minor adverse events [3][49].

Muscle Strength and Physical Function in Older Adults — NMN

Healthy older men (n=20): 250 mg NMN daily for 12 weeks increased blood NAD+ but did NOT significantly increase muscle mass, walking speed, leg strength, grip strength, or improve cognitive function compared to placebo (Igarashi et al., NPJ Aging, 2022) [50].

Different trial (n=20): 250 mg daily NMN for 12 weeks showed significant gains in left-hand grip strength (p=0.019), gait speed (p=0.033), and chair-stand performance at 6 weeks (p=0.031) [3][16].

Older men with impairments (n=14): 250 mg daily NMN for 24 weeks found NO significant differences in grip strength or walking speed versus placebo in men with diabetes and baseline physical impairments [3][51].

Sleep — NMN

Older Japanese adults (n=108): 250 mg NMN daily for 12 weeks did NOT improve overall sleep quality or duration compared to placebo. Afternoon dosing modestly reduced daytime drowsiness (Kim et al., Nutrients, 2022) [52]. Additional trials have reported improvements in PSQI sleep scores and reduced daytime dysfunction with NMN supplementation, but evidence remains inconsistent [3].

Anti-Aging Claims — NMN

The central claim driving NMN's popularity is that it counters age-related decline by restoring NAD+ levels. However, the translation to humans has been disappointing. Human trials consistently show NAD+ elevation but inconsistent and small effects on clinical outcomes [3][43][49]. No RCTs have extended beyond several months to evaluate long-term endpoints. The Interventions Testing Program (ITP) evaluating NR found NO significant lifespan extension in mice across multiple strains [3][55]. The scientific consensus as of 2026 is that while NAD+ precursors reliably increase NAD+ levels, there is no strong evidence for benefits in longevity or age-related diseases [3][43][55].

Preclinical Evidence — NMN (Animal Studies)

While human evidence remains limited, preclinical research in animal models has been more promising. Long-term oral NMN supplementation in aging mice suppressed weight gain, improved energy metabolism, enhanced insulin sensitivity, eye function, and physical activity (Mills et al., Cell Metab, 2016) [53]. NMN also reversed vascular endothelial dysfunction in aged mice, improved cardiac function in heart failure models, enhanced autophagy and reduced amyloid pathology in Alzheimer's models, and restored oocyte quality in aged female mice [3]. However, these results have not translated convincingly to human outcomes due to species-specific differences in NAD+ metabolism and much higher relative doses used in animal studies [3][54].

Recommended Dosing

NADH

Clinical studies have used 5-20 mg daily of stabilized NADH [1]:

• Chronic fatigue syndrome: 10-20 mg daily, alone or combined with 200 mg CoQ10 [20][22][23]
• Cognitive support: 10 mg daily [25][26]
• Parkinson's disease: 5 mg orally (enteric-coated) or 12.5-25 mg by infusion [27][28][29]

NADH supplements should be taken on an empty stomach for optimal absorption [1].

Nicotinamide Riboside (NR)

Clinical studies have used doses ranging from 100 mg to 3,000 mg daily, often divided into two doses [1][13][14][31]:

• General NAD+ boosting: 250-300 mg daily (typical commercial dose) [1]
• Higher-dose protocols: 500-1,000 mg twice daily (used in PAD, long COVID, and cognitive trials) [33][38][42]
• Onset of effect: NAD+ increases are detectable within 2 weeks and maintained with continued use [14]

Nicotinamide Mononucleotide (NMN)

Clinical studies have used 250-1,200 mg daily [1][3]:

• General NAD+ boosting: 250-500 mg daily [44][46][50]
• Exercise performance: 600-1,200 mg daily in divided doses [48]
• Onset of effect: Blood NAD+ increases within hours; sustained elevations within 14-30 days [3]

NMN should be taken in divided doses with meals to minimize stomach discomfort [3][10]. No peer-reviewed studies have compared daily supplementation to cycling protocols, and daily administration remains the standard in research [3].

Methylation Considerations

High intake of NAD+ precursors (particularly NMN and niacinamide) can increase production of methylated metabolites like N1-methyl-nicotinamide, potentially straining methylation capacity over time [3]. This theoretical concern may be mitigated by methyl donors such as trimethylglycine (TMG) [3]. Dr Brad Stanfield's MicroVitamin includes 500 mg of TMG (betaine anhydrous) alongside niacin (vitamin B3, 8 mg), which supports methylation capacity and may help offset this concern for those also taking NAD-boosting supplements.

Safety and Side Effects

NADH

NADH is generally well tolerated at doses of 5-20 mg daily. Reported side effects are rare and mild — one CFS trial participant reported feeling overly stimulated [20]. No serious adverse events have been reported in clinical trials.

Nicotinamide Riboside

NR is generally well tolerated at doses up to 1,000 mg twice daily. Commonly reported side effects include [1][14][31][41]:

• Flushing: Reported at 300 mg and 1,000 mg in one study, generally less common than with niacin [13]
• Gastrointestinal: Nausea, bloating, changes in stool, abdominal discomfort [12][41]
• Musculoskeletal: Leg cramps, muscle cramps [31][42]
• Other: Headache, itching, excessive sweating, increased bruising, rash, vertigo [31][41][42]
• At high doses (1,500 mg twice daily): Increased risk of abdominal pain (Berven et al., Nat Commun, 2023) [56]
• LDL cholesterol: NR combined with pterostilbene caused a slight LDL increase [12]. NR alone did not elevate LDL [14]

Nicotinamide Mononucleotide (NMN)

NMN has been well tolerated in human trials at doses up to 1,250 mg daily [3][10]:

• Gastrointestinal: Minor GI issues (nausea, gas, diarrhea) are the most common side effects [3][46]
• No serious adverse events reported in clinical trials [3][10]
• Preclinical safety: NOAEL of 1,500 mg/kg/day in rats for 90 days, with no genotoxic or mutagenic potential [3][57]

Vitamin B3 Upper Intake Level

All NAD boosters are sources of vitamin B3, which has a US Tolerable Upper Intake Level of 35 mg/day for adults (based on skin flushing from nicotinic acid, not nicotinamide). European levels are higher: 500 mg in the UK and 900 mg in the EU for nicotinamide specifically [1]. Toxicities at high intakes include liver injury, macular damage, gout, platelet declines, impaired glucose control, and increased anticonvulsant drug levels [1].

Cancer Concerns

There is a theoretical concern, based on animal research, that compounds raising NAD+ levels may promote cancer growth and metastasis [1][58][59]. A mouse study found that NR-enriched diet increased tumor development (70% vs 55%) and brain metastases (82% vs 25%) in triple-negative breast cancer models (Maric et al., Biosens Bioelectrol, 2022) [58]. One group of researchers has suggested that reducing NAD+ levels may be a more promising cancer approach (Gujar et al., PNAS, 2016) [62].

One consumer reported a sharp PSA rise (1.8 to 4.9) after one year taking Elysium Basis, which returned to 1.9 after stopping for one month [1]. There is no evidence linking other forms of B3 (niacin, niacinamide) with cancer risk — in fact, niacinamide may reduce some types of skin cancer [1].

While no evidence demonstrates that NR, NMN, or NADH causes cancer in humans, it would be prudent to avoid NAD-boosting supplements if you have been diagnosed with cancer [1].

Kidney Concerns — NMN

Aged mice given NMN for 8 weeks showed increased kidney inflammation (IL-1beta) and kidney injury, with buildup of toxic breakdown products (Saleh et al., bioRxiv, 2024 — preprint) [63]. It may be prudent for people with impaired kidney function to avoid NMN until more is known [1].

Drug Interactions

No clinical studies have specifically examined interactions between NAD-boosting supplements and common medications. No interactions have been reported in existing trials, but due to the absence of dedicated research, potential interactions remain unknown [3][10].

General precautions include:

• Anticonvulsant drugs: High-dose nicotinamide may increase blood levels of anticonvulsant drugs [1]
• Glucose-lowering medications: High-dose nicotinamide may impair glucose control [1]
• Blood thinners: Niacinamide has mild anticoagulant potential at high doses [3]
• Cancer treatments: Given the theoretical concern about NAD+ promoting tumor growth, consult an oncologist before use [1][58]
• Levodopa: NADH may modestly increase levodopa blood levels; coordinate with a neurologist [28]

Consultation with a healthcare professional is recommended before starting NAD-boosting supplementation, especially for those with pre-existing conditions, those taking medications, pregnant or nursing women, and people with liver or kidney conditions [3][10].

Dietary Sources

NAD+ Precursors from Food

The primary dietary source of NAD+ is niacin (vitamin B3). Most people obtain adequate B3 from food alone. The RDA is 14 mg/day for women and 16 mg/day for men [1].

Top dietary sources of niacin (vitamin B3):

Food	Serving	Niacin (mg NE)
Chicken breast	3 oz (85g)	11.4
Tuna (light, canned)	3 oz (85g)	8.6
Turkey breast	3 oz (85g)	10.0
Salmon	3 oz (85g)	8.6
Beef (lean)	3 oz (85g)	6.2
Peanuts	1 oz (28g)	4.4
Mushrooms	1 cup	3.5
Brown rice	1 cup cooked	3.0
Fortified cereals	1 serving	20.0+
Lentils	1 cup cooked	2.1

NE = niacin equivalents (includes tryptophan conversion, where 60 mg tryptophan = 1 mg niacin).

NMN in Foods

NMN occurs naturally in trace amounts in certain foods, though quantities are far below supplemental doses [3][64]:

Food	NMN Content (mg/100g)
Edamame	0.47-1.88
Avocado	0.36-1.60
Broccoli	Variable, relatively high
Cabbage	0.0-0.90
Tomato	0.26-0.30
Raw meats/seafood	0.06-0.42

To obtain the equivalent of a 250 mg supplement dose from food alone, one would need approximately 13-53 kg of edamame — making supplementation the only practical way to achieve trial-level doses [64].

Nicotinamide Riboside in Foods

NR is found naturally in cow's milk (approximately 3.9 micromol/L) and trace amounts in other foods, but dietary amounts are too low to achieve clinical trial doses [9].

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14. Conze D, Brenner C, Kruger CL. "Safety and Metabolism of Long-term Administration of NIAGEN." Sci Rep. 2019;9(1):9772. https://doi.org/10.1038/s41598-019-46120-z

15. Irie J, et al. "Effect of oral administration of nicotinamide mononucleotide on clinical parameters in healthy Japanese men." Endocr J. 2020;67(2):153-160. https://doi.org/10.1507/endocrj.EJ19-0313

16. Igarashi M, et al. "Chronic nicotinamide mononucleotide supplementation elevates blood NAD+ levels and alters muscle function in healthy older men." NPJ Aging. 2022;8(1):5. https://doi.org/10.1038/s41514-022-00084-z

17. Grozio A, et al. "Slc12a8 is a nicotinamide mononucleotide transporter." Nat Metab. 2019;1(1):47-57. https://doi.org/10.1038/s42255-018-0009-4

18. Yi L, et al. "The efficacy and safety of beta-NMN supplementation in healthy middle-aged adults." GeroScience. 2023;45(1):29-43. https://doi.org/10.1007/s11357-022-00705-1

19. No direct peer-reviewed comparison of sublingual vs. oral NMN in humans as of 2026.

20. Forsyth LM, et al. "Therapeutic effects of oral NADH on symptoms of patients with chronic fatigue syndrome." Ann Allergy Asthma Immunol. 1999;82(2):185-191. https://doi.org/10.1016/S1081-1206(10)62595-1

21. Santaella ML, et al. "Comparison of oral NADH versus conventional therapy for CFS." P R Health Sci J. 2004;23(2):89-93. https://pubmed.ncbi.nlm.nih.gov/15377055/

22. Castro-Marrero J, et al. "Does oral CoQ10 plus NADH supplementation improve fatigue in CFS?" Antioxid Redox Signal. 2015;22(8):679-685. https://doi.org/10.1089/ars.2014.6181

23. Castro-Marrero J, et al. "Effect of CoQ10 Plus NADH Supplementation on Heart Rate after Exercise Testing in CFS." Nutrients. 2021;13(7):2379. https://doi.org/10.3390/nu13072379

24. Nacul L, et al. "EUROMENE Expert Consensus on ME/CFS Care in Europe." Medicina (Kaunas). 2021;57(5):510. https://doi.org/10.3390/medicina57050510

25. Rainer M, et al. "No evidence for cognitive improvement from oral NADH in dementia." J Neural Transm (Vienna). 2000;107(12):1475-1481. https://doi.org/10.1007/s007020070011

26. Demarin V, et al. "Treatment of Alzheimer's disease with stabilized oral NADH." Drugs Exp Clin Res. 2004;30(1):27-33. https://pubmed.ncbi.nlm.nih.gov/15134388/

27. Birkmayer JGD, et al. "NADH — a new therapeutic approach to Parkinson's disease." Acta Neurol Scand Suppl. 1993;146:32-35. https://pubmed.ncbi.nlm.nih.gov/8333244/

28. Kuhn W, et al. "Parenteral application of NADH in Parkinson's disease." J Neural Transm. 1996;103(10):1187-1193. https://doi.org/10.1007/BF01271203

29. Dizdar N, et al. "Treatment of Parkinson's disease with NADH." Acta Neurol Scand. 1994;90(5):345-347. https://doi.org/10.1111/j.1600-0404.1994.tb02735.x

30. Birkmayer W, Birkmayer JGD. "NADH as biological antidepressive agent." New Trends Clin Neuropharmacol. 1991;5:19-25.

31. Martens CR, et al. "Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults." Nat Commun. 2018;9(1):1286. https://doi.org/10.1038/s41467-018-03421-7

32. Cusodero AL, et al. "Impact of nicotinamide riboside on functional capacity." Exp Gerontol. 2020;140:111065. https://doi.org/10.1016/j.exger.2020.111065

33. McDermott MM, et al. "Effect of Nicotinamide Riboside on Walking in PAD: The PACE Trial." Nat Commun. 2024;15:4174. https://doi.org/10.1038/s41467-024-48542-8

34. Szarvas Z, et al. "Nicotinamide riboside supplementation and cognitive function in PAD." J Pharmacol Exp Ther. 2025.

35. Gong B, et al. "Nicotinamide riboside restores cognition in Alzheimer's mouse models." Neurobiol Aging. 2013;34(6):1581-1588. https://doi.org/10.1016/j.neurobiolaging.2012.12.005

36. Zhang H, et al. "NAD(+) repletion improves mitochondrial and stem cell function and enhances life span in mice." Science. 2016;352(6292):1436-1443. https://doi.org/10.1126/science.aaf2693

37. Vreones M, et al. "Oral nicotinamide riboside raises NAD and lowers biomarkers of neurodegenerative pathology." Aging Cell. 2023;22(1):e13754. https://doi.org/10.1111/acel.13754

38. Orr ME, et al. "Nicotinamide Riboside Clinical Trial in Older Adults with MCI." Geroscience. 2024;46:5361-5373. https://doi.org/10.1007/s11357-024-01217-2

39. Wu J, et al. "NR supplementation in adults with cognitive decline or MCI." Alzheimers Dement (N Y). 2025.

40. Lee HJ, et al. "Nicotinamide riboside ameliorates hepatic metaflammation." J Med Food. 2015;18(11):1207-1213. https://doi.org/10.1089/jmf.2015.3439

41. Dollerup OL, et al. "Nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects." Am J Clin Nutr. 2018;108(2):343-353. https://doi.org/10.1093/ajcn/nqy132

42. Wu J, et al. "Nicotinamide riboside supplementation in long COVID." eClinicalMedicine. 2025.

43. Liao B, et al. "NMN supplementation enhances aerobic capacity in amateur runners." J Int Soc Sports Nutr. 2021;18(1):54. https://doi.org/10.1186/s12970-021-00442-4

44. Yoshino M, et al. "Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women." Science. 2021;372(6547):1224-1229. https://doi.org/10.1126/science.abe9985

45. Yi L, et al. "The efficacy and safety of beta-NMN supplementation in healthy middle-aged adults." GeroScience. 2023;45(1):29-43. https://doi.org/10.1007/s11357-022-00705-1

46. Katayoshi T, et al. "NMN supplementation in healthy Japanese adults: a 12-week RCT." 2022.

47. Brenner C. "Mononucleotide is not a natural metabolite of nicotinamide riboside." Science. 2021;373(6556):eabi1560. https://doi.org/10.1126/science.abi1560

48. Liao B, et al. "NMN supplementation enhances aerobic capacity in amateur runners." J Int Soc Sports Nutr. 2021;18(1):54. https://doi.org/10.1186/s12970-021-00442-4

49. Systematic review of 10 RCTs on NMN physical performance outcomes, 2024.

50. Igarashi M, et al. "Chronic NMN supplementation elevates blood NAD+ and alters muscle function in healthy older men." NPJ Aging. 2022;8(1):5. https://doi.org/10.1038/s41514-022-00084-z

51. Prospective double-blind study in 14 older men with diabetes, 250 mg daily NMN for 24 weeks.

52. Kim M, et al. "Effect of 12-Week NMN Intake on Sleep Quality, Fatigue, and Physical Performance." Nutrients. 2022;14(4):755. https://doi.org/10.3390/nu14040755

53. Mills KF, et al. "Long-Term NMN Administration Mitigates Age-Associated Physiological Decline in Mice." Cell Metab. 2016;24(6):795-806. https://doi.org/10.1016/j.cmet.2016.09.013

54. Multiple systematic reviews noting absence of long-term human RCTs for NAD+ precursors as of 2026.

55. Harrison DE, et al. "Nicotinamide riboside and three other drugs do not affect lifespan in either sex." Aging Cell. 2021;20(5):e13328. https://doi.org/10.1111/acel.13328

56. Berven H, et al. "Dose-finding study of nicotinamide riboside." Nat Commun. 2023.

57. Preclinical toxicology: NOAEL 1,500 mg/kg/day in rats, 90-day sub-chronic, per OECD guidelines.

58. Maric T, et al. "Nicotinamide riboside supplementation reduces tumor growth in triple-negative breast cancer." Biosens Bioelectrol. 2022.

59. Poljsak B. "NAD+ in Cancer Prevention and Treatment: Pros and Cons." J Clin Exp Oncol. 2016;5(4). https://doi.org/10.4172/2324-9110.1000165

60. Hamity MV, et al. "Nicotinamide riboside and pain-related cancer models." Pain. 2020.

61. Acklin S, et al. "Nicotinamide riboside in neuro-oncology." Neurooncol Adv. 2022.

62. Gujar AD, et al. "An NAD+-dependent transcriptional program governs self-renewal in glioblastoma." PNAS. 2016;113(51):E8247-E8256. https://doi.org/10.1073/pnas.1610921114

63. Saleh T, et al. "NMN and kidney inflammation in aged mice." bioRxiv. 2024. Preprint.

64. Mills KF, et al. Cell Metab. 2016. First quantitative detection of NMN in foods reported in 2016.

65. FDA. "FDA responses to citizen petitions on NMN dietary supplement status." September 29, 2025.

66. International regulatory status: Japan, Canada, Australia TGA, China, EU novel food.