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VitaminClinical dose · 100–1,000mg/day raised blood NAD+ (+22% at 100mg, +51% at 300mg, +142% at 1,000mg after 8 weeks); cognition and fatigue trials used 1,000–2,000mg/day in patient groups and found no benefitOnset · Blood NAD+ rose within 2 weeks and stayed higher to week 8; no trial has shown an effect on cognition or energy

Nicotinamide Riboside (NR)

NR raises NAD+ in human blood: in an 8-week trial in 140 healthy overweight adults, whole-blood NAD+ rose 22%, 51% and 142% at 100, 300 and 1,000mg/day (Conze et al., 2019, funded by ChromaDex), and the rise has been reproduced by other groups, including Nestlé researchers. That is a biomarker, not a health outcome. No randomized cognition trial in healthy adults was found. Three placebo-controlled trials in mild cognitive impairment or subjective cognitive decline (1,000mg/day for 8–12 weeks) and a long-COVID trial (2,000mg/day) found no cognitive benefit, even though blood NAD+ rose 2- to 3-fold. In the largest trial, NOPARK (410 people with early Parkinson's disease, 1,000mg/day for 52 weeks, published in JAMA in 2026), symptom scores worsened more on NR than on placebo. A 2023 review of 25 human studies concluded that oral NR has shown few clinically relevant effects. Most NR trials are funded, supplied or co-authored by ChromaDex/Niagen Bioscience or Elysium Health.

By The Nootropic Lab editorial teamUpdated 8 min read✓ Fact-checked

Evidence reviewed:

Mechanism of action

Nicotinamide riboside (NR) is a form of vitamin B3 and a precursor of NAD+. Supplements usually contain the salt nicotinamide riboside chloride, sold as NIAGEN by Niagen Bioscience (formerly ChromaDex). Taking NR reliably raises NAD+ in human blood; the authors of a 2026 trial propose that it works partly through gut bacteria converting it to nicotinic acid. Blood NAD+ is a surrogate marker: no trial has shown that raising it improves thinking, memory or energy.

Clinical evidence summary

NR raises NAD+ in human blood: in an 8-week trial in 140 healthy overweight adults, whole-blood NAD+ rose 22%, 51% and 142% at 100, 300 and 1,000mg/day (Conze et al., 2019, funded by ChromaDex), and the rise has been reproduced by other groups, including Nestlé researchers. That is a biomarker, not a health outcome. No randomized cognition trial in healthy adults was found. Three placebo-controlled trials in mild cognitive impairment or subjective cognitive decline (1,000mg/day for 8–12 weeks) and a long-COVID trial (2,000mg/day) found no cognitive benefit, even though blood NAD+ rose 2- to 3-fold. In the largest trial, NOPARK (410 people with early Parkinson's disease, 1,000mg/day for 52 weeks, published in JAMA in 2026), symptom scores worsened more on NR than on placebo. A 2023 review of 25 human studies concluded that oral NR has shown few clinically relevant effects. Most NR trials are funded, supplied or co-authored by ChromaDex/Niagen Bioscience or Elysium Health.

Human effect matrix

Based on human clinical trials only. Animal and in-vitro data excluded.

EffectEvidenceMagnitudeStudies
Blood NAD+ (Biomarker) strong
Large
5
Memory & Thinking (Healthy Adults) preliminary
Negligible
—
Cognition (MCI & Subjective Decline) preliminary
Negligible
3
Fatigue & Energy preliminary
Negligible
2
Parkinson's Disease moderate
Negligible
3
Healthy Ageing preliminary
Negligible
2

Evidence key: Strong = multiple consistent RCTs · Moderate = smaller/fewer RCTs · Preliminary = early trials or small n · Mixed = conflicting results

Documented benefits

  • Raises NAD+ in blood, more at higher doses (biomarker only; replicated in several trials)
  • No more adverse events than placebo at 100–1,000mg/day over 8 weeks in healthy overweight adults (one trial)

Side effects & cautions

  • In the NOPARK phase 3 trial (early Parkinson's disease, 1,000mg/day for 52 weeks, n=410), Parkinson's symptom scores worsened more on NR than on placebo (+2.72 points, p=.02) and non-motor symptoms worsened more; serious adverse events were less common on NR (8.3% vs 14.1%). The authors say the results do not support NR as a disease-modifying treatment
  • EFSA judged nicotinamide riboside chloride safe at up to 300mg/day for healthy adults, but only up to 230mg/day in pregnancy and breastfeeding
  • In a 2021 opinion, EFSA noted experimental data indicating several ways in which intakes of nicotinamide or its precursors well above physiological needs might cause adverse effects
  • Healthy-adult safety data stop at 8 weeks: in that trial there was no flushing, no LDL-cholesterol rise and no difference in adverse events between NR and placebo
  • At 3,000mg/day for 4 weeks in Parkinson's disease there were no moderate or severe adverse events, but serum homocysteine rose slightly at first
  • In a long-COVID trial at 2,000mg/day, 51% of the group that took NR for 20 weeks dropped out, versus 14% in the group that took placebo first; the abstract gives no reasons

How to take

DosageFor raising blood NAD+, 100–1,000mg/day of nicotinamide riboside chloride was tested (300mg/day: +51% after 8 weeks). EFSA judged up to 300mg/day safe for healthy adults (230mg/day in pregnancy and breastfeeding). No dose has been shown to improve cognition or energy
TimingOnce daily after breakfast in the dose-ranging trial; blood NAD+ rose within 2 weeks.
With foodThe dose-ranging trial gave it after breakfast; the trials reviewed set no other rule.
FormsCapsule. Supplements usually contain nicotinamide riboside chloride (NIAGEN or TRU NIAGEN), and most trial product was supplied by ChromaDex, now Niagen Bioscience. Trials that name the form (Trammell 2016, Conze 2019) give doses as mg of nicotinamide riboside chloride, so a label stating mg of the chloride compares directly. NMN, niacin and nicotinamide are different compounds whose trials are not evidence for NR.

Frequently asked questions

Does raising NAD+ improve memory or focus?

Not in the trials so far. No randomized cognition trial in healthy adults was found, and trials in mild cognitive impairment, subjective cognitive decline and long-COVID (1,000–2,000mg/day) found no cognitive benefit even though blood NAD+ rose 2- to 3-fold.

What dose raises NAD+?

In an 8-week trial, whole-blood NAD+ rose 22% at 100mg/day, 51% at 300mg/day and 142% at 1,000mg/day. No trial of 250mg of NR alone with NAD+ as the outcome was found; a combination of 250mg NR with 50mg pterostilbene raised it about 40%.

Is NR safe?

Trials of 100–1,000mg/day for up to 8 weeks found no more adverse events than placebo. EFSA judged up to 300mg/day safe for healthy adults but only up to 230mg/day in pregnancy and breastfeeding. In early Parkinson's disease, a year of 1,000mg/day was followed by worse symptom scores than placebo. Long-term safety in healthy people has not been established.

Who funds NR research?

Most trials were funded, supplied or co-authored by Niagen Bioscience (formerly ChromaDex), which sells NIAGEN, or by Elysium Health. The NAD+ rise has been reproduced by Nestlé researchers, and the trials that found no cognitive benefit come from academic groups, some using vendor-supplied product.

Nicotinamide Riboside (NR) in the EU

Products in the EU

None of the stacks we have audited are listed in our catalogue in the EU yet.

EU food supplement (Reg. 1924/2006 claims)

EU country guides

Regulatory note

Cognitive-effect language on this page describes ingredient mechanisms studied in clinical trials. Health claims on supplements sold in the EU are governed by Regulation (EC) No 1924/2006; only European Food Safety Authority (EFSA) approved claims may appear on product labelling. This page is editorial, not promotional, and does not constitute medical advice. Consult a qualified healthcare professional before starting any supplement.

Sources (17)expand
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