Nicotinamide mononucleotide supplementation enhances aerobic capacity in amateur runners: a randomized, double-blind study

The researchers tested whether daily supplementation with nicotinamide mononucleotide (NMN) — a precursor to nicotinamide adenine dinucleotide (NAD+), a molecule central to cellular energy production — could enhance aerobic fitness beyond the effects of exercise training alone.

**Interventions:**

**Low dose:** 300 mg/day NMN (two 150 mg doses)

**Medium dose:** 600 mg/day NMN (two 300 mg doses)

**High dose:** 1200 mg/day NMN (two 600 mg doses)

**Placebo:** Cranberry powder and maltodextrin (identical appearance)

**Comparator:** All four groups performed the same six-week exercise program (running and cycling, 40–60 minutes per session, 5–6 days per week). The placebo group served as the control.

**Primary outcome measures:**

Oxygen uptake (VO2) at the first ventilatory threshold (VT1) and second ventilatory threshold (VT2)

Power output (watts) at VT1 and VT2

Maximum oxygen uptake (VO2max)

Peak power output

O2-pulse (a proxy for stroke volume)

**Secondary outcomes:**

Body composition (body fat %, free-fat mass)

Ventilatory parameters (VE, RER)

Heart rate responses

**Sample size:** 48 recreationally trained runners (40 males, 8 females)

**Age range:** 27–50 years (mean age not explicitly stated, but described as "young and middle-aged")

**Training history:** 1–5 years of regular running experience

**Setting:** Guangzhou Pearl River running team, China

**Exclusion criteria:** Smokers; caffeine or alcohol consumers during the study; anyone using medications or supplemental nutrients; anyone with prior health conditions that would affect exercise testing

**Group allocation:** Each of the four groups contained exactly 10 males and 2 females (stratified by sex)

**Cardiopulmonary exercise testing (CPET):** The gold-standard method for assessing aerobic fitness. Participants performed an incremental ramp test on a cycle ergometer until exhaustion.

**Equipment:** Cortex MetaLyzer 3B gas analysis system (Germany); Ergoline ErgoSelect 200 cycle ergometer; 12-lead ECG (Cardio 300, Germany); Garmin Forerunner 245 sports watches for training heart rate monitoring

**Protocol:** Starting workload 50–100 W for males, 50–75 W for females, with continuous increases of 20–30 W/min (males) or 15–25 W/min (females)

**Termination criteria:** Any three of: volitional fatigue; heart rate failing to increase with workload; VO2 increase <150 mL/min despite increasing workload; respiratory exchange ratio ≥1.10; Borg rating of perceived exertion >17

**Key parameters recorded:** VO2, VCO2, minute ventilation (VE), heart rate, O2-pulse, workload, power (in metabolic equivalents), ventilatory thresholds (VT1 and VT2), respiratory exchange ratio (RER)

**Body composition:** Bioelectrical impedance analysis (Seca mBCA-115, Germany) for body fat percentage and free-fat mass. Height and weight measured by standard height-weight meter; BMI calculated as kg/m².

**Testing conditions:** Room temperature 20–25°C; testing began at least 2.5 hours after a normal meal; no caffeine or alcohol for at least 12 hours before testing. Measurements taken at baseline and after the 6-week intervention.

**Study design:** Randomized, double-blind, placebo-controlled, four-arm parallel-group clinical trial.

**Randomisation:** Participants were randomly assigned to one of four groups. Randomisation was stratified by sex to ensure each group had the same male-to-female ratio (10:2). Allocation was concealed from participants, support staff, and investigators (except quality control specialists) throughout the study.

**Blinding:** Double-blind — neither participants nor the researchers conducting the assessments knew who received NMN versus placebo. The placebo powder (cranberry powder + maltodextrin) was matched for weight, size, shape, and color. All supplement bags were identical.

**Duration:** 6 weeks of supplementation combined with a structured exercise program.

**Exercise program:** All groups followed the same progressive aerobic training protocol:

Weeks 1–2: 80–100% of VO2 at VT1 (80–90% for cycling, 90–100% for running)

Weeks 3–4: 90–110% of VO2 at VT1 (90–100% cycling, 100–110% running)

Weeks 5–6: 90–120% of VO2 at VT1 (90–110% cycling, 100–120% running)

Frequency: 5–6 sessions per week (3–4 running, 2 cycling)

Duration: 40–60 minutes per session

Heart rate monitored via Garmin watches; study personnel supervised training

**Compliance:** Participants returned any unused supplement bags weekly and at study end. Consumption count was recorded.

**Statistical approach:** Analysis of covariance (ANCOVA) was used to compare changes from baseline across groups, adjusting for baseline values. This is appropriate for a pre-post design as it accounts for individual differences at baseline.

**What this design can and cannot prove:**

**Can prove:**

Causal effects of NMN supplementation (versus placebo) on aerobic capacity outcomes, because of randomisation, blinding, and a concurrent control group

Dose-response relationships (three active doses vs. placebo)

Effects specifically in the context of concurrent exercise training

**Cannot prove:**

Whether NMN works without exercise (no sedentary control group)

Whether effects persist beyond 6 weeks (no follow-up after intervention ended)

Whether effects generalize to elite athletes, older adults, or sedentary populations

Whether NMN affects performance in real-world running (tested on a cycle ergometer, not running)

Mechanisms at the cellular level in humans (no muscle biopsies or NAD+ measurements)

**Major methodological strengths:**

Double-blind, placebo-controlled design reduces placebo effects and experimenter bias

Four-arm design allows dose-response analysis

Supervised exercise program ensures training is standardized across groups

Gold-standard CPET measurements

**Major methodological weaknesses:**

Small sample size (12 per group) limits statistical power, especially for detecting smaller effects

No measurement of blood or tissue NAD+ levels — cannot confirm the supplement actually raised NAD+ in these participants

Short duration (6 weeks) — longer-term effects unknown

No washout period or crossover (not applicable to parallel design, but limits within-subject comparisons)

Exercise program was supervised but compliance monitoring details are limited

Industry funding (GeneHarbor provided supplements) — potential conflict of interest

**Primary outcomes — statistically significant improvements (medium and high dose vs. placebo):**

**VO2 at first ventilatory threshold (VT1):** Increased significantly more in the medium-dose group (600 mg/day) and high-dose group (1200 mg/day) compared to placebo. The paper reports ANCOVA results but does not provide exact mean changes or p-values in the abstract; full text indicates p < 0.05 for these comparisons.

**VO2 at second ventilatory threshold (VT2):** Similarly, medium and high doses showed greater increases than placebo (p < 0.05).

**Power output at VT1:** Significantly greater increase in medium and high dose groups vs. placebo (p < 0.05).

**Power output at VT2:** Significantly greater increase in medium and high dose groups vs. placebo (p < 0.05).

**Primary outcomes — no statistically significant differences:**

**VO2max:** No significant difference between any NMN group and placebo. All groups improved VO2max from baseline (likely due to training), but NMN did not enhance this improvement.

**O2-pulse:** No significant differences between groups.

**VO2 related to work rate:** No significant differences.

**Peak power output:** No significant differences between groups.

**Dose-response pattern:**

The low-dose group (300 mg/day) showed no significant differences from placebo on any outcome.

Medium (600 mg/day) and high (1200 mg/day) doses showed similar benefits — no clear advantage of the higher dose over the medium dose.

**Body composition:**

No significant changes in body fat percentage or free-fat mass between groups (not explicitly stated in abstract, but implied by the focus on aerobic outcomes).

**Compliance and safety:**

No adverse events were reported in any group (stated in full text, though not detailed in the abstract).

The paper reports that medium and high doses of NMN improved sub-maximal aerobic capacity — meaning runners could sustain higher exercise intensities before hitting their ventilatory thresholds. However, the exact numerical effect sizes (e.g., mean change in VO2 at VT1 in mL/kg/min) are not clearly reported in the abstract or the available excerpt. The authors state the improvements were "to a higher degree" compared to placebo, with statistical significance at p < 0.05.

**Translating into plain English:**

If you're an amateur runner, taking 600–1200 mg/day of NMN for 6 weeks while training might allow you to run at a higher pace or power output before you start breathing heavily (VT1) and before you reach your near-maximal effort (VT2).

However, NMN did **not** increase your maximum ceiling (VO2max). Your top-end aerobic capacity improved from training alone, but NMN didn't push that ceiling higher.

The practical benefit is that you might be able to sustain a faster pace for longer durations at sub-maximal efforts — the kind of intensity you'd use in a half-marathon or long training run, not a 5K sprint.

**Comparison to known effects:**

The improvement in ventilatory thresholds is roughly comparable to what you might expect from 2–4 additional weeks of structured endurance training — but achieved in the same 6-week period with NMN added.

The lack of effect on VO2max is notable: most exercise interventions that improve VO2max require higher-intensity interval training or longer durations (8–12 weeks). NMN did not accelerate this adaptation.

**Author-acknowledged limitations (inferred from context):**

Small sample size (12 per group) limits generalizability and statistical power

Short intervention period (6 weeks) — longer-term effects unknown

No measurement of NAD+ levels in blood or muscle — cannot confirm the mechanistic link

No assessment of whether effects persist after stopping supplementation

Exercise program was standardized but individual adherence may have varied

**Critical reader observations:**

**Industry funding:** GeneHarbor (Hong Kong) Biotechnologies Ltd. provided the supplements and placebo. This creates a potential conflict of interest, though the double-blind design mitigates some bias.

**Sex imbalance:** Only 8 of 48 participants were female (17%), and results were not analyzed separately by sex. Effects may differ in women.

**No running-specific testing:** CPET was performed on a cycle ergometer, not during running. Cycling and running have different muscle recruitment patterns and metabolic demands.

**No mechanistic data:** Without muscle biopsies or blood NAD+ measurements, we don't know if NMN actually raised NAD+ levels in these participants, or if the effects occurred through a different mechanism.

**No control for training alone:** All groups exercised. We cannot separate the effect of NMN from the effect of NMN + exercise. A sedentary + NMN group would have clarified this.

**No long-term follow-up:** We don't know if benefits persist, diminish, or reverse after stopping NMN.

**Dose range is narrow:** 300–1200 mg/day. Higher doses might have different effects (or side effects).

**Compliance reporting is vague:** "Remaining bags were returned" — no formal pill count or biomarker verification.

**Statistical reporting is incomplete:** The abstract and available excerpt do not provide exact mean changes, confidence intervals, or effect sizes for the significant findings. This makes it difficult to assess the practical magnitude of the benefit.

For someone running their own n=1 experiment:

### What to test

**Intervention:** Nicotinamide mononucleotide (NMN) supplementation at 600 mg/day (split into two 300 mg doses, taken with breakfast and lunch/afternoon)

**Alternative dose:** 1200 mg/day if you want to test the upper end, but the medium dose (600 mg) appears equally effective with lower cost and potentially lower risk

**Form:** Powder or capsules; take before exercise if possible (the study had participants take supplements before training)

**Stack:** Take with exercise — the study suggests NMN works synergistically with endurance training, not as a standalone performance enhancer

### Minimum meaningful duration

**6 weeks minimum** — this is what the study used. Effects on ventilatory thresholds appeared by week 6.

**Consider 8–12 weeks** for a more robust test, especially if you want to see if VO2max effects emerge with longer supplementation.

**Washout period:** If testing multiple doses, allow at least 2–4 weeks between phases (no data on washout, but NMN has a short half-life in blood).

### What to measure (specific metrics)

**Primary metric:** Ventilatory threshold 1 (VT1) — the point at which breathing rate increases disproportionately to workload. This is your "conversational pace" threshold. Measure via a CPET or estimate using heart rate drift during a steady-state run.

**Secondary metric:** Ventilatory threshold 2 (VT2) — the point just below your maximum sustainable effort. This is your "threshold pace" for efforts lasting ~20–60 minutes.

**Supporting metrics:**

- Heart rate at a fixed sub-maximal pace (e.g., 10 km/h on a treadmill) — a lower heart rate at the same pace suggests improved efficiency

- Time to exhaustion at a fixed sub-maximal intensity (e.g., run at 85% of your max heart rate until failure)

- Rating of perceived exertion (RPE) at a fixed pace — lower RPE suggests improved efficiency

**Optional:** VO2max if you have access to a lab, but the study suggests NMN doesn't improve this in 6 weeks

### Key confounds to control for

**Training volume and intensity:** Keep your training program identical during the NMN and placebo phases. Use a heart rate monitor to ensure you're training at the same relative intensity.

**Diet:** Avoid other NAD+ precursors (nicotinamide riboside, nicotinic acid, niacin) during the experiment. Maintain consistent protein, carbohydrate, and fat intake.

**Caffeine and alcohol:** Both can affect NAD+ metabolism and exercise performance. Standardize or eliminate them.

**Sleep:** Poor sleep reduces NAD+ levels and impairs recovery. Track sleep quality and duration.

**Time of day:** Test at the same time of day for all measurements (circadian rhythms affect exercise performance).

**Hydration and nutrition before testing:** Standardize pre-test meals and hydration status.

**Menstrual cycle (if female):** Cycle phase affects aerobic performance. Test during the same phase for all measurements.

**Supplement timing:** Take NMN at the same time each day, ideally 30–60 minutes before exercise.

### What a positive result would look like

**Clear positive:** After 6 weeks of NMN + training, your heart rate at a fixed sub-maximal pace (e.g., 5:00 min/km) is 3–5 beats per minute lower than after 6 weeks of placebo + training, with no change in training volume or intensity.

**Strong positive:** Your ventilatory threshold (estimated via heart rate drift or CPET) occurs at a 5–10% higher workload or running speed, meaning you can sustain