NAD Precursors Adverse-Event Management Protocols

What adverse events have been reported with NMN?

Human trials of NMN have been short, and the largest studied dose is 1,250 mg once daily for up to 4 weeks. In that randomized, double-blind, placebo-controlled trial of 31 healthy adults aged 20-65, there were no severe adverse events and no changes beyond normal physiological variation in hematology, biochemistry, urine, or body composition [5]. A 12-week trial of NMN 250 mg/day in 30 healthy adults found no abnormalities in physiological and laboratory tests and no obvious adverse effects [1]. A 60-day trial of 80 middle-aged adults taking 300, 600, or 900 mg/day reported no safety issues based on adverse-event, laboratory, and clinical monitoring [2]. A single-dose study in 10 healthy men tested 100, 250, and 500 mg NMN and found no significant clinical symptoms or changes in heart rate, blood pressure, oxygen saturation, or body temperature; laboratory changes, including small increases in bilirubin and decreases in creatinine, chloride, and glucose, stayed within normal ranges [10].

What adverse events have been reported with NR?

NR trials have used higher doses than NMN trials, and the reported events are mostly mild. In a 2 x 6-week randomized, double-blind, placebo-controlled crossover trial in adults aged 55-79, NR 500 mg twice daily (1,000 mg/day) produced 14 mild adverse events in 7 participants, including nausea, flushing, leg cramps, and bruising; there were no serious events [3]. A 12-week trial of NR 1,000 mg twice daily (2,000 mg/day) in 40 obese men found no serious adverse events and normal safety blood tests [6]. In a 20-person Parkinson's disease trial (10 on NR), NR 1,500 mg twice daily (3,000 mg/day) for 4 weeks produced no moderate or severe adverse events and no significant difference in mild adverse events versus placebo; recipients had a slight initial rise in serum homocysteine [4]. A 30-day trial of NR 1,000 mg/day in 30 newly diagnosed Parkinson's patients was also well tolerated [11].

One small trial reported an unexpected finding. In a 21-day crossover study of 12 men aged 70-80 taking NR 1 g/day, four men (33%) self-reported increased libido on NR and none on placebo; no clinical adverse events were reported [12].

What did the trials monitor?

The trials that reported safety checked adverse events, vital signs, hematology, biochemistry, urine, and body composition, depending on the study [1][2][5][6]. The reports describe monitoring and adverse-event counts, not a stepwise protocol for what to do if nausea, flushing, or a laboratory change occurs.

What is known about niacin?

Niacin is a different case, and this trial studied people with high cholesterol, not NMN or NR. A 1994 randomized, double-blind, parallel comparison of immediate-release and sustained-release niacin in 46 adults escalated doses from 500 to 3,000 mg/day, each dose for 6 weeks [7]. Eighteen of 23 participants (78%) assigned to sustained-release niacin withdrew before completing the 3,000 mg/day dose; the most common reasons were gastrointestinal symptoms, fatigue, and increases in liver aminotransferases, often with symptoms of hepatic dysfunction. Twelve of the 23 (52%) taking sustained-release niacin developed hepatotoxic effects, while none of the 23 taking immediate-release niacin did. Nine of 23 (39%) on immediate-release niacin withdrew, most often for vasodilatory symptoms, fatigue, and acanthosis nigricans [7]. The authors concluded that sustained-release niacin is hepatotoxic, and that immediate-release niacin, although preferred in the trial, can also cause significant adverse effects [7].

What about drug interactions and special populations?

A 2023 review of NAD+-boosting supplements identified no human drug-interaction studies of NMN or NR, including CYP, transporter, or pharmacodynamic studies [9]. Whether either supplement interacts with a prescription drug is therefore unknown. Long-term safety data beyond about 12 weeks are lacking; trials were short and small, with 12 to 140 participants [9]. Pregnancy, breastfeeding, children, and people with cancer or kidney or liver disease were not studied in these trials, so safety in these groups is unknown [9]. A theoretical concern that chronic NAD+ boosting could promote cancer has been raised, but no human data were identified [9].