NAD+ Supplementation Dosing
For NAD+ supplementation, use niacin (the dietary precursor to NAD+) at 16 mg/day for adult males and 14 mg/day for adult females, with higher doses of 18 mg/day during pregnancy and 16 mg/day during lactation. 1
Standard Dietary Recommendations
The recommended daily intake of niacin, which the body converts to NAD+, varies by population 2, 1:
- Adult males (>14 years): 16 mg/day 2, 1
- Adult females (>14 years): 14 mg/day 2, 1
- Pregnant women: 18 mg/day 2, 1
- Lactating women: 16 mg/day 2, 1
Clinical Nutrition Settings
For patients requiring nutritional support 2:
- Enteral nutrition: 18-40 mg per day of niacin in 1500 kcal 2, 3
- Parenteral nutrition: At least 40 mg of niacin per day 2, 1, 3
Safety Limits and Toxicity Concerns
The upper intake level for free nicotinic acid is 10 mg/day, based on flushing effects observed at 30 mg/day in young subjects. 2, 1 However, this creates a practical challenge since therapeutic doses often exceed this limit 2.
For nicotinamide (a different form), the upper limit is approximately 900 mg/day for adults 1, 3.
Common Side Effects
- Flushing: Can occur at doses as low as 30 mg with nicotinic acid, typically affecting the face, arms, and chest within 30 minutes of ingestion 2, 4
- Hepatotoxicity: Risk increases significantly at doses around 3 g/day, ranging from mild enzyme elevation to acute liver failure 2, 4
- Gastrointestinal symptoms: Nausea, vomiting, and abdominal discomfort may occur 1
Alternative NAD+ Precursors
Nicotinamide Riboside (NR)
Human trials have tested NR at doses of 100-1000 mg/day, showing dose-dependent increases in blood NAD+ levels (22% at 100 mg, 51% at 300 mg, and 142% at 1000 mg) without causing flushing 5. NR does not typically cause flushing unlike nicotinic acid. 1, 4
Nicotinamide Mononucleotide (NMN)
Human studies have used 250 mg/day for 6-12 weeks, demonstrating good tolerability and increased blood NAD+ levels 6. However, animal studies suggest caution: doses around 100 mg/kg had minimal harmful effects on atherosclerosis, while 300 mg/kg promoted atherosclerosis despite improving dyslipidemia 7.
Critical Clinical Considerations
When treating suspected niacin deficiency (pellagra), use 15-20 mg/day of nicotinic acid or 300 mg/day of nicotinamide orally. 2 The oral/enteral route should be used whenever the gastrointestinal tract is functional 2.
For patients at risk of deficiency (chronic alcoholism, malabsorption, carcinoid tumors, or corn-based diets), higher supplemental doses may be required beyond standard dietary recommendations 2.
Monitoring Requirements
- Baseline liver function tests, with monthly monitoring if underlying liver disease exists 2
- Blood or tissue NAD levels may be measured when clinical symptoms suggest deficiency (diarrhea, dermatitis, dementia) 2
- Storing a blood sample and awaiting symptom response to supplementation is a pragmatic alternative when measurement is difficult 2