Vitamin B3 (Niacin)

Your intake

What each level of vitamin b3 (niacin) does

Approximate dose-response bands. Individual response varies — these are starting points, not prescriptions.

1. Severely lowYOU ARE HERE

   0 mg – 5.28 mg

   Well below target. Risk of deficiency symptoms tied to nad+ precursor.

2. Insufficient

   5.28 mg – 16 mg

   Below the recommended daily target. Long-term adequacy not assured.

3. Adequate

   16 mg – 24 mg

   Daily target met. Standard nutritional support for nad+ precursor.

4. Therapeutic

   24 mg – 32 mg

   Common for specific health goals. Check the evidence for your situation before sustaining this level.

5. High

   32 mg – 35 mg

   Approaching the tolerable upper limit. Monitor and consider clinical guidance.

6. Over upper limit

   35 mg – +

   Above the tolerable upper limit. Risk of adverse effects — back off or consult a clinician.

Overview

Niacin (nicotinic acid and nicotinamide) is the precursor to NAD+ and NADP+ — central redox cofactors for ~400 enzymes spanning energy metabolism, DNA repair (PARP), and sirtuin-mediated signalling. NAD+ has become a focal point in aging research because tissue levels decline with age.

Functions

• ●Forms NAD+/NADH and NADP+/NADPH — universal electron carriers
• ●Substrate for sirtuins (deacetylases that regulate aging-related pathways)
• ●Substrate for PARP enzymes during DNA repair
• ●Required for cholesterol, fatty acid, and steroid synthesis

Mechanism

NAD+ is consumed (not just recycled) by sirtuins, PARPs, and CD38 — these reactions cleave NAD+ and release nicotinamide. Cells salvage nicotinamide back to NAD+ via the NAMPT enzyme; aging reduces NAMPT activity, contributing to NAD+ decline. Pharmacologic nicotinic acid (1.5–3 g/day) raises HDL and lowers LDL/triglycerides via GPR109A receptor and lipolysis inhibition.

Benefits

• ●Pharmacologic niacin lowers LDL and triglycerides, raises HDL (but AIM-HIGH and HPS2-THRIVE found no CV outcome benefit added to statins)
• ●Nicotinamide reduces non-melanoma skin cancer recurrence (ONTRAC trial, 23% reduction)
• ●Treatment for pellagra (the 4 D's: dermatitis, diarrhea, dementia, death)
• ●NR/NMN raise blood NAD+ but human healthspan outcomes are still TBD

Deficiency

Pellagra is rare in developed countries; was historically epidemic in corn-dependent populations because corn niacin is bound and unbioavailable without lime treatment (nixtamalisation).

Excess

Pharmacologic nicotinic acid causes intense cutaneous flushing via prostaglandin D2 release. Sustained-release forms cause hepatotoxicity. Nicotinamide does not flush and has higher UL.

Forms

• Nicotinic acid (niacin)
  Causes flushing; lipid effects; UL 35 mg/day as supplement
• Nicotinamide (niacinamide)
  No flush, no lipid effect; preferred for general supplementation
• Nicotinamide riboside (NR)
  NAD+ precursor; raises blood NAD+ ~50%; long-term outcomes pending
• Nicotinamide mononucleotide (NMN)
  Direct NAD+ precursor; FDA disputes dietary-supplement status
• Inositol hexanicotinate ('no-flush niacin')
  Hydrolysis is slow; minimal lipid effect

Food sources

• Cooked chicken breast · 3 oz10 mg
• Cooked tuna · 3 oz9 mg
• Cooked turkey breast · 3 oz10 mg
• Peanuts · 1 oz4 mg
• Brown rice (cooked) · 1 cup5 mg
• Cooked salmon · 3 oz9 mg

Supplement forms

Nicotinamide for a daily multivitamin (no flushing, no liver risk at common doses). Reserve nicotinic acid for medically supervised lipid management — the doses required (1.5–3 g/day) are above the UL and need monitoring. NR/NMN are popular for NAD+ restoration but expensive and unproven for longevity endpoints.

Bioavailability

Niacin and nicotinamide are nearly 100% absorbed at dietary doses; 60 mg of tryptophan also converts to ~1 mg niacin equivalent (NE). Corn niacin is bound (niacytin) and bioavailable only after alkaline treatment (nixtamalisation). NR is absorbed intact through specific transporters.

Longevity relevance

NAD+ decline with age is a leading mechanistic hypothesis in aging biology. NR/NMN robustly restore blood NAD+ in human trials; whether this translates to extended healthspan in humans is the big open question (rodent data are mixed). Sirtuin activation depends on adequate NAD+ substrate.

Relationships

References

• NIH ODS — Niacinguideline
• Linus Pauling Institute — Niacinreview
• ONTRAC — nicotinamide & skin cancer (NEJM 2015)study
• AIM-HIGH trial (NEJM 2011)study

About Vitamin B3 (Niacin)

NAD/NADP cofactors; energy metabolism, DNA repair.

Role

NAD+ precursor

Daily target

16 mg (DV)

Upper limit

35 mg

Also called

niacin, vitamin b3, vitamin b-3, nicotinic acid, nicotinamide, niacinamide