🧬 Family & Essentiality

🌿 Plain-Language Summary

Vitamin B3 helps convert food into energy and supports cell repair and communication. The body can obtain niacin directly from foods or make it from tryptophan (an amino acid in protein foods). NAD and NADP, its active coenzymes, are critical to life-sustaining reactions in every cell.

⚗️ Molecular & Chemical IDs

• Nicotinic acid: C₆H₅NO₂ (CAS 59-67-6)
• Nicotinamide: C₆H₆N₂O (CAS 98-92-0)
• Units: NE (niacin equivalents). 1 mg niacin = 1 mg NE; ~60 mg tryptophan ≈ 1 mg NE

⚡ Functions

• NAD: Coenzyme in catabolic pathways (glycolysis, TCA cycle, oxidative phosphorylation)
• NADP: Coenzyme in anabolic reactions (fatty acid synthesis, cholesterol, antioxidant systems)
• DNA repair & gene regulation: NAD is substrate for PARPs & sirtuins (cell signalling, longevity research)

🍽️ Absorption & Bioavailability

🇦🇺 Australian NRVs (NHMRC)

• Adult men: 16 mg NE/day
• Adult women: 14 mg NE/day
• Pregnancy: 18 mg NE/day
• Lactation: 17 mg NE/day

UL (adults): 35 mg/day for preformed niacin (to avoid flushing)

🚨 Deficiency & Excess

Deficiency

• Pellagra: “3 Ds” — dermatitis, diarrhoea, dementia (and death if untreated)
• Glossitis, stomatitis, fatigue, irritability
• Risk ↑ with alcohol misuse, malabsorption, maize-heavy diets without alkali treatment, carcinoid syndrome (Trp diverted to serotonin)

Excess

High-dose nicotinic acid can cause flushing, itching, hypotension. Very high or prolonged use may elevate liver enzymes — only under medical supervision.

🥗 Food Sources

• Meat, poultry, fish (richest sources)
• Whole and fortified grains, legumes, peanuts
• Coffee provides small amounts; protein foods contribute tryptophan (→ NE)

🧪 Testing & Monitoring

• Functional marker: urinary N-methylnicotinamide (NMN) and 2-pyridone excretion
• Clinical signs of pellagra in severe deficiency

🔗 Interactions

• B2 (riboflavin) and B6 (pyridoxine) needed for tryptophan → niacin conversion
• Alcohol misuse and malabsorption ↑ deficiency risk
• Therapeutic doses of nicotinic acid interact with lipid-lowering and antihypertensive medications

📊 Evidence Snapshot

• 🔬✅ Well-established: Roles of NAD/NADP in energy metabolism & DNA repair
• 🧪⚖️ Therapeutic: Prescription nicotinic acid used for dyslipidaemia; requires medical supervision
• ⚠️❌ Unproven/hype: Longevity or “NAD booster” supplements lack strong clinical evidence in healthy people