Facts, Articles, Research

What the science says (1990–2026): Niacin (Vitamin B3)

These citations support correction of deficiency, specified forms, and elemental amounts — the same logic used in MD's Choice formulas. They are not claims that a supplement treats disease.

HPS2-THRIVE 2014; AIM-HIGH 2011; 2022–2024 lipid reviews. Niacin is an essential vitamin. High-dose nicotinic acid as a heart drug did not beat modern statin care and can cause flushing and liver strain. Food-level and modest supplemental niacin is a different question from gram-doses.

These products are not intended to diagnose, treat, cure, or prevent disease. Historic monograph text below is kept for the original library.

Niacin (Vitamin B3)

I. Chemistry

Structure
Coenzymes containing nicotinamide
Oxidation and reduction of nicotinamide moiety

II. Sources of niacin equivalents

NAD may be synthesized from Tryptophan in the liver
1. 1g complete, high-quality protein contains 10 mg tryptophan
2. 60 mg tryptophan generates 1 mg niacin equivalents
3. Therefore, 6 g protein = 60 mg tryptophan = 1 mg niacin equivalents
B. Dietary sources
1. Milk (tryptophan)
2. Fish, beef, chicken, turkey, port, other meats
3. NAD and NADP undergo hydrolysis following slaughter so meats provide free nicotinamide
C. Cereal grains, seeds, and legumes (except corn)
1. Niacin in corn is bound and unavailable
  1. Nound niacin for be released by alkali
  2. American Indians soaked corn in lime or potash solutions in making hominy and before grinding meal
2. Jowar, a millet used in India, is also pellagragenic
  1. Unlike corn, its nicotinic acid is free
  2. It has a good tryptophan content
  3. Like corn, it is relatively high in leucine
  4. Excess leucine inhibits a key enzyme (quinolinate phosphoribosyltransferase) in conversion of tryptophan to NAD
  5. Leucine also stimulates a key enzyme (picolinate carboxylase) in the degradation pathway of tryptophan
D. Tea and Coffee
1. Trigonellin in raw-coffee is converted to nicotinic acid on roasting
2. Absence of pellagra in Central and South American countries whose staple is corn is attributed to widespread consumption of coffee

III. Functions

Approximately 200 enzymes, primarilyy dehydrogenases, require NAD and NADP
Functions of NAD and NADP in the cells are quite different
1. The major role of NADH is to transfer electrons from intermediated through the electron transport chain to produce ATP
2. Oxidative reactions in which NAD is reduced to NADH. Examples are:
  1. Glycolysis - glucose is degraded into pyruvate
  2. Oxidative decarboxylation of pyruvate
  3. Oxidation of acetate via the tricarboxylic acid cycle
  4. B-Oxidation of fatty acids
  5. NAD is required for catabolism of vitamin B₆ (pyridoxal) to its excretory product (pyridoxic acid)
3. NAD has some nonredox functions
  1. NAD acts as a donor of ADP ribose for posttranslational modification of proteins. This suggests niacin is involved in growth and differentiation of cells
  2. Niacin along with chromium is thought to be a component of glucose tolerance factor (GTF)
4. Functions of NADP
  1. Hexose monophosphate shunt which generates important intermediates not produced in other pathways (pentose phosphates, NADPH)
  2. Malate shuttle which transports acetyl CoA out of the mitochondria
5. NADPH is used in a variety of reductive biosyntheses
  1. Fatty acid synthesis
  2. Cholesterol and steroid hormone synthesis
  3. Oxidation of glutamate
  4. Synthesis of deoxyribonucleotides
  5. Reduction of vitamin C
  6. Glutamine reductase (GSSG ® 2GSH) requires NADPH
  7. Conversion of folate to its active forms

IV. Metabolism

Absorption and Transport
1. NAD and NADP are hydrolyzed in the intestinal tract to release nicotinamide
2. Nicotinamide and nicotinic acid are absorbed primarilyy from the small intestine
  1. By a Na-dependent, saturable system at low concentrations
  2. By passive diffusion at high concentrations
3. Nicotinic acid converted into nicotinamide in the mucosal cells
  1. First incorporated into NAD
  2. Then released through NAD hydrolysis
4. Found in plasma primarilyy as nicotinamide
5. Nicotinamide and nicotinic acid cross cell membranes by simple diffusion (kidney tubules and red blood cells require a Na-dependent carrier system)
6. Nicotinamide is taken up by the tissues and incorporated into the coenzymes
B. Excretion
1. NAD and NADP can be degraded by glycohydrolase into nicotinamide and ADP-ribose
2. Nicotinamide is methylated and oxidized into a variety of products excreted in urine

V. Requirements

Estimation of niacin requirements is complicated by tryptophan-derived NAD which is affected by a variety of influences
1. Amount of tryptophan and niacin ingested
2. Protein and energy intake
3. Adequacy of riboflavin and vitamin B₆
Recommendations in humans are given in niacin equivalents (NE)
1. Adult human.........9.2-13.3 NE
2. Swine...................5-10 mg/lb feed
3. Chicks..................12 mg/lb feed
4. Dogs....................100-180 mg/lb BW/day

VI. Deficiency

Human – Pellagra
1. Dermatitis of areas subject to mechanical urolutein, photosensitivity
2. Dementia (May be due to elevated pyruvate)
  1. Irritability
  2. Headaches
  3. Sleeplessness
  4. Loss of memory
  5. Delirium
3. Diarrhea, indigestion and anorexia
4. Glossitis - scarlet red tongue
Dog – Black tongue
1. Inflammation of gums, redness of palate
2. Beet red tongue with black necrotic areas
3. Bloody diarrhea
Chick
1. Inflammation of mouth, esophagus and crop
2. Poor feathering
3. Normocytic anemia
Pigs
1. Diarrhea, vomiting
2. Dermatitis
3. Normocytic anemia

VII. Toxicity

Niacin is not stored and appears to be relatively nontoxic in large doses
3-6 g/day is sometimes used to lower serum cholesterol and low density lipoproteins but may have side effects
1. Release of histamine resulting in uncomfortable flushing
2. Possible liver damage
3. Competition of niacin with uric acid thereby increasing serum urate
4. Dermatologic problems, itching
5. Elevated plasma glucose

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Niacin (Vitamin B3) — C₆H₅NO₂

A small ring vitamin (nicotinic acid or nicotinamide). Cells use it in NAD/NADP, the “helper” molecules that run hundreds of energy reactions. Flushing can happen with nicotinic acid, not usually with nicotinamide.

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Vitamin A	Vitamin B1 (Thiamin)	Vitamin B2 (Riboflavin)	Vitamin B3 (Niacin)
Vitamin B5 (Pantothenic Acid)	Vitamin B6	Vitamin B12	Vitamin C
Vitamin D	Vitamin E	Vitamin K	Biotin
Folic Acid

Calcium	Magnesium	Phosphorus	Sodium, Potassium, Chloride
Sulfur (Sulfer)

Boron	Chromium	Cobalt	Copper
Fluorine	Iodine	Iron	Manganese
Molybdenum	Nickel (Nickle)	Selenium	Silicon
Tin	Vanadium	Zinc	Ultra Trace

Aluminum	Arsenic	Cadmium	Lead
Mercury

What the science says (1990–2026): Niacin (Vitamin B3)

Niacin (Vitamin B3)

Vitamins, Major Elements, Trace Elements, Toxic Elements

Vitamins

Major Elements

Trace Elements

Toxic Elements

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