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Vitamin B3 (Niacin, Niacinamide)

Vitamin B3 (Niacin) Functions

Vitamin B3 is a water soluble vitamin, an essential nutrient, which main function is to help produce energy from food [1].

The other name for vitamin B3 is nicotinic acid or niacin, because it was discovered during the study of nicotine from tobacco, but niacin is not related to nicotine.

Another form of vitamin B3 is niacinamide (nicotinamide) in which a carboxyl group (COOH) is replaced by a carboxamide group (CONH2). Nicotinamide is part of Nicotinamide Adenosine Dinucleotide (NAD), a coenzyme involved in conversion of nutrients into energy, and part of NADP (NAD Phosphate) needed in synthesis of fatty acids, among other [1].

In the human body, niacin can be converted to niacinamide and vice versa.

Vitamin B3 is also called pellagra preventative or PP factor.

Chart 1. Differences Between Niacin and Niacinamide



Naturally occurs in foods Yes Yes
To fortify foods No Yes
In supplements Yes Yes
Treats vitamin B3 deficiency Yes Yes
Raises HDL, lowers LDL Yes No
Causes flushing Usually Rarely

Recommended Daily Intake

The Recommended Dietary Allowance (RDA) for vitamin B3 for adult men is 16 mg/day, for women 14, during pregnancy 18 and during breastfeeding 17 mg/day [1].

Foods Rich in Vitamin B3

  • PLANT FOODS: ready-to-eat cereals (especially enriched), wheat, buckwheat, millet, spelt, rice, rice bran, barley, peanuts, spirulina (seaweed), bread, potatoes, mushrooms, peaches
  • ANIMAL FOODS: chicken, turkey, pork, beef, veal, lamb, fish
  • OTHER FOODS: yeast extract spread, baker’s and brewer’s yeast, beer
  • Breast milk contains enough niacin to meet the needs of infants 1-6 months old
  • References: [1,2]

The human body can synthesize some vitamin B3 from the amino acid tryptophan from meat, fish, dairy, legumes and other foods; 60 mg of tryptophan is needed for synthesis of 1 mg of niacin [3].

Cooking can decrease the niacin content of foods by 40% and draining for additional 15%; freezing and drying have no significant effect [4].

Vitamin B3 Deficiency (Pellagra): Causes, Symptoms

Causes [1]:

  • Low niacin intake in chronic alcoholism
  • Predominantly cornmeal-based diet (vitamin B3 from cornmeal is not absorbed well) in certain parts of India, China or Africa, especially among refugees [5].
  • Niacin malabsorption (niacin is absorbed in the stomach and upper small intestine) in celiac disease, Crohn’s disease and tryptophan malabsorption in the genetic disorder called Hartnup disease
  • Increased demand for niacin in carcinoid syndrome
  • Interaction with the anti-tuberculosis medication isoniazid


Vitamin B3 deficiency lasting for few months [7] causes pellagra (Italian pella agra = rough skin) with “four D” symptoms: dermatitis with burn-like blisters and later rough, scaly and painful, but not itchy, lesions on the sun-exposed areas (face, extension side of the hands/arms and leg/feet), diarrhea, dementia and death (if not treated) [1]. Other symptoms may include fatigue, depression and memory loss [1].

Pellagra, vitamin B3 (niacin) deficiency

Picture 1. Pellagra: rough, scaling skin on sun exposed parts
(source: Samuel Freire da Silva, MD, Atlasdermatologico


Vitamin B3 Supplements

Forms without prescription (over-the-counter):

  • Niacin and niacinamide:
    • Crystalline or immediate-release
    • Slow- or sustained-release
    • As part of vitamin B complex vitamins and multivitamins
  • Inositol hexanicotinate (“flush-free” niacin)

Prescription forms:

  • Niacin:
    • Intermediate release
    • Extended-release

Possible Benefits

Vitamin B3 supplements are effective for [1,9]:

  • Prevention and treatment of niacin deficiency
  • Increasing HDL and decreasing LDL cholesterol and decreasing triglyceride levels. This effect can be achieved by niacin (but not nicotinamide or inositol hexanicotinate) in high amount (2-3 g/day). Antioxidants (beta carotene, vitamin C and E, selenium) decrease the niacin’s HDL raising effect [9,18].

Vitamin B3 is possibly effective for [1,9]:

  • Cardiovascular disease. According to one 2010 meta-analysis [10] and one 2012 systematic review [11], niacin (but not nicotinamide) reduces “cardiovascular events” but not necessary by increasing HDL cholesterol and not necessary in all individuals.
  • Lowering phosphate levels in individuals with kidney disease on hemodialysis (both niacin and nicotinamide) [12].

There is insufficient evidence about vitamin B3 supplements effectiveness in prevention or treatment of acne, age-related macular degeneration (AMD), alcohol dependence, Alzheimer’s disease, anemia, anxiety, arthritis, attention deficit-hyperactivity disorder (ADHD), Bell’s palsy, blood flow disorders, cancer, cataracts, depression, diabetes mellitus type 1 or 2, diarrhea, dizziness, erectile dysfunction, glossitis (tongue inflammation), drug-induced hallucinations, hepatic encephalopathy, hepatitis C, hearing loss, high blood pressure, HIV/AIDS, insomnia, liver disease, menstrual pain, migraine headache, motion sickness, multiple sclerosis, osteoarthritis, parasite infestation, Raynaud’s disease, ringing in the ears (tinnitus), seizures (epilepsy), skin conditions, stroke, swelling (edema), tardive dyskinesia (involuntary movements), thrombosis, thyroid disorders, tuberculosis, ulcers, vasculitis, vascular spasm, vertigo, wound healing [13,17].

It is also insufficient evidence about the vitamin B3 effectiveness as an antioxidant, anti-agent substance, growth, memory, sexual arousal or weight loss enhancer, sedative, aid in smoking cessation or sun protection [17].

Vitamin B3 Safety: Side Effects, Toxicity

The Tolerable Upper Intake Level (UL)–the amount that should not cause side effects–for non-prescribed (OTC) niacin and niacinamide for adults is 35 mg/day [1].

Possible side effects of niacin, but less likely niacinamide, supplements in usual doses: flushing, paresthesia (tingling), rashes, jaundice, itch, skin hyperpigmentation, nausea, mouth pain, runny nose, slightly elevated blood glucose, stomach upset, intestinal gas, low blood pressure, dizziness, excessive sweating, irregular heartbeat (arrhythmia), worsening of gallbladder disease and allergies [1,9,14,19].

Niacin Flush Reaction

Niacin, but less likely niacinamide, supplements in high doses (>50 mg) can cause flushing of the face, arms and chest; flushes usually appear within 15-30 minutes (or up to 4 hours) after taking and may last for 1-2 hours [6,20]. Flushing increases with the dose and can be prevented by slowly increasing the dose to the prescribed dose over several weeks and by taking it with food. Aspirin in a low dose (325 mg), 30 minutes before niacin, can prevent flushing [20]. Tolerance to flushing often develops in several weeks [14]. Flushing is due to skin vessels dilation [19].

Over-the-counter immediate-release niacin tablets cause flushing more likely than slow-release ones; the prescription extended-release niacin causes flushes the least likely [16].

Foods and drugs that can worsen flushing when taken along with niacin: alcohol, hot drinks, zinc supplements and nicotine patches [9].

“No-flush” niacin usually contains inositol hexanicotinate, which releases niacin slowly and does not cause flushes but also provides your body with only little niacin and is not effective in raising HDL cholesterol levels [16].

Niacin and Drug Tests

There is no scientific evidence that niacin can alter the results of drug tests [15].


Niacin or niacinamide doses higher than 3 g/day may cause dry skin, fever, diarrhea, vomiting, frequent urination, joint pain, muscle aches, unusual thirst or tiredness, liver, gallbladder, stomach, intestinal or kidney problems, gout, blurred vision, high blood sugar, irregular heartbeat, low platelet count (thrombocytopenia) [9,19].

Who should avoid niacin?

Do not take vitamin B3 supplements if you have liver or kidney damage, peptic ulcer, bleeding problems or allergy to niacin and stop taking them at least two weeks before scheduled surgery [14].

During Pregnancy and Breastfeeding

Niacin is a pregnancy category C drug, which means no harmful effects have been observed in human infants so far but insufficient studies have been done to exclude all possible adverse effects [14]. Speak with your doctor if you intend use niacin during pregnancy or breastfeeding.

Vitamin B3 Interactions With Drugs

  • A combination of niacin and statins (lovastatin, simvastatin) may, rarely, cause a breakdown of muscle fibers (rhabdomyolysis) resulting in a kidney failure.
  • A combination of niacin and clonidine may cause low blood pressure (hypotension).
  • A combination of niacin and chromium may cause low blood sugar (hypoglycemia).
  • Niacin in combination with androstenedione, borage leaf, chaparral, comfrey, dehydroepiandrosterone (DHEA), germander, kava, pennyroyal oil or red yeast extract may cause liver damage.
  • Cholestyramine and colestipol may reduce the absorption of niacin and niacinamide.
  • Niacin may reduce the effectiveness of allopurinol, sulfinpyrazone and probenecid in treating gout.

  1. Niacin  Linus Pauling Institute
  2. List of foods high in niacin  US Department of Agriculture
  3. Metabolism and excretion of niacin  The National Academic Press
  4. Nutritional effects of food processing  Self NutritionData
  5. Clinical effects of inadequate intake of niacin  The National Academic Press
  6. Vitamin B3 (Niacin)  University of Maryland, Medical Center
  7. Pellagra and its prevention and control in major emergencies  World Health Organization
  8. Dermatologic Manifestations of Pellagra Clinical Presentation  Emedicine
  9. Niacin and Niacinamide (vitamin B3)  MedlinePlus
  10. Duggal JK et al, 2010, Effect of niacin therapy on cardiovascular outcomes in patients with coronary artery disease  PubMed
  11. Lavigne PM et al, 2012, The Current State of Niacin in Cardiovascular Disease Prevention : A Systematic Review and Meta-Regression  ScienceDirect
  12. He YM et al, 2014, Benefits and harm of niacin and its analog for renal dialysis patients: a systematic review and meta-analysis  PubMed Health
  13. Kuzniarc M et al, 2001, Use of vitamin supplements and cataract: the Blue Mountains Eye Study  PubMed
  14. Niacin  Drugs.com
  15. Use of Niacin in Attempts to Defeat Urine Drug Testing — Five States, January–September 2006  Centers for Disease Control and Prevention
  16. Niacin: the facts on flushing  British Columbia Drug and Poison Information Centre
  17. Niacin (vitamin B3, nicotinic acid), Niacinamide  Mayo Clinic
  18. Cheung MC et al, 2001, Antioxidant Supplements Block the Response of HDL to Simvastatin-Niacin Therapy in Patients With Coronary Artery Disease and Low HDL  Arteriosclerosis, Thrombosis and Vascular Biology
  19. Niacin side effects  Drugs.com
  20. Niacin Medscape

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