Vitamins: Vitamin B3 - Niacin

Question 1

Vitamin B3 – Niacin
Vitamin- when is it essential?
What are the two compounds wit niacin activity?
What are the active forms?

Answer 1

Vitamin B3 (Niacin) Is not strictly a vitamin as it can be synthesised by the body from the amino acid tryptophan: 60 mg of tryptophan produces 1 mg niacin.
* Vitamin B3 is only essential when tryptophan metabolism is altered
* The two compounds with niacin activity are: nicotinic acid and nicotinamide.
* The active forms of niacin are: NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate), which are energy-carrying molecules

Question 2

Food sources

Answer 2

• Mushrooms
• Green leafy vegetables
• Yeast extracts
• Sunflower seeds
• Salmon
• Sardines
• Peanut
• Avocado
• Meat
• Poultry
• Tryptophan-rich foods e.g. bananas, turkey

Question 3

Food prep

Answer 3

Cooking reduces B3 in foods

Question 4

Dosage

Answer 4

• Recommendations are stated as niacin equivalents (NE). Equal to the total niacin compounds in food plus 1/60th of the tryptophan content of the food (i.e. 60 mg tryptophan = body produces 1 mg B3)
• Synthesis of B3 from tryptophan requires B2, B6 and iron (cofactors)

Question 5

Niacin flush

Answer 5

• Skin flush and itch due to supplementation
• Avoid flush by using initial dose of 25 mg (gradually increased) alongside 1 g vitamin C

Question 6

Absorption and storage

Answer 6

• Absorption of vitamin B3 is in the small intestine
• Stored niacin (NAD) Is mostly in the liver, heart, muscles and kidney

Question 7

Energy (ATP) Production: function and therapeutic uses

Answer 7

• Functions:
  o The two coenzymes (NAD and NADP) participate in:
   Glycolysis
   Acetyl CoA formation
   Krebs cycle
   Fatty acid oxidation
• Therapeutic uses:
  o Fatigue
  o Supporting energy production in increased need
  o Alzheimer’s

Question 8

Cardiovascular: function and therapeutic uses

Answer 8

• Functions:
  o Lowers secretion of LDL
  o Vasodilator effects (Lowest BP)
• Therapeutic uses:
  o Hyperlipidaemia
  o Cardiovascular disease

Question 9

Insulin: function and therapeutic uses

Answer 9

• Functions:
  o Glucose-tolerance factor (GTF), which plays an important role in the insulin response, employs niacin
• Therapeutic uses:
  o Insulin resistance (i.e. type II diabetes, PCOS)

Question 10

Deficiency signs and symptoms

Answer 10

Severe deficiency (‘Pellagra’):
* Four D’s:
o Diarrhoea
o Dermatitis (Characteristic collar rash)
o Dementia
o Death (within 4-5 years)
* Pellagra can occur in diets deficient in both protein and niacin.
* It is common in Africa, Indonesia and China.
* In the West, pellagra is associated with homelessness, alcoholism or anorexia nervosa.
* Crohn’s or intestinal disease may also lead to deficiency.
* Pellagra is treated with up to 500 mg B3 daily by a doctor

Mild deficiency/insufficiency symptoms:
* Unrelenting fatigue
* Vomiting
* Depression
* Indigestion
* Canker sores
* Sensitivity to strong light
* Red tongue and inflamed gums

Question 11

Toxicity / Adverse Events

Answer 11

• Adverse events can occur at high levels:
  o Hypotension
  o Hyperuricaemia
  o Flush
  o Hepatotoxicity
• Do not megadose
• Niacin competes with urate for excretion so supplementation can worsen gout (200 mg+ / day)

Question 12

Vitamin b3 niacin functions

Answer 12

Energy (atp) production
Cardiovascular
Insulin