Niacin (B3)

Question 1

How is Niacin absorbed?

Answer 1

Niacin bioavailability is low in grains as it is tightly bound to proteins, less than 30% is absorbed

Soaking in lime water improves bioavailability, this is often done when corn is the staple food in the diet

Some antibiotics inhibit niacin absorption

Small amount absorbed in stomach, most in small intestine, actively or passively depending on conc.

Question 2

What is the active form of Niacin?

Answer 2

NAD+ and NADP+

Converted to active form in all tissues

Question 3

What is the function of Niacin

Answer 3

Niacin is utilised in over 200 reactions of cellular metabolism

Required in oxidatinon/reduction reactions as NAD+ and NADP+

• catabolism of carbs, fats and proteins
• NAD+ is an electron acceptor in glycolysis and CAC
• needed in gluconeogenesis to produce oxaloacetate

Question 4

What occurs with Niacin deficiency?

Answer 4

Pellagra (rough skin)

4 Ds

• Dermatitis
• Diarrhoea
• Dementia
• Death

Question 5

What foods are good sources of Niacin?

Answer 5

• Chicken
• Tuna
• Salmon
• Peanut butter

Question 6

How is Niacin synthesised?

Answer 6

Niacin can be endogenously synthesised by the body by dietary tryptophan, however it is a very inefficient process

60mg tryptophan = 1mg niacin
1g protein = 10mg of tryptophan