|
- Niacin is a white crystalline compound soluble in water, stable to heat, light, acids and alkalies. In the body niacin is converted into niacinamide
Functions
- Thiamine, riboflavin and niacin take part in the metabolism of carbohydrates, proteins and fats through the enzymatic action. It is a part of co-enzyme I and co-enzyme II which are essential for the conversion of pyruvic acid to lactic acid. They are otherwise known as NAD and NADH.
- More than 40 biochemical reactions depend on these coenzymes. Dehydrogenation reaction in Kreb’s cycle, oxidation of alcohol to aldehyde, glucose to gluconic acid, malic acid to oxaloacetic acid, pyruvic acid to lactic acid, glucose-1-6-diphosphate to phosphohexouric acid and reactions in the synthesis of fatty acids, cholesterol and for the conversion of phenylalanine to tyrosine are some of them. It takes part in tissue oxidations.
- Nicotinic acid is essential for the normal functioning of the skin, intestinal and nervous systems.
Deficiency
- In a mild deficiency state weakness, loss of weight, loss of appetite, lassitude, irritability, burning tongue and constipation occur.
- Pellagra is the characteristic disease resulting from niacin deficiency.
- It is otherwise known as three ‘D’s disease-dermatitis, diarrhea and dementia.
- The dermatitis of pellagra is different from other skin diseases.
- It occurs mainly on the exposed portions of the body. Lesions are seen on the face, neck, surfaces of the hands, elbows, feet and other parts of the body which are exposed to sunlight.
- Another peculiarity of dermatitis is that the skin lesions are symmetrical in shape and they always occur on both sides of the body simultaneously.
- The skin is cracked and scaly. Burning sensation and itching are common. The lesions leave a reddish, dark brown colour.
- The mucous membrane of the alimentary canal is affected and glossitis, abdominal pain and loss of appetite are some of the symptoms.
- Nausea, vomiting and diarrhea are the other symptoms of niacin deficiency.
- Delirium is the common mental disturbance in pellagra.
- Earlier symptoms of nervous disturbances are depression, dizziness and insomnia. It leads to death.
- Pellagra is common among sorghum eaters. sorghum has a very high leucine content and this excessive leucine interferes with the utilization of nicotinic acid.
- Leucine precipitates mental changes but isoleucine promptly reverses them to normal.
Sources
- Good sources: Cereals, especially whole cereals, dried yeast, liver, groundnut,legumes, fleshy foods and fish
- Fair source : Milk, eggs and vegetables.
Requirements
RDA of niacin
| Age Group
|
Category
|
Body weights
kg
|
Niacin equivalents mg/d
|
| Man
|
Sedentary
|
60
|
16
|
| Moderate
|
60
|
18
|
| Heavy
|
60
|
21
|
| Woman
|
Sedentary
|
55
|
12
|
| Moderate
|
55
|
14
|
| Heavy
|
55
|
16
|
| Pregnant
|
55
|
+2
|
Lactation
0-6m
6-12m
|
55
|
+4
+3
|
| Infants
|
0-6 m
|
5.4
|
710μg/kg
|
| 6-12m
|
8.4
|
650μg/kg
|
| Children
|
1-3y
4-6y
7-9 y
|
12.9
18.0
25.1
|
8
11
13
|
| Boys
|
10-12y
|
34.3
|
15
|
| Girls
|
10-12y
|
35.0
|
13
|
| Boys
|
13-15y
|
47.6
|
16
|
| Girls
|
13-15y
|
46.6
|
14
|
| Boys
|
16-17y
|
55.4
|
17
|
| Girls
|
16-17y
|
52.1
|
14
|
|
Participants
