Lack of food or essential nutrients also leads to disease.
Sub-division of nutrients :
- Energy yielding
- Carbohydrates
- Proteins
- Fats
- Essential elements
- Vitamins
Energy-yielding
I. Carbohydrate (4 Kcal/gm) :
- They usually provide major part of energy in normal diet. If the carbohydrates intake is less than 100 gm per day, there occurs ketosis.
- Sugars are found in fruits, milk (lactose) and some vegetables. Starches are mostly found in cereals and root vegetables and legumes.
Sources of carbohydrates :
- Sugars :
- Monosaccharides – glucose, ribose, fructose
- Disaccharides – sucrose, lactose
- Polysaccharides :
- Starch, glycogen
II. Fats (9 Kcal/g) :
- Main cause of obesity for sedentary people.
* Sedentary = lifestyle involving little or no physical activity. - Saturated Fats – especially containing palmitic acid and myristic acids increase low-density lipoproteins (LDL) and total cholesterol.
- Mono saturated fatty acids – containing one double bond e.g. Oleic acid.
- Monounsaturated fatty acids – contains two or more double bond.
The principle fatty acid in plant seed oils is linolenic acid. This and arachidonic acid are the essential fatty acids, which are precursors of prostaglandins and part of structure of lipid membrane in cells.
Essential fatty acid deficiency is rare in man.
III. Proteins :
- They provide 20 amino acids in which 8 are essential for normal synthesis of different proteins in the body. These are –
| Tryptophan | Leucine |
| Valine | Lysine |
| Methionine | Phenylalanine |
| Isoleucine | Threonine |
Trick :- TV MILL PATH
Proteins of animal origin (milk,egg,meat) are of higher biological value than the proteins of vegetable origin (which are deficient of one or more essential amino acids).
So it is possible to have a diet of mixed vegetable proteins. For example –
- Wheat contain about 10% protein and are deficient in lysine.
- Legumes contains about 20% protein and are deficient in methionine.
so the best diet is –
2 parts of wheat + 1 part of legume - Wheat has enough methionine.
- Legumes have enough lysine.
An adequate protein is 10% of the total calories i.e. about 65 gm/day for an adult.
Starvation :
It is sever undernutrition from a prolonged energy balance.
Causes :
- Insufficient food
- Persistent vomitting
- Anorexia (loss of appetite)
- Malabsorption (due to small intestine diseases)
- Increased BMR (Thyrotoxicosis)
- Loss of Calories (Diabetes)
Clinical Features :
- Weight loss
- Weakness
- Thirst
- Feeling cold
- Skin is lax, pale, dry
- Hair loss
- Subcutaneous fat disappears
- Pulse is slow, blood pressure is low
- Distended abdomen
- Diarrhoea is common
- Susceptible to infections
Investigations :
- Hypoglycaemia
- Ketosis (mild metabolic acidosis)
- Plasma free fatty acid increased
- Diminished insulin secretion
- Reduced resting metabolic rate
- Anaemia, leucopenia, thrombocytopenia
Management :
- Mild Starvation – no danger (give proper diet)
- Moderate starvation – need extra feeding
- Severe starvation – hospital care needed
In severe cases, food should be given in small amounts. Food should be bland for example a cereal with sugar, milk powder. Salt should be restricted and a multivitamin preparation is desirable. A refeeding schedule of 1 month to replace every 5% loss of body weight.