Qualitative Dietary Deficiency

Energy-yielding Nutrients

Deficiency

Carbohydrates. These usually provide the greater part of the calories in a normal diet but no individual carbohydrate is an absolute dietary necessity in the sense that the body needs it but cannot make it for itself from other nutrients. If the carbohydrate intake is less than 100 g per day ketosis is likely to occur.

Fats. With their high caloric value, fats are useful to people with large energy expenditure; moreover they are helpful in cooking and making food appetizing. Though rats need linoleic or arachidonic acids in their diet deficiency

of these essential fatty acids is rare in man. It has been demonstrated in patients who have been fed intravenously for long periods without fat emulsions.

The possible role of cholesterol, fats and different fatty acids in the pathogenesis of atherosclerosis and coronary thrombosis will be discussed later. (Dietary Deficiency)

Proteins. Proteins provide amino acids, of which eight are essential for normal protein synthesis and for maintaining nitrogen balance in adults. These are termed essential amino acids because the body cannot make them for Itself and so must obtain them from the diet. They are methionine, lysine, tryptophan, phenylalanine, leucine, isoleucine, threonine, and valine. There is evidence that histidine and perhaps arginine are needed for growth in infants.

The ‘biological value’ of different proteins depends on the relative proportions of essential amino acids they contain. Proteins of animal origin, particularly from milk, eggs, meat and fish, are generally of higher biological value than the proteins of vegetable origin. Most vegetable proteins are deficient in one or more of the essential amino acids; but it is possible to have a diet of mixed vegetable proteins with high biological value if the principle of supplementation is used. For example cereals, e.g. wheat, contain about 10 per cent protein and are relatively deficient in lysine. Legumes contain around 20 per cent of protein which is relatively deficient in methionine. If two parts of wheat are mixed (or eaten) with one part of legume, a food results which contains 13 per cent of a protein of high biological value. This happens because cereals contain enough methionine and legumes enough lysine to supplement the other component of the mixture.

A deficient intake of protein leads to (a) negative nitrogen balance; (b) wasting of tissues; and (c) fall in plasma albumin. The usual recommended allowance for an adequate protein intake is 10 per cent of the total calories. The minimum requirement is less, around 40 g per day of good biological value protein for an adult.

PROTEIN-CALORIE MALNUTRITION (Dietary Deficiency)

(PROTEIN-E ERGY MALNUTRITION) (Dietary Deficiency)

Aetiology and Classification. Protein-calorie malnutrition (PCM) in early childhood is now regarded as a spectrum of disease. At one end there is kwashiorkor in which the essential feature is deficiency of protein with relatively adequate calorie intake. At the other end is nutritional marasmus which is total inanition of the infant, usually under 1 year of age, and is due to a severe and prolonged restriction of calories and protein as well as other nutrients. In the middle of the spectrum is marasmic kwashiorkor in which children have some clinical features of both disorders.

Table 1

Classification of PCM

	Body weight as percentage of international standard for age	Oedema	Deficit in weight for height
KwashiorkorMarasmic KwashiorkorMarasmusNutritional dwarfing Underweight Child	80-60 <60 <60 <60 80-60	+ + 0 0 0	+ ++ ++ Minimal +

Based on Joint FAO/WHO Committee on Nutrition. 8th Report, 1971 (with modifications in weight/height column).

Some children adapt to prolonged calorie and/or protein shortage by nutritional dwarfism. The most prevalent of all the varieties of PCM is mild to moderate PCM or the Underweight Child (see Table 1).

Children with one form of PCM often shift to another form. Thus a child with mild to moderate PCM may develop kwashiorkor after an infection. When such a child is treated and loses oedema he may look marasmic.

The incidence of PCM in its various forms is high in India and South-east Asia, in most parts of Africa and the Middle East, in the Caribbean islands and in South and Central America. PCM is the most important dietary deficiency disease in the world, affecting tens of millions of children; hence it will be described in considerable detail. (Dietary Deficiency)