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Proteins are composed of carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur and iron. They make up the greater part of plant and animal tissue and provide the amino acids essential for the growth and repair of tissue. Protein in the body in muscle, connective tissue and enzymes is constantly being broken down, while dietary protein is hydrolysed to amino acids that are both essential and non-essential. A complete protein is one that contains all the nine indispensable amino acids, namely, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.
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Protein in animal products (fish, meat and milk) is of high quality and that in vegetable products is lower because of a limited supply of lysine (in cereals) and methionine and cysteine (in legumes).3 Vegetarian diets are usually adequate in protein, especially if the combining vegetable groups complement each other in basic amino acid groups. Diets that exclude all animal products may be inadequate, especially in children. Infants and children require 2–2.2 g protein/kg/day.
High protein content foods—lean beef and lamb, chicken, fish, eggs, milk, cheese, soy beans
Medium protein content foods—bread, spaghetti, corn, potatoes (cooked), rice (cooked), cabbage, cauliflower
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This is a deficiency syndrome with a reduction in all macronutrients, energy (kilojoules) and many micronutrients due to an inadequate intake of protein and energy foodstuffs.
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It is commonly found in infants and children in developing countries but can occur in persons of any age in any country.
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Clinically, protein-energy malnutrition has three forms:
dry (thin, desiccated)—marasmus
wet (oedematous, swollen)—kwashiorkor
combined—marasmic kwashiorkor
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Clinical features:
grossly underweight
gross muscle wasting
abdominal distension
no fat
hungry
‘old man's’ face
no oedema
normal hair
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Caused by a diet low in protein and calories.
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Caused by a diet low in protein with some carbohydrate, leading to hypoalbuminaemia.