Chapter 10

### Introduction

On the 20th of May 1747 on board the Salisbury at sea I took 12 patients in the scurvy with putrid gums, the spots and lassitude and weakness of their knees. They had a common diet—two were ordered a quart of cyder a day—two, elixir vitriol three times a day—two, 2 spoonfuls of vinegar three times a day—two were put on a course of sea water—two had 2 oranges and one lemon each day—two, nutmeg, garlic and other additives to barley water. The consequence was, that the most sudden and visible good effects were perceived from the use of the oranges and lemons with one being at the end of 6 days fit for duty.

James Lind 1747, A (Summarised) Account of Scurvy

Good nutrition is fundamental to good health. It influences management in all branches of medicine. Modern people's health varies from the excesses of inappropriate nutrition, resulting in obesity and various degenerative disorders, to malnutrition and other deficiency states seen in those unfortunates deprived of nutrients.

The essential components of nutrition1 can be classified as:

• macronutrients—proteins, fats and carbohydrates, which are interchangeable sources of energy and also water

• macrominerals—sodium, chloride, potassium, calcium, phosphate and magnesium

• micronutrients—water-soluble vitamins (e.g. C, B); fat-soluble vitamins (e.g. A, E, K); essential trace elements (e.g. copper, iodine, iron, zinc)

Nutritional factors may play a vital role in the causation of several of the major diseases, such as coronary artery disease, hypertension, diabetes and cancer.

Special diets are important in the management of many hereditary metabolic disorders, such as phenylketonuria and galactosaemia, and several other disorders such as coeliac disease.

### Protein2

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.

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, ...

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