Eating is fundamental to good physical, social and mental health, and is equally important in restoring good health during and after illness. This applies to cancer as much as the flu or any other illness. We need nutrition, not just for the provision of energy (although this is very important), but also for establishing resistance to infection, maintaining the healing process and ensuring that the metabolic processes of the cells continue to function normally. Without these functions the body would succumb to the disease process and die. And central to this need for nutrition is water. Without it the body becomes dehydrated, and all the cellular activities grind to a halt. Integral to nutrition, therefore, is fluid balance (Figure 11.1), the monitoring of water intake and output from the body. Patients with problems that affect the normal intake of food, e.g. vomiting, will have disturbance of fluid balance as well (Figure 11.2)
The ‘well-balanced diet’ contains seven major categories of nutrients. They are proteins, carbohydrates, fats, vitamins, minerals, fibre and water. Of these, the proteins, carbohydrates and fats need some degree of digestion in order to render them available for absorption into the blood. Vitamins and minerals, however, need no digestion as they will be absorbed into the blood as they are. Fibre also needs no digestion simply because it is not absorbed; instead it remains in the gut and forms the bulk of faecal waste. This does not mean it is use-
less and unnecessary to humans, as we shall see. Water, of course, also needs no digestion but is absorbed into blood directly.