1.1 Diet Therapy

Diet therapy is the branch of applied nutrition that uses food, and the way food is prepared and served, as part of the treatment and prevention of disease. A food and beverage manager at Level 6 does not diagnose or prescribe, but runs the kitchens, menus and service systems that turn a doctor's or nutritionist's diet prescription into safe, appetising meals. Understanding the language of diet therapy and why the body depends on correct nutrition is the foundation for every later topic in this unit, from modified diets to home nursing care.

Example: the catering manager of a county referral hospital in Endebess meets the hospital nutritionist every Monday to translate new diet prescriptions on the wards into the week's patient menus.

Definition of terms

Diet therapy uses a small set of technical terms that appear on diet cards, ward orders and menu specifications. Food and beverage staff must use them precisely, because a wrong reading of a diet order (for example serving a normal meal to a patient on a liquid diet after surgery) can harm the patient and expose the establishment to liability. The four core terms below are defined as they are used in hospitals, care homes and institutional catering.

Diet

A diet is the total food and drink that a person habitually takes in over a period of time. The word describes the pattern of eating as a whole, not only a weight-loss plan. A person's diet is shaped by culture, income, availability of food, health and personal preference.

• Normal or regular diet: the usual balanced pattern of meals for a healthy person, with no restriction of texture or nutrients.
• Habitual diet: what a person actually eats day to day, which may or may not be balanced.
• Balanced diet: a diet that supplies all nutrients (carbohydrates, proteins, fats, vitamins, minerals, water and fibre) in the right proportions for the person's age, sex, activity and health.
• Diet history: a record of a person's usual eating pattern, used by nutritionists to plan therapy.
• House diet: in a hospital, the standard menu served to patients who have no special dietary prescription.

Diet therapy

Diet therapy is the planned use of food and nutrition to treat, manage or prevent a disease or condition, or to support recovery from illness, injury or surgery. It is prescribed by a doctor or a qualified nutritionist or dietitian, based on the patient's diagnosis and nutritional assessment, and carried out by the food service team. Diet therapy works alongside medicine, not in place of it.

• Purpose: to maintain or restore good nutritional status while the body copes with disease.
• Basis: it starts from the normal balanced diet and changes only what the condition requires.
• Team approach: the doctor diagnoses, the nutritionist prescribes the diet, the food service team prepares and serves it, and nurses or carers monitor intake.
• Individual: two patients with the same disease may need different diets because of age, weight, other illnesses or medication.
• Dynamic: the diet is reviewed and changed as the patient's condition improves or worsens.

Therapeutic diet

A therapeutic diet is a meal plan that controls the intake of particular foods or nutrients, or changes their form, as part of the treatment of a medical condition. It is the practical product of diet therapy: the actual menu a patient receives. Examples are a low-sodium diet for high blood pressure, a carbohydrate-controlled diet for diabetes and a high-protein diet for a burns patient. Therapeutic diets are covered in detail in 1.5.

• Prescribed: it is ordered for a named patient and recorded on a diet card or in the patient's file.
• Specific: it states what is restricted, increased or changed, and by how much where necessary.
• Nutritionally adequate: it must still meet the patient's needs for all other nutrients.
• Time-limited or long-term: some therapeutic diets last a few days (after surgery), others for life (coeliac disease).
• Monitored: the patient's tolerance and progress are checked and the diet adjusted.

Modified diet

A modified diet is a normal diet that has been changed in consistency (texture), in nutrient content, in energy value or in the number and size of meals to meet a person's needs. All therapeutic diets are modified diets, but a modified diet can also be used for a non-medical reason, such as soft meals for an elderly resident with poor teeth or vegetarian meals for religious reasons. Types of modified diet are discussed in 2.3.

• Consistency modification: liquid, pureed, minced or soft foods for people who cannot chew or swallow normally.
• Nutrient modification: more or less of a nutrient, for example low fat, high protein or low sodium.
• Energy modification: fewer or more kilocalories, for weight reduction or weight gain.
• Meal pattern modification: smaller, more frequent meals, for example six small meals a day for a patient with a poor appetite.
• Elimination modification: removal of a specific food, for example gluten for coeliac disease or groundnuts for an allergy.

1.1.1 Importance of Dietary Requirements

Dietary requirements are the amounts of energy and of each nutrient that a person needs every day to stay healthy. Meeting them matters even more during illness, because disease, fever, injury and surgery raise the body's need for nutrients at the very time appetite and digestion are often reduced. A food and beverage manager who understands why these requirements matter can explain to staff, patients and families why a prescribed diet must be followed and why skipped meals or wrong portions undermine treatment.

To promote repair of worn-out tissue

The body constantly breaks down and replaces its tissues: skin cells, the lining of the gut and blood cells are renewed every few days or weeks. Injury, burns, surgery and infection add to this need for repair. Adequate protein, energy, vitamin C, zinc and vitamin A in the diet supply the raw materials and cofactors for rebuilding tissue.

• Protein: provides amino acids, the building blocks of new tissue, from foods such as eggs, fish, beans, milk and meat.
• Vitamin C: needed to make collagen, the protein that holds wounds together, from oranges, guavas, kale and tomatoes.
• Zinc: supports cell division and wound healing, from meat, fish, whole grains and pumpkin seeds.
• Energy: if energy intake is too low the body burns protein for fuel instead of using it for repair.
• Fluids: keep tissues hydrated and carry nutrients to the site of repair.

To promote growth

Growth is the increase in size and number of body cells, most rapid in infancy, childhood, adolescence and pregnancy. A diet that falls short of requirements during these stages leads to stunting, underweight and delayed development, which in Kenya remain significant public health problems among children under five. Correct dietary requirements support normal growth curves and the development of bones, muscles and the brain.

• Energy: fuels the extra metabolic work of building new tissue.
• Protein: supplies material for new muscles, organs and blood.
• Calcium and vitamin D: build strong bones and teeth during growth spurts.
• Iron: supports the rapid increase in blood volume in growing children and in pregnancy.
• Iodine: needed for thyroid hormones that control growth and brain development; supplied in Kenya mainly through iodised salt.

Maintenance of body cells

Even when a person has stopped growing, every body cell needs a steady supply of energy and nutrients to carry out its functions and stay alive. Meeting dietary requirements keeps the heart beating, the brain working, the kidneys filtering and the muscles contracting. Deficiency shows first in cells that work hardest or renew fastest, such as blood cells (anaemia) and the lining of the mouth (sores at the corners of the mouth in riboflavin deficiency).

• Carbohydrates and fats: provide the energy that keeps cells working.
• B vitamins: help cells release energy from food.
• Minerals such as sodium and potassium: keep fluid balance and nerve and muscle function inside and around cells.
• Essential fatty acids: form part of every cell membrane.
• Water: the medium in which all cell reactions take place.

Improve immune system

The immune system defends the body against infection, and it depends heavily on good nutrition. Malnourished people catch infections more easily and recover more slowly, and infection in turn worsens malnutrition, a cycle often seen in children and in people living with HIV. A diet that meets requirements strengthens the skin and mucous membranes, which are the first barrier, and supports the production of white blood cells and antibodies.

• Protein: antibodies and many immune cells are made of protein.
• Vitamin A: maintains the linings of the eyes, gut and lungs; deficiency raises the risk of severe measles and diarrhoea.
• Vitamin C and vitamin E: act as antioxidants that protect immune cells.
• Zinc and iron: needed for the normal development and action of immune cells.
• Probiotics in fermented foods: fermented milk such as mala may support healthy gut bacteria, part of the body's defence.