Cystic Fibrosis

Question 1

Aetiology of CF

Answer 1

A genetic defect in chromosome 7 results in abnormalities in production and function of CFTR.

CFTR disrupts electrolyte and fluid balance across epithelial cells. In turn a thick sticky mucus obstructs small airways

Question 2

How does CF affect the body?

Answer 2

Respiratory function: Chronic and severe respiratory infections
Progressive lung disease

GI Function:
Pancreatic Insufficiency
Pancreatitis
Malabsorption/Maldigestion
Malnutrition
Prolonged diarrhoea

Male infertility

Question 3

How does CF affect energy intake?

Answer 3

Poor appetite
Taste changes due to oxygen therapy
Depression
Early satiety

Question 4

How does CF affect energy expenditure?

Answer 4

Some medications increase BMR
Coughing and infections increase EE
CFRD
In transplantation, EE is higher

Question 5

Nutritional Consequences of CF

Answer 5

Impaired nutrient absorption
Deficiencies in Vitamins A, D, E and K (fat-soluble vits)

Question 6

Nutritional Management of CF

Answer 6

Optimisation of PERT

Nutritional Status has important prognostic significance

Question 7

Energy Requirements

Answer 7

Energy requirements are usually higher. 110-200% higher than that of the healthy population

Question 8

Protein Requirements

Answer 8

Generally accepted that protein intakes should be higher due to the loss of nitrogen in faeces and sputum.

Question 9

Fat Requirements

Answer 9

Not to restrict fat to reduce steatorrhoea.

PERT needs to be taken with all fat-containing meals.

Fat is needed for energy density.

Question 10

Vitamin and Mineral Requirements

Answer 10

Vitamins A, D, E and K should be supplemented. Annual monitoring of plasma levels is recommended.

Reduced bone mineral density is common in CF. Attention to calcium is important.

Question 11

Stages of achieving nutritional requirements

Answer 11

Stage 1: Improving food and energy intake
Stage 2: Supplementation
Stage 3: Enteral tube feeding (Usually overnight 30-50% of total energy requirements)

Question 12

CFRD

Answer 12

CFRD is a distinct entity even though it shares the features of DM.

Insulin deficiency due to thick sticky mucus damaging insulin-producing beta cells.

Insulin is most effective in the management of CFRD.

Maintaining a diet high in energy, fat, protein and sodium is essential to compensate for losses.

Question 13

CF-related low bone mineral density

Answer 13

Dietetic management should include
Optimisation of weight gain and growth with particular attention to LBM
Optimising Vit D and K status
Optimisation of skeletal use of calcium, monitoring calcium intakes and supplement as necessary
Encourage PA where appropriate