Nutrition
The secretion of digestive juice from the pancreas is severely reduced in most CF patients from an early age and, unless treated with pancreatic enzyme supplements, the digestion and absorption of food are severely impaired. Inadequate absorption of food from the bowel will lead to unpleasant digestive symptoms, malnutrition, poor growth and specific deficiencies of fat soluble vitamins A, D, E and K.
Well-nourished patients have fewer infections, better quality of life and increased life span. It is, therefore, essential that CF patients be referred to a dietician experienced in the management of CF. Every effort must be made to achieve normal growth in CF as good nutrition promotes good quality of life and longevity.
Feeding of Infants
Most infants with CF will thrive on breast milk (or a standard infant milk formula if breast feeding is problematic). A predigested medium chain triglyceride fat containing formula may be beneficial for infants who have undergone bowel resection for meconium ileus or those who have co-existing cow milk intolerance. If the infant is breast fed and thriving, this method of feeding should be encouraged. Bottle fed infants may require up to 200ml/kg body weight/day. Nutritional outcome is no better when babies are formula fed. If the infant is failing to thrive despite adequate pancreatic enzyme supplements and an adequate oral intake, additional energy supplements are added to the milk. Early weaning is not usually necessary. Some babies may require sodium supplementation.
Pancreatic Enzyme Supplementation
Virtually all CF patients (95%) require pancreatic enzyme supplementation owing to inadequate pancreatic secretion. A number of preparations are available. Higher doses than those recommended in the manufacturers' literature are usually required. The acid-resistant microsphere preparations are significantly more effective than the older pancreatic enzyme preparations which should NOT be used for CF patients.
High Lipase Pancreatic Preparations
Pancreatic preparations containing three to five times the quantity of lipase (Creon 25000®) are available for older children. Care should be taken to avoid total daily lipase intake of greater than 10000 U/kg/day.
General guidelines on use of pancreatic enzyme supplements
Type
Use one of the acid-resistant microsphere preparations.
Time
Enzymes are best given at the beginning or early in the meal. Half the dose at the beginning and half in the middle of the meal is recommended.
Method
Capsules should be swallowed whole from as early an age as possible. If removed from the capsule, the microspheres should not be sprinkled on or mixed with the whole meal. Microspheres should be mixed with a little fluid and taken in one swallow. If mixed with food or fruit puree, they should be mixed with one teaspoonful and taken in one or two swallows. Microspheres must not be chewed.
Dose
Enzymes are required with all meals and drinks that contain fat. Start with or ½ capsule (i.e. 3000 to 5000 units) in infants and one or two capsules per meal in older patients. Increase gradually until the bowel symptoms are controlled. Increase the dose with more fatty meals. It is advisable not to exceed a dose of 3000 units of lipase/kg body weight/meal or 10 000 units of lipase/kg body weight/day. Some patients may require higher doses.
Changes in dose should be made gradually to avoid constipation.
Insufficient pancreatic enzyme will cause symptoms of malabsorption e.g. abdominal pain, pale, loose, fatty, offensive stools, and will eventually lead to growth failure.
Patients who require larger doses than recommended may warrant the addition of an H2 blocker or proton pump inhibitor to reduce gastric acid secretion. This may permit a reduction in the number of capsules required.
Nutritional Management
Most individuals who have CF have higher than normal energy requirements due to incompletely controlled intestinal malabsorption, increased energy expenditure, chest infections and physical therapy.
A diet that is high in both energy and protein is required to achieve normal weight gain and growth. Individual requirements vary but most patients need 20 to 80% more energy than an unaffected individual of the same age. The food intake of most patients does not meet this increased energy requirement.
Patients are encouraged to take foods rich in energy such as fried foods, crisps and chocolate and those rich in protein such as milk, cheese and meat as part of their total balanced diet. Dietary sources of fat such as butter, margarine, cream or mayonnaise can be added to food to increase the energy density.
Dietary fat intake should never be restricted as this nutrient is essential to achieve a high energy intake and a normal nutritional state with growth. If foods with a high fat content cause abdominal pain or more frequent and paler stools, the dose of pancreatic enzymes should be increased whenever that food is taken. The dose is gradually increased until the food is tolerated and the steatorrhoea resolves.
It is very important that children are given frequent meals and snacks (5-6 per day) from a young age to maximise daily energy intake. Toddlers should get into the habit of regular eating. This habit will stand them in good stead as they grow up.
Psychological factors may play a major role in poor food intake patterns in some children and adolescents.
A booklet by Dr. Tony Westwood of the Red Cross Children's Hospital in Cape Town provides useful recipes and advice on CF nutrition (available from SACFA or CF centres)
Dietary Supplements
If the patient's weight gain is inadequate or the appetite poor, dietary energy supplements can improve energy intake. See Appendix 9 for a list of available products and their use. The type and amount of supplement recommended depends on the patient's age, preference and requirements and should be prescribed on an individual basis. The supplements should be taken in addition to normal food to increase the total daily energy intake. They should not replace a meal. They should be given with a snack between meals or as a drink after meals.
Salt
There is excessive loss of salt in sweat in CF. Most South African diets contain sufficient salt to compensate for this. There are two circumstances under which excess salt loss may cause clinical problems for someone with CF.
All infants with CF lose about 0.5 mmol/kg more sodium than non-CF infants. Salt deficiency can contribute to poor weight gain and must be sought where other explanations (e.g. inadequate pancreatic supplementation) are not present. Hyponatraemic dehydration may be a presenting feature of CF. In these circumstances, 0.5-1mmol/kg of salt per day in a 3% solution should be given until the age when solids constitute most of the child's diet.
Older children who live in and all who exercise in conditions of high environmental temperature should take salt tablets (1-3 per day) or increase their dietary salt and also increase their fluid intake.
Salt intake should not be restricted but excessive salt intake is dangerous.
Vitamins
All CF individuals should receive supplements of the fat soluble vitamins A, D and E. The recommended daily supplements that usually achieve normal plasma levels are considerably greater than the usual daily recommended intake. The plasma fat soluble vitamin levels should be checked annually and the dose adjusted depending on the levels. Dosages are given in Appendix 8.
Vitamin A
Vitamin A deficiency may cause night blindness in older patients. Clinical progress improves when low levels of vitamin A detected at assessment are corrected.
Vitamin D
Vitamin D deficiency may cause rickets (which is rare) and osteomalacia. Osteoporosis and low levels of vitamin D metabolites are well documented, particularly in older patients.
Vitamin E
Vitamin E deficiency may cause haemolytic anaemia in infants. In older CF individuals Vitamin E deficiency may cause neurological problems. Vitamin E appears to be important as an anti-oxidant in CF.
Vitamin K
Vitamin K may be low, particularly if there is an associated liver problem, and supplements of Vitamin K, 10mg daily, may be required if the INR is abnormal or if elective surgery is planned. Vitamin K is also important in bone disease.
Minerals
Iron
Iron supplements are not routinely needed. Full blood count should be monitored annually. Patients with moderate to severe lung disease require iron supplementation.
Calcium
Many CF patients take insufficient dietary calcium. Calcium supplementation is recommended to maximise bone mineral accretion.
Zinc
If the child is malnourished at the time of diagnosis, zinc acetate should be given for a month at a dose of 10mg daily for infants and 20mg a day for those over this age.
Assessment of Growth and Nutritional status
Growth and nutritional status need to be assessed at a specialised CF clinic every 1 to 3 months
Weight, length/height and head circumference
These must be measured and plotted on growth charts at regular intervals, looking at the pattern of growth. Current standards used in South Africa are the WHO z-score charts of weight and length/height for age and weight for height. Body mass index (BMI) is a useful index and plotted on WHO charts for children and standard tables for adults. Children under 5 years of age should have their head circumference measured every 6 months.
Mid arm muscle circumference and triceps skinfold thickness are useful indicators of lean body mass and body fat.
Growth velocity is an important measure and can assist in identifying sub-optimal growth.
Dietary Assessment
Many CF patients do not eat enough. Dietary intakes must be assessed regularly to ensure that energy requirements are being met. As part of their annual assessment, patients should record a 3-day dietary diary from which their nutritional intake is analysed and advice is given accordingly.
Nasogastric & Enterstomy Feeds
Supplemental tube feeds are frequently useful in patients with severe lung involvement. Before embarking on these forms of feeding the diet must be optimised, pancreatic enzyme replacement therapy has to be maximised and H2 blockers/protein pump inhibitors have been introduced.
Indications:
- Children less than 5 years: weight/height less than 85% expected; weight loss or plateau in weight gain over 4 months.
- Children 5-18 years: weight/height <85% expected; weight loss or plateau in weight gain over 6 months
- Adults: a BMI of <19; weight loss of >5% body weight for more than 2 months duration
Methods:
- Fine nasogastric tube left in permanently or replaced every morning (not usually well tolerated in the long term).
- Gastrostomy:
- Percutaneous endoscopic gastrostomy (PEG) with gastrostomy button.
- Traditional surgical placement.
Technique:
- Feed for 10-12 hours at night (stop 2 hours before morning physiotherapy session).
- Eat normally during the day. At least 40-50% of the total daily energy requirement should be given at night.
- Ideally use a peristaltic pump to avoid the tube blocking.
- Use Ensure® as food source (not semi-elemental expensive preparations).
- Take two thirds of enzymes at beginning and one third in morning on wakening or half on starting and half on going to sleep. Dosage to be adjusted according to usual enzyme requirement per gram of fat for the patient.
- Patients tolerate smaller volumes of higher concentration feeds (1 or 1.5kcal/ml) better than larger volumes of less concentrated formulae.
- Prokinetic agents may be required. Patients should be encouraged to sleep with the head elevated (30%).
Dangers:
- Vomiting, aspiration and increase in gastro-oesophageal reflux.
- Hyperglycaemia. Baseline oral GTT should be done before this type of feeding is commenced. Some patients will require insulin supplementation during feeding at night (see Diabetes mellitus Chapter 8 page *)
- Leakage, bleeding or ulceration at the gastrostomy site.