Journal of the Royal Society of Medicine Supplement No. 18 Volume 84 1991

Nutritional strategies in cystic fibrosis: current issues

Anita MacDonald


Christine Holden RGN RSCN

Gillian Harris


The Children's Hospital, Ladywood Middleway, Ladywood, Birmingham B16 8ET Keywords:

The observation that better nutritional status may improve survival in cystic fibrosis (CF)', together with the introduction of combined heart-lung transplantation means that the achievement and maintenance of optimal nutritional status is now even more important. Aggressive nutritional therapy has been associated with improved growth, weight gain, sense of well being2 together with maintenance of pulmonary function3. Since the early 1980s, patients with CF have been encouraged to take a diet which provides 150% of the recommended daily energy intake (RDI) for age4. In practice, even on a high energy diet, few CF patients consume more than the RDI for age, although some still grow normally on this. Pencharz and co-workers now consider a more realistic recommendation to be 120% of the normal RDI for the majority of CF patients, although it may be higher for patients with advanced pulmonary disease5. Many workers have monitored the energy intakes of patients on a high energy, normal fat containing diet. The results of these are summarized in Table 17-10 and the energy intakes vary between 99% and 114% of the normal recommended amount. These results are not ideal but they have improved significantly from the days when patients followed a low fat regimen, when energy intake varied between 80% and 90% of the RDI. It is known that CF males have a better survival and nutritional status than CF females. Two recent studies have compared the dietary intake of CF males and females to see if this contributes to the difference in their nutritional status, but no difference in dietary intake was noted9


High energy diets Obtaining the maximal energy intake from ordinary foods should always be the first step towards achieving a high energy intake in CF. Fat, being the most concentrated source of energy in the diet, should be encouraged liberally and should provide


*-. C.-.

% Fat intake Contrbuted by Different Foods 10 12 14 0 2 4 6 8






Figure 1. Percentage fat intake contributed by different foods

approximately 40% of total energy intake. The relative importance of different fat containing foods is demonstrated in Figure 1. This identifies the percentage of fat and ultimately energy contributed by foods in the diet of a group of 35 CF children at Birmingham Children's Hospital. Frequent meals and snacks are important. As this type of diet directly opposes normal healthy eating recommendations, it is commnon to find resistance to it by parents, older patients, school teachers and even some health professionals, particularly dentists. It is therefore essential that all personnel connected with CF understand fully the rationale for this dietary treatment and are able to apply it successfully to the specific needs of an individual patient. In addition, it is advised that the protein intake should be increased, although the exact protein requirements are unclear. Protein losses occur through nitrogen loss in the faeces and sputum; there may also be altered protein metabolism". It has been

Table 1. Energy intake of CF patients on a normal diet MacDonald et al., 1989

Number of patients studied Age range (years) Energy intake of the UK RDI (%) Range (%) Mean daily fat intake (g) Range (g) % Fat/kcal

20 6.6-16.6 103 58-161 101 38-148 33.3

Buchdahl et al., 1989 20 5.3-17.3 99 (WHO RDA) 67-133 73 36-133 30



et al., 1990

et al., 1990

30 (mean age=11) 100 71-141

51 10-15 114 -






Journal of the Royal Society of Medicine Supplement No. 18 Volume 84 1991

Table 2. Examples of dietary supplements used in cystic fibrosis Analysis per 100 ml/100 g Energy kcal kJ



Fresubin Fortisip Liquisorb Maxijul Super Soluble (SHS) Maxijul Liquid (SHS) Caloreen (Roussel) Polycal (C & G) Fortical (C & G)

Supplemented milk shake drink Supplemented milk shake drink Supplemented milk shake drink Glucose polymer powder Liquid glucose polymer Glucose polymer powder Glucose polymer powder Low electrolyte, glucose polymer liquid Low electrolyte glucose flavoured liquid Glucose polymer LCT & MCT fat mixture Supplemented milk shake drink

Hycal (Beechams)

Duocal Powder (SHS) Paediasure

suggested that 15-20% of the energy intake should be provided by protein sources12. However, the protein intakes are usually satisfactory and do not warrant special supplementation. Dietary supplements Dietary supplements provide a useful source of energy when growth is inadequate or to compensate for poor nutrient intake during an acute exacerbation. Although manufacturers have made great efforts to improve the palatability and presentation of these products their use is inconsistent2 both by health professionals and by patients and we frequently find they are discontinued soon after initiation by the patients themselves. Some patients have a strong antipathy towards supplements, regarding them to be the latest 'magic potion' concocted by the dietitian and resolutely refuse to try them. However, when patients do accept them, they provide a relatively cheap and convenient source of nutrition. Over the last 3 years a new range of fortified milk shakes in cartons has been introduced. These include Fresubin (Fresenius), Fortisip (Cow & Gate) and Liquisorb (Merck), the composition of which

Protein Fat


420 630 420 1512 800 1680 1596 1033

100 150 100 360 187 400 380 246

3.8 5.0 4.0 -

3.4 6.5 4.0 -



13.8 17.9 11.8 95.0 50.0 96.0 94.0 61.5
















are given in Table 2. They are particularly useful for packed school lunches and bedtime drinks. Other useful energy supplements include the powdered glucose polymers, ie Maxijul (Scientific Hospital Supplies), Polycal (Cow & Gate) and Caloreen (Roussel) and concentrated glucose drinks, ie Hycal (Beechams) and Fortical (Cow & Gate). The quantity and timing of dietary supplements is important so as not to impair appetite and decrease nutrient intake from normal foods. We advise they are given twice daily, after a meal and at bedtime. The quantity recommended is age dependent'3 and the following is a useful guide: 1-2 years - a daily supplement providing 200 kcal 3-5 years - a daily supplement providing 400 kcal 6-11 years - a daily supplement providing 600 kcal 12 years+ - a daily supplement providing 800 kcal.

Enteral feeding When nutritional status cannot be maintained with an oral high energy diet, overnight supplementary tube feeding is now being frequently advised. In a recent survey in the USA, enteral feeding was being practised in 73% of 68 CF centres'4. Many workers

Table 3. Effect of short-term feeding in CF

Number of patients studied Age range (years) Criteria for feeding

Type of feed Method of administration Duration of feeding Short-term weight gain Long-term weight gain after feed had stopped

Pulmonary function

Bertrand et al., 1984 Moore et al., 1986 Daniels et al., 1989

Pierce et al., 1990




3.5-12.0 >than 90% weight for height

4 weeks

0.66-13.0 1.9-13.5 6.3-20.0 No weight gain for Below 3rd centile for Not stated 6 months height & weight or 1 SD of weight for height age Elemental Elemental Semi-elemental Nasogastric Nasogastric Nasogastric 3 months 13 days 14 days








No improvement

No improvement

No improvement

Improvement maintained but still intermittent feeding continued to co-

No improvement


Insufficient data

incide with IV antibiotics No data



Journal of the Royal Society of Medicine Supplement No. 18 Volume 84 1991

Table 4. Effect of long-term feeding in CF

Levy et al., 1985 Shepherd et al., 1986 O'Loughlin et al., 1986 Boland et al., 1986 Number of patients studied 14 10 4.9-21.5 3.0-13.2 Age range (years) Criteria for feeding

Nutritional strategies in cystic fibrosis: current issues.

28 Journal of the Royal Society of Medicine Supplement No. 18 Volume 84 1991 Nutritional strategies in cystic fibrosis: current issues Anita MacDon...
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