Nutritional status is indicated as a relevant factor determining the long-term survival and well-being of CF patients.
Malnutrition is an important problem in CF, although now not as common as in the past, with a lower percentage of children and adolescents whose weight and height are less than the 5th percentile. As pointed out in a recent editorial (Wolfe SP, 2017) and confirmed by updated european standards of care (Castellani C et al, 2018) the face of nutrition in CF is changing, with one major advance due to national newborn screening programmes, with the subsequent ability to start treatment early. In clinical trials, poor weight and height have been shown to be independent predictors of mortality in CF.
Generally, inadequate weight gain is mainly caused by an energy imbalance resulting from chronic respiratory disease, malabsorption of nutrients, anorexia and increased metabolic rate.
- when present fat malabsorption leads to increased energy losses in the stools. However, even with adequate control of fat malabsorption using pancreatic enzyme supplements, several people with CF may still be unable to meet their increased energy need;
- oral caloric intake may be reduced by a general malaise associated with respiratory infection, nausea from swallowed sputum or nausea as a side effect of medications;
- the exact mechanism of anorexia in CF remains uncertain. The aetiology of anorexia is likely to be multifactorial; it may be caused in part by chronic infection due to factors such as increased mucus production and in part by the anorectic effects of elevated serum inflammatory cytokines, such as TNF-alfa. In addition, anorexia is likely to be related to chronic sinusitis, gastroesophageal reflux, and protein or energy malnutrition or both when present.
To offset the energy needs of CF patients, treatment recommendations just pointed out several years ago (Stallings VA, 2008), including the need of an energy consumption of 120 up to 150% of the recommended daily allowance (RDA) for calories and adequate pancreatic enzyme replacement therapy.
- How to achieve normal growth in childhood and to maintain this in adult life.
- To identify what are the evidences in favor of enteral tube feeds (nasogastric or gastrostomy) usually overnight when routine treatments and oral supplements fail to reach normal nutritional status.
What is known
1 CDSR (Conway S, 2019) attempted to evaluate growth, nutritional status, respiratory function and mortality in CF patients of any age with enteral tube feeding, but no clinical trial satisfied incusion criteria.
Regarding the first issue nutritional education of the CF patient and family, involving nutritional information, the correct use of pancreatic enzyme replacement, the positive reinforcement of appropriate eating and use of high-calorie supplements, when indicated, may ensure that patients will achieve optimal nutritional therapy. In order to help CF clinicians guidelines have been published for the care of preschool children between the ages of 2 and 5 years performed by a multidisciplinary committee convened by the CF Foundation to develop comprehensive evidence-based and consensus recommendations on routine surveillance for nutritional care (Lahiri T, 2016). Guidelines were developed by an international multidisciplinary working group to define nutritional care recommendations in infants, adolescents and adults with CF, in accordance with officially accepted standards (Turk D et al, 2016). Some of the key points in the nutritional management of people with CF were updated in 2017 (Collins S et al).
The relevance of the long-term follow-up of diet on the impact of nutrition has been reported (Woestenenk JW et al, 2014). A dietary food record was performed in over 1500 children and adolescents with CF compared with that of healthy controls by using independent sample t-tests. Caloric intake varied highly with age (88-127% estimated average requirement EAR), which is below or in the lower range of the recommended 110-200% EAR. However, the absolute caloric intake in CF children was significantly higher compared to controls at all ages, although the fat intake resulted in a considerable consumption of saturated fat. A Cochrane Database Systematic Review (Francis DK, et al, 2015) was unable to show whether oral protein calorie supplements may improve the nutritional status of children with chronic diseases including CF.
Regarding the second issue enteral tube feeding is widely accepted as a treatment or intervention in CF care centers, but the evidence base for this does not include RCTs. As reported in the European Cystic Fibrosis Society Standard of Care (Castellani C et al, 2018) interventions should be tried stepwise for a limited period of time or until nutritional status is optimised, depending on the severity of malnutrition and the age of the patient.
Few clinical randomized controlled trials are available that may respond to specific issues. A RCT (Stallings V et al , 2016) including 110 children showed that an absorbable lipid matrix (LYM-X-SORBTM) improved dietary fat absorption compared to placebo as indicated by plasma FA and LA and was associated with better growth. Behavioral intervention appeared to be as effective in improving weight gain in patients with CF as more invasive medical procedures. A recent published RCT (NCT NCT00241969) showed that behavioral and nutritional intervention may improve energy intake and height Z-score for preschoolers aged 2 to 6 years with CF and pancreatic insufficiency (Powers SW et al, 2015), but not weight z-score. Recently data derived from a clinical trial (NCT01897233) evaluated the effect of Lumacaftor/Ivacaftor in patients aged 6-11 years with CF and homozygous for F508del-CFTR, showing improvement in nutritional status beyond lung clearance index, sweat chloride, and health-related quality of life after 24 weeks of treatment (Milla CE et al, 2017). These new therapies are expected to further improve caloric intake (Kerem E 2017).
1 CDSR last updated in 2014 (Chinuck Ruth, 2014) systematically evaluated evidence on the beneficial effects of appetite stimulants in the management of CF-related chronic anorexia and reports of any side-effects through randomised and quasi-randomised controlled trials, as cyproheptadine hydrochloride and megesterol acetate, compared to placebo or no treatment for at least one month up to nine months in adults and children with CF. Despite a larger increase in weight z-score at three months compared to placebo the small number of recruited subjects (N=47) and the quality of data cannot be conclusive to recommend appetite stimulants.
Several anecdotal reports concerning appetite stimulants in CF are not conclusive for their use, in particular for:
- glutamine alone or combined with rhGH;
- cyproheptadine, mirtazapine, pizotifen, dronabinol or other anti-psychotic drugs;
- megestrol acetate;
- IGF-1 as promoting linear growth in prepubertal children with CF and increasing insulin sensitivity;
- oxandrolone and prednisone as anabolic androgenic steroids;
- insulin therapy for improving body mass index (BMI).
1 study (NCT03931252) will evaluate in 2020 in adult CF patients the thermic effect of food intake (TEF), which is the amount of energy expended to digest food, to overall energy expenditure in Cystic Fibrosis.