Low glycaemic index dietary interventions in youth with cystic fibrosis: a systematic review and discussion of the clinical implications

Quality of dietary macronutrients is associated with glycemic outcomes in adults with cystic fibrosis

Objective

Poor diet quality contributes to metabolic dysfunction. This study aimed to gain a greater understanding of the relationship between dietary macronutrient quality and glucose homeostasis in adults with cystic fibrosis (CF).

Design

This was a cross-sectional study of N = 27 adults with CF with glucose tolerance ranging from normal (n = 9) to prediabetes (n = 6) to being classified as having cystic fibrosis-related diabetes (CFRD, n = 12). Fasted blood was collected for analysis of glucose, insulin, and C-peptide. Insulin resistance was assessed by Homeostatic Model Assessment for Insulin Resistance (HOMA2-IR). Subjects without known CFRD also underwent a 2-h oral glucose tolerance test. Three-day food records were used to assess macronutrient sources. Dietary variables were adjusted for energy intake. Statistical analyses included ANOVA, Spearman correlations, and multiple linear regression.

Results

Individuals with CFRD consumed less total fat and monounsaturated fatty acids (MUFA) compared to those with normal glucose tolerance (p < 0.05). In Spearman correlation analyses, dietary glycemic load was inversely associated with C-peptide (rho = -0.28, p = 0.05). Total dietary fat, MUFA, and polyunsaturated fatty acids (PUFA) were positively associated with C-peptide (rho = 0.39-0.41, all p < 0.05). Plant protein intake was inversely related to HOMA2-IR (rho = -0.28, p = 0.048). Associations remained significant after adjustment for age and sex.

Discussion

Improvements in diet quality are needed in people with CF. This study suggests that higher unsaturated dietary fat, higher plant protein, and higher carbohydrate quality were associated with better glucose tolerance indicators in adults with CF. Larger, prospective studies in individuals with CF are needed to determine the impact of diet quality on the development of CFRD.

[Other specific types of diabetes and exocrine pancreatic insufficiency (update 2023)]

The heterogenous category "specific types of diabetes due to other causes" encompasses disturbances in glucose metabolism due to other endocrine disorders such as acromegaly or hypercortisolism, drug-induced diabetes (e.g. antipsychotic medications, glucocorticoids, immunosuppressive agents, highly active antiretroviral therapy (HAART), checkpoint inhibitors), genetic forms of diabetes (e.g. Maturity Onset Diabetes of the Young (MODY), neonatal diabetes, Down‑, Klinefelter- and Turner Syndrome), pancreatogenic diabetes (e.g. postoperatively, pancreatitis, pancreatic cancer, haemochromatosis, cystic fibrosis), and some rare autoimmune or infectious forms of diabetes. Diagnosis of specific diabetes types might influence therapeutic considerations. Exocrine pancreatic insufficiency is not only found in patients with pancreatogenic diabetes but is also frequently seen in type 1 and long-standing type 2 diabetes.

Effects of low glycemic index/high-fat, high-calorie diet on glycemic control and lipid profiles of children and adolescence with cystic fibrosis: A randomized double-blind controlled clinical trial

PURPOSE

Low glycemic index diets seem to be potentially effective to improve glycemic control and reduce lipid profiles. Hence, this study aimed to evaluate the effect of a low glycemic index/high fat, high-calorie diet on glycemic status and lipid profiles of patients with cystic fibrosis.

METHODS

In this randomized clinical trial, 44 children and adolescents with cystic fibrosis were randomized to receive for three months either a high fat, high-calorie diet (n = 22) or a low glycemic index/high fat, high-calorie diet (n = 22) with similar calorie and macronutrients composition. Patients in high fat, high-calorie diet arm were allowed to use all sources of carbohydrates with different glycaemic indices; whereas those in another arm consumed carbohydrates from low glycemic index sources. Serum levels of lipid profiles (triglyceride, total cholesterol, HDL cholesterol, LDL cholesterol), insulin, fasting blood glucose, and glycated hemoglobin were measured at baseline and after the intervention.

RESULTS

Between-group differences were significant only for fasting blood glucose (P < 0.001). However, fasting blood glucose (P = 0.003) and glycated hemoglobin (P = 0.002) significantly decreased after the intervention in the low glycemic index group, while in another group a significant increase in fasting blood glucose (P = 0.038) and triglyceride (P = 0.004) was found. No significant within-group differences were observed in other variables in both groups.

CONCLUSIONS

It seems that adherence to a low glycemic index/high fat, high-calorie diet can improve glycemic indices in children and adolescents with cystic fibrosis compared to the high fat, high-calorie diet.

TRIAL REGISTRATION

IRCT2017102325267N5.

Dietary intake in cystic fibrosis and its role in glucose metabolism

BACKGROUND

Dietary intervention in cystic fibrosis (CF) has historically focused on high-energy diets to address malnutrition, with little attention on diet quality. With increased survival, CF complications such as impaired glucose tolerance (IGT) and cystic fibrosis related diabetes (CFRD) have increased in prevalence. In the absence of consensus on the management of IGT, the role of dietary intake, specifically carbohydrate quality, requires consideration.

AIMS

The aims of this study were to: 1) determine nutritional quality of dietary intake at an adult CF clinic and compare this to the Australian Dietary Guidelines 2) explore relationships between dietary intake, including glycaemic index (GI) and glycaemic load (GL), and glucose response variables using continuous glucose monitoring (CGM).

METHODS

Adults attending a Sydney hospital were recruited to undergo CGM for five-seven days and record dietary intake using a food record over the CGM period. The relationship between variables of dietary intake, including GI and GL and variables of glycaemic response, including mean amplitude of glycaemic excursions (MAGE), percentage of time in hyperglycaemic and euglycaemic range, were determined.

RESULTS

Eighteen participants completed the study with 87 full days of dietary and CGM data. Dietary intake was higher than recommendations in the Australian Dietary Guidelines in relation to grains and protein foods and only slightly higher in saturated fat. Bivariate correlations showed dietary GI was significantly positively associated with percentage of time in hyperglycaemic range. Dietary GL was significantly associated with SD, MAGE and percentage of time in euglycaemic range on CGM. Results remained significant when controlled for energy intake in partial correlation analyses.

CONCLUSIONS

This study suggests GI and GL may be important dietary factors influencing glucose metabolism in CF. Further studies exploring low GI or GL diets as a dietary intervention in CF are the next step.

[Other specific types of diabetes and exocrine pancreatic insufficiency (Update 2019)]

The heterogenous catagory "specific types of diabetes due to other causes" encompasses disturbances in glucose metabolism due to other endocrine disorders such as acromegaly or hypercortisolism, drug-induced diabetes (e. g. antipsychotic medications, glucocorticoids, immunosuppressive agents, highly active antiretroviral therapy (HAART)), genetic forms of diabetes (e. g. Maturity Onset Diabetes of the Young (MODY), neonatal diabetes, Down Syndrome, Klinefelter Syndrome, Turner Syndrome), pancreatogenic diabetes (e. g. postoperatively, pancreatitis, pancreatic cancer, haemochromatosis, cystic fibrosis), and some rare autoimmune or infectious forms of diabetes. Diagnosis of specific diabetes types might influence therapeutic considerations. Exocrine pancreatic insufficiency is not only found in patients with pancreatogenic diabetes but is also frequently seen in type 1 and long-standing type 2 diabetes.

Challenges with optimizing nutrition in cystic fibrosis

Introduction. Optimizing nutrition remains the cornerstone of therapy for patients with cystic fibrosis (CF) since it is associated with better pulmonary function and survival. However, a significant proportion of patients still fail to achieve normal growth and nutritional status. Areas covered. This review describes the current challenges in providing effective nutritional therapy in CF with a focus on the current issues related to energy imbalance, dietary composition, adherence to nutritional recommendations, pancreatic enzyme replacement therapy, and the effects of modulators of the CF transmembrane conductance regulator. Expert opinion. CF is a multisystemic disease that requires a personalized nutritional approach with accurate evaluation of energy balance. There is an urgent need for evidence-based recommendations on the dietary composition, in consideration of the increasing prevalence of overweight, diabetes and the potential effects of fatty acids on inflammation and immune response. More research into new pancreatic enzyme formulations is also required.

Cystic fibrosis-related diabetes: optimizing care with a multidisciplinary approach

Cystic fibrosis-related diabetes (CFRD) is a common complication of cystic fibrosis and can be present in over 50% of adults with the disease. CFRD is associated with poorer clinical outcomes, including accelerated pulmonary function decline and excess morbidity. The management of CFRD is complex and differs from that of type 1 and type 2 diabetes mellitus such that clinicians responsible for the care of people with CFRD must work closely with colleagues across a number of different specialities and disciplines. This review aims to discuss why a multi-disciplinary approach is important and how it can be harnessed to optimize the care of people with CFRD.

Dietary interventions for managing glucose abnormalities in cystic fibrosis: a systematic review protocol

BACKGROUND

Glucose abnormalities in cystic fibrosis (CF) are common, but there is limited evidence to guide their dietary management. Progressive impaired glucose tolerance eventually leads to cystic fibrosis-related diabetes (CFRD), the most prevalent complication of CF, which is associated with increased morbidity and mortality. Optimising glycaemic control improves clinical status and reduces mortality; insulin therapy is the primary means of controlling glycaemia in CFRD, but its role in managing pre-diabetes is less clear. CF dietary therapy requires a high calorie diet due to increased energy expenditure and malabsorption, but this energy-dense diet is typically high in fat and sugar, and high sugar intakes often result in hyperglycaemia in individuals who have impaired glucose handling. Current guidelines for the dietary management of glucose abnormalities in CF are based on clinical consensus rather than empirical evidence. A systematic review conducted in 2012 on the effects of low glycaemic index dietary intervention in CF concluded that there is a dearth of evidence in this area. This review will update the systematic review by Balzer et al. in 2012 and will broaden the scope of their review to include any type of dietary intervention for managing glucose abnormalities in CF.

METHODS

Quantitative studies of dietary interventions to manage glucose abnormalities in individuals aged over 5 years with CF and glucose abnormalities will be reviewed. No limits will be placed on language or study design. The comparator will be standard CF dietary therapy (energy dense, high-fat diet) in addition to insulin therapy for individuals with CFRD. Electronic databases will be searched for completed quantitative studies published in peer-review journals that focus on dietary interventions for managing glucose abnormalities in CF. Searches will be conducted from 2000 up to the present day to reflect the evolving improvements in CF management. No restrictions will be placed on study design or language. Duration of the dietary intervention must be a minimum of 2 months and only interventions in out-patient or community settings will be included. Studies must report on dietary intervention, glycaemic control, anthropometry and lung function. Evidence will be assessed for heterogeneity and a narrative review or meta-analysis conducted as appropriate.

DISCUSSION

This systematic review will elucidate current knowledge of the effects of dietary interventions for managing glucose abnormalities in the vulnerable CF clinical population.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42018085569 www.crd.york.ac.uk/prospero/.

Hypoglycaemia in cystic fibrosis in the absence of diabetes: A systematic review

BACKGROUND

Hypoglycaemia in CF in the absence of diabetes or glucose lowering therapies is a phenomenon that is receiving growing attention in the literature. These episodes are sometimes symptomatic and likely have variable aetiologies. Our first aim was to conduct a systematic review of the literature to determine what is known about hypoglycaemia in CF. Our second aim was to assess evidence based guidelines for management strategies.

METHODS

A comprehensive search of databases and guideline compiler entities was performed. Inclusion criteria were primary research articles and evidence based guidelines that referred to hypoglycaemia in CF in the absence of insulin treatment or other glucose lowering therapies.

RESULTS

A total of 11 studies (four manuscripts and seven abstracts) and five evidence-based guidelines met the inclusion criteria. Prevalence rates of hypoglycaemia unrelated to diabetes varied between studies (7-69%). Hypoglycaemia was diagnosed during oral glucose tolerance testing or continuous glucose monitoring (CGM). Associations between hypoglycaemia and clinical parameters of BMI, lung function, liver disease and pancreatic insufficiency were measured in some studies. There was no unifying definition of hypoglycaemia in the absence of diabetes. Only two evidence based guidelines reported possible management strategies.

CONCLUSION

The systematic review found limited data on this clinical problem and supports the need for high quality methodological studies that are able to describe the experience and the aetiology(ies) of hypoglycaemia in CF.