High vs Low Glycemic Index Meals for Cystic Fibrosis

Overseen By Jocelyn McNeany

Age: < 65

Sex: Any

Trial Phase: Academic

Sponsor: Emory University

Must not be taking: Glucocorticoids

Disqualifiers: Pulmonary exacerbation, Liver transplant, CFRD, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: Unknown

Duration: 2 hours per session

40 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial aims to explore how different types of meals affect blood sugar levels in people with cystic fibrosis (CF), with a focus on the risk of developing CF-related diabetes. Participants will try meals with either a high or low glycemic index (a measure of how quickly foods cause blood sugar levels to rise) and with or without sugary drinks to assess how these combinations impact blood sugar. The trial seeks individuals with CF who experience pancreatic insufficiency, consume a lot of added sugars, and regularly drink sugary beverages. As an unphased trial, this study offers a unique opportunity to contribute to understanding dietary impacts on the risk of CF-related diabetes.

Will I have to stop taking my current medications?

If you are currently using medications that affect blood sugar levels, you will need to stop them at least 4 weeks before joining the study. However, if you are using CFTR modulators, you can continue them as long as you've been on them for at least 2 months.

What prior data suggests that this dietary protocol is safe for individuals with cystic fibrosis?

Research has shown that both high and low glycemic index meals are generally safe for people with cystic fibrosis, diabetes, or insulin resistance. Studies have found no major safety concerns with these diets. Specifically, earlier research in adults with cystic fibrosis and unusual blood sugar levels found low glycemic index meals to be safe and manageable. These findings support future studies, suggesting that participants are unlikely to encounter major safety issues when consuming these meals. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about this trial because it explores how different glycemic index meals might impact people with cystic fibrosis (CF), a condition where nutrition plays a crucial role in managing health. Unlike standard CF nutritional guidelines, which focus mainly on calorie intake and balanced macronutrients, this trial specifically examines how high versus low glycemic index meals affect metabolic responses. By focusing on the glycemic index, researchers hope to uncover new dietary strategies that could optimize energy levels and overall health in CF patients. This approach could lead to more personalized nutrition plans, potentially improving quality of life and disease management for those with CF.

What evidence suggests that this trial's treatments could be effective for cystic fibrosis-related diabetes?

Research shows that consuming foods with a high glycemic index (GI) can stress the body and cause larger spikes in blood sugar after meals, worsening conditions like cystic fibrosis-related diabetes. Conversely, studies indicate that low GI diets are generally safe and help stabilize blood sugar levels. For individuals with cystic fibrosis, this could lead to better blood sugar control and improved overall health. In this trial, participants will undergo both high and low GI meal tests to examine their effects on blood sugar and insulin levels. ^{2 5 6 7 8}

Who Is on the Research Team?

Tanicia Daley, MD, MPH

Principal Investigator

Emory University

Are You a Good Fit for This Trial?

This study is for adolescents and young adults with Cystic Fibrosis. It's designed to see if different types of sugar in meals affect their blood sugar levels and insulin function. Participants will be given meals with high or low glycemic index sugars, some including sugary drinks.

Inclusion Criteria

English speaking

My pancreas does not work properly.

I consume a lot of added sugars and drink sugary beverages weekly.

Exclusion Criteria

Restrictive dietary patterns (e.g, vegan, ketogenic, intermittent fasting) for more than one month within the last two months prior to screening

My BMI is either very low or very high for my age and sex.

I have been diagnosed with cystic fibrosis-related liver disease.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Treatment

Participants undergo a randomized 2x2 factorial design evaluating acute postprandial changes in glucose over 2 hours following ingestion of a mixed meal challenge

2 hours per session

Multiple sessions (in-person)

Follow-up

Participants are monitored for safety and effectiveness after treatment

4 weeks

Long-term Monitoring

Monitoring of primary and secondary outcome measures such as acceptability, retention rates, and changes in plasma markers

2 years

What Are the Treatments Tested in This Trial?

Interventions

• High vs Low Glycemic Index Mixed Meal Tolerance Test

Trial Overview

The trial tests how the body reacts to meals that have sugars which are absorbed at different rates (high vs low glycemic index) and whether adding a sugary drink makes a difference. Blood samples before and after eating measure changes in glucose, insulin function, and hormones related to digestion.

How Is the Trial Designed?

Group I: SSB+ HI- GI Experimental Treatment 2 Interventions

All standardized mixed meal challenges will be similar in calories (kcal) and percent of calories from carbohydrates (45%), protein (15%), and fat (40%). Each meal will provide 1/3rd of the subject's estimated kcal needs per current CF nutrition guidelines

Group II: SSB + LO- GI Experimental Treatment 2 Interventions

All standardized mixed meal challenges will be similar in calories (kcal) and percent of calories from carbohydrates (45%), protein (15%), and fat (40%). Each meal will provide 1/3rd of the subject's estimated kcal needs per current CF nutrition guidelines

Group III: NSSB+ LO- GI Experimental Treatment 1 Intervention

All standardized mixed meal challenges will be similar in calories (kcal) and percent of calories from carbohydrates (45%), protein (15%), and fat (40%). Each meal will provide 1/3rd of the subject's estimated kcal needs per current CF nutrition guidelines

Group IV: NSSB+ HI- GI Experimental Treatment 1 Intervention

All standardized mixed meal challenges will be similar in calories (kcal) and percent of calories from carbohydrates (45%), protein (15%), and fat (40%). Each meal will provide 1/3rd of the subject's estimated kcal needs per current CF nutrition guidelines

Who Is Running the Clinical Trial?

Emory University

Lead Sponsor

Trials

1,735

Recruited

2,605,000+

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Collaborator

Trials

2,513

Recruited

4,366,000+

Published Research Related to This Trial

Cystic fibrosis (CF) patients experience higher glucose levels after eating compared to healthy controls, but their glucose levels return to normal more quickly after a high-fat meal, suggesting a unique metabolic response.

The study involved 16 CF patients and 16 controls undergoing both an oral glucose tolerance test and a high-fat meal test, revealing that while CF patients have abnormal glucose responses, their lipid levels remain stable, indicating a potential area for further research in diagnosing CF-related diabetes.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dichotomy between postprandial glucose and lipid profiles in adults with cystic fibrosis: a pilot study. Hammana, I., Coderre, L., Potvin, S., et al.[2011]

In a study of 48 cystic fibrosis patients aged 2-28, 15 showed impaired glucose tolerance, but their nutritional status and severity of lung and liver disease were similar to those with normal glucose tolerance.

Patients with impaired glucose tolerance had significantly delayed peak insulin levels and higher HbA1C levels compared to those with normal glucose tolerance, indicating a potential risk for developing diabetes, although overall HbA1C levels did not change significantly over one year.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Oral glucose tolerance testing in cystic fibrosis: correlations with clinical parameters and glycosylated haemoglobin determinations. De Schepper, J., Dab, I., Derde, MP., et al.[2022]

In a study of 58 youth with cystic fibrosis, alternative glycemic markers like HbA1c, 1,5-anhydroglucitol, fructosamine, and glycated albumin showed low diagnostic accuracy for identifying cystic fibrosis-related diabetes (CFRD) and pre-diabetes (CFPD) when compared to the standard oral glucose tolerance test (OGTT).

Specifically, HbA1c at a cut point of 5.5% had a sensitivity of 78% but a low specificity of 41% for identifying CFRD, indicating that while it can detect some cases, it is not reliable enough for screening purposes.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Screening for cystic fibrosis-related diabetes and prediabetes: Evaluating 1,5-anhydroglucitol, fructosamine, glycated albumin, and hemoglobin A1c. Tommerdahl, KL., Brinton, JT., Vigers, T., et al.[2022]

In a pilot study involving 12 obese youth with type 2 diabetes or impaired glucose tolerance, consuming low glycemic index meals resulted in significantly lower mean daytime blood glucose levels.

The study also indicated a trend towards reduced variability in blood glucose levels, highlighting the potential benefits of low glycemic index diets for managing blood sugar in this population.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

High and low glycemic index mixed meals and blood glucose in youth with type 2 diabetes or impaired glucose tolerance. Gellar, L., Nansel, TR.[2021]

In a study of 25 cystic fibrosis patients, 20% showed alterations in glucose homeostasis, with one patient diagnosed as diabetic and four others exhibiting glucose intolerance or hyperinsulinemia, indicating a higher frequency of these issues compared to the general population.

The study found a direct correlation between insulin levels and the duration of cystic fibrosis symptoms, suggesting that longer disease duration may increase the risk of glucose metabolism problems, highlighting the need for regular glucose tolerance testing in these patients.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

[Study of the frequency of diabetes mellitus and glucose intolerance in patients with cystic fibrosis] Castro, FA., Fernandes, MI., Júnior, RM., et al.[2020]

Hypoglycemia is common in adolescents and young adults with pancreatic insufficient cystic fibrosis (PI-CF) after meals, occurring in 9 out of 34 subjects, and is linked to higher peak glucose levels and impaired early-phase insulin secretion.

Individuals experiencing hypoglycemia showed lower levels of GLP-1 and higher levels of GIP, suggesting a potential disruption in incretin response, which may contribute to glucose dysregulation in this population.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dysregulated insulin in pancreatic insufficient cystic fibrosis with post-prandial hypoglycemia. Kilberg, MJ., Sheikh, S., Stefanovski, D., et al.[2021]

In type-1 diabetes, studies show that low versus high glycemic index (GI) diets do not significantly improve HbA1c levels, with mixed results on fructosamine, indicating limited efficacy of GI in meal planning.

For type-2 diabetes, while some studies report benefits of low GI diets on HbA1c, the overall evidence is inconsistent, suggesting that total carbohydrate intake is a more important factor for managing diabetes than GI alone.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The argument against glycemic index: what are the other options? Franz, MJ.[2019]

In a study involving 15 obese adolescents with insulin resistance, a low glycaemic index and low insulin index (LGI-LII) meal significantly reduced postprandial insulin responses by up to 56.1% compared to a high insulin index meal (LGI-HII).

The LGI-LII meal also decreased feelings of hunger by 25.8% to 27.5%, suggesting that using the food insulin index could help manage insulin levels and appetite in this population.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Does food insulin index in the context of mixed meals affect postprandial metabolic responses and appetite in obese adolescents with insulin resistance? A randomised cross-over trial. Caferoglu, Z., Hatipoglu, N., Gokmen Ozel, H.[2020]

In a study involving 10 obese subjects with type 2 diabetes under intensive insulin therapy, a low glycemic index (GI) breakfast resulted in a significant 46% reduction in the area under the curve for glucose levels compared to a high GI breakfast, indicating better glycemic control.

Eight out of ten participants consuming the low GI breakfast achieved postprandial glucose levels below 180 mg/dL, suggesting that low GI meals may be beneficial for managing blood sugar levels in individuals with diabetes.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of high and low glycemic index breakfast on postprandial metabolic parameters and satiety in subjects with type 2 diabetes mellitus under intensive insulin therapy: Controlled clinical trial. Lobos, DR., Vicuña, IA., Novik, V., et al.[2018]

The systematic review of 11 studies, involving participants aged 6 to 82, found inconsistent effects of glycemic index (GI) on cognitive function, with some studies favoring high-GI meals and others favoring low-GI meals, or showing no significant differences.

Methodological factors such as study design, sample characteristics, and cognitive testing methods contributed to the inconsistencies, suggesting that future research should address these issues to clarify the relationship between carbohydrate absorption rates and cognitive performance.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The influence of glycemic index on cognitive functioning: a systematic review of the evidence. Philippou, E., Constantinou, M.[2023]

A systematic review of low glycaemic index (GI) diets in youth with cystic fibrosis (CF) found insufficient evidence to recommend these diets for improving glycaemic control, weight, or quality of life, based on only two relevant studies.

Despite the lack of strong evidence in CF, low GI diets have shown benefits in diabetes management, suggesting that further research is needed to explore their potential advantages for individuals with cystic fibrosis.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Low glycaemic index dietary interventions in youth with cystic fibrosis: a systematic review and discussion of the clinical implications. Balzer, BW., Graham, CL., Craig, ME., et al.[2021]

In a study of 32 nondiabetic cystic fibrosis patients, 50% exhibited impaired oral glucose tolerance, indicating a significant risk for developing diabetes due to pancreatic dysfunction.

The study found that malnourished cystic fibrosis patients had a higher rate of impaired glucose tolerance, and those with impaired tolerance showed delayed and excessive insulin responses after glucose intake, suggesting a complex disruption in glucose metabolism.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

[Glucose homeostasis in mucoviscidosis]. Skopnik, H., Schüttler, A., Döhmen, H., et al.[2022]

A study of 56 cystic fibrosis patients found that hemoglobin A1C (HbA1c) levels did not significantly differ between those with normal glucose tolerance and those with pre-CFRD states (INDET, IFG, IGT), indicating HbA1c is not an effective screening tool for these conditions.

The results suggest that relying on HbA1c for screening could lead to missed diagnoses of pre-CFRD dysglycemia, highlighting the need for more efficient screening methods to reduce the burden of annual oral glucose tolerance tests.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Use of hemoglobin A1c to identify dysglycemia in cystic fibrosis. Darukhanavala, A., Van Dessel, F., Ho, J., et al.[2022]

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