Full-fat Yogurt and Glucose Tolerance

Pre-Diabetes Clinical Trial

Official title: Full-fat Yogurt and Glucose Tolerance

Status Completed

Clinical Trial Summary

This study determines if substituting full-fat yogurt (i.e., whole, 3.25% fat) for non-fat yogurt in the diet can reduce the risk of type 2 diabetes and inflammation in association with changes in the composition of the gastrointestinal bacteria prediabetic male and female volunteers. The central hypothesis is that dairy fat impacts whole body glucose handling and insulin sensitivity as well as inflammation both directly, and indirectly via influencing the gut microbiota composition.

Clinical Trial Description

The overall objective of this study is to determine if substituting full-fat yogurt (i.e., whole, 3.25% fat) for non-fat yogurt in the diet can i) improve whole body glucose handling and insulin sensitivity, ii) modulate systemic inflammation, and iii) induce putatively beneficial changes in the composition of the colonic microbiota in prediabetic men and women. By comparing a diet containing non-fat yogurt with a diet comprising of full-fat yogurt, the investigators will address the following specific hypotheses and aims:

Hypothesis 1: Dietary intake of full-fat yogurt will improve fasting and postprandial markers of glucose homeostasis, insulin sensitivity, and pancreatic cell function. Aim 1: Evaluating the diet-induced changes in blood glucose and endogenous insulin secretion. This will be assessed through a mixed meal tolerance test and oral glucose tolerance test.

Hypothesis 2: Dietary intake of full-fat yogurt will relatively reduce systemic inflammation. Aim 2: Examine diet-induced changes in inflammatory tone. This will be assessed through measurements of circulating (plasma) pro- and anti-inflammatory cytokines, cytokine production assays from in vitro-stimulated peripheral blood mononuclear cells, and plasma stimulated cytokine production in immortalized human cell lines.

Hypothesis 3: A diet containing full-fat yogurt will alter the colonic bacteria structure (e.g. decrease the Firmicutes/Bacteroidetes ratio). Aim 3: Characterize diet-induced alterations in colonic bacteria structure (composition and density) via next-generation sequencing and real-time Polymerase Chain Reaction Assays (PCR).

This study recruits 32 pre-diabetic female and male volunteers (50:50) aged 45-75 using a double-blinded, randomized crossover design to compare two experimental diets, 1) a low-fat diet containing fat-free yogurt (total fat: 28% energy), and 2) a higher fat diet consisting of whole 3.25% fat yogurt (total fat: 38% energy). Fat in the whole yogurt accounts entirely for the arithmetic difference in fat of 10% energy between the two diets. The study will consist of two 21-day experimental diet periods preceded by a 7-day control diet. The total length of study will be 8 weeks. The diet during the control diet periods will be an average U.S. diet to establish a normalized fatty acid intake among the subjects and to standardize the subject's physiologic state before each experimental diet. At the end of the first control period ("run-in") and at the end of each of the experimental diets, a mixed meal tolerance test and an oral glucose test will be performed to assess diet-induced changes in whole-body glucose handling and insulin sensitivity. In addition, blood and stool samples will be collected to examine diet-induced alterations in inflammatory tone and gastrointestinal microflora. ;

Related Conditions & MeSH terms

• Pre-Diabetes
• Prediabetic State

• NCT number: NCT03577119
• Study type: Interventional
• Source: University of Vermont Medical Center
• Status: Completed
• Phase: N/A
• Start date: June 1, 2018
• Completion date: June 30, 2022