Background:
Diet is one of the most modifiable behaviors affecting health. But diet assessment measures that are based on self-report can be inaccurate. Researchers want better ways to address the role of diet in chronic disease. They want to see if stable isotopes can be used to better assess what people eat.
Objective:
To see if stable isotopes can help scientists identify things people eat.
Eligibility:
Healthy adults ages 18 to 65
Design:
Participants will be screened with a medical history and physical exam. They will have blood and urine tests. These tests will be repeated during the study.
Participants will stay in the inpatient unit of the NIH in Phoenix, Arizona, for 13 weeks.
For 7 days, participants will eat a diet prepared by the NIH kitchen. They will get balanced meals that are 50% carbohydrates, 20% protein, and 30% fat. Then participants will be randomly placed on one of 3 diets containing different percentages of carbohydrates from soda.
Participants height and weight will be measured. The amount of fat and muscle in their body will be measured by body scans that are similar to x-rays.
Participants will have oral glucose tolerance tests. They will consume a sugar drink and then give blood samples over 3 hours.
Participants will give hair and stool samples.
Participants will complete a diet questionnaire. It assesses their food intake over 24 hours.
Participants will complete behavioral questionnaires and computer performance tests.
Participants will have fat biopsies taken from their stomach and thigh.
Participants will have three 24-hour stays in a metabolic chamber. It is used to measure metabolism.
...
Body mass index less than or equal to 35 kg/m² to minimize the impact of body size on isotope measurements.
Women and men between the ages of 18-65 years will be recruited for this study
Healthy, as determined by medical history, physical examination, and laboratory tests.
Fasting plasma glucose greater than or equal to 126 mg/dL
Alopecia totalis or inability to grow hair (at least one inch of hair required to obtain sample)
Use of medication affecting metabolism and appetite in the last three months
Medically- or self-imposed dietary restrictions that would limit a participant s ability/willingness to consume the diet to which they are randomized
Parallel
Diet with no soda
BehavioralWeight-maintaining diet without soda, with all carbohydrates originating from sources other than corn and sugar cane
Diet with 50% of carb intake from soda
BehavioralWeight-maintaining diet with 50% of carbohydrates provided as soda, and all other carbohydrates originating from sources other than corn and sugar cane
Diet with 20% of carb intake from soda
BehavioralWeight-maintaining diet with 20% of carbohydrates provided as soda, and all other carbohydrates originating from sources other than corn and sugar cane
Change in the blood carbon stable isotope ratio (13C/12C) from baseline to 12 weeks.
We will test biomarker diet relationships at the week 8, 10 and 12 sampling time points, using linear mixed effects models to evaluate single CIR biomarkers of SSB in plasma. Specifically, we will also test the time x group interaction by including it as a fixed effect in the mixed model analysis to evaluate the differences in the rate of CIR change over time across groups. Baseline CIR will be included as covariate in the mixed model analysis.
Change in the hair carbon stable isotope ratio (13C/12C) from baseline to 12 weeks.
We will test biomarker diet relationships at baseline and 12 weeks to determine differences in values over time and dose.
Change in the carbon stable isotope ratio of alanine from baseline to 12 weeks.
We will examine the time response of CIR-alanine. We will use a difference of 1.5 (Infinite) (+/-) from baseline as a preliminary criterion and adjust to ensure balanced representation of treatments in the 'time response' subset of participants. From these participants we will measure CIR-alanine at all timepoints. We will assess temporal change in CIR- alanine by examining week-to-week correlations to identify the time point at which biomarker measurements become independent of baseline, and by using linear mixed models to model the longitudinal trends over time.
Change in urinary sucrose/fructose over time and with varying levels of SSB intake.
Repeated measures two-way ANOVA will be employed to assess the between-subjects effect and to compare the daily sugars excretion during different levels of sugars intake.
24h EE and its components from the metabolic chamber.
Diet-induced changes in EE will be assessed for significance using a paired t test (before/after intervention) and ANCOVA (dose).
To determine the effect of dietary changes on the microbiome of the gut, single stool samples will be collected upon admission and completion.
We will measure 16s rRNA on stool samples before and after dietary intervention.
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