Microbial derived uremic solutes (p-cresol sulfate, indoxyl sulfate, and phenylacetylglutamine) are present in blood and excreted into the urine. Uremic solutes have high inter-individual variability of unclear etiology, that the investigators hypothesize is due to intestinal microbiome variation and/or dietary variation between people. In this study, the investigators will collect baseline samples on participant's habitual diet. The investigators will then administer a homogenous diet to all participants for 7 days and examine levels of uremic solutes in the urine via 24-hour urine collection during this period. In parallel, the investigators will monitor microbiome composition. The investigators predict that during the period subjects are consuming the same, homogenous diet, their excretion of uremic solutes (p-cresol sulfate, indoxyl sulfate, and phenylacetylglutamine) into the urine will have less inter-individual variation.

Participants will be asked to eat exactly the same meal for one week and to eat this same meal three times each day. Subjects will be allowed to eat as much of this meal as they want and to eat enough so that they do not lose weight. The food will provide a nutritionally adequate diet, designed by a registered dietitian. Participants will be asked not to eat anything else including candy, snacks, etc. and not to drink anything except water including coffee, tea, sodas, or alcoholic drinks.

Samples will be collected at 5 time points:

2 weeks prior to starting test diet, Baseline (day 1 on diet), day 4 on the diet, day 7 on the diet, 7 days after end of diet.

Samples collected include:

Blood sample Stool sample 24 hr urine collection Diet and Gastrointestinal questionnaires

Inclusion Criteria:

• Healthy individuals

Exclusion Criteria:

• pregnancy
• diabetes
• gastrointestinal disease
• use of medications thought by the investigators to have a significant effect on the microbiome