This is an Outpatient clinical trial of 20 healthy people assigned to drink nutritional shakes for either 60% of their calories or 100% of their calories for up to 4 days to understand changes in microbiome and metabolome resulting from consumption of the assigned diet.   Participants assigned to drink the nutritional formula for 60% of their calories will be given food for the other 40% of their calories.  The assignment related to whether you will drink nutritional shakes and food vs. just nutritional shakes is random.  You will not be able to choose your assignment.  Participants may only drink the nutritional formula and the food provided along with water or black coffee for the 4 days of the study. You will need to come for 5 visits.  One visit is for screening to see if you are eligible.  The four other visits will take place in one week and will be in the morning, as fasting before the visit is required.   Blood is collected at screening and on 3 other days. Stool and urine are collected at home around the time of screening and on 5 additional days. Participants are given sitz markers on day 1 and will undergo 1 or 2 x-rays. Diet surveys will also be collected. Participants who complete the entire study will receive $750.

This is an observational study that includes patients with breast cancer or non-small cell lung cancer who will be treated with immune checkpoint inhibitor (ICI) therapy. The investigators will use echocardiograms, blood draws, and PET stress tests to understand how ICI therapy affects the heart and circulatory system.