Randomization, blinding, food logs, and surveys
Sample size was determined by budget, and we utilized a 2:1 (probiotic:placebo) ratio for randomization in order to increase the number of participants in the active arm to perform within arm comparisons over time. Both the participants and the study team administering the supplements were blinded. Participants were randomized into probiotic or placebo arms using a random number generator in Excel by a statistician from the Quantitative Science Unit at Stanford School of Medicine not involved in the intervention or data collection, the randomization assignments were stratified by sex in blocks of 3, there were no additional stratifications performed. Once participants completed the baseline data collection, they were assigned their arm based on the randomization described above and provided with bottles containing either probiotic or placebo and labeled with only bottle number, participant number, and appointment date. The bottle and labels were generated by the probiotic manufacturer. Participants were unblinded by e-mail after completion of the entire protocol. Investigators were unblinded after primary outcome calculation. Participants were asked to keep detailed food logs 3 days per week (two weekdays and one weekend) every other week through the duration of the study using the HIPAA compliant HealthWatch360 app (