The Effect of Increasing Dietary Protein on the Gut Microbiome and Its Metabolites

This study will determine the effect of dietary protein not absorbed in the small intestine on the bacteria in the large intestine and the metabolites those bacteria produce when they break down the protein. The three specific goals are: 1. Determine if increasing dietary protein increases the purine breakdown product, allantoin, as observed in our previous study. 2. Establish a model to examine the effect of dietary protein on the gut microbiota and metabolites. 3. Identify gut bacteria and metabolite changes that occur with increased consumption of animal (whey) or plant (pea) protein sources.

Healthy male and female participants were recruited following specific inclusion/exclusion criteria. Participants were excluded if they 1) were less than 25 years of age, 2) consumed pre or probiotics in the last week, 3) had taken any antibiotics in the last three months, 4) were taking any prescribed medicines for a chronic disease such as diabetes, hypertension, cancer, anxiety, depression, or GI-related diseases. and 4) had taken any laxatives or antidiarrhea inhibitors in the last week. The study design was pre/post, with each person serving as their own control. Interested participants were randomly assigned to one of two study groups: 50 g whey protein supplement or 50 g pea protein supplement. They were asked to consume the supplement along with their usual dietary intake. Participants were located within the contiguous USA and were sent a fecal collection kit, the protein supplement, and a shaker bottle using overnight shipping. We used the fecal collection kit developed by the Biocollective. A fecal sample was collected before and after the participant consumed the protein supplement daily for seven days. At both time points, the participants were asked to recall the foods they ate during the previous 24 hours using ASA24-2020, provide information on their physical activity (International Physical Activity Questionnaire, IPAQ), and answer questions about the stool sample they collected. The stool sample will be analyzed for the microbes and metabolites present. These will be correlated with the dietary protein they consume.