How Differences in the Composition of Microorganisms in the Soil Affect the Microorganisms in the Human Gut, Through the Vegetables That Grow in it: a Process Pilot Study With Healthy Participants

Overview

There are two objectives for this clinical trial. The first is to test whether, with the current logistics and study setup it is possible to perform the study well and see where there might be bottlenecks we couldn't predict. The second objective is to investigate the relation between the composition of the microorganisms in the soil, the crops that grow in that soil, and the human gut. During the study participants will drink three vegetable smoothies a day, for two periods of one week. The only difference between the two periods is whether the vegetables come from a farm with a low diversity of microorganisms in the soil or a high diversity. Participants will be asked to give blood samples and turn in fecal samples before and after each period.

This randomized, double-blind, crossover pilot study will be used to assess the feasibility of logistics including vegetable delivery and preparation of the intervention product by the participants themselves. Besides feasibility, we will aim to identify live bacteria and fungi present in the intervention product (smoothies) and trace these back in stool samples. The gut microbiome is also called the "second genome" to which many protective and life-supporting functions have been externalized. It orchestrates the crosstalk between our own cells and environmental metagenome. Diet and food choices can modulate gut microbiome species and functional diversity, but the mechanisms by which this occurs are unclear. The nutritional quality of crops, the crop microbiome and the soil microbiome may therefore all be involved. Ten participants will be randomized in a cross-over design, with each participant drinking three 150 mL vegetable smoothies per day for two separate intervention weeks (HiDi vs LoDi soil origin, randomized 1 : 1). During the first week, smoothies will be prepared with the vegetables derived from microbiome-enriched soil (HiDi) or microbiome-impoverished soil (LoDi). Vegetables, a blender, and detailed instructions to prepare the smoothies on-site will be delivered to the participant. Each participant is asked to keep a diary (in the form of a daily Castor questionnaire), with special attention to dietary habits and intake. Furthermore, before and after this specified diet week, blood and stool samples will be collected. After a washout period of two weeks, participants will be offered identical meals in a crossover design.