Environmental Influences on the Human Gut Microbiota: A Longitudinal Pilot Study
Abstract Objectives Urbanization has reduced environmental microorganism exposure, with most Americans spending over 90% of their time indoors. However, gardening remains a viable means of exposure to soil microorganisms and harvesting of edible produce. Accordingly, we aimed to determine relations between gardening, dietary habits, and gut microbiota. Methods Gardening families (N = 10) and non-gardening (control) families (N = 9) were enrolled in a longitudinal pilot trial. Families included two adults and a child (5–18 years) for a total sample size of 54 participants. Fecal samples were collected prior to and at the end of the gardening season. Garden soil samples (n = 9) were collected prior to and at the end of the season. Diet history questionnaires were collected at the beginning and end of the study to measure Healthy Eating Index (HEI) scores. Fecal and soil DNA were extracted, sequenced (V4 region of 16S rDNA gene), and analyzed using DADA2 and QIIME2. Alpha diversity measures were assessed, including Faith's phylogenetic diversity (PD) and observed operational taxonomic units (OTUs). Results Gardening families had significantly more fecal OTUs compared to control families (172.3 ± 44.2 vs. 157.0 ± 44.2, respectively; P = 0.03). Gardening families had greater (P = 0.02) Faith's PD scores and tended (P = 0.08) to have more fecal OTUs than the control group at peak gardening season. In the gardening families, fecal OTUs and Faith's PD were numerically but not statistically greater at the end of the season compared to baseline (all p’s > 0.05). Prior to the gardening season, gardening adults had greater HEI scores compared to control families (57 ± 9.1 vs. 49 ± 8.8, P = 0.03). HEI scores were not different between groups at the end of the study. Conclusions This study revealed that the fecal microbiota of families that garden differs from non-gardening families, and there are detectable changes in the fecal microbial community of gardeners and their family members over the course of the gardening season. Further research is needed to understand the role of diet in these changes and if microbes within the soil move between the soil and gastrointestinal environments. Funding Sources This research was funded by the Christopher Family Foundation Food and Family Grant Program.