Impact of a Dietary Wheat Intervention on the Gut Microbiota of Adult Humans

Abstract

ObjectivesDiet is a key factor shaping the gut bacterial community of humans. Consumption of whole grain increases the diversity of the gut microbiota as well as beneficial microbes and their metabolites. However, previous research has not investigated the effect of different wheat types on the gut microbiome. MethodsIn this study, a sample of 28 adults consumed 100g per day of two different types of Michigan-grown whole grain wheat in the form of crackers made with flour of whole grain soft white wheat or whole grain soft red wheat. The study took place over a four-week period, each week representing a different treatment (A, B, C, and D). In weeks B and D participants consumed crackers made from white and red wheat, respectively. In weeks A and C, participants consumed crackers made from refined soft white wheat flour (washout). At the end of each 7-day period, participants submitted fecal samples for microbiota analysis as well as fiber and dietary questionnaires to assess their dietary intake. ResultsThe average daily fiber intake was 21.1g ± 13.8 g per day with a maximum fiber intake of 102.3 g and a minimum fiber intake of 6.7g. The average dietary diversity score in week A was 6.5, week B was 5.9, week C was 6.5, and week D was 5.6. The fecal bacterial communities did not differ in alpha diversity across time points. Bifidobacterium changed significantly throughout the treatment period. Community structure was similar across timepoints. However, four participants displayed a change in enterotype during the study period. A subset of six responders exhibited an increase in alpha diversity in test weeks (B and D). ConclusionsThe present study illustrated that these whole grain wheat treatments may not affect the composition of the gut microbiota in all adult humans, but a subset of participants did respond to the wheat treatment. The subset of responders suggests that baseline microbiota or background diet may influence changes in gut microbiota in response to whole grain wheat treatment. A larger sample size and increased treatment dose or treatment time period could further elucidate these relationships. Funding SourcesMichigan Soft White Wheat Endowment and Michigan State University AgBioResearch.