Dietary fiber and the human gut microbiota: application of evidence mapping methodology

Authors: SAWICKI, CALEIGH - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; LIVINGSTON, KARA - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; OBIN, MARTIN - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; ROBERTS, SUSAN - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; CHUNG, MEI - Tufts University; MCKEOWN, NICOLA - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: Nutrients
Publication Type: Review Article
Publication Acceptance Date: 2/4/2017
Publication Date: 2/10/2017
Citation: Sawicki, C.M., Livingston, K.A., Obin, M., Roberts, S.B., Chung, M., McKeown, N.M. 2017. Dietary fiber and the human gut microbiota: application of evidence mapping methodology. Nutrients. 9(2). https://doi.org/10.3390/nu9020125.
DOI: https://doi.org/10.3390/nu9020125

Interpretive Summary: There is rapidly growing interest in the role of the human gut microbiota, the bacteria that live primarily in our large intestine, in health maintenance. In particular, there is a lot of new research on how dietary fiber, the primary food source for the microbiota within our digestive system, may influence the number, type, and activity of these microbes. Evidence mapping is a technique used to summarize evidence and provide a "snapshot" of the current research on a specific topic. It is cost-effective and allows researchers to identify potential areas of future research. We created an evidence map to summarize and evaluate the published human intervention studies on the topic of dietary fiber and gut microbiota and identify potential new directions for studies in this area. We identified 188 dietary fiber intervention studies that measured outcomes related to the microbiota. These studies included a variety of fiber types and outcome measures; however, whole-diet interventions, measures of bacterial activity, and studies in subjects with higher health risks were identified as three gaps in the current evidence. This evidence map efficiently captured the variability in characteristics of expanding research on dietary fiber, gut microbiota, and physiological health benefits, and identified areas that may benefit from further research. We hope that this evidence map will provide a resource for researchers to direct future work on dietary fiber and health.

Technical Abstract: Interest is rapidly growing around the role of the human gut microbiota in facilitating beneficial health effects associated with consumption of dietary fiber. An evidence map of current research activity in this area was created using a newly developed database of dietary fiber intervention studies in humans to identify studies with the following broad outcomes: (1) modulation of colonic microflora; and/or (2) colonic fermentation/short-chain fatty acid concentration. Study design characteristics, fiber exposures, and outcome categories were summarized. A sub-analysis described oligosaccharides and bacterial composition in greater detail. One hundred eighty-eight relevant studies were identified. The fiber categories represented by the most studies were oligosaccharides (20%), resistant starch (16%), and chemically synthesized fibers (15%). Short-chain fatty acid concentration (47%) and bacterial composition (88%) were the most frequently studied outcomes. Whole-diet interventions, measures of bacterial activity, and studies in metabolically at-risk subjects were identified as potential gaps in the evidence. This evidence map efficiently captured the variability in characteristics of expanding research on dietary fiber, gut microbiota, and physiological health benefits, and identified areas that may benefit from further research. We hope that this evidence map will provide a resource for researchers to direct new intervention studies and meta-analyses.