Low intake of dietary fiber is associated with gastrointestinal inflammation in healthy U.S. adults

Authors: BOUZID, YASMINE - University Of California, Davis; Alkan, Zeynep; Stephensen, Charles; Lemay, Danielle

Submitted to: Current Developments in Nutrition
Publication Type: Abstract Only
Publication Acceptance Date: 8/14/2022
Publication Date: 8/14/2022
Citation: Bouzid, Y.Y., Alkan, Z., Stephensen, C.B., Lemay, D.G. 2022. Low intake of dietary fiber is associated with gastrointestinal inflammation in healthy U.S. adults. Current Developments in Nutrition. 6/974. https://doi.org/10.1093/cdn/nzac068.003.
DOI: https://doi.org/10.1093/cdn/nzac068.003

Interpretive Summary: The role of dietary fiber in the gastrointestinal (GI) health of adults is not fully known. We investigated whether clinical or subclinical levels of GI inflammation has any relationship with consumption of dietary fiber by healthy U.S. adults. We used markers of GI inflammation from fecal and plasma samples. We found that a marker associated with the activation of immune cells in the gut is higher when dietary fiber intake is lower than the recommended amounts. We also found that a marker associated with pieces of bacteria in the bloodstream is also higher with lower intake of dietary fiber. Adequate fiber consumption may be protective against GI inflammation even in healthy adults.

Technical Abstract: Objective: We examined associations between reported fiber intake and markers of gastrointestinal (GI) inflammation in a healthy human population. Methods: Participants in the USDA Nutritional Phenotyping Study completed up to three unannounced 24-hour recalls using ASA24 and a Block 2014 Food Frequency Questionnaire (FFQ) to assess recent and habitual intake, respectively. Stool samples were stored on ice immediately after collection and homogenized within 24 hours. Markers of inflammation from stool, including calprotectin, neopterin, and myeloperoxidase (MPO) were measured by ELISA along with LPS-binding protein (LBP) from plasma. Associations were tested using regression models. GI marker levels were compared between participants who consumed low and adequate amounts of fiber according to both dietary assessment tools. Analyses were repeated with the subset of participants who had subclinical levels of calprotectin (<100 µg/g) and myeloperoxidase (<2000 ng/g). Results: There were no significant associations between fiber intake and calprotectin or MPO levels (n = 295) by regression. Recent and habitual fiber intake was negatively correlated with neopterin levels (n = 289, p = <0.001, p = 0.023). Fiber groups were determined by lower and upper quartiles of both dietary instruments (low: <16.5 g/day mean ASA24 & FFQ, n = 28; adequate: >31.25, n = 47). Participants with low fiber intake had higher neopterin levels (29.9 ± 8.9 nmol/L) than the adequate fiber intake group (14.8 ± 2.4 nmol/L, p = 0.003). Plasma LBP was higher in participants with low fiber intake (12.8 ± 1.3 µg/mol) than those with adequate intake (9.56 ± 0.65 µg/mL, p = 0.013) (low: <15.95 grams/day, n = 33; adequate: >30.9, n = 54). When fiber was expressed as g/1000 kcal consumed (low: <7.8 g/1000 kcal, n = 52; adequate: >14.65, n = 47), LBP levels were higher in the low fiber intake group (13.0 ± 0.86 µg/mL) than adequate (9.81 ± 0.83 µg/mL, p = 0.005). Habitual fiber intake was negatively correlated with calprotectin in the subset of participants with subclinical levels (p = 0.04). Conclusions: Dietary fiber intake was negatively correlated with neopterin and subclinical calprotectin levels. Participants with low intake of fiber on both dietary instruments had higher neopterin and LBP than those with adequate intake. Fiber consumption may be protective against GI inflammation in healthy adults.