Fig. 1

Linking the gut microbiome, dietary fiber, and systemic inflammation in a cohort of adult males. A 307 participants nested within the Health Professionals Follow-Up Study [23, 25] provided up to four stool samples with concurrent blood samples over a 6-month study period, generating 925 metagenomes from all participants and 372 metatranscriptomes from a subset of 96 selected because they provided stool at both sampling periods and did not report antibiotic use during the past year. B Overall recent dietary fiber intake and C-reactive protein (as a biomarker of systemic inflammation) levels were distributed representatively across this population. C Recent dietary fiber intake was inversely correlated with body mass index as expected (r =−0.24), but not correlated with age (r =−0.02). D Major food sources of fiber intake included cereals, vegetables, and fruits. E Principal coordinate analysis based on species-level Bray-Curtis dissimilarity decorated by quartiles of C-reactive protein and continuous fruit fiber intake suggested that fiber intake and CRP levels were not the overall largest sources of microbial community variability (other fiber subsets in Additional file 1: Figure S1)