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Abstract:
Background Prebiotic dietary fiber and related metabolites have been suggested to attenuate low-grade systemic and central inflammation through improving gut-brain axis signaling. We here aimed to test whether habitual or short-term high-dose fiber intake is linked to inflammatory markers in blood and to indicators of central hypothalamic inflammation.
Methods In total, 59 adults (19 women, aged 28.3 years ± 6.6 SD, mean body mass index, BMI, 27.3 ± 1.5 SD) were included into analyses. Participants completed a food frequency questionnaire, underwent diffusion-weighted magnetic resonance imaging (MRI) at 3 Tesla for provision of mean diffusivity (MD) as a marker of brain tissue inflammation and donated fasting blood. Measurements took place at up to 4 timepoints, i.e. before and after 14 days of supplementary fiber and placebo intake, respectively. High-sensitive C-reactive protein (CRP), tumor-necrosis factor alpha (TNF-α) and interleukin-6 (IL6) were assessed in serum. The study was preregistered at https://osf.io/uzbav.
Results Habitual and interventional high-fiber diet was not significantly associated with neither inflammatory markers (|ßintervention|> 0.1, p > 0.32) nor with hypothalamic MD (|ßintervention| = 1.8, p = 0.07) according to linear mixed effects modeling. Male sex and higher body fat mass related to higher CRP. Further, higher BMI was borderline related to lower hypothalamic MD.
Conclusions In this sample of overweight adults, dietary fiber intake was not related to inflammatory blood markers or hypothalamic microstructure. Instead, sex and body composition were of higher importance for prediction of interindividual differences in markers of (neuro)inflammation.
