Role of whole grains versus fruits and vegetables in reducing subclinical inflammation and promoting gastrointestinal health in individuals affected by overweight and obesity: a randomized controlled trial

Abstract

BackgroundWhole grains (WG) and fruits and vegetables (FV) have been shown to reduce the risk of metabolic disease, possibly via modulation of the gut microbiota. The purpose of this study was to determine the impact of increasing intake of either WG or FV on inflammatory markers and gut microbiota composition.MethodsA randomized parallel arm feeding trial was completed on forty-nine subjects with overweight or obesity and low intakes of FV and WG. Individuals were randomized into three groups (3 servings/d provided): WG, FV, and a control (refined grains). Stool and blood samples were collected at the beginning of the study and after 6 weeks. Inflammatory markers [tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), lipopolysaccharide binding protein (LBP), and high sensitivity C-reactive protein (hs-CRP)] were measured. Stool sample analysis included short/branched chain fatty acids (S/BCFA) and microbiota composition.ResultsThere was a significant decrease in LBP for participants on the WG (− 0.2 μg/mL, p = 0.02) and FV (− 0.2 μg/mL, p = 0.005) diets, with no change in those on the control diet (0.1 μg/mL, p = 0.08). The FV diet induced a significant change in IL-6 (− 1.5 pg/mL, p = 0.006), but no significant change was observed for the other treatments (control, − 0.009 pg/mL, p = 0.99; WG, − 0.29, p = 0.68). The WG diet resulted in a significant decrease in TNF-α (− 3.7 pg/mL; p < 0.001), whereas no significant effects were found for those on the other diets (control, − 0.6 pg/mL, p = 0.6; FV, − 1.4 pg/mL, p = 0.2). The treatments induced individualized changes in microbiota composition such that treatment group differences were not identified, except for a significant increase in α-diversity in the FV group. The proportions of Clostridiales (Firmicutes phylum) at baseline were correlated with the magnitude of change in LBP during the study.ConclusionsThese data demonstrate that WG and FV intake can have positive effects on metabolic health; however, different markers of inflammation were reduced on each diet suggesting that the anti-inflammatory effects were facilitated via different mechanisms. The anti-inflammatory effects were not related to changes in gut microbiota composition during the intervention, but were correlated with microbiota composition at baseline.Trial registrationClinicalTrials.gov, NCT02602496, Nov 4, 2017.Electronic supplementary materialThe online version of this article (10.1186/s12937-018-0381-7) contains supplementary material, which is available to authorized users.

The Combination of Whey Protein and Dietary Fiber Does Not Alter Low-Grade Inflammation or Adipose Tissue Gene Expression in Adults with Abdominal Obesity

“…We cannot exclude that the sample size may have been too small to detect differential effects on plasma cytokines. However, previous studies of similar or smaller sample sizes and shorter durations have detected differences in circulating TNF-α between a wholegrain wheat diet and a refined wheat diet in subjects with overweight and obesity [25,26]. This discrepancy in results could be due to differences in study populations; the previous studies included only individuals with low intakes of wholegrain and dietary fiber at baseline, while our study population was adapted to a relatively high dietary fiber intake, corresponding to the Danish national average of 22 g/day [27].…”

Human Postprandial Nutrient Metabolism and Low-Grade Inflammation: A Narrative Review

“…However, they did not find an association between macronutrient, energy density, fibre intake and LPS levels [138]. In a study with obese or overweight subjects and low fruit, vegetable and whole grain intake [139], nutrition that was rich in whole grains or fruits and vegetables significantly decreased LPS biomarker LPS binding protein (LBP) levels at baseline. The vegetable and fruit group also decreased IL-6 levels at baseline, whereas whole grain consumption reduced TNF-α levels.…”

“…The vegetable and fruit group also decreased IL-6 levels at baseline, whereas whole grain consumption reduced TNF-α levels. Furthermore, the baseline proportions of Clostridiales of the phylum Firmicutes correlated with LBP changes after the nutritional intervention, with subjects with lower Bacteroidetes and higher Firmicutes showing a greater LBP decrease during the interventions [139]. Interestingly, in mice studies, a high abundance of Clostridiales has been associated with the development of RA [140], suggesting that microbiota and endotoxemia are associated with each other.…”

Physical Activity and Diet Shape the Immune System during Aging

“…Strategies to combat metabolic inflammation associated with alterations in the gut microbiome may include time-restricted feeding [105], diets rich in fibers [106] and restricted in carbohydrates [107,108], and further n-3 PUFA supplementation [109]. In addition, kynurenic acid, a downstream metabolite of the kynurenine pathway that is activated by exercise training, has been shown to promote the expression of genes involved in lipid metabolism and anti-inflammatory immune responses in adipose tissue [110].…”