Objective To investigate whether a whole grain diet alters the gut microbiome and insulin sensitivity, as well as biomarkers of metabolic health and gut functionality.
Design 60 Danish adults at risk of developing metabolic syndrome were included in a randomised cross-over trial with two 8-week dietary intervention periods comprising whole grain diet and refined grain diet, separated by a washout period of ≥6 weeks. The response to the interventions on the gut microbiome composition and insulin sensitivity as well on measures of glucose and lipid metabolism, gut functionality, inflammatory markers, anthropometry and urine metabolomics were assessed.
Results 50 participants completed both periods with a whole grain intake of 179±50 g/day and 13±10 g/day in the whole grain and refined grain period, respectively. Compliance was confirmed by a difference in plasma alkylresorcinols (p<0.0001). Compared with refined grain, whole grain did not significantly alter glucose homeostasis and did not induce major changes in the faecal microbiome. Also, breath hydrogen levels, plasma short-chain fatty acids, intestinal integrity and intestinal transit time were not affected. The whole grain diet did, however, compared with the refined grain diet, decrease body weight (p<0.0001), serum inflammatory markers, interleukin (IL)-6 (p=0.009) and C-reactive protein (p=0.003). The reduction in body weight was consistent with a reduction in energy intake, and IL-6 reduction was associated with the amount of whole grain consumed, in particular with intake of rye.
Conclusion Compared with refined grain diet, whole grain diet did not alter insulin sensitivity and gut microbiome but reduced body weight and systemic low-grade inflammation.
Trial registration number NCT01731366; Results.
- colonic microflora
- immune response
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HMR and JKV contributed equally.
Contributors Conception and design of the study: MK, LL, MIB, HF, RG, KK,HV, TH, OP, TRL; collection of data and biological samples: MK, SI, RG, MVL,RBM, LL; analysis of markers of host physiology: RBM, HF, LL, MVL, SB, JJH; faecal microbiota: JKV, LBSH, RLN, MIB, MDD, VC, HBN, RG; plasma short-chainfatty acids: RL; plasma alkylresorcinols: MVL, ABR; urine metabolome: HMR, HLF,SVB; intestinal transit time: MHS, AFC; lactulose-mannitol excretion: ABR; study products: MK, SI, MVL, JH, ASM, AB; data analysis and interpretation: HMR, JKV,MK, LBSH, MVL, RBM, MIB, RLN, HF, CTE, CR, HBN, RG, LL, TLR; manuscript drafting: HMR, JKV, MK, MIB, LL and TLR. All authors read, revised and approved the final manuscript.
Funding This study was supported by the Innovation Fund Denmark (grant no. 11-116163/0603-00487B; Center for Gut, Grain and Greens (3G Center)). RLN was supported by a grant from DTU and the Sino-Danish Center for Education and Research.
Competing interests MV Lind was partly supported by an unrestricted grant from Cereal Partners Worldwide, a joint venture between Nestlé SA and General Mills Ltd. There were no conflict of interest to declare for the other authors. Intervention products were sponsored by Kohberg, Lantmännen, AXA, Wasa, Urtekram, Finax and Doves Farm. Sponsors of grants and products played no role in the design, methods, data management and analysis nor in the decision to publish.
Ethics approval Municipal Ethical Committee of the Capital Region of Denmark.
Provenance and peer review Not commissioned; externally peer reviewed.
Correction notice This article has been corrected since it published Online First. An additional author has been added.
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