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Whole grain-rich diet reduces body weight and systemic low-grade inflammation without inducing major changes of the gut microbiome: a randomised cross-over trial.
Roager, HM, Vogt, JK, Kristensen, M, Hansen, LBS, Ibrügger, S, Mærkedahl, RB, Bahl, MI, Lind, MV, Nielsen, RL, Frøkiær, H, et al
Gut. 2019;68(1):83-93
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Whole grain consumption has been linked with decreased risk of lifestyle-related diseases. While animal studies have shown the gut microbiome to be a mediator of metabolic health, human studies examining the effect of whole grain intake of the gut remain inconclusive. The aim of this study was to investigate the effects of a whole grain diet on the gut microbiome, gut functionality and biomarkers of metabolic health. In this randomised, controlled, crossover study, 50 participants completed two 8-week dietary intervention periods comprising of a whole grain diet and a refined grain diet with a 6-week washout period. Examinations were done at the beginning and end of each intervention period to assess anthropometry and various plasma and gut markers. This study found that a whole grain diet as compared with a refined grain diet reduced energy intake and body weight as well as circulating markers of inflammation. Contrary to the hypothesis, these benefits were all observed independent of changes in the gut microbiome. Based on these results, the authors conclude higher intake of whole grains should be recommended to those at risk of inflammation-related disease.
Abstract
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.
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Favourable effects of consuming a Palaeolithic-type diet on characteristics of the metabolic syndrome: a randomized controlled pilot-study.
Boers, I, Muskiet, FA, Berkelaar, E, Schut, E, Penders, R, Hoenderdos, K, Wichers, HJ, Jong, MC
Lipids in health and disease. 2014;13:160
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The prevalence of metabolic syndrome (MetS) is increasing rapidly worldwide and is a major risk factor for type 2 diabetes (DM2) and cardiovascular disease (CVD). Modern lifestyle-induced insulin resistance and chronic systemic low grade inflammation are considered at the root of the MetS. Therefore, dietary patterns of our Palaeolithic ancestors may be ideal for prevention and treatment of metabolic disorders since they are thought to be in line with the evolution of human physiology and metabolism. The aim of this randomized controlled pilot study was to assess the efficacy of a Palaeolithic-type diet in improving the characteristics of MetS, compared to a diet based on healthy eating guidelines. The study included 34 participants with MetS who consumed their allocated diets for two weeks. Efforts were made to prevent weight loss so that any favourable effects could be explained by the dietary intervention and not by the positive health effects of weight loss. The findings of this study showed that the Palaeolithic-type diet significantly lowered blood pressure, total cholesterol and triglycerides, as well as improved HDL-cholesterol, compared to the reference diet. The participants in the Palaeolithic diet intervention also had fewer characteristics of MetS and a tendency to higher insulin sensitivity at the end of the study. Despite efforts to keep body-weight stable, more weight was lost by the participants in the Palaeolithic group. No changes were observed in the secondary outcomes of inflammation, intestinal permeability and salivary cortisol, which the authors explain by the short duration of the intervention and the attempt to prevent weight loss. The authors conclude that future studies should take full additional advantage of the greater weight loss with the Palaeolithic diet, which may be more satiating than other diets, hence allowing weight loss to happen.
Abstract
BACKGROUND The main goal of this randomized controlled single-blinded pilot study was to study whether, independent of weight loss, a Palaeolithic-type diet alters characteristics of the metabolic syndrome. Next we searched for outcome variables that might become favourably influenced by a Paleolithic-type diet and may provide new insights in the pathophysiological mechanisms underlying the metabolic syndrome. In addition, more information on feasibility and designing an innovative dietary research program on the basis of a Palaeolithic-type diet was obtained. METHODS Thirty-four subjects, with at least two characteristics of the metabolic syndrome, were randomized to a two weeks Palaeolithic-type diet (n = 18) or an isoenergetic healthy reference diet, based on the guidelines of the Dutch Health Council (n = 14). Thirty-two subjects completed the study. Measures were taken to keep bodyweight stable. As primary outcomes oral glucose tolerance and characteristics of the metabolic syndrome (abdominal circumference, blood pressure, glucose, lipids) were measured. Secondary outcomes were intestinal permeability, inflammation and salivary cortisol. Data were collected at baseline and after the intervention. RESULTS Subjects were 53.5 (SD9.7) year old men (n = 9) and women (n = 25) with mean BMI of 31.8 (SD5.7) kg/m2. The Palaeolithic-type diet resulted in lower systolic blood pressure (-9.1 mmHg; P = 0.015), diastolic blood pressure (-5.2 mmHg; P = 0.038), total cholesterol (-0.52 mmol/l; P = 0.037), triglycerides (-0.89 mmol/l; P = 0.001) and higher HDL-cholesterol (+0.15 mmol/l; P = 0.013), compared to reference. The number of characteristics of the metabolic syndrome decreased with 1.07 (P = 0.010) upon the Palaeolithic-type diet, compared to reference. Despite efforts to keep bodyweight stable, it decreased in the Palaeolithic group compared to reference (-1.32 kg; P = 0.012). However, favourable effects remained after post-hoc adjustments for this unintended weight loss. No changes were observed for intestinal permeability, inflammation and salivary cortisol. CONCLUSIONS We conclude that consuming a Palaeolithic-type diet for two weeks improved several cardiovascular risk factors compared to a healthy reference diet in subjects with the metabolic syndrome. TRIAL REGISTRATION Nederlands Trial Register NTR3002.