Plain language summary
Cross-sectional studies have shown that whole grain cereal consumption can reduce the risk of cardiovascular disease (CVD, as well as reduce systemic inflammation, which is linked to many chronic diet associated diseases. Aleurone is a wheat grain fraction composed of a single cell layer that constitutes the outermost portion of the endosperm and contains many of the beneficial substances. The primary aim of this study was to investigate the effect of aleurone consumption on plasma homocysteine concentrations in overweight/ obese subjects. Secondary aim was to measure the impact of chronic aleurone supplementation on markers of CVD risk and on the human gut microbiota and its metabolic output. This study is a placebo-controlled, randomised, double-blind parallel trial with 2 test foods, wheat aleurone-rich foods or placebo foods (cellulose). Participants (n=74) were randomised to receive the active supplementation (aleurone 27 g per day) or placebo for 4 consecutive weeks. Results show that although average plasma homocysteine levels decreased upon wheat aleurone supplementation treatment, this change was not statistically significant, and homocysteine levels did not differ between groups after intervention. Furthermore, there was a significant increase in bifidobacteria both over time and compared to the placebo. Several significant and useful biomarkers of wheat aleurone intake, all related to wheat polyphenol metabolism by the gut microbiota, were identified. Authors conclude that wheat aleurone supplementation has the potential to modulate the gut microbial metabolic output and increase faecal bifidobacterial abundance, but it does not impact plasma homocysteine or other CVD biomarkers.
Abstract
PURPOSE Aleurone is a cereal bran fraction containing a variety of beneficial nutrients including polyphenols, fibers, minerals and vitamins. Animal and human studies support the beneficial role of aleurone consumption in reducing cardiovascular disease (CVD) risk. Gut microbiota fiber fermentation, polyphenol metabolism and betaine/choline metabolism may in part contribute to the physiological effects of aleurone. As primary objective, this study evaluated whether wheat aleurone supplemented foods could modify plasma homocysteine. Secondary objectives included changes in CVD biomarkers, fecal microbiota composition and plasma/urine metabolite profiles. METHODS A parallel double-blind, placebo-controlled and randomized trial was carried out in two groups of obese/overweight subjects, matched for age, BMI and gender, consuming foods supplemented with either aleurone (27 g/day) (AL, n = 34) or cellulose (placebo treatment, PL, n = 33) for 4 weeks. RESULTS No significant changes in plasma homocysteine or other clinical markers were observed with either treatment. Dietary fiber intake increased after AL and PL, animal protein intake increased after PL treatment. We observed a significant increase in fecal Bifidobacterium spp with AL and Lactobacillus spp with both AL and PL, but overall fecal microbiota community structure changed little according to 16S rRNA metataxonomics. Metabolomics implicated microbial metabolism of aleurone polyphenols and revealed distinctive biomarkers of AL treatment, including alkylresorcinol, cinnamic, benzoic and ferulic acids, folic acid, fatty acids, benzoxazinoid and roasted aroma related metabolites. Correlation analysis highlighted bacterial genera potentially linked to urinary compounds derived from aleurone metabolism and clinical parameters. CONCLUSIONS Aleurone has potential to modulate the gut microbial metabolic output and increase fecal bifidobacterial abundance. However, in this study, aleurone did not impact on plasma homocysteine or other CVD biomarkers. TRIAL REGISTRATION The study was registered at ClinicalTrials.gov (NCT02067026) on the 17th February 2014.
Methodological quality
Jadad score
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5
Allocation concealment
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Yes
