Highlights Commercial oat products contained ten phenolic acids and three avenanthramides. Commercial oats provide 15.79–25.05 mg total phenolic acids in a 40 g serving of oats. The concentrations and compositions in the products were broadly similar. Major component was ferulic acid (58–78.1%) in all products. Oatbran concentrate has the highest levels of phenolic acids and avenanthramides.

Wholegrain oats are known to modulate the human gut microbiota and have prebiotic properties (increase the growth of some health-promoting bacterial genera within the colon). Research to date mainly attributes these effects to the fibre content; however, oat is also a rich dietary source of polyphenols, which may contribute to the positive modulation of gut microbiota. In vitro anaerobic batch-culture experiments were performed over 24 h to evaluate the impact of two different doses (1 and 3 % (w/v)) of oat bran, matched concentrations of β-glucan extract or polyphenol mix, on the human faecal microbiota composition using 16S RNA gene sequencing and SCFA analysis. Supplementation with oats increased the abundance of Proteobacteria (P <0·01) at 10 h, Bacteroidetes (P <0·05) at 24 h and concentrations of acetic and propionic acid increased at 10 and 24 h compared with the NC. Fermentation of the 1 % (w/v) oat bran resulted in significant increase in SCFA production at 24 h (86 (sd 27) v. 28 (sd 5) mm; P <0·05) and a bifidogenic effect, increasing the relative abundance of Bifidobacterium unassigned at 10 h and Bifidobacterium adolescentis (P <0·05) at 10 and 24 h compared with NC. Considering the β-glucan treatment induced an increase in the phylum Bacteroidetes at 24 h, it explains the Bacteriodetes effects of oats as a food matrix. The polyphenol mix induced an increase in Enterobacteriaceae family at 24 h. In conclusion, in this study, we found that oats increased bifidobacteria, acetic acid and propionic acid, and this is mediated by the synergy of all oat compounds within the complex food matrix, rather than its main bioactive β-glucan or polyphenols. Thus, oats as a whole food led to the greatest impact on the microbiota.

ScopeWholegrain has been associated with reduced chronic disease mortality, with oat intake particularly notable for lowering blood cholesterol and glycemia. To better understand the complex nutrient profile of oats, we studied urinary excretion of phenolic acids and avenanthramides after ingestion of oat bran in humans.Methods and resultsAfter a 2‐d (poly)phenol‐low diet, seven healthy men provided urine 12 h before and 48 h after consuming 60 g oat bran (7.8 μmol avenanthramides, 139.2 μmol phenolic acids) or a phenolic‐low (traces of phenolics) control in a crossover design. Analysis by ultra‐high performance liquid chromatography (UPLC)–MS/MS showed that oat bran intake resulted in an elevation in urinary excretion of 30 phenolics relative to the control, suggesting that they are oat bran‐derived. Mean excretion levels were elevated between 0–2 and 4–8 h, following oat bran intake, and amounted to a total of 33.7 ± 7.3 μmol total excretion (mean recovery: 22.9 ± 5.0%), relative to control. The predominant metabolites included: vanillic acid, 4‐ and 3‐hydroxyhippuric acids, and sulfate‐conjugates of benzoic and ferulic acids, which accounted collectively for two thirds of total excretion.ConclusionOat bran phenolics follow a relatively rapid urinary excretion, with 30 metabolites excreted within 8 h of intake. These levels of excretion suggest that bound phenolics are, in part, rapidly released by the microbiota.

Existing scientific data suggest that a high intake of wholegrain foods contributes to improved gut health and a reduced risk of cardiovascular disease. Wholegrain oats are rich in dietary fibre and an important source of many bioactive components, including minerals, vitamins and phenolic compounds. The oat b-glucans have been reported to lower low-density lipoprotein cholesterol through their ability to increase the viscosity of intestinal chime, change the gut microbiota composition and increase the production of short-chain fatty acids, which may contribute to the inhibition of hepatic cholesterol synthesis. Oats are also a rich source of phenolic acids, which are predominantly bound to cell wall polysaccharides through ester bonds. This bound state within oats means that phenolic acid bioavailability will largely be determined by interactions with the colonic microbiota in the large intestine. However, results from in vitro, animal and human studies have been inconsistent in relation to the impact of oats on the gut microbiota, possibly due to differences in experimental techniques and because compounds in oats, other than b-glucans, have not been considered. This review focuses on the interaction of oat b-glucans and phenolic acids with gut microbiota, and the subsequent link to cardiovascular health.

AbstractWholegrain consumption is linked to a lower risk of cardiovascular disease. Evidence from randomized controlled trials have established that the consumption of wholegrain oats lowers blood cholesterol, via a mechanism partly mediated by β-glucan soluble fiber. However, oats contain an array of phenolic acids, including ferulic acid and also structurally related avenanthramides, which may also contribute to the cardiovascular health benefits of oat intake. We investigated whether 4 weeks, daily consumption of oat phenolics leads to improvement in markers of CVD risk men and women.In a 3 arm crossover single-blind, placebo-controlled trial, 28 volunteers consumed either: 1) oatmeal/oatcake intervention (-containing 48.9 mg of phenolic acids and 19.2 mg of avenanthramides); 2) oatbran concentrate + rice porridge/wheat cracker intervention (-containing 38.4 mg of phenolic acids and 0.5 mg of avenanthramides) or 3) rice porridge/wheat cracker intervention (containing 13.8 mg of phenolic acids). All treatments were matched in soluble fiber (4.8g) and energy (500kcal). The primary endpoint was FMD and other cardiovascular endpoints were blood pressure, LDI, LDL/HDL cholesterol, platelets and endothelial cell-derived extracellular vesicles (EVs). All measures were taken at baseline and after three, 4 week long intervention periods and two washout periods.Our data indicates an increase by 1.09 % ± 0.41 %(Mean ± SEM) in FMD response following high phenolic oat intake with a significant difference (P = 0.007) between baseline and post-intervention. Consumption of high phenolic oats also led to a significant improvement in 24-hour SBP, day time SBP and night time SBP (P < 0.01, P < 0.01 and P < 0.05) and day time and night time DBP (p < 0.05). There was also a significant decrease with total and LDL cholesterol after the consumption of moderate and high phenolic oat interventions (P < 0.05) and a small improvement in LDI (both Ach and SNP) but not significant. The number of resting endothelial EVs were also found to be increasing after the consumption of high phenolic oats.The findings of this study may provide evidence about the role of oat phenolic acids and avenanthramides in cardiovascular health and contribute to more effective public health advice about the consumption of oats and healthy cardiovascular aging.