Abstract
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.
Highlights
Increasing the daily intake of wholegrain cereals by 90g has been associated with reduction mortality from cardiovascular disease by 27%, total cancer by 15%, respiratory disease by 22%, diabetes by 51% and infectious diseases by 26%, as indicated by recent meta-analysis of 45 prospective studies [1]
Oat bran phenolics follow a relatively rapid ADME, with 33 metabolites excreted within 8h of intake, suggesting that bound phenolics are, in part, rapidly released by the microbiota
Oats only account for 1% of world grain production, they, unlike more widely consumed grains, are almost exclusively consumed as wholegrains and a rich dietary source of high quality proteins, minerals, vitamins, soluble β-glucan fiber and phenolic compounds, all of which are concentrated in the outer bran layers [5]
Summary
Increasing the daily intake of wholegrain cereals by 90g has been associated with reduction mortality from cardiovascular disease by 27%, total cancer by 15%, respiratory disease by 22%, diabetes by 51% and infectious diseases by 26%, as indicated by recent meta-analysis of 45 prospective studies [1]. Oats only account for 1% of world grain production, they, unlike more widely consumed grains, are almost exclusively consumed as wholegrains and a rich dietary source of high quality proteins, minerals, vitamins, soluble β-glucan fiber and phenolic compounds (i.e. phenolic acids and avenanthramides), all of which are concentrated in the outer bran layers [5]. Phenolic acid intake in Europe is on average 605 mg/d, with the main dietary sources being coffee (75%), fruits (5.6%) and wholegrain products (5.5%) [8]. Wholegrain is the richest dietary source of ferulic acid, which has a mean intake of 38 mg/d in Europe [8], a number of other phenolic acids and phenolic alkaloids, notably the avananthramides, are present in oats, either in the ‘free form’, as soluble conjugates, or as insoluble bound forms (including ester-linked to fiber) [9]. Understanding the absorption, distribution, metabolism and excretion (ADME) of oat phenolic compounds following the dietary intake of whole oats or oat bran is a key prerequisite for determining which phenolic metabolites may mediate the health benefits of oats
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