Phytochemical Pharmacokinetics and Bioactivity of Oat and Barley Flour: A Randomized Crossover Trial

Abstract

While dietary fiber plays an important role in the health benefits associated with whole grain consumption, other ingredients concentrated in the outer bran layer, including alkylresorcinols, lignans, phenolic acids, phytosterols, and tocols, may also contribute to these outcomes. To determine the acute bioavailability and pharmacokinetics of the major phytochemicals found in barley and oats, we conducted a randomized, three-way crossover trial in 13 healthy subjects, aged 40–70 years with a body mass index (BMI) of 27–35.9 kg/m2. After a two-day run-in period following a diet low in phytochemicals, subjects were randomized to receive muffins made with either 48 g whole oat flour, whole barley flour, or refined wheat flour plus cellulose (control), with a one-week washout period between each intervention. At the same time, an oral glucose tolerance test was administered. In addition to plasma phytochemical concentrations, glucose and insulin responses, biomarkers of antioxidant activity, lipid peroxidation, inflammation, and vascular remodeling were determined over a 24-h period. There was no significant effect on acute bioavailability or pharmacokinetics of major phytochemicals. Administered concurrently with a glucose bolus, the source of whole grains did not attenuate the post-prandial response of markers of glucoregulation and insulin sensitivity, inflammation, nor vascular remodeling compared to the refined grain control. No significant differences were observed in the bioavailability or postprandial effects between whole-oat and whole-barley compared to a refined wheat control when administered with a glucose challenge. These null results may be due, in part, to the inclusion criteria for the subjects, dose of the whole grains, and concurrent acute administration of the whole grains with the glucose bolus.

Composition and content of phenolic acids and avenanthramides in commercial oat products: Are oats an important polyphenol source for consumers?

“…A diet rich in oats can provide phenolic acids and avenanthramides that may contribute to the beneficial health effects. Although there are mixed findings from different studies testing different foods, well designed randomized controlled trials investigating a variety of foods such as coffee and blueberries showed protective effects of circulating phenolics against CVD (Mills et al, 2017, Rodriguez-Mateos et al, 2016, Rodriguez-Mateos et al, 2013, Sawicki et al, 2016, Schar et al, 2015). Avenanthramides have also been shown to be bioavailable in humans and may exert anti-inflammatory, anti-proliferative and vasodilatory effects to protect against CVD and colon cancer (Bryngelsson et al, 2002, Chen et al, 2007, Liu et al, 2004, Nie et al, 2006, Xie et al, 2017).…”

Protective Role of Antioxidant Huskless Barley Extracts on TNF‐α‐Induced Endothelial Dysfunction in Human Vascular Endothelial Cells

“…The different constituents of the water extracts (beta-glucans) and alkali extracts (arabinoxylans) might contribute to the differences in their bioactivities [ 14 ]. Sawicki et al considered that in addition to the dietary fiber, other ingredients in the outer bran layer, including phenolic acids, alkylresorcinols, lignans, phytosterols, and tocols, may also contribute to health benefit outcomes [ 11 ]. Zhu et al found that the extracts from four varieties of dehulled highland barley ( Hordeum vulgare L.) showed excellent antioxidant activities as determined by ORAC and cellular antioxidant activity (CAA) assays; additionally, these varieties showed potent antiproliferative activity towards HepG2 human liver cancer cells.…”

“…As a major cereal crop that is used extensively as an industrial commodity and in fermentation products, barley is a functional cereal that is rich in dietary fiber. Dietary fiber (mainly non-starch polysaccharides) plays an important role in the health benefits associated with whole grain consumption, which has increasingly attracted the interest of scientists [ 11 ]. The physiological and functional properties of dietary fiber depend on the food source, extraction method, chemical composition, structure, and particle size [ 12 , 13 ].…”

Molecular Mechanism of Functional Ingredients in Barley to Combat Human Chronic Diseases

“…Barley grains are extremely rich in nutritional functional ingredients (Table 1). Barley whole grains and its outer bran layer are rich in functional ingredients, especially fiber, phenolic acids, flavonoids, phytosterols, alkylresorcinols, benzoxazinoids, lignans, tocol, and folate, which have antidiabetes, anticancer, antiobesity, preventive cardiovascular disease, antioxidant, antiproliferative, and cholesterol lowering abilities [18][19][20], such as β-glucan (2.40~7.42%) and total tocols (39.9~81.6 μg/g); 64 compounds in barley were 27 anthocyanins, 9 flavanols, 9 flavone glycosides, and 19 phenolic acids and aldehydes [21].…”