Postprandial Glycemia, Insulinemia, and Antioxidant Status in Healthy Subjects after Ingestion of Bread made from Anthocyanin-Rich Riceberry Rice

Abstract

Riceberry rice, a gluten-free grain, contains many nutrient components, including carbohydrates, proteins, certain fatty acids, and micronutrients, as well as bioactive non-nutrient compounds, such as polyphenolic compounds. This study aimed to evaluate the effect of bread made from anthocyanin-rich Riceberry rice on the postprandial glycemic response, glucagon-like peptide-1 (GLP-1), antioxidant status, and subjective ratings of appetite. In the crossover design, 16 healthy participants (six men and 10 women) completed four sessions involving blood collection in the fasting state and at 30, 60, 90, 120, 150, and 180 min after food consumption (50 g of available carbohydrate) in a randomized order: 1) glucose solution, 2) wheat bread (WB), 3) Riceberry rice bread (RRB), and 4) Hom Mali bread (HMB). Consumption of RRB resulted in significantly lower postprandial plasma glucose concentration at 30 and 60 min when compared to HMB. No difference in postprandial glucose concentration between RRB and WB was observed. In addition, postprandial plasma insulin showed a significant decrease in the group which received RRB at 15 and 60 min, as compared to HMB. In comparison with 50 g of glucose, as a reference, the glycemic index (GI) of RRB, WB, and HMB was 69.3 ± 4.4, 77.8 ± 4.6, and 130.6 ± 7.9, respectively. Interestingly, the ferric-reducing ability of plasma (FRAP) level was shown to significantly increase after consumption of RRB. In the meantime, a significant decrease in the postprandial FRAP level was also observed following an intake of WB and HMB. All breads caused increases in the postprandial plasma protein thiol group and had similar effects on hunger, fullness, desire to eat, and satiety ratings. However, consumption of RBB, WB, and HMB did not change plasma GLP-1 and malondialdehyde (MDA) levels when compared to the baseline. The findings suggest that anthocyanin-rich Riceberry rice can be a natural ingredient for gluten-free bread which reduced glycemic response together with improvement of antioxidant status in healthy subjects.

Postprandial Effect of Yogurt Enriched with Anthocyanins from Riceberry Rice on Glycemic Response and Antioxidant Capacity in Healthy Adults

“…A reduction in the postprandial glucose excursion (40.23%) after consumption of riceberry rice yogurt was observed in healthy subjects. Cross-over studies have explored acute effects riceberry rice bread (50 g) on postprandial glycemic and insulin response in healthy volunteers [ 15 ]. After the riceberry rice bread intake, the AUC was 60% lower in comparison to jasmine rice bread.…”

“…Furthermore, it was found to produce an attenuated postprandial insulin concentration after 15 min of consumption. The main reason to explain these effects is the ability of riceberry rice and its phytochemical compounds to inhibit carbohydrate digestive enzymes [ 15 , 24 , 25 ]. A previous study supports this reason that the anthocyanin-rich extract of riceberry rice was capable of inhibiting intestinal α-glucosidase such as maltase and sucrase [ 14 ].…”

“…The Trolox equivalent antioxidant capacity (TEAC) assay was measured using 2,2′-azinobis (3-ethyl benzothiazoline-6-sulfonic acid) (ABTS) radical (ABTS ●+ ) [ 15 ], which was prepared by mixing 7 mM ABTS in 0.1 M PBS (pH 7.4) together with 2.45 mM K 2 S 2 O 8 in distilled water (1:1, v/v) . After incubation for 16 h at room temperature, the ABTS ●+ solution was diluted with 0.1 M PBS (pH 7.4) to adjust the absorbance between 0.9 and 1.0 at 734 nm.…”

“…Plasma malondialdehyde (MDA), a lipid peroxidation product, was quantified using thiobarbituric acid reactive substances (TBARS) assay. The plasma sample (200 μL) was mixed with trichloroacetic acid (10% w/v ) and 50 mM 2,6-Di-tert-bytyl-4-methylphenol (BHT) and centrifuged at 12,000 rpm for 10 min [ 15 ]. The supernatant (200 μL) was separated and further mixed with 0.67% TBA before boiling at 100 °C for 10 min.…”

“…It has been shown that the extract from riceberry rice possesses various biological activities such as antioxidant, anti-hyperglycemic, anti-hyperlipidemic, anti-glycation, and anti-inflammatory activities [ 13 , 14 ]. Consumption of riceberry rice bread had lower glycemic response with increased antioxidant capacity in healthy subjects when compared to Hom mali rice bread [ 15 ]. The probiotic yogurt enriched with anthocyanin-rich extract from riceberry rice was successfully developed and improved its functionality by increasing the amount of total phenolic compounds and antioxidant activity [ 16 ].…”