Whole-grain cereal products based on a high-fibre barley or oat genotype lower post-prandial glucose and insulin responses in healthy humans

Abstract

Several factors can affect glycemic and insulinemic responses from cereal foods. Some suggested factors lowering the responses are; intact botanical structure, high amylose/high ss-glucan cereal varieties, organic acid produced during fermentation and food processes inducing retrogradation of starch. To evaluate the impact of fermented whole grain cereal kernels with high content of amylose (40%) and/or beta-glucan (4.6%) on postprandial glucose and insulin responses in healthy adults. Thirteen healthy volunteers (4 men and 9 women) were given 25 g available carbohydrate portions of: glucose solution; tempe fermented whole-grain barley and tempe fermented whole-grain oat. Blood samples were collected directly before the meal (fasting) and 15, 30, 45, 60, 90 and 120 min after the start of the meal. The GI (glycemic index) and II (insulin index) of meals were calculated for each subject according to FAO/WHO standards. Peak glucose response was lowest after the tempe meal with high-amylose/ high-ss-glucan barley tempe while insulin response was lowest after the meal with high beta-glucan oat tempe. The mean blood glucose responses for both the barley and the oat tempe meals were significantly lower than from the reference glucose load (P < 0.0001) during the first 60 min. The calculated GI:s for barley and oat tempe were 30 and 63, respectively. Mean serum insulin responses from barley and oat tempe were significantly lower compared with the glucose load (P < 0.002) during the first 60 min, and the calculated II was lower for oat tempe (21) compared with barley tempe (55). The results suggest that cereal products with beneficial influence on postprandial plasma glucose and insulin responses can be tailored by fermentation and enclosure of high-amylose and/or high-beta-glucan barley and oat kernels.