ABSTRACT Oats are rich sources of soluble dietary fibers, particularly β‐glucan, which is linked to improved postprandial glycemic control. Oats and oat‐based cereals cause a slow and moderate increase in the postprandial blood glucose levels; however, the mechanisms by which different processing and preparation methods affect the glucose levels remain unclear. Consumption of fiber‐rich meals attenuates the glucose responses to subsequent meals, a phenomenon known as the second‐meal effect. This study examined the effects of various oat‐based foods with different processing and preparation conditions on the postprandial blood glucose and insulin responses and their second‐meal effect on the postprandial interstitial glucose in healthy Japanese adults. Two randomized crossover trials were conducted. In Experiment 1, 11 participants consumed white rice or one of three oat‐based foods (fruit granola, baked oatmeal, and cooked oats). Postprandial blood glucose and insulin levels were measured over 120 min. In Experiment 2, 10 participants underwent continuous interstitial glucose monitoring. They consumed white rice, oat‐based food, or no breakfast as their first meal, followed by a standardized second meal. In Experiment 1, all oat‐based foods in this study reduced the postprandial blood glucose levels compared to white rice. Fruit granola and baked oatmeal exhibited low incremental areas under the glucose curve and were classified as low glycemic index foods, whereas cooked oats exhibited a medium glycemic index. In Experiment 2, only cooked oats suppressed the interstitial glucose elevation after the second meal. Overall, these findings suggest that oat‐based foods may help moderate postprandial glycemia, and that cooked oats may show the second‐meal effect in healthy Japanese adults.
Sasaki et al. (Fri,) studied this question.