Attenuation of Postmeal Metabolic Indices with Red Raspberries in Individuals at Risk for Diabetes: A Randomized Controlled Trial

OBJECTIVE: This study investigated the effect of red raspberry intake on meal-induced postprandial metabolic responses in individuals who have overweight or obesity with prediabetes and insulin resistance (PreDM-IR), and in metabolically healthy individuals (Reference). METHODS: Thirty-two adults (PreDM-IR, n = 21; Reference, n = 11) were randomized to a controlled, three-arm, single-blinded, crossover trial. Participants were provided 0 g of frozen red raspberries (Control), 125 g of frozen red raspberries (RR-125) (~1 cup), or 250 g of frozen red raspberries (RR-250) (~2 cups), with a challenge breakfast meal (high carbohydrate/moderate fat) on three separate days. Multiple blood samples were collected up to 8 hours post breakfast with a final blood sample at 24 hours. A snack was provided at 6 hours. RESULTS: Breakfast containing RR-125 and RR-250 significantly reduced 2-hour insulin area under the curve, and RR-250 reduced peak insulin, peak glucose, and 2-hour glucose AUC compared with Control in the PreDM-IR group (P 0.05). No significant meal-related differences were observed for oxidative stress or inflammatory biomarkers. CONCLUSIONS: Our findings suggest that red raspberries aid in postmeal glycemic control in individuals with PreDM-IR, reducing glycemic burden with less insulin, which may be related to improved tissue insulin sensitivity.