The Effect of the Addition of Four Different Protein Isolates to A Fruit-Based Smoothie On Postprandial Blood Glucose in a Healthy Population

PURPOSE. The aim of this study was to investigate the effect of the addition of whey, soy, milk, or pea protein to fruit-based smoothies on postprandial blood glucose levels. METHOD. Eight subjects (1 male, 7 female, age 22.6 ±1.6 years, BMI 23.3 ± 2.5 kg/m2) participated in a randomized controlled study. Subjects consumed a 625 mL (2.5 cups) smoothie that contained 30 grams of either whey, soy, milk, or pea protein. A smoothie with no added protein was used as a control. All subjects were given the same type of smoothie on each test day. Finger sticks were used to measure blood glucose levels at baseline, 50 minutes, and 120 minutes after consumption of the smoothies. RESULTS. There was no difference in fasting blood glucose among subjects prior to drinking the smoothies (p = .92). The rise in blood glucose was significantly less at 50 minutes after consumption of the smoothies containing soy and whey protein in comparison to the control smoothie (p\u3c.05), while at 120 minutes the soy and control were significantly lower than pea protein (p\u3c.05). The blood glucose levels from the control smoothie at 50 to 120 minutes after consumption decreased significantly in comparison to all of the proteins additives. CONCLUSIONS. The addition of protein to smoothies has an effect on blood glucose response. Our study found that smoothies containing soy and whey proteins produced a lower glucose response from baseline to 50 minutes (96.4 mg/dL and 101.4 mg/dL, respectively) when compared to smoothies containing protein extracts from pea, milk, or the control (103.25 mg/dL, 103.3 mg/dL, and 118.0 mg/dL, respectively)