Red Raspberries on Insulin Action and Oxidative Stress

The proposed study is a randomized, 3-arm, diet-controlled, cross-over study using a multi-sampling postprandial paradigm to evaluate the relative bioavailability and absorption/kinetic profile of red raspberry polyphenols consumed with a typical American breakfast meal and further to determine the relationship of these findings on meal-associated metabolic- oxidative- and inflammatory- responses in relatively insulin sensitive and insulin resistant individuals. A planned sample size of 24 will be recruited into the study. This study will require one initial screening visit, 1 pre-study visit, and 3 study visits. This study will take 4-6 weeks per subject to complete.

The trial will initiate with a screening visit, which will last for about 1-1.5 hours and include measuring subjects' height, weight, waist circumference, fasting blood glucose, insulin sensitivity, body temperature, blood pressure and heart rate as well as collecting general eating, health and exercise habits via questionnaire.

If willing and eligible to participate, a 3-day food record (2 weekdays and 1 weekend) will be given to be completed over the following week to assess subject's baseline dietary intake patterns. Information will be used to help subjects adopt a relatively low polyphenolic diet over the course of the study. Prior to each postprandial study visit, a dinner meal will be provided the day before the study visit to help control for visit to visit variability in due to differences in meals the night before the study visit.

Subjects will arrive at the center in a fasting state for at least 10 hours, well hydrated and rested (with normal sleep). Each study visit will require blood draws throughout the visit. After evaluation of subject's health status (via anthropometric, vital sign and blood glucose measurements and in-person interview), a qualified health professional will place a catheter in subject's arm for the purpose of multiple blood sample collections and take the initial blood draw in the fasting state. Each subject will be randomized to receive 1 of 3 meal treatments: Control meal (0 g red raspberry), red raspberry meal 1 [~125 g fresh weight (1 cup equivalent)] or red raspberry meal 2 [~250 g fresh weight (2 cup equivalent)], based on randomization sequence on 3 Study Day Visits. At each Study visit, after the first blood draw (0 h), subjects will be served with the standard breakfast meal (a moderate to high fat/carbohydrate) along with fruit variable based on the order randomly selected by computer generated sequence. From this point forward, blood collection will occur at the following time points: 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 6.5 h, 7 h, 8 h and 24 h to test for polyphenol metabolites and other metabolic markers. After the 6h blood draw, a standardized lunch meal (polyphenol free) will be provided to subjects. After the 8 h blood draw, the catheter will be removed from subjects arm. Subject will be provided with a dinner meal (low polyphenol) to take home and asked not to consume anything else other than the provided dinner meal except plain water. Subject will be scheduled to come back the next morning for the 24 h blood sample collection.