Strawberry Polyphenols and Insulin Resistance: a dose‐response study in Obese Individuals with Insulin Resistance

Abstract

Insulin resistance is a major risk factor for developing type 2 diabetes mellitus (T2DM). Epidemiological data suggest that dietary anthocyanins (ACN) are associated with lower insulin resistance (IR) and T2DM risk. The present study assessed the effects of strawberries, a major dietary source of ACN, on acute insulin and glucose responses in individuals with IR. In a randomized 4‐arm crossover study, 23 obese adults consumed beverages containing freeze‐dried strawberry powder (FDS) at 4 levels [0, 10, 20, or 40 g corresponding to ~0 to 368 umol ACN]. The FDS beverages were fiber controlled and served with a standard meal with blood collected before and for 6 h after meal consumption on 4 occasions. Mean 6 h insulin was significantly lowered after consuming the 40 g FDS beverage/meal compared to all other beverages (p<0.05). No differences were observed in 6 h glucose responses, although the magnitude of increase from baseline was significantly lower (~29%) after the 40 g FDS beverage compared to other beverages (p<0.05). In adults with higher fasting insulin and greater IR, significant reductions in peak post meal insulin was apparent with 20 g and 40 g FDS beverages (p<0.05), whereas in those with a lesser degree of IR the 40 g FDS reduced peak post meal insulin. Oxidative stress was not different between groups, whereas IL‐6 was lowest after the 10 g FDS beverage. FDS ACN increased in plasma dose‐dependently reaching peak concentrations between 130 and 189 ± 45 min. These data support the view that strawberries have a role in improving insulin sensitivity in people with insulin resistance. Supported by CA Strawberry Commission, CA Dept of Food and Ag, Sacramento, CA. USA