Dietary supplementation with whole blueberries in a preclinical study resulted in a reduction in glucose concentrations over time. We sought to evaluate the effect of daily dietary supplementation with bioactives from blueberries on whole-body insulin sensitivity in men and women. A double-blinded, randomized, and placebo-controlled clinical study design was used. After screening to resolve study eligibility, baseline (wk 0) insulin sensitivity was measured on 32 obese, nondiabetic, and insulin-resistant subjects using a high-dose hyperinsulinemic-euglycemic clamp (insulin infusion of 120 mU(861 pmol)⋅m−2⋅min−1). Serum inflammatory biomarkers and adiposity were measured at baseline. At the end of the study, insulin sensitivity, inflammatory biomarkers, and adiposity were reassessed. Participants were randomized to consume either a smoothie containing 22.5 g blueberry bioactives (blueberry group, n = 15) or a smoothie of equal nutritional value without added blueberry bioactives (placebo group, n = 17) twice daily for 6 wk. Both groups were instructed to maintain their body weight by reducing ad libitum intake by an amount equal to the energy intake of the smoothies. Participants’ body weights were evaluated weekly and 3-d food records were collected at baseline, the middle, and end of the study. The mean change in insulin sensitivity improved more in the blueberry group (1.7 ± 0.5 mg⋅kg FFM−1⋅min−1) than in the placebo group (0.4 ± 0.4 mg⋅kg FFM−1⋅min−1) (P = 0.04). Insulin sensitivity was enhanced in the blueberry group at the end of the study without significant changes in adiposity, energy intake, and inflammatory biomarkers. In conclusion, daily dietary supplementation with bioactives from whole blueberries improved insulin sensitivity in obese, nondiabetic, and insulin-resistant participants.
Supported in part by the NIH training grant T32 AT004094 (supporting A.J.S.), by the United States Highbush Blueberry Council, and P50AT002776-01 from the National Center for Complementary and Alternative Medicine and the Office of Dietary Supplements (W.T.C.), which funds the Botanical Research Center of Pennington Biomedical Research Center and The Biotech Center of Rutgers University. This project used facilities that are supported in part by Centers of Biomedical Research Excellence (NIH P20-RR021945) and Clinical Nutrition Research Unit (NIH 1P30-DK072476) center grants from the NIH.
Author disclosures: A. J. Stull, K. C. Cash, W. D. Johnson, and C. M. Champagne, no conflicts of interest. W. T. Cefalu received research funds from the United States Highbush Blueberry Council.
