An anthocyanin-rich mixed-berry intervention may improve insulin sensitivity in a randomized trial of overweight and obese adults

Authors: SOLVERSON, PATRICK - University Of Maryland; Henderson, Theresa; DEBELO, HAWI - North Carolina State University; FERRUZZI, MARIO - North Carolina State University; Baer, David; Novotny, Janet

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2019
Publication Date: 11/25/2019
Citation: Solverson, P.M., Henderson, T.R., Debelo, H., Ferruzzi, M.G., Baer, D.J., Novotny, J.A. 2019. An anthocyanin-rich mixed-berry intervention may improve insulin sensitivity in a randomized trial of overweight and obese adults. Nutrients. 11:2876. https://doi.org/10.3390/nu11122876.
DOI: https://doi.org/10.3390/nu11122876

Interpretive Summary: Tens of animal studies have demonstrated that berries can provide protection against a high fat diet. Certain animals on a high fat diet develop obesity and diabetes; however, when berry preparations are added to that high fat diet, the animals remain lean and healthy. It is thought that the red, purple, and blue pigments found in berries may be responsible for the protection, though fiber may also play a role. To learn more about how berries might be protecting against obesity and diabetes, we conducted a study in which men and women ate a diet with different berry or fiber preparations. The berry/fiber preparations were (1) whole mixed berries consisting of blackberries, blueberries, cranberries, strawberries, and raspberries, (2) juice pressed from the same berry mix, (3) sweetened red gelatin enriched with fiber (a control food with fiber but no natural pigments), and (4) sweetened red gelatin with no fiber (a control food with neither fiber nor natural pigments). After eating the controlled diets for one week, we tested their ability to metabolize blood sugar. We found that while neither whole berries nor berry juice provided strong protection compared to the gelatin treatments, but when the data for the whole berries and berry juice were combined, the berry preparations overall improved blood insulin, demonstrating potential decreased risk for diabetes. These results suggest that berry pigments play a role in protection against diabetes. These findings will be used by scientists and health care providers.

Technical Abstract: Evidence supports the beneficial effects of berries on glucoregulation, possibly related to flavonoid content, fiber content, or both. The purpose of this study was to assess the potential of mixed berries to improve insulin sensitivity and to identify the potential role of flavonoids and fiber. In a randomized cross-over trial with four treatment periods, overweight/obese men and women were fed a controlled 45% fat diet for one week prior to a meal-based glucose tolerance test. The same base diet was provided during each feeding period with the addition of one of four treatments: whole mixed berries, sugar matched mixed berry juice, sugar matched gelatin, and sugar/fiber matched gelatin. Subjects then completed a meal-based oral glucose tolerance test. Serum glucose, insulin and non-esterified fatty acids were not different between individual treatments. However, in a secondary analysis, the combined berry preparations resulted in a lower serum insulin area under the curve (difference of 0.15 +/- 0.066 ln pmol min/mL, mean +/- SE, p = 0.0228), compared to the combined gelatin treatments, while the difference for serum glucose did not quite meet statistical significance (difference of 0.17 +/- 0.093 ln mg.min/dL, mean +/- SE, p = 0.0738). These results suggest the potential for mixed berry preparations to improve post-prandial insulin response.