Chardonnay Grape Marc Powder Supplementation May Increase Insulin Sensitivity in Obese and Overweight Men and Women

Abstract

Objectives Chardonnay grape marc (CM) is the remaining skins and seeds from winemaking that offers a rich source of phytonutrients. The objective was to evaluate glucose metabolism following the addition of CM to the diet. Methods Overweight or obese men and women with mild hyperlipidemia between 35–65 y were recruited for this double-blinded 16-week crossover study. Subjects consumed 1500mg of 1) microcrystalline cellulose (MCC), 2) high chardonnay seed extract/WellVine™ marc blend (HE) or 3) high WellVine™ chardonnay marc/seed extract blend (HM) in a randomized order. Each intervention arm lasted 3 weeks and included two 3-week washout periods. Following each intervention, fasting blood was drawn and assayed for glucose and insulin. Indexes of insulin resistance (HOMA-IR, McAuley) and insulin sensitivity (QUICKI) were calculated. Data were transformed before conducting analyses, when appropriate. Analyses were conducted with 24 completed subjects and intention to treat (ITT) with 3 subjects who withdrew using linear mixed model ANOVA. Results In the ITT analysis, fasting glucose and insulin showed a significant main effect of intervention (P = 0.04 and P = 0.03, respectively). For both glucose and insulin, pairwise comparisons showed a significant difference between HM and MCC (P = 0.03 and P = 0.03, respectively). The indexes, HOMA-IR and QUICKI showed a significant main effect of intervention (P = 0.04 and P = 0.03, respectively), whereas there was no effect with the McAuley index. For HOMA-IR and QUICKI, pairwise comparisons showed a significant difference between HM and MCC (P = 0.04 and P = 0.03, respectively). Conclusions There was an increase in QUICKI, indicating an increase in insulin sensitivity following the HM arm compared to MCC. This has important implications if it is followed up in a larger cohort. Following the HM arm there was also a decrease in fasting insulin and decrease in HOMA-IR compared to the MCC arm; in this case, the magnitude of these changes are not sufficient to suggest improvement in insulin resistance by clinical definitions. This was a proof of concept study, thus future studies should further explore these findings. Funding Sources NIFA Phase II Small Business Innovation Research Grant awarded to Sonomaceuticals, LLC, USDA CRIS 2032–51,530-025–00D.