Beneficial immune effects in humans after regular consumption of juice from Concord grapes as determined by structural equation modeling

Abstract

In a 9‐wk, randomized, double blind, placebo controlled human study, we measured several biological functions related to immunity. We previously reported that regular consumption of 100% grape juice made from Concord grapes resulted in increased γδ T cell numbers and higher serum vitamin C while consumption of a placebo juice resulted in reduced γδ T cell proliferation, lowered serum antioxidant capacity and increased DNA strand breaks in response to an oxidative stress. Structural equation modeling (SEM) was utilized to explore multiple relationships in the data. SEM is advantageous over traditional analyses in that it permits looking at an unobserved construct (in this case, biological function) which represents a multivariate combination of measures variables (in this case, the γδ T cell data, vitamin C, and DNA strand breaks). Our analysis shows that juice consumption was the strongest predictor of biological function at Time 2 (9 weeks), accounting for 61% of the variance. This analysis should be viewed as exploratory because it is, to our knowledge, the first attempt to test this type of model of biological function. Funded by Welch Foods, Inc. and the UF/IFAS Agriculture Experiment Station