Differences between the three age groups at baseline were tested by Analysis of Variance (ANOVA) and post hoc analysis, with the Fisher’s least significant difference (LSD) test for multiple comparisons. Linear regression analysis was used to assess the relationship between 8-isoprostane concentrations, Gallic Acid Equivalents (GAE) in urine, and total polyphenol intake. Significance was defined as a value of p < 0.05.
Finally, in order to study the relationships between the different variables that were measured, and to reduce their number to a few factors that help us to interpret their similarities, a Factorial Analysis (FA) was applied. The method used to extract the factors was the Principal Component Analysis. The rotation method applied was the Varimax rotation. For this statistical analysis, the Stat Graphics Centurion XVI software (Stat Point Technologies, Inc., Dallas, TX, USA, 2013) was used.