Polyphenol intake has been estimated in some populations; however, information about day-to-day and individual differences in polyphenol intake has not been well-evaluated. In this study, we aimed to examine within- and between-individual variation in polyphenol intake in Japanese male workers. First, 56 male subjects (aged 37.9±10.4 y) completed detailed 7-d dietary records (DR). We then calculated their total polyphenol intake using our polyphenol content database and the within- and between-individual variations. We also estimated the minimum number of days of dietary assessment required both to rank individuals within a group and to assess an individual's usual polyphenol intake with acceptable accuracy. The estimated daily total polyphenol intake was 965±471 mg/d, which was largely sourced from beverages. The day-to-day variation (CVw) for polyphenol intake was 43.6%, and the variation between the individuals in the population (CVb) for polyphenol intake was 45.9%. A 4-d DR was required to rank individuals within a group with high correlation coefficients (r=0.9), and a 19-d DR was required to assess the individual's usual polyphenol intake with 20% deviation. The CVw for polyphenol intake was intermediate between those of the other nutrients, but the CVb for polyphenol intake was largest among the nutrients. These results suggest that the dietary intake of polyphenols should be carefully estimated considering its within- and between-individual variation.
Keywords: between-individual variation; dietary record; polyphenol intake; within-individual variation.