High intra-individual variability in dietary flavonoid intake following repeated dietary measures in older Australian adults

: It is well established that an individual has considerable day-to-day variation in nutrient intake, which adversely effects the reliability of dietary assessment in studies requiring estimates of usual intake. However, the variability associated with dietary flavonoid intakes has not been considered. Inter-individual (the degree of variation between individuals) and intra-individual (the degree of variation within an individual) variability between repeated measures of flavonoid intake, and intake of flavonoid subclasses was determined in older adults (n=79). Flavonoids and subclasses were assessed using three 4-day weighed food records (WFR) collected approximately 4 months apart. Intra and inter-individual variability was assessed using coefficient of variation (CV) (a standardised measure of dispersion indicating the validity and repeatability of a measure, expressed as a %). Inter-individual variability was similarly high for each 4-day WFR for total flavonoid intake (mean CV=55%). The inter-individual variation was similar for flavonoid subclasses of flavonols (mean CV=45%), and flavon-3ols (mean CV=58%) but showed a wider range for flavanones (mean CV=102%), flavones (mean CV=140%) and anthocyanins (mean CV=115%). Intra-individual variability between the 3 WFRs was substantial for total flavonoid intake (mean CV=29%), flavan-3-ols (mean CV=34%), flavonols (mean CV=26%), flavones (mean CV=76%), flavanone (mean CV=77.7%), and anthocyanins (mean CV=80%). These results indicate excessive intra-individual variation associated with estimating flavonoid intake, which has implications for the interpretation study findings which employ a single measurement of intake. It is recommended that future research evaluates the number of days of recorded intake required to obtain an accurate estimate of intake of flavonoids and flavonoid subclasses.