FFQ-NutriForHer: Reproducibility and Validity of a Semi-Quantitative Food Frequency Questionnaire for Young and Older Women

<b>Background</b>: Despite the growing interest in the relationship of diet and women's health conditions, a limited number of Food Frequency Questionnaires (FFQs) have been specifically developed and/or validated for use among women, and those that exist have been primarily developed and validated in non-European countries. This study aimed to evaluate the reproducibility and validity of the FFQ-NutriForHer among young and older Polish women. <b>Methods</b>: The reproducibility and validity of the 138-item FFQ-NutriForHer were evaluated in 121 young (18-30 years) and 88 older women (70-90 years). Reproducibility was assessed using energy-adjusted Pearson and intraclass correlation coefficients (PCCs, ICCs) from two FFQ administrations. Validity was evaluated by comparing energy-adjusted and de-attenuated PCCs between FFQ-mean and 3-day dietary records. The Bland-Altman method estimated mean differences and limits of agreement. <b>Results</b>: The mean PCCs and ICCs for macronutrient reproducibility were 0.69 ± 0.12 and 0.69 ± 0.11 among young women and 0.67 ± 0.06 and 0.65 ± 0.11 among older women, respectively, indicating moderate correlation and reliability in both groups. For micronutrients, the mean PCCs were 0.72 ± 0.05 among young women and 0.69 ± 0.05 among older women, while ICCs were 0.71 ± 0.05 and 0.69 ± 0.09, respectively, indicating a good and moderate correlation and moderate reliability. Mean PCCs for macronutrient validity indicated good concordance with values of 0.51 ± 0.25 among young women and 0.46 ± 0.13 among older women. For micronutrients, the mean PCC for validity was 0.63 ± 0.13 among young women and 0.44 ± 0.14 among older women. Bland-Altman analysis indicated good overall agreement between methods in both groups. <b>Conclusions</b>: Given its high reproducibility and satisfactory validity in both age groups, the FFQ-NutriForHer is a reliable tool for assessing dietary intake and exploring its links to women's health across different ages.