Dietary assessment methods for intakes of iron, calcium, selenium, zinc and iodine

The EURopean micronutrient RECommendations Aligned (EURRECA) Network of Excellence is working towards developing aligned micronutrient recommendations across Europe. The purpose of the present study was to conduct a review of methods used in validation studies carried out in adults assessing dietary intake of EURRECA priority minerals. A search strategy and inclusion criteria were defined and a scoring system was developed to rate the quality of each validation study that produced a quality index with possible scores obtained ranging from 0.5 to 7. A MEDLINE and EMBASE literature review was conducted. Articles/validation studies meeting the inclusion criteria included: 79/88 for Fe; 95/104 for Ca; 13/15 for Se; 29/30 for Zn; 7/9 for iodine. The most frequently used method to ascertain dietary intake was the Food Frequency Questionnaire (FFQ), whereas dietary records (DR) and 24 h recalls were the most used reference methods. The correlation coefficients (CC) between study mineral intakes estimated by FFQ and the reference method were weighted according to the study's quality index and obtained acceptable to good ratings, ranging from 0.36 to 0.60 when the reference method was DR and from 0.41 to 0.58 when the reference was 24 h recalls. A minority of studies (n 9) used biomarkers for validation and among these, five included iodine obtaining a CC of 0.47. The FFQ was seen as a valid method for assessing mineral intake, particularly for Ca and, to a lower extent, for iodine and Zn. Se and Fe showed only acceptable correlations. The present review provides new insights regarding the characteristics that assessment methods for dietary mineral intakes should fulfil.