Evaluation of a digital food photography atlas used as portion size measurement aid in dietary surveys in Greece.

Objective: To evaluate how well respondents perceive digital images of food portions commonly consumed in Greece.

Design: The picture series was defined on the basis of usual dietary intakes assessed in earlier large-scale studies in Greece. The evaluation included 2218 pre-weighed actual portions shown to participants, who were subsequently asked to link each portion to a food picture. Mean differences between picture numbers selected and portions actually shown were compared using the Wilcoxon paired signed-rank test. The effect of personal characteristics on participants' selections was evaluated through unpaired t tests (sex and school years) or through Tukey-Kramer pairwise comparisons (age and food groups).

Setting: Testing of participants' perception of digital food images used in the Greek national nutrition survey.

Subjects: Individuals (n 103, 61 % females) aged 12 years and over, selected on the basis of the target population of the Greek nutrition survey using convenience sampling.

Results: Individuals selected the correct or adjacent image in about 90 % of the assessments and tended to overestimate small and underestimate large quantities. Photographs of Greek traditional pies and meat-based pastry dishes led participants to perceive the amounts in the photos larger than they actually were. Adolescents were more prone to underestimating food quantities through the pictures.

Conclusions: The digital food atlas appears generally suitable to be used for the estimation of average food intakes in large-scale dietary surveys in Greece. However, individuals who consistently consume only small or only large food portions may have biased perceptions in relation to others.