Assessment of bias and associated factors for food portion quantification with photos in Brazil

ABSTRACT Background Food portion size estimation is an important source of error in obtaining dietary data. While food portion photos are known to aid the food portion estimation, the validation of photos are required. Objective This study aimed at evaluating the bias and associated factors in quantifying the size of food portions eaten during lunch, and estimated by a 24-Hour Recall (24HR) interview, with and without the use of photos. Design and Participants: A validation study was carried out with 140 adults in the Brazilian cities of Curitiba and Aracaju. Data collection began in the first semester of 2017, lasting approximately one year. On the first day, participants consumed foods during a lunch with 10 possible items; each weighed after selection. The following day, a 24HR interview was applied. Participants were randomly allocated into two groups, according to the use of food portion photos during the interview. Main outcome measures Means of the consumed and reported food amounts, and the difference between them were estimated. Statistical analyses performed The effect of the use of photos was obtained by evaluating the odds of correctly estimating each food portion, (±10% and ±25%), using logistic regression. Additionally, the effect of using photos, the main predictor, was adjusted by other variables (e.g. age and educational level). Results: Rice, beans and meatballs had the greater differences between the assessed groups. The odds of success in estimating the portion size were greater amongst those that used the photo to estimate their consumption of rice and beans; while the contrary was observed for meatballs. Carrot, lettuce and juice had similar biases between the groups. Furthermore, educational level, cooking habit, and study centre location influenced the correct estimation of some foods. Conclusion The evaluated photos can assist to estimate food consumption, especially two traditionally Brazilian foods, rice, and beans. The use of the meatball photo was unsatisfactory and further assessments are needed for the remaining photos. Thus, the evaluated photos album can be a useful tool in estimating Brazilian food consumption although further developments and assessments are also granted.