Validity of digital photography as a novel method for estimating portion size, energy intake and protein intake of the Scottish student population: A pilot study.

Abstract

Introduction: The student population are particularly vulnerable to poor dietary habits. Given the increasing prevalence of diet related chronic disease, accurate dietary assessment is necessary to inform health interventions and policies specific to this population. However, inaccurate portion size estimation is a major error in dietary assessment. Utilising technology such as digital photography in free-living populations can help improve the accuracy of dietary assessment. Aims and objectives: To assess the validity of digital photography in estimating portion size, energy intake and protein intake in a free-living Scottish student population using a self-recorded weighed food record as the reference method. Materials and Methods: A convenience sample of student volunteers were required to capture digital photographs of their three main meals using a camera-enabled mobile phone over a 24-hour period under free-living conditions, while simultaneously keeping a weighed food record. The photographs were analysed by the researcher to ascertain portion size using a food atlas. Energy and protein intake from each meal was calculated using the dietary analysis software program, NetWisp. Comparisons were made between the portion size, energy intake and protein intake calculated using the digital photography method with those obtained from the weighed food record. Results: Sixteen student volunteers participated in the study (88%=female). No statistically significant differences were found between the two methods for portion size, energy intake or protein intake. Bland-Altman plots illustrated a positive bias for breakfast and a negative bias for lunch and evening meals over levels of portion size, energy intake and protein intake, with acceptable limits of agreement and the differences between methods were random. Conclusion: The results demonstrated the potential of digital photography as a valid method for estimating portion size, energy intake and protein intake of the Scottish student population. Keywords: dietary assessment, digital photography, weighed food record, portion size, energy intake, protein intake