Validity of digital photography as a novel method for estimating energy and nutrient intake of the Scottish student population.

Abstract

Background and aim: Accurate dietary assessments are required to understand the role of the diet in relation to the cause or prevention of disease. Common dietary assessment methods (24 hour recall, food frequency questionnaires, weighed-food records) used in the community, clinical settings and within research, estimate nutritional intake from patients or participants. These methods, however, can be burdensome on participants, expensive and resource intense. In recent years, dietary assessment methodologies using digital photography have been frequently used to capture individual dietary eating habits. This pilot study tested the validity of using digital photographs of participants' meals compared to the 'gold standard' weighed food records to assess energy and nutrient intake of Scottish students. Methods and study design: A convenience sample of students (N=18) were recruited by advertisement through the Queen Margaret University Moderator and through personal contacts. In free-living conditions, participants used their mobile phone cameras to photograph all food consumed at meal-times (breakfast, lunch and evening meal) in one day. The photographs were analysed by a Nutrition student to estimate the portion size (weight (g), energy (kcal), and protein (g)). In addition, participants also weighed and recorded the same meals on a diet record. Comparisons were made of the weight and nutritional composition of foods from the weighed intakes and the estimations from the photographs using a paired T-test. Validity was tested by using Bland-Altman analysis. Results: The total weight (g), energy (kcal) and protein (g) content between the digital photographs and the weighed food records for all meals combined showed no statistical difference (p=0.481, p=0.244 and p=0.299 respectively) between methods. Bland-Altman analysis showed good limits of agreement between both methods (mean ± 1.96). Conclusions: The digital photography method is valid for dietary assessment estimation in free-living conditions of the Scottish student population. Key words: Digital photography, dietary assessment methods, dietary intake, energy intake, portion sizes, free-living individuals.