Feasibility and relative validity of a digital photo-based dietary assessment: results from the Nutris-Phone study.
OBJECTIVE
For dietary assessment, mobile devices with a camera can be used as an alternative to hand-written paper records. The Nutritional Tracking Information Smartphone (Nutris-Phone) study aimed to examine relative validity and feasibility of a photo-based dietary record in everyday life.


DESIGN
Parallel to the photo-based technique, a weighed record was performed. Participant satisfaction was assessed by questionnaire. A trained nutrition scientist evaluated portion sizes and nutrient content was calculated (DGExpert). Spearman correlation and Bland-Altman analyses were applied.


SETTING
Healthy, non-pregnant volunteers (≥18 years) without intent to lose weight recruited at Ulm University, Germany.


SUBJECTS
Sixty-six participants (36 % males, median age 22·0 (interquartile range 20·0-25·0) years) took pictures of foods and beverages consumed with a commercially available mobile phone.


RESULTS
Significant correlation between the photo-based and weighed record was observed: energy (r=0·991), carbohydrate (r=0·980), fat (r=0·972), protein (r=0·988), fibre (r=0·941). Bland-Altman analyses indicated comparable means and acceptable 95 % limits of agreement (energy: -345·2 to 302·9 kJ (-82·5 to 72·4 kcal); carbohydrate: -15·2 to 13·1 g; fat: -6·4 to 6·4 g; protein: -5·9 to 5·6 g; fibre: -2·7 to 2·5 g). However, with increasing intake level, underestimation by the digital method was present (except for fat, all P&lt;0·01). Over 80 % of participants were satisfied with the photo-based record. In nearly 90 %, technical implementation was without major problems.


CONCLUSIONS
Compared with a weighed record, the photo-based dietary record seems to be valid, feasible and user-friendly to estimate energy, macronutrient and fibre intakes, although a systematic bias with increasing levels of intake should be kept in mind.