Food labels play a critical role in communicating nutrition information to the consumer. Given their potential to influence dietary choice, it is imperative to understand the consumers' use and comprehension of food labels if the presentation of nutrition information is to become both mandatory and standardized in the EU(1). The present study aims to assess the validity and reliability of a short (self-complete) questionnaire designed to assess consumers' use and understanding of food labels.
The questionnaire content was determined by gaps highlighted in a recent literature review of food labelling(Reference Mackison, Anderson and Wrieden2). Nineteen questions (forty-nine items) assessing frequency of label reading, perceived importance of food labels, regularity of dining out, desire to have nutrition information at specific catering outlets and ability to perform nutrition information tasks were formulated and presented on four pages of A4. With the exception of two open questions, all items were presented as closed (field box) structures and in accordance with best practice guidelines(Reference Edwards, Roberts and Clarke3). Content validity, face validity, item analysis, repeat reliability and internal reliability were assessed.
Nutrition experts (n 26) completed detailed content validity assessments, resulting in high scores for appropriateness, importance and phrasing of questions, although grammar and terminology changes were required. Face validity indicated the questionnaire was quick to complete (<15 min), easy to follow and comprehensible. Cronbach's alpha scores(Reference Bland and Altman4) (internal reliability) for questions with multiple sections ranged from 0.72 to 0.91, indicating good internal consistency. Repeat reliability testing showed Spearman correlation coefficients ranging from 0.51 to 0.97 (all P<0.001) indicating high temporal stability. Both item difficulty(Reference Kline5) and item discrimination analysis(Reference Kline6) indicated questions were at an appropriate level (Table).
In conclusion, this questionnaire is a suitable tool for assessing consumers' use, understanding and perception of food labels.
This work was funded by the Food Standards Agency Postgraduate Scholarship Scheme.