This between-subjects randomised controlled trial aims to test the effect of a menu featuring salt warning labels on perceived message effectiveness relative to a menu with no labels in a real-world restaurant environment. The study will also act as a pilot experiment for examining the impact of the salt warning label on food choice and subsequent salt intake in real-world conditions. Primary objectives: * To measure the PME of a menu featuring salt warning labels relative to a menu with no labels * To measure label awareness, perceived knowledge gain, and perceived influence of the label on food choice Secondary objectives: * To identify whether there is an effect of the salt warning label on: * Food choice (label/no label) * Total salt selected * Total salt intake * To examine support for the introduction of a salt warning label policy in the UK
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
SINGLE
Enrollment
465
A salt warning label will feature on the restaurant menu next to menu items that are high in salt (\>3g, more than 50% of guideline daily amount \[GDA\] in the UK).
University of Liverpool
Liverpool, Merseyside, United Kingdom
Perceived message effectiveness (PME)
Participants will answer 3 PME questions using a Likert scale ranging from 1 - 5 anchored by "not at all" and "a great deal": Prompt: "Think back to the menu that you ordered from…" "The menu made me concerned about the health effects of consuming items high in salt", "The menu made consuming items high in salt seem unpleasant", "The menu discouraged me from wanting to consume items high in salt". The mean response to the three items will be calculated.
Time frame: Post - meal assessment (within 10 minutes)
Label awareness
"Did you notice any warning labels next to any of the menu items when making your meal selection?" (yes/no). If \[yes\], "What did the label tell you about?" Response options: Healthy items, Organic, Calcium, Sustainable, Added sugars, Vegetarian, Unhealthy items, Salt, Fibre, Gluten Free, None of these, Not sure. If \[yes\], "Please describe what the label said" (open text response). Responses that mention high in salt or similar will be coded as aware.
Time frame: Post - meal assessment (within 10 minutes)
Salt awareness
"Did you think about the salt content of the meals when making your selection?" (yes/no)
Time frame: Post - meal assessment (within 10 minutes)
Perceived knowledge gain
For this question, both conditions will be shown an image of the labelled menu. "Did you learn something new from the salt labels on the menu?" (yes/no).
Time frame: Post - meal assessment (within 10 minutes)
Perceived influence
For this question, both conditions will be shown an image of the labelled menu, and some question phrasing is slightly altered. "Did the salt label influence which food you ordered from the menu" (yes/no). "If \[yes\], how did the salt label influence your choice?" Response options: I avoided choosing a meal high in salt; I chose a meal high in salt; Other (free text response) Control: "Would the salt label have influenced what food you ordered from the menu?" (yes/no) If \[yes\], how would the salt label have influenced your choice? Response options: I would have avoided choosing a meal high in salt; I would have chosen a meal high in salt; Other (free text response)
Time frame: Post - meal assessment (within 10 minutes)
Policy support
For this question, the both conditions will be shown an image of the labelled menu. If the UK Government introduced policy requiring restaurant menu items high in salt to feature these labels, how would you feel?" Likert scale ranging from 1 - 5 anchored by "strongly oppose" and "strongly support".
Time frame: Post - meal assessment (within 10 minutes)
Total salt purchased
Determined based on the total order of the participant, including food and drink. Prior to study commencement, all menu items will be sent for nutritional analysis to determine salt content/100g. Menu items will be weighed before being sent for analysis using kitchen scales (Vitafit VT706), so that specific salt content per serving can be calculated.
Time frame: Post - meal assessment (within 10 minutes)
Labelled item selected
Determined based on whether the food item selected featured a high in salt warning label (yes = 1, no = 0).
Time frame: Post - meal assessment (within 10 minutes)
Total salt consumed
Salt consumption will be determined from the order that the researcher takes and an estimation of the proportion of the meal that was consumed. The researcher will take a photograph before and after consumption and will estimate the percentage consumed component(s) of the meal, taking into account whether participants leave a proportion of all meal components or specific components (e.g., low salt or high salt components). Participants will also be asked whether they shared any of their meal with someone else. A random 10% selection of percentage estimates will be performed by a second researcher to measure reliability. Food consumption will then be calculated by subtracting an estimation of the proportion of the meal that was consumed (taking into account if any has been shared) from the food purchase.
Time frame: Post - meal assessment (within 10 minutes)
Later salt intake
Participants will receive a link to a dietary recall questionnaire (Intake24, https://intake24.co.uk/) via email on the same day after taking part in the study, which they will be prompted to complete before bed. They will be asked to provide as much detail as possible on what they had for dinner, snacks, and drinks after the restaurant visit. Based on this information and salt values calculated by Intake24, the total salt consumed by the participants for the rest of the day after the visit will be estimated.
Time frame: Follow-up assessment (next morning, 8AM, to be completed within 24 hours)
Other macronutrient intake
This platform is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.
Total kcal, sugar, and saturated fat intake \[i.e., other nutrients that are not the main warning focus\] will be calculated based on the nutritional content of the order of the participant.
Time frame: Post - meal assessment (within 10 minutes)