Front-of-pack nutrition labels: an equitable public health intervention

The FOP-ICE data collection protocol received institutional ethics clearance and is registered at http://www.ANZCTR.org.au/ACTRN12618001221246.aspx. Briefly, an ISO-accredited web panel provider administered an online survey to ~1000 respondents from each of the following countries: Argentina, Australia, Belgium, Bulgaria, Canada, Denmark, France, Germany, Italy, Mexico, the Netherlands, Poland, Portugal, Singapore, Spain, Switzerland, the UK, and the USA (N = 18,393).

Quotas were used to recruit samples equivalised by gender (50% females), age (one-third in each category: 18–30, 31–50, 51+), and household income (one-third low, medium, high). Income category was calculated by estimating the median household income per country and constructing a bracket of +/−33% around the median to create the medium-income band. Values below the medium band were categorised as low income and values above as high income. Other assessed consumer characteristics included education level, whether they were a regular grocery buyer for their household, self-reported nutrition knowledge, and self-reported diet quality.

The survey included an experiment measuring objective understanding (respondents’ ability to correctly rank the nutritional quality of a set of three notional products from three product categories) and product choice (using the same product choice sets as for understanding). The selected product categories (breakfast cereals, cakes, pizzas) are commonly consumed in the participating countries and have considerable nutritional variability across alternatives available in the marketplace. Figure 1 shows the ordering of the outcome variable survey items pre and post random assignment to one FoPL type. Choice was assessed prior to understanding for each product, and the ordering of product categories and individual product options was randomised to minimise priming and order effects.

Fig. 1figure 1

Ordering of understanding and choice tasks and front-of-pack label randomisation [7]. FoPL front-of-pack label.

Average pre- and post-exposure frequencies for correctly ranking the products by nutritional quality (yes/no) and choosing the healthiest option within the choice set (yes/no) were calculated. This dichotomous approach was taken to accommodate the ‘I don’t know’ responses that were significantly more prevalent among low-income respondents in both the pre and post FoPL exposure conditions (p < 0.001), with such responses considered incorrect. Two-sample z-tests were conducted to determine differences between income categories (low vs medium, low vs high, medium vs high) at p < 0.05.

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