Costing a healthy diet: measurement and policy implications.

Health-related food taxes and subsidies are a hot topic in public health research. A number of countries have recently introduced such pricing strategies with the aim to promote healthier food choices. One of the most recent examples is Mexico, which introduced an excise tax on sugar-sweetened beverages of 1 peso per litre (approximately a 10% price increase based on 2013 prices) and a sales tax on several highly energy-dense foods (containing 1151 kJ (≥275 kcal) per 100 g). The relatively high cost of healthy food is often cited as an important argument to introduce food taxes and subsidies and thereby make healthy food (relatively) more affordable. Likewise, the cost of healthy foods is listed by consumers, and particular lower socio-economic groups, as an important barrier to purchasing healthier foods. However, there is much debate in the literature about whether healthy foods indeed cost more, where it has been argued that it is possible to eat healthily on a limited budget, but also that this is only possible if people are willing to divert hugely from culturally acceptable dietary patterns. A recent systematic review and metaanalysis revealed that, on average, healthier diets cost more than unhealthy diets; however, that review also highlights the importance of carefully considering the metric of healthfulness, intensity of contrast and unit of comparison. As it turns out, measuring the price of foods and diets is a lot more complicated than it might appear at first sight. The current issue of Public Health Nutrition features a new systematic review that looked into measuring food prices in more detail. The aim of that review was to determine similarities and differences in metrics and results between tools, protocols and methods used for monitoring (Australian) healthy food prices and affordability. The authors reviewed thirty-nine reports and twenty-four journal articles which described fifty-nine distinct food pricing surveys undertaken in Australia. The included surveys measured the cost of healthy foods by using a food basket approach. This approach involves measuring the cost of a predetermined selection (basket) of foods by collecting prices of these foods from retail outlets (mostly supermarkets). From these surveys, the authors identified six ‘major’ food pricing tools (used in multiple areas and multiple time periods) and five ‘minor’ food pricing tools (only used in one survey or during one time period). The authors identified large differences in the tools and protocols used in the different surveys, even when the same food pricing tool was used in different areas or time periods. They observed differences in: selection of ‘healthy’ basket contents; reference household composition; inclusion of availability and/or quality measures; household income sources; store sampling methods; season of data collection; and data collection protocols and analysis. This divergence in measurements makes it virtually impossible to make food price comparisons between countries or regions or over time and the authors argue it is important to establish a single measurement of (healthy) food costs. The INFORMAS (International Network for Food and Obesity/non-communicable diseases Research, Monitoring and Action Support) network is currently leading initiatives for establishing such a standardized monitoring approach.