Background The public health importance of monitoring the affordability of a nutritious diet has been highlighted by the UK Department for Food, Environment and Rural Affairs. The economic and health-related aspects of food and diet are currently tracked by separate government agencies. Here we demonstrate how linking routine economic and health data can facilitate the study of food prices in relation to nutrition and investigate food price trends for the period 2002-2012.

Methods We obtained national median price data for 94 foods and beverages included in the UK Consumer Price Index from 2002-2012 from the Office of National Statistics and linked these foods to items in the National Diet and Nutrition Survey food database. This linkage produced a unique dataset containing nutrition information per 100 g and price per 1000kcal across an 11 year period. Each food and beverage item was categorised as either ‘unhealthy’ or ‘healthier’ using the Food Standards Agency’s (FSA) Ofcom nutrient profiling model, developed by the FSA as a tool to differentiate foods based on their nutritive value. We tested statistical significance using a t-test for cross-sectional analyses and repeated measures ANOVA for time-series analyses.

Results There were 43 foods categorised as ‘unhealthy’ and 51 as ‘healthier’. The mean 2012 price/1000 kcal was £2.50 for unhealthy items and £7.49 for healthier items (p < 0.001). From 2002 to 2012 the absolute price of unhealthy and healthier products had risen by £0.74 and £1.92/1000 kcal, respectively. The ANOVA results confirmed that prices had risen over time, that there was a difference in price between the unhealthy and healthier items, and that the effect of time on price was different for unhealthy and healthier foods, with the price of healthier foods rising more substantially (p < 0.001).

Conclusion Analyses of UK price trends for foods in relation to their nutrient content revealed that foods and beverages designated as unhealthy cost less than healthier foods per unit of energy. Moreover, since 2002, absolute prices per 1000 kcal for healthier foods and drinks have been rising faster than prices per 1000 kcal for unhealthy items. A widening price gap between healthy and unhealthy foods may indicate that a nutritious diet is increasingly difficult to afford, a trend that may contribute to social inequalities in nutrition. The novel linkage we have demonstrated could serve as the basis for on-going monitoring of food prices to inform public health policy relating to diet and non-communicable disease.