Consumers in the UK are more likely to buy non-perishable, unhealthy foods during supermarket sales that evenly promote unhealthy and healthy foods, according to a recent study Medical Daily reported.

Price promotions are commonly used in stores to boost sales through price reductions and stimulate impulsive purchases by increasing items' prominence through tags and positioning. However, there is growing concern that such promotional activities by the food industry may contribute to poor dietary choices and might lure consumers away from healthier, higher priced options.

"There's plenty of anecdotal evidence, but very little empirical evidence, about the impact of price promotions on people's diets," researcher Theresa Marteau said in a statement. "In this study, we examined whether less healthy foods are more likely to be promoted than healthier foods and how consumers respond to price promotions."

For the study, researchers analyzed detailed data on purchase records of all foods and beverages by 27,000 households in the UK. More than 11,000 purchased products from 135 food and drink categories were assigned healthiness scores -- following UK Food Standards Agency (FSA) criteria -- based on the FSA nutrient profiling model.

They found that on the whole less healthy items were no more frequently promoted than healthier ones. However, after accounting for price, price discount, and brand characteristics, the magnitude of the sales increase was larger in less healthy than in healthier food categories. A 10 percent increase in the frequency of promotions led to a 35 percent sales increase for less healthy foods and a just under 20 percent sales increase for healthier foods.

This may be because products from less healthy food categories are often non-perishable, while those from healthier food categories -- in particular fruit and vegetables -- are perishable: stockpiling during promotion may therefore be more likely to happen in less healthy food categories.

The findings are detailed in the American Journal of Clinical Nutrition.