People love to think that their purchases are going to good causes. That’s the whole idea behind social good–oriented companies like TOMS or campaigns like Product Red that pledge to give something back with every purchase. But when it comes to food, this notion can backfire for customers, a new study finds. 

Marketing researchers from the University of Oregon and the University of Wyoming write in the Journal of Consumer Affairs that when food companies partner up with health-oriented nonprofits, like Keebler linking up with the American Red Cross or Kentucky Fried Chicken pledging donations to a breast cancer foundation, consumers get a little confused about how healthy the for-profit food companies’ products are. For instance, the Academy of Nutrition and Dietetics abandoned a plan earlier this year to put their “Kids Eat Right” logo on Kraft American cheese singles after nutrition experts argued that it would look like the academy was endorsing the processed product. 

In one test, the researchers asked 109 undergraduate students which food choice was healthier: cookies with the logo of the American Heart Association or Goodwill. They reported that the AHA logo cookies seemed healthier than cookies with the Goodwill logo or with no logo at all. In another study with 140 participants, students were asked about their attitudes towards packages of crackers with logos from the American Heart Association, the World Health Fund, and Goodwill. The AHA logo made people more likely to choose those crackers for health reasons. While people also reported a willingness to buy the other crackers because they were for a worthy cause, they didn’t report a greater perception of health. 

So not all charity logos skew people’s perceptions of unhealthy foods, but slapping a specifically health-related nonprofit logo on a package does make people infer that the nonprofit is somehow endorsing that product as a healthy choice. 

The researchers’ advice? When you see a nonprofit logo on a package, take an extra second to think about what it means. Does the American Heart Association actually think you should eat more cookies? Or does the snack company just give some of its profits from selling unhealthy food to a charity?