In physiology research, the term “placebo effect” refers to the positive effects that result from our perception of something being healthy. For example, exercise benefits our health, but just knowing exercise is good for us may also enhance its benefits.

There’s also a phenomenon known as the “nocebo effect”—negative effects that happen when we expect something to be harmful. The nocebo effect may be relevant when it comes to what we eat and how it affects our body. Studies have shown that eating foods high in fat and sugar can impair our blood vessel function. While this might be because of the fat and sugar, it’s also possible that just thinking a meal is unhealthy can cause harm.

Eating food deemed to be “unhealthy”—by us or society—can cause physiological stress and shame. It’s possible that these emotions, along with the perceived unhealthiness of the food we’re eating, contribute to decreased heart health. A study published in the Journal of Applied Physiology looked at this hypothesis.

A group of young women participated in the study, all of whom said they were prone to food stress and shame, which perhaps made them more susceptible to nocebo effects related to food.

On one occasion, the women drank a milkshake that contained 540 calories, 14 grams of fat, 80 grams of sugar and 20 grams of protein. They were given accurateinformation about the nutritional content of the shake. In other words, the participants drank an unhealthy milkshake that they were told was unhealthy.

On another day, the women drank the same milkshake, but with a catch—they were given inaccurate information on the shake’s nutritional content. They were told the shake contained 100 calories, 4 grams of fat, 3 grams of sugar and 10 grams of protein. In other words, the participants drank an unhealthy shake that they thought was a healthy nutrishake.

When asked about the beverages, the volunteers said they thought the milkshake was more harmful and less healthy than the nutrishake. Interestingly, they also perceived the nutrishake as being more harmful and less healthy than in a control condition when they drank plain water.

Endothelial function, a marker of blood vessel health, was impaired after drinking the unhealthy milkshake compared to when the participants drank water. But endothelial function didn’t worsen when participants drank the nutrishake, even though they were drinking the same fat- and sugar-laden milkshake!

What explains this apparent nocebo effect? It wasn’t related to stress or shame—these ratings were similar when the volunteers drank the milkshake and the nutrishake. It wasn’t physiological stress either, as cortisol (a stress hormone) and inflammation levels didn’t change after either beverage consumption. Ultimately, perceiving a beverage as unhealthy and harmful seemed to affect the women’s endothelial function, but scientists haven’t yet figured out why.

Do these findings give us the liberty to eat whatever we want without consequence? Does a burger and fries suddenly become part of a healthy diet just because we think (or tell ourselves) it’s good for us? Probably not, but there’s no doubt that how we perceive what we eat—and our exercise and other lifestyle habits—influences our physiology. Let’s embrace the nourishing aspects of our food and go easy on ourselves when we eat something that society doesn’t deem to be “healthy.” Stressing out about it or feeling shame might do more harm than good.