It’s possible that the benefits of multivitamins can be chalked up to the placebo effect. So says a study in BMJ Open based on data from the 2012 National Health Interview Survey of more than 21,600 people.

Nearly 5,000 participants who reported taking multivitamins—supplements that contain a mixture of vitamins and minerals—self-reported their overall health as being around 30% better than those who didn’t use multivitamins. But here’s the thing: The researchers found no notable health differences between the two groups based on medical history (an assessment of numerous physical and mental illnesses).

This study leaves several questions unanswered, including which specific supplements people were taking, but it appears that multivitamins work in part by tricking people into thinking they have better health. This conclusion doesn’t discount the role that multivitamins may play in combating actual nutritional deficiencies.

It’s ideal for people to get their nutrients from foods. But if individuals believe their daily multipill is helping them feel like a million bucks and the supplement is safe to take (i.e., no megadoses), they should not necessarily be encouraged to give it up.

See also: Multivitamins Ease Illness Symptoms in Older Adults