You know those people who take a million dietary supplements a day and act kind of healthier-than-thou about it?

A study to be published in an upcoming issue of Psychological Science, a journal of the Association for Psychological Science, might take some wind out of their sails.

In a set of small but clever experiments, researchers from three educational institutions in Taiwan worked to examine whether people who take dietary supplements might treat that behavior as a kind of safety net that entitled them to indulge in foods and activities that aren’t so conducive to good health.

Researchers divided a pool of 82 people into one group that thought it was being given a vitamin pill and another that thought it was receiving placebo. (In truth, all participants were given placebos.) Participants were asked about their typical daily supplement use. They were also administered surveys to determine the extent to which they were inclined to take part in risky leisure-time activities such as casual sex, wild parties and excessive drinking. Another survey ascertained the extent to which participants felt vulnerable or invulnerable to harm, injury or disease.

The people who thought they were on supplements consistently were more likely to say they’d engage in the risky behaviors; those who had reported using the most supplements outside the experiment were even more likely than those who typically took fewer or none. They also were far more likely to report feeling invulnerable to harm. The results were about the same for males and females.

After they completed their surveys, the students were given food vouchers to use on either a buffet meal or an organic one. Another survey they completed indicated that they perceived the buffet meal to be less healthful than the organic one. Still, the supplement users largely opted for the buffet.

The supposed supplement takers also reported less inclination toward engaging in healthful leisure-time behaviors than the supplement-free folks. But would those expressions of inclination play out in real life?

The researchers tested that on a different group of 68 undergraduate students whom they divided into supplement and non-supplement (in reality, all placebo) groups. They told them they were helping to test pedometers. Each was given a pedometer to wear for an hour and then return to one of two familiar sites on campus. One of the sites was twice as distant as the other. They were allowed to walk wherever they wanted when wearing the pedometer, so long as they returned it to one of those sites in an hour. Before they were set loose, they were asked to read a paper that explained the health benefits of walking.

By now you can guess what went down. The supplement takers walked far fewer steps in total than the others, and they overwhelmingly chose to return their pedometers to the closer location. Those results were independent of gender and of BMI. Again, the results were amplified by participants’ customary supplement use outside the experiment. The more supplements they used, the less likely they were to walk any extra steps.

All of this adds up to a pattern, the study suggests. People who take supplements may feel that behavior gives them license to enjoy other activities without regard to health; they may feel that taking their pill is enough of a contribution to make to healthful living. Another way to look at it, the researchers explain, could be that people who make progress toward a goal (in this case, better health) via one means may feel they don’t have to exert much effort in other means of attaining that goal.

The study’s introduction rightly points out that dietary supplement use continues to rise, despite a dearth of evidence that they do anyone any good. The experiments expose a potential hypocrisy among supplement users. Beyond that, they suggest that efforts to help people understand a healthful diet and plenty of exercise are more likely than dietary supplements to do a body good may be in order.

Do you take dietary supplements — even a daily multivitamin? Do you feel as though doing so allows you some wiggle room in your diet and exercise regimen?