Popping a vitamin in the morning leads to unhealthy decisions later in the day, researchers say. As long as people believe they are swallowing something healthful, a false sense of security and likelihood of risky behavior follows, two new studies indicate.

Study participants in Taiwan were given sugar pills and then told either that the pills were vitamins or placebos. Those who believed they were taking vitamins reported greater feelings of invulnerability, and were more likely to engage in casual sex, sunbathing, binge drinking, cigarette smoking, and overeating. They were also less inclined to exercise.

The results were no surprise to the director of sports nutrition at the University of Pittsburgh Medical Center.

“You see this even in professional athletes,” Leslie Bonci said. “Sometimes they attribute to supplements superhuman properties that let them off the hook for healthy behaviors.”

The studies were published in the journal Psychological Science and the journal Addiction.

About half of the U.S. population takes daily supplements, including 70 percent of adults over the age of 70.