Dietary Supplements Fuel Bad Health Habits
Credit: Steve Knight (stevekrh19)

People who take dietary supplements may ironically make worse health choices than those who don't, a new study says.

The results suggest taking these supplements leads people to believe they are immune to the hazards of eating junk food or getting too little exercise, the researchers say. In other words, taking a pill entitles them to slack off with regard to other health-promoting behaviors.

Participants were more likely to choose a buffet meal over an organic meal, and more likely to avoid additional exercise, if they had previously taken a dietary supplement than if they had consumed a placebo.

"People who rely on dietary supplement use for health protection may pay a hidden price, the curse of licensed self-indulgence," said study researcher Wen-Bin Chiou, of National Sun Yat-Sen University in Taiwan. People should be aware that such a change in behavior can occur and closely monitor their actions so that they don't fall victim to this sense of entitlement, Chiou said.

It's also important to note there is no evidence dietary supplements – including vitamins -- actually provide health benefits.

Wrong food choice

Chiou and colleagues conducted two experiments.

In the first, 82 Taiwanese subjects -- about half male, half female with an average age of 30 -- were randomly assigned to receive a multivitamin or a placebo. Unbeknownst to the subjects, both pills were placebos.

Participants were asked to rate the desirability of several hedonic behaviors, including excessive drinking and wild parties, as well as several leisure activities, such as yoga and swimming.

In addition, they answered questions about their sense of vulnerability -- or lack thereof -- including: "Nothing can harm me;" "Special problems, such as getting an illness or disease, are not likely to happen to me;" and "I'm a fragile person."

Afterward, subjects were offered a coupon for a free meal: either a buffet or an organic meal. Previous studies had indicated individuals perceive buffet meals as less healthy than organic meals.

Seventy-one percent of individuals who thought they took a multivitamin chose the buffet meal compared with just 44 percent of those who took a placebo. Individuals in the multivitamin group also expressed more desire to engage in hedonic activities and reported greater feelings of invulnerability.

Less walking

In the second experiment, 68 undergraduates at a Taiwanese university were given placebos, with half of the group taking what they believed to be a multivitamin. They were then told they had to return a pedometer to another experimenter on campus. They could walk to a location either 600 meters or 12,000 meters away. Participants also read a medical report discussing the benefits of walking for health.

Sixty-eight percent of those who thought they took a multivitamin chose to walk to the nearer location compared with  41 percent who took the placebo.

"Ironically and interestingly, participants taking dietary supplements walked less, even after an explicit  reminder about the health benefits of walking," the researchers write.

These experiments were conducted in a laboratory setting, so more research is needed to determine if the results apply to the real world and to the general population.

The study is published in an upcoming issue of the journal Psychological Science.

Pass it on: Those who take a multivitamin may feel they don't need to act healthy in other ways, such as getting additional exercise.

Follow MyHealthNewsDaily staff writer Rachael Rettner on Twitter @RachaelRettner.

This story was provided by MyHealthNewsDaily, a sister site to LiveScience.