A recent study revealed that smokers who take multivitamins actually make up for their healthy habit by smoking more. Psychologists call this the licensing effect, which happens when someone makes a good choice which later enables them to make a bad choice such as, when a person feels 'entitled' to a weekend binge drinking by avoiding alcohol all week. In this case, smokers believe that by taking multivitamins it will reduce the risk of cancer and permit them to smoke more. No evidence indicates that multivitamins protect against cancer.

Published online today in the journal Addiction, the study describes two experiments conducted by the authors.

The first experiment - 74 daily smokers who believed they were taking part in a health-food test were given a placebo, half were told they had taken a Vitamin C supplement. The smokers then participated in a one-hour unrelated survey, during which they could smoke. The people who believed they had taken Vitamin C smoked almost twice as much and their invulnerability was reported higher, than the control group who knew they had taken a placebo.

The second experiment - an extended version of the first, took 80 participants from a larger community. This time half were told they were taking a multivitamin supplement. The one-hour survey contained questions about attitudes to multivitamins. Once again those who believed they had taken a multivitamin smoked more than the control group. However, smokers with positive attitudes toward multivitamins experienced a rise in perceived invulnerability, and smoked even more than those who were not as enthusiastic, researchers discovered.

Smokers who are health-conscious and take multivitamins may activate important but false beliefs that they are immune to major health hazards associated with smoking, leading them to smoke more and increase their overall health risk.

Wen-Bin Chiou lead author said:

"Smokers who take dietary supplements can fool themselves into thinking they are protected against cancer and other diseases. Reminding health conscious smokers that multivitamins don't prevent cancer may help them control their smoking or even encourage them to stop."

Grace Rattue