Previous studies have shown damages of the arterial function among people who smoke regularly, said Kevin McCully, the co-author of the study, published in the early online edition of the journal Ultrasound in Medicine and Biology.

However, what's surprising about his finding is that even occasional smoking (less than a pack a week) could impair people's arteries, McCully said in a statement on Tuesday.

The study used ultrasound to measure how the arteries of young, healthy adults respond to changes in blood flow and it showed that the arteries of occasional smokers were 36 percent less responsive to changes in blood flow than the non-smokers.

After the occasional smokers underwent their initial test, they smoked two cigarettes and had their arteries re-examined. The researchers found that smoking dropped their arterial responsiveness by another 24 percent compared to their conditions before they smoked.

The healthier an artery is, the more responsive it is to changes in blood flow. A reduction in responsiveness, known as impaired flow-mediated dilation, is an early sign of arterial damage that often foreshadows cardiovascular disease.

McCully said that the study used a relatively small sample size and further research is needed to determine if the impaired arterial function is a relatively short-term phenomenon or could cause long-term damage.

In light of his findings, McCully said, people should not assume that smoking occasionally allows them to avoid the harmful effects of tobacco.