Smoking one cigarette a day isn't as harmless as some people think. Researchers said that lighting up even once daily may up a person's risk of heart disease and stroke.

The average pack of cigarettes contains 20 sticks, so the researchers thought the risk of heart disease or stroke for those who smoke one stick per day would just be about 5 percent of that of a pack-a-day smoker.

Low Cigarette Consumption, Heart Disease, And Stroke

In the study published in The BMJ on Jan. 24, Allan Hacksaw, of UCL Cancer Institute at University College in London, and colleagues looked at data from 141 studies. It turned out that low-cigarette consumption still significantly ups risk for coronary heart disease and stroke.

The researchers found that in men who smoke one cigarette a day, their risk of developing heart disease is still 46 percent of that of a heavy smoker. The odds for stroke is also high at 41 percent of a heavy smoker's risk. In women, those who light up one stick a day have 31 percent of a pack-a-day smoker's risk of heart disease, and 34 percent of their risk of stroke.

"This probably comes as a surprise to many people. But there are also biological mechanisms that help explain the unexpectedly high risk associated with a low level of smoking," the study authors said.

The authors said that the take-home message for smokers is there is no safe level of smoking. Smokers should quit the habit and not just cut down.

"Smoking only one to five cigarettes per day is associated with a risk of coronary heart disease and stroke that is substantially higher than many health professionals or smokers recognise (as much as half the risk of smoking 20 per day)," the researchers wrote in their study.

The findings can also serve as a warning to young adults who often smoke lesser amount of cigarettes than older adults. Light smoking still carries a high price for health.

"Light smoking, occasional smoking, and smoking fewer cigarettes all carry substantial risk of cardiovascular disease. Only complete cessation is protective and should be emphasised by all prevention measures and policies," wrote Kenneth C Johnson, from the University of Ottawa, in an editorial.

Smoking Down Not Necessarily Useless

Other health experts, however, said that while people who smoke needs to stop their habit, smoking down is not necessarily useless.

"There is more reason to believe that lower cigarette consumption will reduce the risk of chronic lung disease and lung cancer, the other two big causes of early death from smoking," said Paul Aveyard, from the University of Oxford.