Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

Smoking just one single cigarette a day can significantly raise your risk of heart disease and stroke, researchers say in a new report.

While it’s better to cut down than to smoke heavily, the study contradicts the common belief that cutting way down also reduces risk quite a bit.

For men, smoking one cigarette a day on average raised the risk of heart disease by 48 percent over a non-smoker. Matt Cardy / Getty Images file

In fact, cutting back from a pack a day just one cigarette a day only lowers the heart health risks a little bit, Allan Hackshaw at the UCL Cancer Institute at University College London and colleagues found.

Their findings could be important as federal regulators in the U.S. consider how to regulate e-cigarettes and new “heat not burn” cigarette products. Makers tout them as ways to help smokers cut back and lower their health risks.

“We have shown that a large proportion of the risk of coronary heart disease and stroke comes from smoking only a few cigarettes,” Hackshaw’s team wrote in the British Medical Journal’s online publication The BMJ.

“This has important consequences for smokers who believe that light smoking carries little or no harm.”

Hackshaw’s team went back through all the credible health studies they could find dating back to 1946. They looked at how many cigarettes people reported smoking and looked at what happened to those smokers.

Related: Panel considers heat-not-burn cigarettes

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

For men, smoking one cigarette a day on average raised the risk of heart disease by 48 percent over a non-smoker, while smoking 20 cigarettes a day doubled the risk.

For a woman the risks were even higher. Smoking one cigarette a day raised heart disease risk for women by 57 percent and 20 cigarettes a day raised the risk 2.8 times.

“This has important consequences for smokers who believe that light smoking carries little or no harm.”

Men who smoked one cigarette per day did not have 1/20th the risk — 5 percent — compared to a pack-a-day smoker, but instead had 46 percent of the extra risk of heart disease.

"No safe level of smoking exists for cardiovascular disease,” Hackshaw’s team concluded.

“Smokers should quit instead of cutting down, using appropriate cessation aids if needed, to significantly reduce their risk of these two common major disorders."

Heart disease is the leading cause of death in the U.S. and most developed countries, and smoking causes one in three heart disease deaths, the U.S. Surgeon-General says. About a billion people around the world smoke.

“The take-home message for smokers is that any exposure to cigarette smoke is too much,” Kenneth Johnson, an epidemiologist at the University of Ottawa who was not involved in the research, wrote in an editorial.

“New tobacco products, such as e-cigarettes and heat-not-burn cigarettes, may carry substantial risk for heart disease and stroke,” Johnson added.

“We cannot afford to wait several more decades to document the illness, disability, and deaths caused by new recreational tobacco and nicotine products. Regulatory approval of these products should be withheld.”

It is still worth trying to cut back, said Paul Aveyard of the University of Oxford, who also was not involved in the study.

RELATED: E-cigarettes may be safer, but they also hook kids

“This well-conducted study confirms what many epidemiologists have suspected but few among the public have: light smoking creates a substantial risk for heart disease and stroke. The implication is obvious —anyone who smokes should stop,” Aveyard said.

“However, it would be wrong to conclude from this study that cutting down smoking is 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, but whether this occurs or not is less clear and the study team did not look at this.”

A new report released this week from the National Academies of Science, Engineering and Medicine found little evidence about the health risks of e-cigarettes but said they might be useful if used to help smokers cut down or quit.

And a Food and Drug Administration Advisory panel is meeting this week to decide if Philip Morris can market its new heat-not-burn cigarette product IQOS in the U.S. as a safer alternative to cigarettes.