The American Heart Association’s first policy statement on electronic cigarettes backs them as a last resort to help smokers quit. The American Cancer Society has no formal policy but quietly took a similar stance in May.

Both groups express great concern about these popular nicotine-vapor products and urge more regulation, especially to keep them away from youth. They also stress that proven smoking cessation methods should always be tried first.

But if those fail, “it is reasonable to have a conversation” about e-cigarettes, said the Heart Association’s president, Dr. Elliott Antman. The Cancer Society said e-cigarettes “may be a reasonable option” for people who could not quit after trying counseling and approved methods, such as nicotine patches.

Neither group recommends e-cigarettes for smoking cessation, and makers of the devices do not market them that way.

E-cigarettes are battery-powered devices that vaporize nicotine. They’ve been sold in the U.S. since 2007 and now have millions of users worldwide and nearly $2 billion in annual sales. They contain less toxic substances than traditional cigarettes do, but little is known about their health effects.

Whether they help or hurt anti-smoking efforts is hotly debated. Some say they encourage smoking by letting people maintain their habit in places where cigarettes are banned. Others say they are a less risky way to satisfy a nicotine craving for people who want to quit, similar to how methadone is used to curb heroin abuse.

This concept, called harm reduction, “is probably the most important and the most contentious issue that the tobacco community is dealing with right now,” said Tom Glynn, who recently retired as the Cancer Society’s top scientist on the e-cigarette issue.

No solid evidence shows that e-cigarettes aid smoking cessation unlike the nicotine patches, gums and medications approved now.

“We need hard-nosed regulation for e-cigarettes and we need more research,” Glynn said, but mostly, “we need to have people stop smoking combustible cigarettes.”

The Heart Association stressed the toll — 20 million deaths in the U.S. alone from tobacco use over the last 50 years.

“We are fiercely committed to preventing the tobacco industry from addicting another generation of smokers,” says a statement from the association’s chief executive, Nancy Brown.

Besides nicotine — “a highly addictive chemical no matter what form it comes in” — some e-cigarettes form other products such as formaldehyde, a carcinogen, Antman said.

“There are many things we see as dark clouds on the horizon” about e-cigarettes’ effects on blood vessels and secondhand exposure, especially to pregnant women, he said.

The Heart Association policy was published Monday in its journal Circulation. The Cancer Society statement was in a patient page accompanying an article on e-cigarettes in the group’s journal for doctors.

In April, the federal Food and Drug Administration proposed treating e-cigarettes as tobacco products with rules such as a ban on sales to those under 18 and warning labels. Earlier this month, attorneys general from more than two dozen states sent a letter asking the agency to also ban flavors — more than 7,000 are available. The American Medical Association also has urged a ban on kid-appealing flavors and other moves to keep e-cigarettes out of young hands.

The Campaign for Tobacco-Free Kids has pushed for regulation and does not embrace the view that e-cigarettes may have a role in smoking cessation.

“Quitting smoking is hard,” and people often try several times before they succeed, says a statement from a spokesman for the group, Vince Willmore. If they can’t, doctors should work with them to come up with a plan, but the focus should be on approved therapies, he wrote.

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