No question, smoking causes cancer, and quitting is really hard for some people.

But the growing popularity of e-cigarettes has some experts wondering if these cigarette substitutes are safer than the original product they were meant to replace.

While nicotine patches and gum can stop some cravings, e-cigarettes help substitute the behavior of putting a cigarette to the lips and inhaling -- which according to some, improves the chances a person will quit the real thing.

Smoker Roger Izaguirre struggled to kick the smoking habit.

"Every day I would wake up, I would be out of breath," said Izaguirre. "I didn't have any energy."

When conventional smoking cessation methods failed him, Izaguirre tried an e-cigarette device.

"I had a friend who was telling me, 'Try this.' I was like, 'I don't know, man, what's this vapor stuff, it's not cigarettes.'"

'Vaping' is growing trend among smokers

Vaping, as it's called, can be done with various e-cigarette gadgets, including some that resemble an actual cigarette.

A lithium battery heats and vaporizes a liquid composed of propylene glycol and glycerin, mixed with flavoring and nicotine. There is no tobacco used or burned so the lung cancer risk is essentially eliminated.

"I think there is a role for something like an electronic cigarette both as a safer alternative to conventional cigarettes and potentially also to help patients quit when other forms of smoking cessation don't work," said Dr. Bruno Digiovine, a lung specialist at Henry Ford Hospital in Detroit.

Research suggests electronic cigarettes do work well to help people quit smoking. A recent study compared nicotine patches to e-cigarettes and found 7.3 percent of e-cigarette users had quit smoking after 6 months compared to 5.8 percent of patch users.

Many e-cigarette users actually prefer them to their old tobacco habit. Christina Larson of Royal Oak, Mich., used to smoke cigarettes, but after trying vaping, the choice was clear.

"I like it a lot better than smoking 'cause I've gotten my freedom back," said Larson. "I'd been vaping for about a week, and I decided, I'm going to have a cigarette and I went and just smoked it and it was, it just smelled bad."

The "juice" as it's called, used to make the vapor, comes in different amounts of nicotine.

"Some of these juices that you can get have no nicotine in it at all so you're just vaping water vapor," said Larson.

The juice is made in seemingly infinite flavors like chocolate or strawberry shortcake. That has critics concerned that these flavors are enticing to kids.

"What we've seen is rapid increase in e-cigarette use in both middle schoolers and high schoolers - in fact it doubled in just a year," said CDC Director Dr. Tom Frieden.

A new report from the CDC found that in 2012, 10 percent of high schoolers had tried an e-cigarette. All together, more than 1.78 million middle and high school students had tried e-cigarettes, some becoming regular users. That's raised concern e-cigarettes might be an entry point for tobacco use.

And there are other concerns.

"The problem is that the FDA has done a number of studies, and they have found that the vapor does contain some cancer causing chemicals and they have found some toxins in them," said Dr. Mark Block, a lung surgeon.

Most people aren't pushing for a ban, but they are looking for sensible regulation by the FDA. The concern isn't limited to the United States. The United Kingdom will begin regulating e-cigarettes as medicinal in 2016.

E-cigarettes not 'safe' but safer

"I don't think we can say that they're safe," said Digiovine. "I think we can just say they seem to be a safer alternative to conventional cigarettes for those patients who seem to be hopelessly addicted to cigarettes."

The interesting conundrum is, while e-cigarettes were originally developed to assist smokers kicking the habit, and they are a much better alternative to smoking tobacco, e-cigarettes have taken on a new independent life as a nicotine delivery system. Nicotine, like caffeine and alcohol, does produce dependence. However, nicotine by itself can be used long-term like caffeine and alcohol, although there are side effects.

Doctors like Digiovine wonder what will be discovered in time.

"We just don't have the data," said Digiovine. "I would be concerned that teenagers of today in 40 years will look back at us and say, 'Well if you'd only told us that electronic cigarettes were so dangerous, I never would have started.'"

But smokers that have made the switch are not looking back.

"Going up the stairs, I don't get out of breath, running with my kids, everything, I just feel a hundred times better," said Izaguirre.

"It's everything I loved about smoking without everything I hated about smoking," said Larson. "I don't see myself ever going back to smoking cigarettes."