How safe are electronic cigarettes?

Q: After smoking for more than 15 years, I finally quit eight months ago. I think I'm past the physical cravings, but I still miss cigarettes. I recently heard about electronic cigarettes, which vaporize nicotine and don't create actual smoke. Are they a safer alternative to cigarettes?

A: There is no question that cigarette withdrawal symptoms are frustrating. They are the reason most people do not succeed at quitting.

Craving cigarettes is one of the hardest symptoms to deal with for many people. But whatever you do, don't give in to the lure. If you do, all your hard work and health gains will go up in smoke.

By now, you're probably familiar with the ways quitting can improve your health, but let's review:

• While it's never too late to quit smoking, the sooner in life you quit, the greater your benefit. Quitting can reduce your risk of disease and help you live longer. This is true even if it is late in the game, no matter how long or heavily you have smoked. Ex-smokers have lower rates of heart disease, stroke, cancer and lung diseases than people who continue to smoke.

• Even if you already have a smoking-related disease, your prospects will improve if you quit smoking. For example, smokers who stop after a heart attack are less likely to have another attack or to die of heart disease. And although there is no cure for chronic obstructive pulmonary disease (COPD), quitting smoking can slow down lung damage related to the disease and improve symptoms.

Even smokers who quit after a diagnosis of lung cancer will benefit - they have a lower risk of recurrent lung cancer, getting another type of cancer and dying from cancer.

• Should you find yourself needing surgery of any kind, a smoke-free body is better equipped to heal and less likely to suffer complications. And when you quit smoking, you can look forward to a better quality of life and a sense of pride in your accomplishment. You'll also save money by not having to buy cigarettes or pay for the consequences of poorer health.

• Quitting also ends the secondhand smoke that a smoker's family unavoidably breathes, and sets a good example for children, who are less likely to smoke if their parents don't.

Now back to your question. Are electronic cigarettes a safe alternative to regular cigarettes? The short answer is that nobody knows if electronic cigarettes, also marketed as e-cigarettes, are safe. That's because e-cigarette makers have not submitted their products for FDA approval, which would require proof of safety and efficacy. Still, preliminary studies from New Zealand, Greece and the FDA itself raise concerns.

E-cigarettes come in a variety of shapes. Some look like cigarettes, pipes or cigars. Others are disguised as pens or other socially acceptable items.

Whatever their shape, they all are built around a rechargeable battery-operated heating element, a replaceable cartridge that contains nicotine and other chemicals, and an atomizer that converts the chemicals into an inhalable vapor.

There are three reasons to worry about e-cigarettes. First, the dose of nicotine delivered with each puff may vary substantially. An FDA analysis recorded nicotine doses between 26.8 and 43.2 micrograms per puff. It also detected nicotine in all the products labeled as nicotine-free.

Second, the e-cigarettes all deliver an array of other chemicals, including diethylene glycol (a highly toxic substance), various nitrosamines (powerful carcinogens found in tobacco), and at least four other chemicals suspected of being harmful to humans.

Third, by simulating the cigarette experience, e-cigarettes might reactivate the habit in ex-smokers. They could also be a gateway into tobacco abuse for young people who are not yet hooked.

We need scientific studies of e-cigarettes. Until then, it's caveat emptor: Buyer beware!

And for an ex-smoker on the brink of relapse, it's also important to remember that there are a variety of well-studied, FDA-approved nicotine replacement products. Each is vastly preferable to smoking - and to electronic cigarettes.

Submit questions to harvard_adviser@hms.harvard.edu.