E-cigarettes, devices that give you a nicotine-hit by heating up a liquid which you then inhale, have become all the rage. But is the concern about them justified, asks Michael Mosley.

A few years ago they were a rarity, but now there are nearly three million e-cigarettes out there. Many people think that they are as bad for you as normal cigarettes. But are they?

I've recently spent a couple of months making a documentary about e-cigarettes, trying to find out truth behind the headlines. I took up heavy vaping (that's what you do when you inhale vapour from an e-cigarettes). I have never smoked anything before and I wanted to see what effects inhaling nicotine in the form of an e-cig would have on a non-smoker. The results surprised me.

Everyone knows that smoking is bad for you and can lead to lung cancer. It also increases your risk of dying from a range of other conditions including heart attack, stroke and dementia. If you're a man you might like to know (but then again you might not) that smoking is one of the main causes of impotence.

Fans of e-cigarettes say vaping can reduce the burden of smoking either by making it easier for smokers to quit or by providing them with a safer way for them to get a nicotine hit.

Image caption Michael Mosley and Hon Lik, the inventor of the e-cigarette

Critics, however, say that we are gambling with a technology we don't understand and that there is no convincing evidence that e-cigarettes help people quit smoking. It may even encourage non-smokers to start.

Some countries have warily embraced e-cigarettes, while others have effectively banned them.

The UK has so far adopted a liberal approach, but on Friday new European legislation will come into force which will limit the size of refills and the nicotine content of the fluids. Vaping will become more restricted.

Find out more

Horizon: E-cigarettes - miracle or menace? is on BBC Two on Sunday 22 May or catch up later via iplayeriPlayer

So, who's right? Are e-cigarettes one of the greatest public health measures ever invented, with the potential to save millions of lives, or are they just another cunning way to keep us hooked on nicotine? I was keen to find out.

Well the scientific consensus is that vaping, at least in the short term, is a lot safer than conventional smoking. A recent study for Public Health England concluded that e-cigarettes are 95% less harmful than normal cigarettes.

To be honest when I took up vaping I wasn't that worried about the short term health effects. What I was far more concerned about was getting hooked on nicotine. Yet as the weeks went by and I puffed away, nothing happened. When I leapt out of bed I didn't feel a longing to reach for my machine. If anything I found it a bit of a chore.

Chatting to experts I discovered, to my considerable surprise, that although cigarettes are highly addictive, nicotine alone may not be. Although no-one knows for sure, research in animals suggests that nicotine is far more addictive when delivered in combination with the other chemicals found in regular cigarettes.

And nicotine in its pure form may have an upside. There's evidence it can help patients with Alzheimer's and Parkinson's disease.

The National Institute on Aging in the US has recently funded a trial of 300 patients with mild cognitive impairment (a precursor to Alzheimer's). The patients, none of whom are smokers, will be randomly allocated to either nicotine patches or placebo patches. Over the next few years they will have regular health checks, as well as memory and cognition tests.

Image caption Everybody agrees that smoking is bad for you

A similar, smaller study, published in 2012, found that non-smokers given nicotine patches saw improvements in memory, attention and reaction times.

But before you start slapping on the patches or firing up an e-cig you should be aware that though nicotine may help people who already have impaired memory, there's no evidence it will help the rest of us. Although I was tested before and after doing a month of heavy vaping, the nicotine didn't enhance my brain, apart from a small improvement in my fine motor skills.

But the main health justification for e-cigarettes is that they can help those who are keen to quit smoking tobacco, quit. So do they?

There have been very few randomised controlled trials, but the ones that have been done suggest it does.

When Horizon conducted a small study where we randomly allocated a group of hardcore smokers to either e-cigs, nicotine patches or simply giving up (going cold turkey), we found the vapers and those who slapped on the patches were far more successful at abandoning their cigarettes.

E-cigs are not risk free and after a month of heavy vaping there were signs of increased inflammation in my lungs (which rapidly reversed when I stopped). Nonetheless I think that for smokers e-cigarettes could prove to be a game changer.

There is a huge amount at stake. A billion people worldwide spend around £500bn a year on cigarettes and around half of them will die of smoking related diseases. In the UK alone smoking kills around 100,000 a year. Anything which gets people off cigarettes is going to save a lot of lives.

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