"Vaping 'stronger e-cigarettes means ex-smokers inhale fewer cancer-causing toxins," reports the Sun.

This is based on a small study of just 20 e-cigarette users. It found those given low-nicotine rather than high-nicotine devices used them more intensely, potentially increasing their exposure to toxins in the vapour.

When using the low-nicotine liquids, people generally felt a greater urge to vape.

They overcompensated for the lower strength by puffing more frequently and for longer, and by increasing the power of their vaping devices when they were able to.

The researchers also tested urine samples from the e-cigarette users for cancer-causing chemicals like formaldehyde.

There was a trend for levels of formaldehyde to be higher when vapers used the low-nicotine e-cigarettes, although this wasn't actually statistically significant.

It's perhaps not surprising that low-strength e-cigarettes were found to be less satisfying than the higher-strength versions, and interesting that the low-strength vapers compensated with their puffing, potentially exposing them to more toxins.

But this was a tiny study that only looked at habitual users of high-nicotine products, who may have found it harder to adapt to low nicotine. The findings can't necessarily be applied to all vapers.

E-cigarettes – of any strength – are believed to be far less harmful than tobacco smoking as they don't produce tar and carbon monoxide. But we don't yet have the full picture on their safety.

If you're trying to quit smoking and want to try e-cigarettes, it may be a good idea not to jump straight to low-nicotine products.

You may also want to read our advice on other treatments you can try to help you stop smoking.

Where did the story come from?

The study was carried out by researchers from London South Bank University, Queen Mary University of London, and other institutions in the UK and US.

It was funded by Cancer Research UK and published in the peer-reviewed journal Addiction.

The lead author has carried out previous research for e-cigarette companies and acted as a consultant for the pharmaceutical industry. Some of her co-authors also have links to the e-cigarette industry.

The Sun generally reports the findings accurately, but is slightly inaccurate in saying "opting for low nicotine e-cigs means they will inhale more cancer-causing toxins", as the difference in urine chemical levels between the groups wasn't statistically significant.

It's also a shame that the Sun didn't highlight the small study size.

What kind of research was this?

This small randomised crossover trial aimed to compare the effects of high- and low-nicotine e-cigarettes on vaping behaviours and exposure to different toxins.

The crossover design means participants act as their own controls, in this case switching between the different types of e-cigarettes in random order during the trial.

The nicotine content of the liquid, the type of device used and the user's puffing behaviour all influenced their nicotine exposure.

Typically, e-cigarette users often choose lower-nicotine devices over time – but if they switch too soon, it may cause them to take compensatory measures like longer puffs or increasing the power of their device.

These compensatory measures may increase the temperature within the device and so increase the breakdown of solvents in the e-liquid to produce more cancer-causing toxins like formaldehyde, acetaldehyde and acrolein.

The crossover design effectively boosts the number of people within the trial, but this nevertheless remains a small study, and the findings can't necessarily be applied to everyone who uses e-cigarettes.

What did the research involve?

The researchers recruited 20 ex-smokers (aged over 18) who'd been daily e-cigarette users for more than 3 months and used liquids with a nicotine concentration of above 12mg/ml (so were used to being exposed to high nicotine levels).

Participants had quit smoking on average 2 years ago.

They sampled 4 e-liquid flavours and chose one to use for the 4-week study.

They were then provided with a device (eVic Supreme, fitted with a tank containing an atomiser) and given 7 bottles of 10ml e-liquid to use for each week of the study.

Each week they switched to a different type of e-cigarette, so over the 4 weeks they had tried a:

low-nicotine (6mg/ml) device set to fixed power

high-nicotine (18mg/ml) device set to fixed power

low-nicotine device with adjustable power

high-nicotine device with adjustable power

The devices recorded the duration and number of puffs. At the start of the study and each week, participants reported their desire to vape, any withdrawal symptoms, and any other positive or negative effects.

They gave breath samples so the researchers could measure carbon monoxide levels to check they hadn't smoked.

Their saliva was analysed for cotinine levels, which were an indication of nicotine intake, and their urine was analysed for formaldehyde and acrolein, which are potentially cancer-causing chemicals formed when the e-liquid breaks down.

What were the basic results?

Those who used the fixed-power low-nicotine devices puffed more deeply and frequently than those using the high-nicotine devices.

Those who used the adjustable low-nicotine devices tended to increase the power of their device to up their intake.

The low-nicotine users also reported a stronger urge to vape, and generally reported withdrawal symptoms more often than high nicotine users, and when using a fixed-power device rather than an adjustable one, although not all changes were statistically significant.

On lab analysis, saliva cotinine (nicotine) levels were higher in the high-nicotine users, as would be expected.

On urine analysis, there was no difference in acrolein levels. Formaldehyde levels were generally higher when using low-strength devices, but this didn't reach statistical significance.

How did the researchers interpret the results?

The researchers concluded: "Use of a lower-nicotine concentration e-liquid may be associated with compensatory behaviour (such as higher number and duration of puffs) and increases in negative [mood], urge to vape, and formaldehyde exposure."

Conclusion

This small study shows that people may take longer and more frequent puffs when using low-nicotine, rather than high-nicotine, e-cigarettes.

But the study has several important limitations to bear in mind. This was a very small study involving just 20 people, all of whom were habitual users of high-strength e-cigarettes.

They may have found it harder adjusting to low-nicotine products, and so may have taken more compensatory measures and reported a greater urge to vape because of this.

Their responses can't necessarily be applied to all e-cigarette users, such as those who have gradually adapted to a lower nicotine intake.

The Sun understandably highlighted the cancer-causing toxin angle. But the levels of these chemicals detected in urine samples weren't significantly different between the low- and high-nicotine products.

This means this study doesn't provide good evidence that using low-nicotine e-cigarettes will expose people to more toxins.

Allowing just 1 week of use for each type of e-cigarette may also not have been enough to give a good indication of the effects.

Another limitation is that although participants weren't aware of the study's aims, they weren't blinded to the nicotine e-liquid concentration, which may have influenced their puffing patterns and reporting.

But these limitations aside, this study suggests that vapers who want to quit smoking may wish to heed the advice given by lead researcher Dr Lynne Dawkins:

"Some vapers might believe that starting out on low nicotine strength is a good thing, but they should be aware that reducing their nicotine concentration is likely to result in the use of more e-liquid. This obviously comes with a financial cost but also possibly with a health cost.

"The results of our study suggest that smokers who want to switch to vaping may be better to start with higher, rather than lower, nicotine levels to reduce compensatory behaviour and the amount of e-liquid used."

The health watchdog NICE states that e-cigarettes are "substantially less harmful to health than smoking but are not risk free". Evidence on e-cigarettes is still being collected, including the long-term effects on health.

Analysis by Bazian

Edited by NHS Website