Switching to Juul e-cigarettes reduces smokers' risk to cigarette toxins at similar levels to quitting entirely, according to results from a clinical trial presented at a conference Saturday.

Researchers found switching entirely to Juul reduced smokers' exposure to biomarkers, or signals of exposure to cigarette smoking, 99.6 percent as much as abstaining entirely from cigarettes. Juul presented the study, conducted by outside lab Celerion, Saturday at the Society for Research on Nicotine and Tobacco's annual meeting.

These are the first clinical data Juul have presented. Juul is conducting several studies to prepare for an eventual application it and other e-cigarettes manufacturers will need to file with the Food and Drug Administration by 2022. The data could help bolster Juul's credibility as a smoking cessation tool for adults while the company fends off criticism that it has fueled an epidemic of teen e-cigarette use.

"We're committed to durable, clinical research that's published in peer-reviewed journals and presented at major conferences," Josh Vose, Juul's vice president of medical and clinical affairs, said in an interview.

Doctors have been wary of recommending people use e-cigarettes as a way to wean themselves off conventional cigarettes because there hasn't been long-term research on their effects. Supporters say e-cigarettes give smokers a way to keep getting their nicotine fix without all the harm that comes with cigarettes, making them an attractive and realistic option.

A study published last month in the New England Journal of Medicine showed e-cigarettes were nearly twice as effective as nicotine patches, gums and similar therapies in helping people to stop smoking. However, an accompanying editorial penned by professors from the Boston University School of Medicine urged doctors to use caution when recommending e-cigarettes for smoking cessation.

In the study presented Saturday, researchers tested 90 adult smokers for nine biomarkers associated with combustible cigarette smoke. They asked participants to abstain from smoking for 12 hours before they measured the baseline.

They then divided participants into six groups, with one group instructed to abstain altogether, one group assigned to smoke normally and the other four groups to vape different flavors of Juul's nicotine liquids. After five days, they measured the biomarkers in participants' urine and blood and compared them with the baseline.

In the abstinence group, the biomakers were reduced by an aggregate of 85.3 percent, compared with an 85 percent reduction in the groups that used Juul. That equals a 99.6 percent relative reduction of biomarkers, or risk to cigarette smoking, among the Juul group compared to people who quit smoking entirely.

In other words, the study found that using Juul was virtually as effective in reducing one's risk to cigarette smoking as quitting entirely.

"What's important to take away is when we statistically tested these for difference, it was found to be not statistically different," Vose said.

Juul's e-cigarettes contain nicotine, the substance that makes cigarettes highly addictive. Researchers measured the change in participants' nicotine levels at day five compared to baseline. The abstinence group saw a 96.4 percent decrease and the usual cigarette group saw a 26.1 percent increase.

Among participants using Juul, the results varied what flavor they were using. People vaping the Virginia Tobacco flavor saw a 6.5 percent decrease in nicotine levels, while people puffing on mango saw a 25.3 percent increase.

Vose said this study was not designed to measure how different flavors affected nicotine consumption. Juul just completed the first wave of another study aiming to answer that question, he said.

The FDA has said nicotine products exist on a continuum of risk, where combustible cigarettes are the most deadly and nicotine patches, gums and lozenges are the least harmful. E-cigarettes fall somewhere in between, though it's still not entirely clear where.

E-cigarettes are thought to be less harmful than conventional cigarettes because they give people their nicotine fix without combustion, or the chemical process that occurs when tobacco burns and is responsible for releasing deadly toxins. The National Academies of Sciences, Engineering, and Medicine recognizes this, although it warns e-cigarettes may pose their own long-term health risks.

One limitation in the study is that it only measured people who switched entirely to Juul, not people who used Juul in conjunction with cigarettes. Critics often argue that people sometimes use both products simultaneously, dampening any benefits they may receive from switching. Vose said Juul studied only single use because that's what the company ideally wants, for people to switch entirely.

Juul has seven completed and ongoing clinical trials, according to a public database of clinical trials.