It's the speed with which vaping changes the body

(Newser)
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A new study casts a shadow over electronic cigarettes. Researchers at the University of Pennsylvania stated that participants who inhaled only vape juice – no nicotine or flavor – had undergone temporary changes in their cardiovascular system, wired reports. The study found that the 31 cerebral, cardiac and leg arteries were contracted by more than 30%, which reduced the flow of oxygen in the blood by 20%. The arteries also stiffened, a symptom already linked to cardiovascular conditions such as stroke and hypertension. "The results of our study refute the idea that e-cigarette vaping is harmless," said study leader Felix Wehrli.

But Juul, who controls over 70% of the US vaping market, pointed to a possible limitation: participants inhaled 16 times for three seconds each. The San Francisco-based company has described it as a "forced-breathing regime whose volume is unrealistic and whose time between two puffs is very limited." And it's not just vaping that causes such reactions: caffeine and exercise also temporarily affect vascular activity. But after dozens of people have suffered from vaping-related respiratory illnesses and another study has triggered alarm signals about vape juice, caution may be the best choice. "There is no doubt in my mind that vaping is safer than conventional smoking," said a doctor at CNN, "but that does not mean it's safe." (Read more stories about vaping.)