This is almost always a lie.
I would like us, as a community to stop perpetuating this lie.
Unless you are vaping straight VG, you can not make this claim. The flavoring of e-juice most commonly is done by food grade FDA approved flavor essences.
These contain sometimes hundred of chemical substances. All that have been approved for consumption, but not studied in vaporization.
Flavoring is a mystery.
To me, this is why I avoid complex flavors altogether. And also the reason why I would never touch custards since they almost exclusively contain Acetoin or Diacetyl.
Education is key here. We need to understand what we're using before we can make big claims about health. Get educated on flavoring. Understand what it is. Some stuff is pretty rank.
But no, most of us vape hundreds of chemical substances.