I used to have heartburn all the time. Many times a day.
A burning in my chest just above my stomach. I would taste bile and force burps in vain attempts to relieve the pain.
Tums or Rolaids offered temporary relief. OTC reflux meds works better. Milk would offer relief as well, but it was very short lived.
However, when I quit smoking, ALL the heartburn stopped. Just like that.
Now I note that if I'm exposed to heavy smoke, such as in a bar or smokers home for extended periods, I may experience a slight case of heartburn within the next 6-12 hours depending on what I eat.
I believe something in tobacco smoke was loosening the valve muscle between my stomach and esophagus.
I know it isn't nicotine, because nicotine gum and/or the patch did not give me heartburn.