I can't fit it all here, but here is a good article on it too. link
I am an herbalist, I am many of others have been drinking greeen tea (Camellia sinensis) for years, I have never seen or heard of the issues you have spoken about.
Depending on where the mint is derived from, Peppernint or Mint, both in the mint family if they are natural, are Peppermint is a decongestant, cooling, fragrant and bitter herb that is anti-spasmodic, diaphoretic, digestive, antiseptic and slightly anesthetic.
Used to treat morning sickness, nausea, and spastic complaints of the gastrointestinal tract, gallbladder, bile ducts, dyspepsia, flatulence, intestinal colic, flatulence, gastritis and enteritis.
It is furthermore used for indigestion, cramping, stomach ulcers, spastic colon, irritable bowel syndrome and is also used for its stimulant properties.
It can have a powerful stimulant effect on the body and also positively influence the mind and emotions.
Externally it is used to ease bronchial and upper respiratory tract infections, sinusitis, itching skin, burns, ringworm, neuralgia, rheumatism and to ward off insects.
So it will help stomach problems versus cause them. But if you have issues, everybodies systems are different, discomfort will be the symptom, if you have issues, stop using it, but if not, your okay.
That is a good site on info of all herbs. You might need it for future use about something.