I found this fascinating quote today:

I don’t know about you, but as I get older, I find that more foods tend to upset my stomach and/or give me heartburn.   What is heartburn?  It’s when the acid from your stomach, which is there to digest your food, makes its way up into the esophagus and sometimes the throat.  Usually heartburn is characterized by a “churning stomach”, nausea, gas, a burning feeling in the chest and a sour taste in the mouth.  Certainly, you may not experience all these symptoms, but I’m sure you know when you have heartburn!homemade-remedies.net, Homemade Remedies for Heartburn, Mar 2009

You should read the whole article.