The main ingredient of coffee is caffeine? Hmm, not according to
http://www.douwe-egberts.co.uk/uk/Retail/TheWorldOfCoffee/CoffeeFAQ/ , which states:
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"Normal coffee beans contain between 0.8 percent and 2.5 percent caffeine depending on origin and variety
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I've never heard of coffee helping heartburn, rather, that it causes/aggravates the situation. I have acid reflux and have had to limit my intake. See the national institute of health's page on heartburn and look for coffe under foods to avoid:
http://www.nlm.nih.gov/medlineplus/ency/article/003114.htm.
I'm by no means a chemist/biologist, but if I remember right from reading the directions that came with my Prilosec (thinking hard about it, it may have been a journal somewhere), caffeine/coffee can stimulate the proton pump to secrete more acid, backing it up into the esophagus.
Here's a quick Google result (
http://ezinearticles.com/?Heartburn-and-Coffee:-Break-the-Connection&id=86689) By no means a scholarly source, but I have read this several time before in medical literature
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What links heartburn and coffee? The contents of the human stomach are naturally acidic, so that is normal. You don't really feel that acidity as long as things are in control. And that acidity is actually necessary for the proper digestion of food. It is when that acidity grows to abnormal levels and rises from the stomach into the food pipe, that you experience heartburn.
There are many substances that may cause this excess of acidity by irritating the stomach. And among the many kinds of stomach irritants, caffeine is one of the most potent. It stimulates the stomach into producing more acid than normal. This is what connects heartburn and coffee. And this is why doctors advise against coffee for chronic patients of acid indigestion.
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