Espresso, French roast, and other dark-roasted coffee are not harmful for the tummy as was previously believed because these roasts contain a substance that tells the stomach to reduce production of acid, according to a study.

And people who resist from enjoying that much-desired morning cup of coffee, because of fear of stomach irritation can also take a sigh of relief because scientists have discovered the culprits behind that heartburn and stomach pain in every cup.

The research could lead to a new generation of stomach-friendly brews with the rich taste and aroma of regular coffee, said the scientists.

"This discovery is going to help a lot of people who suffer from coffee sensitivity. As coffee-lovers, we're very excited about this research," said Dr. Veronika Somoza from the University of Vienna in Austria, and Dr. Thomas Hofmann, from the Technische Universitat Munchen in Germany, who conducted the study.

Doctors think that chemicals in coffee cause the stomach to overproduce acid, while some coffee drinkers take antacids or drink decaffeinated coffee in an effort to reduce this effect, while others turn to a small but growing number of specialty coffee brews marketed as stomach friendly.

Somoza said that the processes used to produce stomach-friendly coffee also could reduce the amount of healthful substances in the coffee, including some that scientists have linked to benefits such as protection against diabetes and heart disease.

In addition, the processing can affect the robust taste and smell of coffee.

To study the irritants in coffee, the scientists exposed cultures of human stomach cells to a variety of different coffee preparations, including regular, dark-roast, mild, decaffeinated, and stomach-friendly.

They identified several substances that appeared to trigger chemical changes associated with increased acid production.

These substances include caffeine, catechols, and other ingredients.

"Our data show, for the first time, that caffeine, catechols and N-alkanoly-5-hydroxytryptamides are those coffee components that stimulate molecular mechanisms of stomach acid secretion in human stomach cells. Most of them are indeed removed by steam or solvent treatment of the raw coffee bean. We found out there's no single, key irritant. It is a mixture of compounds that seem to cause the irritant effect of coffee," said Somoza.

The scientists unexpectedly found that one of the coffee components, N-methylpyridium (NMP), seems to block the ability of the stomach cells to produce hydrochloric acid and could provide a way to reduce or avoid stomach irritation.

Since NMP is generated only upon roasting and not found in raw coffee beans, darker-roasted coffees contain higher amounts of this stomach-friendly coffee ingredient.

Dark- roasted coffee can potentially contain up to twice as much of the ingredient as light-roasted coffees, but its levels can vary widely depending on the variety of coffee bean and the roasting method, noted Somoza.

"Since NMP is generated upon roasting, dark-roast coffees contain high amounts of this stomach friendly coffee ingredient. Now, there is hope for a good morning start with a freshly brewed cup of optimized stomach friendly coffee," said the researchers.

The scientists are testing different varieties of raw coffee beans and different roasting methods in an effort to boost NMP levels to make a better stomach-friendly coffee.

They hope to test the new brew in human volunteers later in 2010.

The study has been presented at the 239th National Meeting of the American Chemical Society. (ANI)