Have you ever had one of those days? A great day with friends, a terrific meal, a few drinks ... then heartburn. How did it happen? You may be aware of some obvious reasons, but there are some surprising things you may not know about heartburn.

Heartburn, acid indigestion, or acid reflux, is an irritation of the esophagus caused by acid that flows up from the stomach. It really has nothing to do with the heart; it’s simply a burning pain in the chest just behind the breastbone.

Heartburn is fairly common, but chronic, excessive heartburn can cause serious problems such as gastritis, stomach ulcers and esophageal cancer. Chronic heartburn is medically referred to as Gastro-Esophageal Reflux Disease, or GERD. It flares up when partially digested food, hydrochloric acid and enzymes from the stomach back up into the esophagus.

Some causes of heartburn include: overeating; drinking carbonated beverages, alcohol or caffeine; eating spicy foods and sauces; eating processed foods; wearing tight clothing; being overweight; smoking; lying down or bending over after eating; pregnancy; some medications; stress, and insufficient stomach acid.

Surprisingly, a large number of people with symptoms actually are producing too little stomach acid. This condition is referred to as hypochlorhydria.

When there’s not enough stomach acid, the stomach is no longer a sterile environment. This allows bacteria to colonize in the stomach, intestinal tract, and colon. The bacteria putrefy food in the stomach, which produces volatile gases and fatty acids. This creates pressure in the stomach that’s greater than the pressure exerted by the valve at the bottom of the esophagus called the lower esophageal sphincter (LES). When this happens, acids from the stomach are forced up into the esophagus, like a volcano, causing heartburn.

It is thought that low stomach acid plays a role in keeping the LES in a relaxed or open state longer than normal. This causes acids to move from the stomach into the esophagus. Other things that can leave the lower esophageal sphincter in a relaxed or open state are pharmacological, dietary and physical factors.

When you eat and how much you eat can trigger heartburn, so simply changing your eating habits can provide relief. Eat smaller meals and make sure you eat three to four hours before bedtime. Eating too much right before bed can make stomach contents splash up.

When cooking, stick to grilled or steamed foods, as grease can trigger heartburn. Choose lean cuts of meat, load up with veggies and salads, but avoid tomatoes, as they are acidic. Use condiments such as guacamole instead of ketchup for the same reason. Choose water or iced tea instead of carbonated drinks, alcohol or coffee, which trigger heartburn.

Last but not least, make some lifestyle changes: if you’re overweight, slim down; if you smoke, kick the habit (it stimulates acid production and relaxes the LES). Exercise more, but be careful that you don’t eat immediately before, during or just after your routine.

And, of course, relax. A National Heartburn Alliance survey reveals that 58 percent of frequent heartburn sufferers identify “hectic lifestyle” as a factor that contributes to their heartburn and 52 percent point to work-related stress as a heartburn aggravator. Practice deep breathing, yoga, tai-chi or another relaxing stress relief technique.

If you get heartburn daily despite lifestyle and dietary changes, consult a physician.