If you want to avoid nighttime heartburn, then strictly follow this rule: Refrain from eating three to four hours before going to sleep.

The American Journal of Gastroenterology published a study by researchers from the Department of Gastroenterology at Osaka City University in Japan that tested the validity of the rule. Its aim was to determine whether night-time heartburn raised the risk of gastroesophageal reflux disease.

Gastroesophageal reflux disease (GERD) is a condition in which the stomach contents (food or liquid) leak backwards from the stomach into the esophagus the tube from the mouth to the stomach. This action can irritate the esophagus, causing heartburn and other symptoms.

The study involved 147 GERD patients, and 294 non-GERD age- and sex-matched controls. The controls did not experience symptoms of heartburn and acid regurgitation during the previous year. Through a self-report questionnaire, dinner-to-bedtime interval, defined as the time between finishing dinner and going to bed, was investigated. After controlling for drinking and smoking habits and the body mass index of participants, the study found that eating dinner within three hours before sleep increase in risk of reflux symptoms sevenfold.

"Shorter dinner-to-bedtime was significantly associated with an increased OR of GERD (p < 0.0001) and the OR for patients whose dinner-to-bedtime was less than 3 hours was 7.45 (95 per cent CI 3.38-16.4) compared with patients whose dinner-to-bed time was 4 hours or more. These observations were consistent in both patients with non-erosive GERD and erosive esophagitis, and there was no significant difference in dinner-to-bed time intervals between non-erosive GERD and erosive esophagitis," reported the PubMed Web site.

Common GRED symptoms include the following: A feeling that food is trapped behind the breastbone, and nausea after eating. Subject also experience heartburn or a burning pain in the chest (under the breastbone), which usually occurs when bending, lying down or eating, and can become worse at night.

Other symptoms include difficulty in swallowing, coughing and wheezing, sore throat, regurgitation of food, hoarseness, and hiccups.

Another study, by the Walter Reed Army Medical Center, measured the acid levels in 30 reflux patients during two separate nights. "The aim of this study was to determine the difference of supine esophageal acid exposure in patients consuming an early or late standard meal relative to bedtime," said PubMed.

Thirty-two patients with reflux participated in the "prospective, randomized unblended crossover trial." On the first night, participants ate a standard meal for dinner then went to bed two hours after eating. On the second night, the subjects had an early dinner, six hours before sleeping.

Acid exposure was measured, and reflux symptom frequency and severity were documented. The study showed that GERD patients eating a late-evening meal had significantly greater supine acid reflux, compared to when they ate an early meal. This was especially true in overweight patients, and those with esophagitis or hiatal hernias.

These findings support the rule on consuming dinner early. GERD patients will also benefit a lot from losing weight. Three to four hours is the recommended dinner-to-bedtime interval as it is the amount of time necessary to clear the stomach of food.