In a study of 15,314 people with sleep troubles, the scientists found that 1 in 4 suffered heartburn at night. The most common causes were soda and benzodiazepine sleep drugs—such as Valium—as well as overweight, hypertension, and asthma. (Need another reason to skip the soda? Check out 7 Side Effects Of Drinking Diet Soda.)   Soda’s acidity and carbon dioxide can overwhelm the muscle barrier between the stomach and the esophagus, allowing stomach acid to flow upward, says lead researcher Ronnie Fass, MD, a gastroenterologist. Benzodiazepines relax that muscle. For those with heartburn, skip the nighttime soda and ask your doctor about changing your prescription.   More from Prevention: Natural Sleep Remedies That Work