A minty herb that's long been known to quiet the occasional stomach upset, peppermint is now also seen as a powerful treatment for irritable bowel syndrome -- frequent bouts of pain, gas, bloating, diarrhea, or constipation that strike as many as one in five adults. Peppermint-oil capsules bring significant relief to about one in three IBS sufferers, according to the American College of Gastroenterology. Surprisingly, prescription antispasmodic drugs help only one in six. The recommended dose is three 0.2-mL capsules a day and it's safe to try on your own. But don't use it if you have gastroesophageal reflux disease or a hiatal hernia, since it can make their symptoms worse.