Laxation and the like: Assessing digestive health

Digestive complaints are common in medicine, yet no systematic review of normal laxation has been published. Even definitions for digestive problems such as constipation and diarrhea vary greatly and tend to be subjective. Over-the-counter medicines for digestive disorders are commonly prescribed and consumed. However, the success of these treatments is poorly studied because standard protocols to determine "normal laxation" do not exist. With respect to laxation, in addition to food intake, stool size is affected by many factors, including sex, exercise, age, stress, bowel habits, psychological factors, medications, and many health conditions and diseases. In this article, we describe normal stool, review the methods used to determine healthy digestion and the factors that affect stool composition, and support the need for fecal collection and analyses in nutrition and gastroenterology studies.