Psyllium fiber, derived from the husks of Plantago ovata seeds, is primarily recognized for its ability to relieve constipation and support regular bowel movements due to its bulk-forming laxative properties. Regarding indigestion—commonly defined as discomfort or impaired digestion in the upper abdomen—the evidence for psyllium's effectiveness is moderate but not robust. Several clinical studies indicate that psyllium can improve digestive comfort, likely due to its ability to regulate bowel function, soften stool, and modulate gut motility. These effects can indirectly alleviate some symptoms commonly associated with indigestion, such as bloating and irregularity, particularly in individuals who experience these symptoms due to functional gastrointestinal disorders (like IBS). However, while psyllium is scientifically validated for constipation and to a lesser extent for general digestive health, direct studies specifically targeting classic indigestion (dyspepsia) symptoms—such as upper abdominal pain, early satiety, or heartburn—are limited. Most research focuses on its effects on overall gastrointestinal transit and stool consistency rather than upper GI symptoms. Thus, while scientific evidence supports psyllium's overall benefit for digestive health and some symptoms overlapping with indigestion, its direct effect on classic indigestion is less well-established. Therefore, the evidence rating is moderate (3/5), reflecting some scientific support but also a need for more targeted research.