wie lang ist der darm — what are common causes?

The question about intestinal length and common causes is not directly addressed in the provided knowledge context. Generally, the human intestine is about 5–7 meters (small intestine) plus 1.5 meters (large intestine), but this varies. Common causes of intestinal issues include irritable bowel syndrome, inflammatory bowel disease, food intolerances, infections, or dysbiosis. However, the clinical utility of microbiome tests for healthy individuals remains unproven (see context: 'lacks standardized norms'). Without specific diagnostics or medical consultation, no definitive conclusions can be drawn. The provided context focuses on consumer tests and pharmacogenetics, not on intestinal anatomy or disease causes.