What is CSID?Congenital Sucrase-Isomaltase Deficiency (CSID) is a rare, inherited digestive disorder that affects a person's ability to break down certain sugars in the small intestine.Specifically, individuals with CSID have a deficiency or absence of the enzymes sucrase and isomaltase, which are responsible for digesting sucrose (table sugar) and some starches.Without these enzymes, sucrose and starches cannot be properly broken down and absorbed, leading to a range of uncomfortable and disruptive gastrointestinal symptoms.Symptoms of CSID can vary in intensity and often appear in infancy or early childhood when solid foods are introduced into the diet. Common symptoms include: Chronic diarrheaAbdominal painGas and bloatingAcid refluxFailure to thrive in childrenFatigue and irritabilityBecause CSID symptoms overlap with other digestive disorders such as irritable bowel syndrome (IBS) or lactose intolerance, it is often misdiagnosed or undiagnosed for years.Accurate diagnosis typically involves a combination of genetic testing, a hydrogen breath test, or an intestinal biopsy to confirm enzyme levels.There is no cure for CSID, but symptoms can be effectively managed through dietary changes and, in some cases, enzyme replacement therapy.Understanding which foods are safe - and which must be avoided - is essential for managing this condition and maintaining quality of life.