What are Disaccharidases?
Disaccharidases are a group of glycoside hydrolase enzymes located in the brush border of the small intestinal lining. Their primary function is to break down disaccharides, which are double-sugars, into smaller, simpler sugars called monosaccharides. Monosaccharides, such as glucose and fructose, can then be easily absorbed by the body to be used as energy. When a deficiency occurs in one or more of these crucial enzymes, the corresponding sugar cannot be broken down and absorbed properly. Instead, the undigested sugar travels to the large intestine where it is fermented by bacteria, leading to a cascade of gastrointestinal symptoms.
Types of Disaccharidase Deficiency
Disaccharidase deficiency is not a single condition but rather a group of disorders that can be categorized into two main types: primary and secondary.
Primary (Genetic) Deficiency
This is a permanent, inherited condition where individuals are born with a reduced or absent ability to produce one or more disaccharidase enzymes. Primary deficiencies are often caused by genetic mutations that affect the enzyme's production or function.
- Adult-type hypolactasia: The most common form, this is a genetically programmed reduction of lactase synthesis that occurs after early childhood.
- Congenital sucrase-isomaltase deficiency (CSID): A rare, autosomal recessive disorder where infants lack sucrase-isomaltase, presenting symptoms when they start consuming sucrose and starches.
- Congenital lactase deficiency: An extremely rare disorder that manifests soon after birth with the first breast or formula feeding containing lactose.
Secondary (Acquired) Deficiency
Secondary deficiency is a more common, often temporary condition caused by damage to the small intestinal lining (the brush border) where the enzymes are located.
- Infections: Viral gastroenteritis (stomach flu) is a very common cause, particularly in children.
- Inflammatory diseases: Conditions such as celiac disease and Crohn's disease can damage the intestinal mucosa, leading to enzyme deficiencies.
- Medications: Prolonged use of certain drugs, including antibiotics and some chemotherapy agents, can harm the intestinal lining.
- Other factors: Conditions like small intestinal bacterial overgrowth (SIBO), autoimmune enteropathy, and radiation injury can also cause secondary deficiency.
Common Disaccharidase Deficiencies and Their Corresponding Sugars
Different disaccharidase deficiencies are named for the specific sugars they fail to digest.
- Lactase Deficiency: Inability to digest lactose, the sugar found in milk and dairy products. Lactase breaks down lactose into glucose and galactose.
- Sucrase-Isomaltase Deficiency: Inability to digest sucrose (table sugar) and some starches. The sucrase-isomaltase enzyme complex breaks down sucrose into glucose and fructose and starches into glucose.
- Maltase-Glucoamylase Deficiency: Inability to digest maltose and other starches. These enzymes convert complex starches into glucose.
- Trehalase Deficiency: Inability to digest trehalose, a sugar found in mushrooms and some yeasts.
Symptoms of Disaccharidase Deficiency
Symptoms typically appear shortly after consuming the offending sugar. They are primarily a result of the undigested sugar causing an osmotic effect in the gut, drawing excess water into the intestine, and bacterial fermentation producing gas.
- Abdominal pain and cramping
- Bloating and distention
- Excessive gas and flatulence
- Diarrhea, which can be watery and explosive
- Nausea and sometimes vomiting
- For infants, a failure to thrive and malnutrition can occur due to prolonged symptoms
- Symptoms can often overlap with other gastrointestinal disorders, like Irritable Bowel Syndrome (IBS), leading to misdiagnosis.
Diagnosis of Disaccharidase Deficiency
Confirming a disaccharidase deficiency requires a doctor's evaluation and specific tests. The diagnostic approach can vary depending on the suspected enzyme.
- Hydrogen Breath Test: After consuming a specific sugar (e.g., lactose or sucrose), a patient's breath is analyzed for an increase in hydrogen and methane, which are byproducts of bacterial fermentation.
- Sugar Tolerance Test: A doctor monitors a patient's blood glucose levels after they ingest a specific sugar. A flat blood curve suggests malabsorption.
- Small Intestinal Biopsy: Considered the gold standard, this invasive procedure involves an endoscopy to collect a small tissue sample from the intestine. The enzyme activity in the biopsy is then measured directly.
- Elimination Diet: A temporary elimination of the suspected sugar from the diet can help identify if symptoms improve, followed by a reintroduction to confirm the link.
Treatment and Management Options
Treatment for disaccharidase deficiency focuses on managing symptoms through dietary changes and, in some cases, enzyme replacement.
Dietary Management
This is the primary treatment approach. A registered dietitian can provide guidance on identifying and restricting the sugars that cause symptoms.
- Lactose Deficiency: Limiting or avoiding dairy products. Some individuals can tolerate small amounts of lactose, especially with meals or in aged cheeses and yogurt.
- Sucrose Deficiency: Restricting table sugar and starches found in many fruits, vegetables, and processed foods.
- Maltase Deficiency: Avoiding certain starches and processed foods high in maltose.
Enzyme Replacement Therapy (ERT)
Enzyme supplements can be taken orally with meals to help digest the problem sugar.
- Lactase Supplements: Available over-the-counter (e.g., Lactaid), these capsules or drops provide the lactase enzyme to help break down lactose.
- Sucrase Supplements: For congenital sucrase-isomaltase deficiency (CSID), the FDA-approved oral solution Sucraid® (sacrosidase) is available. It replaces the sucrase enzyme but does not fully replace isomaltase activity.
Disaccharidase Deficiency Comparison Table
| Feature | Primary Deficiency | Secondary Deficiency |
|---|---|---|
| Cause | Genetic or inherited mutations affecting enzyme production | Damage to the intestinal lining from disease or external factors |
| Duration | Permanent and lifelong | Often transient; resolves when the underlying cause is treated |
| Associated Conditions | None; occurs in isolation | Celiac disease, Crohn's, gastroenteritis, SIBO, etc. |
| Preventability | Cannot be prevented due to genetic origin | Can sometimes be prevented by avoiding triggers and treating underlying issues |
Conclusion
Disaccharidase deficiency is a common but often underdiagnosed condition responsible for uncomfortable gastrointestinal symptoms triggered by specific sugars. It is critical to differentiate between the permanent primary (genetic) form and the often-temporary secondary (acquired) form, as this impacts treatment and long-term management. For many, symptoms can be effectively managed through a combination of dietary adjustments and targeted enzyme replacement therapy, allowing for significant improvement in quality of life. An accurate diagnosis, often involving invasive testing, is the key to creating an effective treatment plan. For more on testing methodologies, you can find detailed information on authoritative health sites(https://pmc.ncbi.nlm.nih.gov/articles/PMC10226910/).
Disclaimer: The information provided in this article is for informational purposes only and does not constitute medical advice. Please consult with a qualified healthcare professional for diagnosis and treatment.
