What Foods Should You Not Eat with CSID?

November 19, 2025 •

4 min read

According to the IFFGD, congenital sucrase-isomaltase deficiency (CSID) is a rare genetic disorder that impairs the ability to digest sucrose and starch, leading to a range of gastrointestinal symptoms. Knowing what foods should you not eat with CSID is the primary way to manage this condition and improve digestive health.

Quick Summary

Congenital Sucrase-Isomaltase Deficiency (CSID) requires restricting dietary sucrose and starch. This involves avoiding or limiting table sugar, certain fruits, starchy vegetables, and processed foods with added sugars and fillers to alleviate symptoms like diarrhea, gas, and bloating.

Key Points

Sucrose is the main culprit: Due to a deficient sucrase enzyme, table sugar (sucrose) and foods containing it are the primary triggers for CSID symptoms.
Starch tolerance varies: Individuals with CSID have varying levels of starch intolerance; many need to limit or avoid starchy vegetables, grains, and legumes.
Watch for hidden ingredients: Processed foods often contain hidden sucrose or starch fillers in sauces, seasonings, and processed meats, so careful label reading is vital.
Elimination diets help: Conducting an elimination diet is an effective strategy for identifying your unique tolerance levels for sucrose and starch.
Consult a dietitian: A registered dietitian specializing in CSID can provide personalized guidance and help build a balanced, symptom-free diet plan.

Understanding Congenital Sucrase-Isomaltase Deficiency (CSID)

Congenital Sucrase-Isomaltase Deficiency (CSID) is a hereditary condition where the small intestine has insufficient levels of the digestive enzymes sucrase and isomaltase. These enzymes are crucial for breaking down disaccharides like sucrose (table sugar) and starch into simpler, absorbable sugars. When these carbohydrates are not properly digested, they pass into the large intestine where they ferment, causing uncomfortable and painful symptoms such as watery diarrhea, abdominal pain, bloating, and excessive gas. Since symptom severity varies based on the degree of enzyme deficiency and individual tolerance, dietary management is highly personalized but always centers on limiting sucrose and starch intake.

High-Sucrose Foods to Avoid

Sucrose is a major trigger for those with CSID. It is found in both natural and processed forms, requiring vigilance when shopping and dining. For many with CSID, sucrose is the least tolerated carbohydrate due to the specific enzyme deficiency.

Processed Foods and Sweeteners

Reading food labels is essential to identify added sucrose, which often goes by other names.

Added Sugars: Avoid all forms of table sugar, including brown sugar, powdered sugar, raw sugar, and cane sugar. Maple syrup, molasses, coconut sugar, and date sugar are also problematic.
Baked Goods: Many breads, cereals, pastries, muffins, and cakes are sweetened with sucrose.
Desserts: Ice cream, sorbet, cookies, pies, and candies typically contain high levels of sucrose.
Dairy Products: Flavored and sweetened yogurts, kefirs, and milks are common sources of added sugar.
Condiments and Sauces: BBQ sauce, ketchup, and many salad dressings often contain added sucrose.

Fruits High in Sucrose

While fruits are a healthy part of a balanced diet, many contain natural sucrose and can trigger symptoms in CSID patients. Some of the most common offenders include:

Apples
Bananas
Mangoes
Pineapples
Peaches
Oranges and other citrus fruits
Cantaloupe and honeydew melon
Dates

Sugary Beverages

Many common drinks are loaded with sucrose and should be eliminated from a CSID diet.

Fruit Juices: Most fruit juices are high in sucrose, with 100% grape juice being a potential exception for some individuals.
Sodas and Energy Drinks: Regular sodas, energy drinks, and sports drinks are typically sweetened with sucrose.
Sweetened Teas and Coffees: Specialty flavored coffee drinks and sweetened teas are also high in sucrose.

Starches and Grains to Limit or Avoid

For many with CSID, starch digestion is also impaired, and it is common to have varying levels of starch intolerance. An elimination diet can help determine individual tolerance.

Starchy Vegetables

Certain vegetables are high in starch and may cause symptoms. These include:

Potatoes (both white and sweet)
Corn
Peas
Carrots and parsnips
Yams
Butternut and acorn squash

Grains and Legumes

Grains and legumes are also significant sources of starch that require caution.

Grains: Items like bread, pasta, rice, and many cereals contain significant starch. Some individuals may tolerate whole grains better due to their fiber content slowing digestion.
Legumes: All legumes, including beans, lentils, chickpeas, and peanuts, are rich in starch and are generally best avoided in a CSID diet.

Hidden Ingredients and Processed Food Pitfalls

Beyond obvious sources, many processed foods contain hidden sucrose or starch fillers that can trigger symptoms. Careful label reading is critical.

Processed Meats: Bacon, sausage, and deli meats can contain sugar or starch fillers. Avoid breaded meats or those with glazes.
Processed Cheese: Certain types of American cheese and other processed cheeses contain fillers that may not be tolerated.
Seasoning Blends: Many commercial seasoning mixes and rubs include sugar or starch to enhance flavor or as a filler. Stick to simple salt and fresh herbs initially.

Comparison Table: CSID Diet Choices


Food Category	Foods to Avoid or Limit	Often Tolerated Alternatives
Sweeteners	Table sugar, brown sugar, maple syrup, coconut sugar, molasses	Dextrose, fructose (in moderation), stevia, some artificial sweeteners
Fruits	Apples, bananas, mangoes, peaches, dates, cantaloupe, honeydew melon	Berries (e.g., raspberries, strawberries), lemons, some melons (e.g., watermelon), kiwi
Vegetables	Potatoes, corn, peas, carrots, beets, acorn squash	Cauliflower, broccoli, leafy greens, cucumber, zucchini noodles, celery
Grains	White bread, regular pasta, processed cereals	Individual tolerance varies; brown rice, whole oats (may need to be introduced slowly)
Protein	Breaded meats, processed deli meats, sausages, meatballs	Plain, unseasoned meats (beef, poultry, fish), eggs, tofu
Dairy	Flavored milk, sweetened yogurt, ice cream	Plain milk, unsweetened yogurt, hard cheeses

Practical Dietary Management Strategies

The Elimination and Reintroduction Diet

A structured elimination diet is often the most effective way to identify your specific tolerance levels. Start by removing all high-sucrose and high-starch foods from your diet. Once symptoms subside, you can slowly reintroduce individual foods, one at a time, observing for any recurring symptoms. A food diary is an invaluable tool for tracking what you eat and how you react.

Working with a Professional

Dietary management for CSID can be complex. Consulting with a registered dietitian specializing in CSID or GI disorders is highly recommended. A professional can help you navigate label reading, build a balanced meal plan that meets your nutritional needs, and develop a personalized elimination strategy. For many, enzyme replacement therapy with a product like Sucraid® can also be a part of a broader treatment plan, allowing for a less restrictive diet.

Learn more about CSID and treatment options from Sucraid®.

Conclusion: Navigating a CSID-Friendly Lifestyle

Successfully managing CSID relies heavily on avoiding foods that contain high levels of sucrose and being mindful of starch intake. By prioritizing unprocessed foods, reading labels diligently, and working with healthcare professionals, individuals can effectively control their symptoms and significantly improve their quality of life. The journey is personalized, and patience with the process of determining individual food tolerance is key to long-term success. While it may seem daunting at first, a carefully managed CSID diet provides the best path toward digestive comfort and improved well-being.

Frequently Asked Questions

Sucrose is a disaccharide that requires the sucrase enzyme for digestion. Since this enzyme is severely deficient in CSID, sucrose is a major trigger for symptoms. Starch, a polysaccharide, also relies partly on the isomaltase enzyme, and its tolerance varies more widely among individuals.

No, not all fruits are off-limits, but those high in sucrose should be avoided or limited. Lower-sucrose options like berries, lemons, and some melons may be tolerated better.

You can find hidden sucrose by carefully reading the ingredient list. Look for terms like 'sugar', 'brown sugar', 'cane sugar', 'maple syrup', and 'molasses'.

While cooking does not solve the underlying enzymatic issue, some anecdotal evidence suggests that adding healthy fats can slow digestion and potentially improve tolerance of starches. Combining high-starch foods with fats provides more time for existing enzymes to work.

Sweeteners like dextrose, crystalline fructose (often tolerated in moderation), stevia, and some artificial sweeteners may be safe. High-fructose corn syrup might also be tolerated by some, but individuals should determine their specific tolerance with a healthcare provider.

Yes, many children with CSID experience improved tolerance to sucrose and starch as they get older, often around three to four years of age. This is due in part to the growth of the digestive tract.

An elimination diet is a highly recommended tool for determining your specific tolerance levels. Since individual tolerance varies greatly, an elimination diet helps pinpoint which foods and portion sizes trigger symptoms.

Generally, yes. Most legumes, including beans, lentils, and peanuts, are high in starch and should be avoided, especially during the initial elimination phase of the diet. Tolerance can be assessed cautiously later.