Nutrition Diet: What foods should you avoid if you have glycogen storage disease?

October 7, 2025 •

4 min read

Glycogen storage diseases (GSDs) are a group of inherited metabolic disorders caused by enzyme deficiencies that affect how the body stores or uses glycogen, its stored form of glucose. These conditions require precise dietary management to prevent severe health complications, and understanding what foods should you avoid if you have glycogen storage disease? is the cornerstone of effective treatment. Dietary restrictions vary significantly depending on the specific type of GSD, emphasizing the importance of a personalized nutrition plan developed with a healthcare professional.

Quick Summary

Glycogen storage disease (GSD) dietary restrictions depend on the specific type but often require avoiding simple sugars like fructose, galactose, and sucrose found in fruits, dairy, and sweets. A specialized diet is necessary to maintain stable blood glucose levels, prevent complications, and manage symptoms, with major differences existing between GSD Types I and III.

Key Points

Strictly avoid specific sugars in GSD Type I: Individuals with GSD Type I must completely avoid fructose, galactose, and sucrose found in fruits, dairy, and table sugar to prevent severe hypoglycemia.
Dietary rules differ by GSD type: Restrictions vary significantly; GSD Type III, for instance, emphasizes a high-protein diet, while GSD Type VI limits simple sugars but less stringently than Type I.
Use uncooked cornstarch for stable glucose: Uncooked cornstarch therapy is a common treatment, providing a slow-release source of glucose to maintain stable blood sugar levels between meals, especially overnight.
Read labels carefully for hidden sugars: Many processed and packaged foods contain hidden sources of restricted sugars (like fructose in corn syrup), requiring vigilance when reading ingredient lists.
High protein is key for some GSD types: For muscle-affecting GSDs like Type III, a high-protein diet is often recommended to support muscle function and provide an alternative glucose source.
Monitor and manage long-term complications: Lifelong dietary discipline is necessary to prevent long-term issues like liver damage, kidney problems, and hyperlipidemia associated with metabolic imbalances.

Understanding the GSD Diet

Dietary management is the cornerstone of treatment for glycogen storage diseases. Since there are many different types of GSD, dietary restrictions vary based on which specific enzyme is deficient. The primary goal is to prevent hypoglycemia (low blood sugar), manage metabolic imbalances like lactic acid and uric acid accumulation, and minimize excessive glycogen storage. For most GSD types, this involves a consistent intake of complex carbohydrates, often supplemented with uncooked cornstarch, while restricting or avoiding specific simple sugars.

Dietary Restrictions for GSD Type I

Type I GSD (including types Ia and Ib) is one of the most common and requires the strictest dietary protocol because it involves a deficient enzyme, glucose-6-phosphatase, which is critical for converting stored glycogen into glucose. Without this enzyme, consuming certain simple sugars can lead to dangerously low blood sugar and the buildup of unwanted metabolic byproducts.

Sugars to avoid for GSD Type I

Fructose: Found in fruits, fruit juices, honey, and high-fructose corn syrup. This means no fruit, fruit-flavored drinks, or products with these sweeteners. Processed foods often hide these sugars, so reading labels carefully is vital.
Galactose and Lactose: These are the sugars found in milk and most dairy products. Dairy products like milk, yogurt, ice cream, and many cheeses must be avoided or severely restricted. Enriched soy or almond milk that is unsweetened is often used as a substitute.
Sucrose (Table Sugar): A disaccharide made of fructose and glucose, sucrose must be avoided entirely. This means abstaining from sweets, cakes, cookies, candy, and many pre-packaged foods.
Sorbitol: This sugar alcohol is converted to fructose during digestion, making it a forbidden ingredient for those with Type I GSD. It is often found in sugar-free candies and chewing gums.

Other foods to limit or avoid for GSD Type I

Sweetened Beverages: This includes all types of soda, fruit juices, sweetened tea, and sports drinks.
Certain Sauces and Condiments: Ketchup, barbecue sauce, and marinara sauce often contain high-fructose corn syrup or added sugar and should be limited or avoided.
Processed Meats: Many cold cuts and hot dogs contain fillers and added sugars and must be scrutinized for inappropriate ingredients.

Dietary Considerations for Other GSD Types

While Type I has the most severe restrictions on simple sugars, other GSDs, such as Type III (Cori's disease) and Type VI (Hers' disease), have different requirements. For GSD III, the enzyme deficiency also affects muscle tissue, so a high-protein diet is often recommended to support muscle function and provide an alternate source of energy. Simple sugars are typically limited to prevent excessive hepatic glycogen deposition and avoid rapid blood glucose fluctuations. For GSD VI, restrictions on simple sugars are also in place, though generally less severe than in Type I. The following table summarizes key dietary differences:


Dietary Factor	GSD Type I (e.g., Ia, Ib)	GSD Type III (Cori's Disease)	GSD Type VI (Hers' Disease)
Fructose/Galactose	Strictly restricted.	Not strictly restricted, but simple sugars are limited.	Simple sugars limited, but typically less strict.
Sucrose	Strictly restricted.	Limited; focus is on high protein.	Limited; focus is on moderate, complex carbohydrates.
Dairy Products	Avoided or severely restricted.	Can be included as part of a high-protein diet.	Limited amounts are usually allowed.
Protein Intake	Normal or slightly increased; fat-restricted.	High protein intake is often recommended to improve muscle function.	Normal or higher protein intake recommended.
Overnight Glucose Support	Essential, often via uncooked cornstarch or specific formulas.	Often required, but dosage may differ from Type I.	Required less frequently or with different dosing.

The Role of Cornstarch Therapy

For many individuals with GSD, uncooked cornstarch therapy is a staple of their dietary regimen, providing a slow and steady release of glucose. It is a complex carbohydrate that is digested slowly, helping to maintain blood sugar levels for several hours. This therapy, along with frequent meals, is crucial for preventing hypoglycemia and stabilizing metabolism.

Long-Term Dietary Management

Living with GSD requires lifelong vigilance. Poorly managed diets can lead to serious long-term complications, including growth restriction, liver damage, kidney issues, and hyperlipidemia (high cholesterol). Regular monitoring of blood glucose and other metabolic indicators is essential to ensure the dietary plan remains effective as the individual grows and their needs change. Nutrition should be supervised by a multidisciplinary team of healthcare professionals, including a metabolic dietitian, to ensure all nutrient needs are met, and to provide guidance on label reading and meal planning.

Conclusion

For individuals with glycogen storage disease, diet is not merely a lifestyle choice but a critical medical treatment. The specific foods to avoid, particularly simple sugars like fructose, galactose, and sucrose, are highly dependent on the GSD type and must be carefully managed. A strict, consistent, and personalized dietary approach, often incorporating uncooked cornstarch, is vital for preventing hypoglycemia and mitigating the risk of serious, long-term complications. Consulting with a healthcare team is the best approach to developing a safe and effective nutrition plan. For more detailed clinical information on GSD management, an authoritative source is the National Center for Biotechnology Information's GeneReviews publication on the topic.

This information is for educational purposes only and is not a substitute for professional medical advice. Always consult with a qualified healthcare provider before making any changes to your diet or treatment plan.

Frequently Asked Questions

For individuals with GSD Type I, fruits are generally restricted because they contain fructose, a sugar the body cannot properly metabolize due to the enzyme deficiency. This leads to the buildup of metabolic byproducts rather than energy, which can cause serious complications.

Uncooked cornstarch therapy involves consuming regular doses of uncooked cornstarch, a complex carbohydrate, mixed with a liquid. It provides a slow and sustained release of glucose into the bloodstream, helping to prevent hypoglycemia (low blood sugar) for several hours.

No, dairy is typically restricted for those with GSD Type I because it contains lactose (milk sugar), which is metabolized into galactose, another restricted sugar. However, some other types of GSD, like Type III, may allow dairy as part of a high-protein diet.

Many artificial sweeteners, such as sucralose (Splenda), aspartame (Equal), and stevia, are generally considered safe for GSD Type I patients as they do not contain fructose or other restricted sugars. However, some sugar alcohols like sorbitol must be avoided.

To prevent hypoglycemia, individuals with GSD, especially Type I, must eat frequent, small meals or snacks every one to four hours, depending on age and specific needs. Overnight feeding may also be required.

Ingesting restricted foods, especially simple sugars, can lead to metabolic imbalances. This can result in severe hypoglycemia, lactic acidosis, and other complications, with consequences ranging from mild to life-threatening depending on the amount consumed and the specific GSD type.

For GSD Type I, all fruits and fruit juices are generally restricted due to their fructose content. Some lists may specify certain berries or avocado as having lower sugar, but it is always best to follow a dietitian's specific advice and dosage.