The hepatic glycogen storage diseases (GSDs) are a group of disorders where abnormal storage or release of glycogen leads to potentially life-threatening hypoglycemia and metabolic disturbances. Dietary interventions have markedly improved the outcome for these disorders, from a previously fatal condition to one where people can do well with proper care. This article chronicles the evolution of dietary management and treatment of the hepatic GSDs (types 0, I, III, VI, IX, and XI). We examine historic and current approaches for preventing hypoglycemia associated with GSDs. There is a lack of consensus on the optimal dietary management of GSDs despite decades of research, and the ongoing controversies are discussed.

Glycogen storage disease type Ia (GSDIa) is a rare, life‐threatening, inherited carbohydrate metabolism disorder caused by glucose‐6‐phosphatase (G6Pase) deficiency, which is essential for glycogenolysis and gluconeogenesis. GSDIa management includes a strict medically prescribed diet that typically includes daily uncooked cornstarch doses, including overnight, to maintain euglycemia. DTX401 is an investigational adeno‐associated virus serotype 8 vector expressing the human G6PC1 gene that encodes G6Pase. This open‐label, phase 1/2, dose‐escalation, 52‐week gene therapy trial evaluated the safety and efficacy of a single DTX401 infusion in 12 adults with GSDIa (ClinicalTrials.gov Identifier: NCT03517085). Three participants in Cohort 1 received DTX401 2.0 × 10 ¹² genome copies (GC)/kg, and three participants each in Cohorts 2, 3, and 4 received 6.0 × 10 ¹² GC/kg. Corticosteroids were administered to mitigate vector‑induced inflammatory response. All participants experienced a treatment‐emergent adverse event (TEAE) and a related TEAE. No participant experienced a dose‐limiting toxicity, TEAE leading to study discontinuation, TEAE leading to death, or serious treatment‐related TEAE. Mean (SD) time to hypoglycemia in minutes/gram of carbohydrate during a controlled fasting challenge was 5.0 (1.6) at baseline and 6.9 (2.7) at Week 52, a mean (SD) increase of 46% (72%). Mean total daily cornstarch intake was 284 g at baseline and 85 g at Week 52 in the 10 participants with available values at both time points, a mean (SD) total daily cornstarch intake reduction of 68% (20%); p < 0.001. DTX401 showed a favorable safety and efficacy profile at Week 52. Participants in all cohorts showed significant cornstarch need reductions from baseline to Week 52.