Continuous glucose monitoring shows limited impact of daytime cornstarch on glycemia in glycogen storage disease type I.

BACKGROUND AND AIM: Glycogen storage disease type I (GSD I) is characterized by impaired endogenous glucose production, leading to fasting hypoglycemia and multiple metabolic complications. Cornstarch supplementation is a cornerstone of dietary management, primarily to prevent fasting hypoglycemia. However, its role in modulating daytime postprandial glycemia in adults remains unclear. This study aimed to evaluate the impact of mealtime cornstarch supplementation on postprandial glucose dynamics in adults with GSD I under real-life conditions.

METHODS AND

RESULTS

In this cross-sectional observational study, 10 consecutive adults with genetically confirmed GSD I underwent a 7-day dietary assessment and continuous glucose monitoring (CGM). Meals were classified according to the presence or absence of cornstarch supplementation (Starch and noStarch meals). Postprandial glucose responses were analyzed over a 240-min observation window using dynamic CGM-derived metrics, including peak, nadir, time to peak, time to nadir, and incremental area under the curve (iAUC). A total of 102 meals (60 noStarch, 42 Starch) allowed for the 4-h analysis. No significant differences were observed between Starch and noStarch meals in overall 4-h glucose profiles (p = 0.209), iAUC (p = 0.234), peak and nadir glucose levels, or dynamic indices (p always >0.05). Postprandial hypoglycemia was infrequent, with only 14 events <70 mg/dL and a single event <54 mg/dL. Results remained consistent after adjustment for daily starch intake and subject-level effects.

CONCLUSIONS

In adults with GSD I and stable metabolic control, mealtime cornstarch supplementation does not significantly modify postprandial glucose dynamics over 4 h. These findings support individualized, CGM-guided strategies to optimize cornstarch use.