Nutrition & Metabolic Management

Managing Fanconi-Bickel Syndrome (FBS) is a delicate balancing act. Because the body’s glucose transporters are impaired, you are managing two opposite challenges: preventing blood sugar from crashing when your child is not eating, and managing the high spikes after they do ^[1][2].

The goal of nutritional management is to provide a slow, steady stream of energy while replacing the nutrients that the kidneys are losing ^[3]. Postprandial hyperglycemia (high blood sugar after meals) is a characteristic feature of FBS; there is no generic low-carbohydrate or insulin plan to “fix” it. Instead, all dietary interventions must be heavily supervised by your metabolic team.

Preventing the Fasting “Crash”

In FBS, the liver cannot easily release stored sugar to fuel the body between meals. To prevent hypoglycemia (low blood sugar), your metabolic team will likely recommend:

• Small, Frequent Feedings: Meals and snacks are typically spaced closely together to ensure the body always has a fresh supply of glucose ^[1].
• Uncooked Cornstarch (UCCS): This is a cornerstone of treatment for many patients. Because cornstarch digests very slowly, it provides a “time-release” supply of glucose ^[3].
  • Crucial Safety Warning: Never change the cornstarch dose, interval, or preparation method without your metabolic dietitian’s explicit written plan. Dose, interval, and age suitability are highly individualized. Incorrect use, or using cooked starch instead, can result in severe hypoglycemia or aspiration risks.

Supporting Growth and Nutrition

Many children with FBS experience short stature or slow growth because their bodies are constantly in an energy deficit ^[4][5].

• Nocturnal Enteral Nutrition: For children with inadequate intake or severe growth failure, doctors may recommend a feeding tube to provide continuous nutrition overnight ^[5].
• Variable Outcomes: Some observational studies suggest that intensive therapy, like overnight tube feedings combined with cornstarch, can drastically improve growth in some children ^[5]. However, growth outcomes remain variable, and a feeding tube is not required for every child.

Monitoring Blood Sugar

Because the body cannot pull sugar out of the blood quickly after eating, blood sugar can spike very high ^[4].

• Continuous Glucose Monitoring (CGM): A CGM is a wearable sensor that tracks trends in blood sugar levels. It can provide alerts to help identify low or high patterns ^[1][2].
• The Need for Finger-Sticks: CGMs have a physiological lag and may miss rapid glucose changes. A CGM is not a substitute for your emergency plan. Always confirm the CGM reading with a traditional finger-stick test if your child feels poorly but the sensor reads normal, or if the sensor shows a rapid drop ^[6].

Tailoring Carbohydrates (Galactose, Lactose, and Fructose)

Because the GLUT2 transporter handles galactose (found in lactose/dairy) and fructose (found in fruit), some children may need targeted dietary restrictions to prevent these sugars from building up in the liver ^[1][7].

• Do not restrict these on your own. Broadly restricting fruit, table sugar (sucrose), or dairy can cause severe nutritional harm, including calcium and calorie deficits. Your dietitian will determine if a galactose-free or modified carbohydrate diet is appropriate and will ensure alternative sources of vital nutrients are provided ^[8].

Every child with FBS is unique. Your metabolic team will use your child’s growth charts, lab results, and glucose data to create a custom, written “formula” for their daily meals and starch doses ^[2].