Summary  
An autoimmune disease characterized by destruction of insulin-producing β-cells in the pancreatic islets of Langerhans, leading to absolute insulin deficiency and chronic hyperglycemia. Epidemiology  • Typically presents in childhood or adolescence, but can occur at any age
  • Accounts for ~5–10% of all diabetes cases globally
  • Slight male predominance in some populations
  • Associated with HLA-DR3 and DR4 haplotypes

‍Etiology / Risk Factors  
  • Autoimmune β-cell destruction
  • Genetic predisposition (e.g., HLA-DR3, DR4, DQ8)
  • Environmental triggers:
    – Viral infections (Coxsackie B, enteroviruses)
    – Early cow’s milk exposure
    – Low vitamin D
    – Gut microbiota alterations

‍Pathophysiology
‍  • Progressive loss of pancreatic β-cells → absolute insulin deficiency
  • Leads to:
    – ↓ Peripheral glucose uptake
    – ↑ Hepatic glucose production
    – ↑ Lipolysis → ketogenesis → risk of DKA Clinical Presentation  • Polyuria
  • Polydipsia
  • Weight loss despite normal/increased appetite
  • Fatigue
  • Blurred vision
  • In children: bedwetting, failure to thrive Diagnosis
‍  • Fasting glucose ≥126 mg/dL (7.0 mmol/L)
  • 2-hr OGTT glucose ≥200 mg/dL
  • Random glucose ≥200 mg/dL with symptoms
  • HbA1c ≥6.5% (48 mmol/mol)
  • Diabetes-specific autoantibodies:
    – GAD, IA-2, IAA, ZnT8 Complications  Acute:
    • Diabetic Ketoacidosis (DKA)
    • Hypoglycemia (often iatrogenic)  Chronic:
    • Microvascular: retinopathy, nephropathy, neuropathy
    • Macrovascular: CAD, stroke (rare early on)
    • Delayed growth/puberty in poorly controlled pediatric patients
‍
Management
‍  • Lifelong insulin therapy
    – Basal-bolus or insulin pump (CSII)
  • Glucose monitoring: fingerstick or CGM
  • Carbohydrate counting + dietary education
  • Psychosocial and mental health support
  • Screen for autoimmune comorbidities:
    – Celiac disease, thyroiditis
  • Annual complication screening after age 10 or puberty

Prognosis  • With good glycemic control, long-term outcomes are favorable
  • Poor control → ↑ risk of early complications and mortality

Medical Nutrition Therapy

Goals
‍The primary goals of MNT in Type 1 Diabetes are:
‍Achieve and maintain a target HbA1c level of <7.0% (53 mmol/mol), in accordance with American Diabetes Association (ADA) guidelines, to prevent long-term complications.
‍Manage postprandial blood glucose to a target range of 90–130 mg/dL before meals and <180 mg/dL 1-2 hours after meals.
‍Prevent both hypoglycemia and hyperglycemia, aiming for an optimal range of 70–130 mg/dL before meals and <180 mg/dL post-meal.
Support growth and development in children and adolescents with Type 1 Diabetes while ensuring adequate caloric intake.

‍Macronutrient Distribution and Caloric Intake
Carbohydrates (45–65% of total energy intake): Carbohydrate counting is essential for the management of insulin doses. The insulin-to-carbohydrate ratio (ICR)is typically 1 unit of insulin for every 15 grams of carbohydrates, though this may vary based on individual needs.
Fiber intake should be emphasized (25–30 grams/day for adults) to slow glucose absorption and improve glycemic control.

‍Proteins (10–20% of total energy intake):
Adequate protein intake (0.8–1.0 g/kg body weight/day) is required to maintain muscle mass and support metabolic needs without causing significant changes in postprandial glucose levels.

‍Fats (25–35% of total energy intake): Saturated fat intake should be limited to <7% of total calories to reduce the risk of cardiovascular disease. Trans fats should be avoided.
Emphasis on omega-3 fatty acids (from fish and plant sources) helps in managing inflammation and preventing cardiovascular complications.

‍Carbohydrate Counting & Insulin Adjustment
‍Carbohydrate counting is central to MNT in T1DM. The insulin-to-carbohydrate ratio (ICR) varies between individuals, and flexible insulin therapy helps to adjust insulin doses based on the amount of carbohydrate consumed.
        Typical ICR values:
                   - 1 unit of rapid-acting insulin for every 12–15 grams of carbohydrates for most individuals.
                   - Adjustments may be needed based on activity level, insulin sensitivity, and meal composition.
                   - Correction factors are used to adjust insulin doses for pre-meal blood glucose levels, typically ranging from 1 unit per 50–100 mg/dL above target.

‍Glycemic Control and HbA1c
‍Maintaining good glycemic control is a critical aspect of MNT. The ADA recommends an HbA1c goal of <7.0% (53 mmol/mol) for adults, although more lenient goals may be considered for children and adolescents or those with significant hypoglycemia risk.
        In children: The target HbA1c is typically <7.5% (58 mmol/mol).
         Regular monitoring of blood glucose levels (using CGM or fingerstick glucose tests) is necessary for timely insulin adjustments


Keywords

• DIABETES
• MNT
• MACRONUTRIENT
• GLYCEMIC
• TYPE-1