6.3 Diabetes: Types, pathophysiology, and nutritional management

Diabetes is a complex metabolic disorder affecting millions worldwide. This section explores the two main types of diabetes, their causes, and how they impact the body's ability to regulate blood sugar. Understanding these differences is crucial for effective management.

Nutrition plays a vital role in diabetes care. We'll examine strategies like carbohydrate counting, glycemic index, and balanced macronutrient intake. These dietary approaches, combined with physical activity and weight management, form the cornerstone of diabetes treatment and prevention.

Type 1 vs Type 2 Diabetes

Etiology and Pathophysiology

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• Type 1 diabetes is an autoimmune disorder characterized by the destruction of insulin-producing beta cells in the pancreas, leading to absolute insulin deficiency
  • Typically manifests in childhood or adolescence
  • Immune system mistakenly attacks and destroys the beta cells
• Type 2 diabetes is a metabolic disorder characterized by insulin resistance and progressive beta-cell dysfunction, resulting in relative insulin deficiency
  • Often associated with obesity and typically develops in adulthood
  • Body becomes resistant to insulin's effects, and the beta cells gradually lose their ability to produce sufficient insulin

Management and Treatment

• Type 1 diabetes requires lifelong insulin replacement therapy
  • Insulin administration via injections or insulin pump
  • Careful monitoring of blood glucose levels and adjustment of insulin doses
• Type 2 diabetes can often be managed initially with lifestyle modifications and oral medications, with insulin therapy introduced as the disease progresses
  • Lifestyle changes include diet, exercise, and weight management
  • Oral medications (metformin, sulfonylureas) help improve insulin sensitivity or stimulate insulin secretion
  • Insulin therapy may be necessary as beta-cell function declines over time

Insulin Resistance and Beta-Cell Dysfunction

Insulin Resistance

• Insulin resistance occurs when the body's cells become less responsive to insulin's action, leading to impaired glucose uptake and utilization
  • Results in hyperglycemia despite normal or elevated insulin levels
  • Key feature of metabolic syndrome
• Factors contributing to insulin resistance:
  • Obesity, particularly abdominal obesity
  • Physical inactivity and sedentary lifestyle
  • Genetic predisposition and family history of diabetes
  • Certain medications (glucocorticoids, some antipsychotics)

Beta-Cell Dysfunction

• Beta-cell dysfunction in type 2 diabetes is characterized by a progressive decline in the ability of pancreatic beta cells to produce and secrete sufficient insulin to maintain normal glucose homeostasis
• As insulin resistance increases, beta cells initially compensate by increasing insulin production
  • Hyperinsulinemia in the early stages of type 2 diabetes
• Over time, beta cells become exhausted and unable to meet the increased insulin demand, leading to relative insulin deficiency
  • Gradual loss of beta-cell mass and function
  • Impaired insulin secretion in response to glucose stimuli
• The combination of insulin resistance and beta-cell dysfunction creates a vicious cycle that perpetuates hyperglycemia and the progression of type 2 diabetes

Medical Nutrition Therapy for Diabetes

Carbohydrate Counting and Glycemic Index

• Carbohydrate counting is a meal planning approach that involves tracking the amount of carbohydrates consumed at each meal or snack
  • Helps individuals with diabetes match their insulin doses to their carbohydrate intake and maintain consistent blood glucose levels
  • Requires knowledge of carbohydrate content in foods and portion sizes
• The glycemic index (GI) is a measure of how quickly a carbohydrate-containing food raises blood glucose levels compared to a reference food (usually pure glucose)
  • Low GI foods (GI ≤ 55) are preferred in diabetes management as they result in slower and more gradual rises in blood glucose
  • Examples of low GI foods: whole grains, legumes, non-starchy vegetables
  • High GI foods (GI > 70) cause rapid spikes in blood glucose and should be limited

Macronutrient Distribution and Fiber Intake

• MNT for diabetes emphasizes the importance of portion control, regular meal timing, and balanced macronutrient distribution
  • Recommended macronutrient distribution: 45-65% of total daily energy from carbohydrates, 20-35% from fats (with an emphasis on healthy fats), and 15-20% from proteins
  • Consistent carbohydrate intake at meals and snacks to facilitate glycemic control
• Fiber-rich foods are encouraged in diabetes MNT due to their potential benefits
  • Improve glycemic control by slowing glucose absorption
  • Promote satiety and support weight management efforts
  • Examples of fiber-rich foods: whole grains, legumes, fruits, vegetables

Lifestyle Modifications for Glycemic Control

Dietary Modifications

• Following a balanced meal plan with appropriate portion sizes and nutrient distribution
  • Emphasis on whole, minimally processed foods
  • Limiting intake of added sugars, refined carbohydrates, and saturated fats
• Choosing low GI foods to promote stable blood glucose levels
  • Replacing high GI foods with lower GI alternatives (brown rice instead of white rice)
• Increasing consumption of fiber-rich foods to improve glycemic control and support digestive health
  • Aiming for at least 25-30 grams of fiber per day from various sources

Physical Activity and Weight Management

• Regular physical activity, including both aerobic exercise and resistance training, has been shown to enhance insulin sensitivity and improve glucose uptake by skeletal muscles
  • Aim for at least 150 minutes of moderate-intensity aerobic activity per week
  • Incorporate resistance training exercises at least twice a week
• The combination of a healthy diet and regular physical activity can lead to weight loss, which is particularly beneficial for individuals with type 2 diabetes who are overweight or obese
  • Even modest weight loss (5-10% of initial body weight) can significantly improve glycemic control and reduce the risk of complications
  • Strategies for weight loss include calorie reduction, portion control, and increased physical activity
• Lifestyle modifications, along with regular self-monitoring of blood glucose and medication management (when necessary), are essential for the long-term successful management of diabetes and the prevention of complications
  • Adherence to healthy eating habits and regular exercise
  • Monitoring blood glucose levels to assess the effectiveness of lifestyle changes and medication regimens
  • Working closely with healthcare providers to adjust treatment plans as needed