1. Chapter Overview
Nutrition therapy is one of the most powerful tools in diabetes management, yet often the most challenging to implement. For the CDE exam, move away from the idea of a restrictive “Diabetic Diet.” The Diabetes Canada Guidelines emphasize individualization, dietary patterns (rather than single nutrients), and the crucial role of the Registered Dietitian (RD).
2. Key Messages (The "Gold Nuggets")
- The Power of Food: Nutrition therapy can reduce A1C by 1.0% to 2.0%. This is comparable to, or greater than, the effect of many glucose-lowering medications.
- The Role of the RD: People with diabetes should receive counselling by a Registered Dietitian (Grade B, Level 2 for T2D).
- Weight Loss: For those with overweight/obesity, a modest weight loss of 5% to 10% of initial body weight can substantially improve insulin sensitivity and glycemic control.
- No “One Size Fits All”: Macronutrient distribution is flexible. The “best” diet is the one the patient can adhere to long-term.
3. Macronutrients: The Evidence
A. Carbohydrates (45%–60% of Energy)
Quality over Quantity: Focus on low-Glycemic Index (GI) and high-fibre sources.
Glycemic Index (GI): Replacing high-GI foods with low-GI foods has a clinically significant benefit for glycemic control in both Type 1 and Type 2 diabetes.
Fibre:
Target: 30 to 50 g/day (higher than the general population recommendation of 25–38 g/day).
Viscous Soluble Fibre: (e.g., oats, barley, psyllium, legumes) is specifically effective for lowering LDL-C and improving glycemic control. Target: 10–20 g/day.
Sugars: Added sugars (sucrose, fructose) can be substituted for other carbs up to 10% of total energy, provided control is maintained. Sugar-Sweetened Beverages (SSBs) should be avoided due to the risk of weight gain and metabolic syndrome.
B. Fats (20%–35% of Energy)
Saturated Fat: Limit to <9% of total energy. Replace with polyunsaturated (PUFA) and monounsaturated (MUFA) fats.
Trans Fats: Avoid completely.
Omega-3 Supplements: Routine high-dose supplementation (fish oil capsules) is not recommended for glycemic control or CVD prevention (based on the ORIGIN trial). However, consuming oily fish (≥2 servings/week) is beneficial.
C. Protein (15%–20% of Energy)
Plant-Based: Replacing animal protein with plant protein (legumes, soy, nuts) improves glycemic control and lipids.
CKD: In chronic kidney disease, protein intake should not exceed 0.8 g/kg body weight/day.
4. Dietary Patterns (The "Menu" of Options)
The guidelines endorse specific dietary patterns that have evidence of benefit. On the exam, you may be asked to match a patient’s goals (e.g., CVD reduction) with the best dietary pattern.
5. Special Considerations
A. Alcohol
The Risk: Moderate alcohol consumption (with or 2–3 hours after an evening meal) may cause delayed hypoglycemia the next morning (up to 24 hours later).
Mechanism: Alcohol inhibits hepatic gluconeogenesis.
Prevention: Educate patients to eat carbohydrates when drinking and monitor BG frequently.
Limits: ≤2 drinks/day (women), ≤3 drinks/day (men).
B. Sweeteners
Safety: Approved non-nutritive sweeteners (aspartame, sucralose, stevia, etc.) are safe when consumed within Acceptable Daily Intake (ADI) levels.
Benefit: They may help with weight control if used to displace excess calories from added sugars.
C. Vitamin/Mineral Supplements
Routine Use: Not recommended for glycemic control.
Exceptions:
Vitamin D: 10 µg (400 IU) daily for adults >50 years.
Folic Acid: 0.4–1.0 mg daily for women who could become pregnant.
6. Clinical Decision Algorithm (Summary of Figure 1 in the Guidelines)
Assess: Refer to RD for assessment.
Intervene: Initiate healthy behaviour interventions (diet + activity) to achieve healthy body weight.
Individualize: Select a dietary pattern (e.g., Mediterranean, DASH) based on patient preference.
Monitor:
If Target A1C is not met within 2 to 3 months of lifestyle intervention alone -> Add Pharmacotherapy.
If on meds -> Adjust every 3 to 6 months.
7. Diabetes Canada Clinical Practice Guidelines Recommendations
Key Recommendations to Memorize:
Counselling: People with diabetes should receive nutrition counselling by a Registered Dietitian. (Grade B, Level 2).
Weight Loss: In people with overweight/obesity, a nutritionally balanced, calorie-reduced diet should be followed to achieve a healthier body weight. (Grade A, Level 1A).
Fibre: Aim for 30 to 50 g/day of dietary fibre, with 10–20 g from viscous soluble fibre. (Grade C, Level 3).
Glycemic Index: Select carbohydrate food sources with a low-GI to optimize glycemic control. (Grade B, Level 2).
Cardiovascular Protection: To reduce CVD risk, consider a Mediterranean-style dietary pattern. (Grade A, Level 1A).
Alcohol: Educate patients using insulin/secretagogues about the risk of delayed hypoglycemia from alcohol. (Grade C, Level 3).