Module 5 - NUTR 120, Second half

Carbohydrates (CHO) Overview

• CHO are essential components of the diet, classified as digestible and non-digestible.

• Types of CHO:

  • Simple sugars

    • Monosaccharides

    • Disaccharides

  • Oligosaccharides

  • Starch-based carbohydrates (complex CHO) include:

    • Starchinose

    • Verbascos

    • Dextrins (short chains of starch)

    • Glycogen

  • Sugar alcohols (e.g., xylitol, mannitol, sorbitol)

• Resistant Starch:

  • Found in natural sources such as okra and legumes.

  • Similar in function to soluble fiber.

  • Cooling cooked potatoes increases resistant starch.

• Dietary Fiber:

  • Ingestible plant materials, categorized into two types:

Types of Dietary Fiber

1. Soluble Fiber

• Forms a gel-like substance in the gut.

• Slows down food movement through the digestive tract (1/3 of food intake).

• Examples of Soluble Fiber:

  • Pectin

  • Gum

  • Egg whites

• Food Sources:

  • Fruits (especially citrus)

  • Oatmeal

  • Psyllium

2. Insoluble Fiber

• Speeds up the passage of food in the gastrointestinal tract (2/3 of food intake).

• Sources:

  • Strawberry seeds

  • Celery

  • Vegetable skins

  • Legume skins

Functions of Fiber in the Colon

Soluble Fiber Functions

• Creates a loosely structured meshwork allowing for high fermentation, producing gases and short-chain fatty acids (SCFAs).

• Specific ratios and impacts of SCFAs:

  • 2:0 Acetate, 3:0 Propionate, and 4:0 Butyrate can aid in suppressing liver cholesterol synthesis and may lower risks for conditions such as colon cancer.

Insoluble Fiber Functions

• Acts like a metal washcloth, making it difficult for bacteria to penetrate, resulting in lower fermentation rates and increased fecal bulk.

• High soluble fiber intake is linked to a decreased risk of diverticulitis and overall digestive health.

• Wheat bran: A standard for insoluble fiber, rich in B vitamins and iron, with the bran and endosperm providing substantial nutritional value.

Fiber and Cancer Prevention

Soluble Fiber

• Contributes to the formation of SCFAs which can potentially prevent colon cancer due to lowered pH and increased bacterial diversity.

Insoluble Fiber

• Promotes bulking effect, which dilutes fecal matter and allows for better absorption of harmful compounds.

• The ability to bind to harmful substances like nitrates (NH) reduces damage to colon cells and prevents the conversion of bile acids into secondary bile acids that may promote cancer.

Fiber and Blood Cholesterol

• How Soluble Fiber Lowers Cholesterol:

  1. Binds to bile acids and dietary cholesterol, reducing absorption.

  2. Fermented into SCFAs, which can inhibit cholesterol synthesis.

• Soluble and insoluble fiber play a role in managing body weight by increasing satiety due to bulk.

• Delays gastric emptying, leading to slower insulin release and flat insulin curves, which aids in appetite management.

Dietary Fiber Intake Recommendations

• Current fiber intake averages between 12-15 grams per day.

• Historical recommendations for Canadians suggested 35 grams for those consuming 2,500 kcal.

• Emphasis on complex CHO sources, specifically whole grains, vegetables, fruits, and legumes.