Chapter 4&7- Carbohydrates and Alcohol (Ver 2.0)

Human Nutrition: Carbohydrates and Alcohol

Chapter Overview

• Focus on carbohydrates and alcohol metabolism

• Key Themes: Types of carbohydrates, digestion, absorption, health implications

Key Concepts

• Types of carbohydrates: Simple (sugars) and complex (starches, fibers)

• Carbohydrate digestion and absorption processes

• Glycemic response and index definitions

• Functions of carbohydrates in human health

• Carbohydrate needs and dietary impacts

• Lactose intolerance: Symptoms, causes, treatment

• Alcohol metabolism

• Health benefits and risks of alcohol consumption

Carbohydrates - Introduction

• Role of Carbohydrates: Essential macronutrients providing energy for all cells

• Sources: Synthesized by plants through photosynthesis (e.g., glucose)

• Types: Simple carbohydrates (monosaccharides, disaccharides) and complex carbohydrates (polysaccharides like starches)

Composition of Carbohydrates

• Organic compounds with a primary structure of CH₂O

• Glucose (C6H12O6) is the most abundant carbohydrate

• Two categories: Simple (fast-releasing) and complex carbohydrates (slow-releasing)

Classification of Carbohydrates

• Simple Carbohydrates: Sugars divided into mono- and disaccharides

  • Monosaccharides: Single sugar units (e.g., glucose, fructose)

  • Disaccharides: Linked sugar units (e.g., sucrose, lactose, maltose)

• Complex Carbohydrates: Long chains of monosaccharides (e.g., starches, fibers)

Simple Carbohydrates

Monosaccharides

• Types:

  • Glucose: Preferred energy source for all organisms

  • Galactose: Found in milk

  • Fructose: Sweetest, naturally occurring in fruits

  • Pentoses: (5 carbons) important for nucleic acids

Disaccharides

• Examples:

  • Sucrose: Glucose + Fructose (table sugar)

  • Lactose: Glucose + Galactose (milk sugar)

  • Maltose: Glucose + Glucose (rarely found as a disaccharide)

Complex Carbohydrates

Polysaccharides

• Starches: Storage form in plants, found in grains and vegetables (amylose and amylopectin)

• Glycogen: Storage form in animals, highly branched structure

• Fiber: Not digestible by human enzymes (cellulose, soluble and insoluble fibers)

Dietary Fibers

• Types:

  • Soluble: Found in oats, beans (fermentable)

  • Insoluble: Found in whole grains, vegetables (non-fermentable)

  • Functional: Added for health benefits (e.g., psyllium)

• Health Impact: Fiber reduces risks of obesity, diabetes, and heart disease

Carbohydrate Digestion and Absorption

1. Mouth: Salivary amylase begins starch breakdown.

2. Stomach: No carbohydrate digestion occurs.

3. Small Intestine: Primary site for digestion; pancreatic amylase and brush border enzymes complete breakdown.

4. Large intestine: Fiber partially broken down by gut bacteria; remaining fiber excreted.

Monosaccharide Absorption

• Monosaccharides enter bloodstream via the small intestine and are transported to the liver for processing.

Glycemic Index (GI)

• Definition: Measurement of carbohydrate effects on blood glucose levels.

• High GI Foods: Rapidly increase blood glucose (e.g., sugary foods).

• Low GI Foods: Slowly raise blood glucose, associated with better health outcomes.

Alcohol Metabolism

• Alcohol is a non-nutrient yielding 7 kcal/g.

• Main Metabolism: Primarily in the liver via the Alcohol Dehydrogenase System, converting ethanol to acetaldehyde and then to acetate.

• Health Effects: Moderate consumption may reduce heart disease risk; excessive consumption leads to liver damage and nutritional deficiencies.

Health Consequences of Alcohol Abuse

• Risks include obesity, liver disease, brain damage, and nutrient deficiencies.

• Mental effects include impaired judgment and coordination.

Lactose Intolerance

• Caused by insufficient lactase enzyme leading to gastrointestinal issues.

• Common in specific ethnic groups; management includes dietary adjustments.

Dietary Recommendations

• Adults: RDA for carbohydrates is 130g/day; AMDR is 45-65% of total caloric intake.

• Fiber Recommendations: 38g/day for men, 25g/day for women.