Energy Balance and Carbohydrates

Energy Balance and Carbohydrates

• The human body requires more than 40 essential nutrients to function properly.
• These nutrients work together in complex ways and depend on each other.

Lecture Objectives

• Define carbohydrates as a major macronutrient, including their classifications and functions in the human body.
• Explain the concept of balanced energy.
• Answer frequently asked questions about carbohydrates.

Introduction

• Energy is a critical nutritional need for the body to maintain functions like breathing and heart pumping.
• Energy balance is achieved when the energy consumed through food and drinks equals the energy expended through physical activity and basic functions.
• A balanced state is maintained through a balance between energy intake (calories from food) and energy output (calories burned through activity).

Energy Balance

• Energy balance involves the relationship between calories consumed and calories burned.
• A balanced intake of calories and use of energy helps the body maintain proper weight and health.
• Energy in (food) needs to equal energy out (physical activity).

Calorie Density

• Low-energy dense foods allow a person to consume more nutritious foods while maintaining daily calorie needs.

When a Person Overeats (Feasting)

• Carbohydrates, fats, and proteins are broken down to provide energy, and excess energy is stored as glycogen or body fat.
• Proteins are initially used to replace those lost through body processes.
• Excess nitrogen is removed through the urine.

When a Person Overeats (Fasting)

• Liver and muscle glycogen stores are broken down into glucose. The body uses glucose for energy by the nervous system.
• Body fat stores are broken down into fatty acids to provide energy for other cells.

Energy Expenditures

• Basal Metabolism: Includes the energy used for heartbeats, breathing, and maintaining body temperature.
• Voluntary Activities: Energy used for physical activity like walking, lifting, and climbing.

Basal Metabolic Rate (BMR)

• The amount of energy needed to maintain basic physiological functions while at rest.
• BMR varies according to physical conditions, sex, weight, height, and age
• Higher BMR in people with fever or under stress, those who are physically active, growing or pregnant
• Lower BMR in those who are inactive, fasting or malnourished

Carbohydrates

• Main source of energy (calories)

• Food sources: Starchy vegetables, vegetables, grains, products, fruit, fruit juices, dairy, etc.

• Dietary guideline: 55-70% daily intake.

• Recommended intake: 25-30g of dietary fiber per day, 10% of total caloric intake as sugar.

Composition of Carbohydrates

• Organic Compounds of carbon, hydrogen, and oxygen. Usually with a 2:1 H-O ratio (similar to water).
• Biochemistry designation is CHO.

Nature of Carbohydrates

• The major fuel of the human system (starches and sugar).
• Carbohydrates are processed into glucose, the body's energy source.
• Carbohydrates are cost-effective and widely available (grains, fruits, vegetables, legumes).

Functions of Carbohydrates

• Preferred energy source for the body's functions.
• Protein sparing (prevents protein from being used as an energy source).
• Regulator of fat metabolism
• Provides 4 kilocalories per gram of carbohydrate.
• Essential for digestive system function, including promoting positive bacteria, proper gut integrity, and normal waste elimination.

Classifications of Carbohydrates:

• Simple Carbohydrates:

• Monosaccharides (single sugars)

• Disaccharides (double sugars)

• Examples: Glucose, fructose, galactose, sucrose, maltose, lactose.

• Complex Carbohydrates (Polysaccharides):

• Starches

• Glycogen

• Dietary fiber

• Examples: starch, glycogen, fiber.

Simple vs Complex Carbohydrates

• Simple carbohydrates are digested and absorbed quickly.
• Complex carbohydrates are digested and absorbed more slowly.

Chemical Structure

• Sucrose is composed of two monosaccharides (glucose + fructose). The chemical formula is C12H22O11

Monosaccharides

• Single sugar units.
• Examples: Glucose, Fructose, Galactose
• They do not need digestion and are quickly absorbed.

Disaccharides

• Two sugar units bonded together.
• Examples: Sucrose, Maltose, Lactose
• All disaccharides contain glucose.

Disaccharides

• Sucrose (table sugar) - sugar cane and sugar beets; composed of glucose + fructose
• Maltose (grain sugar) - intermediate product of starch digestion; produced during fermentation process
• Lactose (milk sugar) - only animal-origin carbohydrate with significant amount consumed in human diet; composed of glucose + galactose

Relative Sweetness

• Fructose is the sweetest, while lactose is the least.

Complex Carbohydrates (Polysaccharides)

• Starches, glycogen, dietary fibers
• Long chains of glucose molecules.
• Starches are digestible; glycogen is a stored form in the body; dietary fibers cannot be digested.

Starch

• Storage form of carbohydrates in plants.
• Most significant polysaccharide in the human diet.

Glycogen

• Major form of stored carbohydrates in humans and animals.
• Helps maintain normal blood sugar during fasting or sleep.

Dietary Fibers

• Non-starch polysaccharides that cannot be digested by the body's enzymes.
• Promotes digestive health by feeding beneficial gut bacteria.

Classifications of Dietary Fibers

• Insoluble fibers: Cellulose, lignin, most hemicellulose; do not dissolve in water; promote regularity.
• Soluble fibers: Pectin, gums, mucilages, and algal; dissolve in water; regulate bowel movements, help lower blood cholesterol.

Enzyme Action During Carbohydrate Digestion

• Mouth: Amylase breaks down starch into smaller sugars.
• Stomach: No major carbohydrate action.
• Small Intestine: Pancreatic amylase (continues starch breakdown); Sucrase, lactase, and maltase break disaccharides into monosaccharides.

Sugar Alcohols

• Nutritive sweeteners.
• Sweet to taste but yield less energy than sugars (2-3 calories/gram).
• Used as substitutes to sucrose in treats and drinks.

Artificial Sweeteners

• Also called non-nutritive sweeteners
• Non-caloric, non-carbohydrate, and synthetic sweetening agents.
• They make food taste sweet without causing harm to tooth enamel.

Recommended Carbohydrate Intake

• 55-70% of total daily calories as carbohydrates.
• 10% of total caloric intake as sugars.
• 25-30g of dietary fiber per day.

Deficiency and Excess Carbohydrate Intake

• Deficiency: Constipation, chronic diseases, energy malnutrition.
• Excess: Overweight, obesity, dental caries.

Frequently Asked Questions (FAQ):

• Do carbohydrates cause fattening?: No, gram for gram, they have fewer calories than fats; cooking methods affect their calorie content.
• High-carbohydrate diet/sugar cause diabetes?: High intake of carbohydrates can increase the risk. High-fiber foods reduce the risk of Type 2 diabetes.
• Honey or white sugar more nutritious?: Both break down into single sugars in the body.
• Sugar contributes to misbehaviors of hyperactive children?: The relationship between sugar consumption and behavioral changes in children is not definitively established.
• How do carbohydrate-rich foods promote dental caries?: The bacteria that cause dental caries thrive on carbohydrates in food.

Sources of Carbohydrates

• Starchy Vegetables: Potatoes, corn, lima beans
• Legumes: Beans, peas
• Grains: Wheat, oats, barley, rice and grain-based products.
• Fruits and Fruit Juices: Fruits, fruit juices, jams, jellies
• Sweet Foods: Cakes, pies, cookies, sweets
• Sugary Drinks: Sodas, fruit drinks
• Sweet Condiments: Ketchup, BBQ sauce
• Milk and Yogurt

This quiz explores the importance of carbohydrates as a major macronutrient and their role in achieving energy balance in the human body. It covers the classification, functions, and frequently asked questions regarding carbohydrates, emphasizing the balance between energy intake and expenditure. Test your knowledge and understanding of these essential nutritional concepts.