Introduction to Main Nutrients: Functions, Classes, and Food Sources

Introduction to Nutrition

What is a Nutrient?

A nutrient is a chemical substance found in food that is essential for maintaining the body's functions. Nutrients are required for:

• Energy (calories): Fuel for bodily processes and physical activity

• Growth: Building new tissues during development

• Repair: Healing and replacing damaged cells

• Maintenance of Bodily Function: Supporting ongoing physiological processes

Classes of Nutrients

Overview of Nutrient Categories

The human body requires over 50 different nutrients, which are grouped into six major classes. These are further classified as macronutrients and micronutrients based on their roles and energy content.

• Macronutrients (provide energy):

  • Carbohydrates

  • Fats (Lipids)

  • Proteins

• Micronutrients (do not provide energy):

  • Vitamins

  • Minerals

  • Water

Key Point: Macronutrients are needed in larger amounts and supply energy, while micronutrients are required in smaller quantities and do not provide energy but are vital for health.

Carbohydrates

Functions

Carbohydrates are the body's main source of energy. Each gram of carbohydrate provides 4 kilocalories (kcal) of energy.

• Primary dietary energy source

• Found in foods as sugars, starches, and fibers

Formula for energy from carbohydrates:

$\text{Energy (kcal)} = \text{grams of carbohydrate} \times 4$

Food Sources

• Pasta

• Breads

• Cereals

• Rice

• Grains

• Fruits

• Sugars

• Milk

Example: Whole grain bread is a rich source of complex carbohydrates and dietary fiber.

Proteins

Functions

Proteins provide 4 kcal of energy per gram and are essential for building, maintaining, and repairing body tissues.

• Support growth and development

• Repair damaged tissues

• Maintain muscle mass and immune function

Formula for energy from proteins:

$\text{Energy (kcal)} = \text{grams of protein} \times 4$

Food Sources

• Meat

• Poultry

• Fish

• Eggs

• Legumes

• Nuts

• Soy

• Dairy products

Example: Lentils are a plant-based protein source, also providing dietary fiber and micronutrients.

Fats (Lipids)

Functions

Fats are a concentrated source of energy, providing 9 kcal per gram. They contribute to the taste and texture of foods, help absorb fat-soluble vitamins, and are necessary for healthy skin and internal organs.

• Energy storage and supply

• Absorption of vitamins A, D, E, and K

• Protection of organs

• Maintenance of healthy skin

Formula for energy from fats:

$\text{Energy (kcal)} = \text{grams of fat} \times 9$

Food Sources

• Butter

• Oils

• Nuts & seeds

• Meats

• Whole milk products

• Salad dressings

Example: Olive oil is a source of monounsaturated fat, beneficial for heart health.

Summary Table: Macronutrients

Nutrient	Energy Provided (kcal/g)	Main Functions	Food Sources
Carbohydrates	4	Primary energy source	Pasta, breads, cereals, rice, fruits, sugars, milk
Proteins	4	Build, repair, and maintain tissues	Meat, poultry, fish, eggs, legumes, nuts, soy, dairy
Fats (Lipids)	9	Energy, absorption of vitamins, organ protection	Butter, oils, nuts, seeds, meats, whole milk products

Additional info: The slides also mention vitamins, minerals, and water as micronutrients, which do not provide energy but are essential for various physiological functions. Examples include vitamin C, B-complex vitamins, calcium, iron, and water for hydration and metabolic processes.