Human Nutrition Basics

Definition of Basic Terms in Human Nutrition

• Nutrition is the science of ingestion, digestion, absorption, assimilation, and biosynthesis of nutrients in the body.
• Food is any nutritious substance that is culturally acceptable and eaten to maintain life and growth.
• Diet refers to the way people feed themselves and the foodstuffs they use, influenced by people's traditions, religion, economic position, and natural surroundings.
• Nutrients are chemical substances needed for energy, repair of body tissues, growth, and normal functioning of the body system.
• Macronutrients (carbohydrates, fat, and protein) are needed in large amounts to maintain the body's structure and systems.
• Micronutrients (minerals and vitamins) are needed in small quantities for a healthy life.
• Healthy eating means eating a variety of foods that provide essential nutrients for health, energy, and proper growth.
• A healthy diet provides sufficient nutrients, balance, and variety, and contains different foods for optimal functioning of the body.

Nutrients and Their Functions

• There are six main classes of nutrients the human body needs: carbohydrates, lipids, proteins, vitamins, minerals, and water.
• Most nutrients have more than one function: building and maintaining body cells, regulating body functions, and providing energy.
• Carbohydrates, fat/lipid, and protein provide energy, while protein is also for body building and repair.
• Minerals and vitamins regulate body function and defend against diseases, and water is for optimal hydration.

Carbohydrates

• Carbohydrates are sugars, starches, or fibers that provide energy to all cells and tissues in the body.
• One gram of carbohydrate generates four kilocalories of energy.
• Carbohydrates should constitute 45 to 65% of daily calorie intake for optimal nutrition.
• Free sugar should be limited to 5% of total energy intake in children and 10% for adults.

Lipids

• Lipids include all fats and oils that occur in human diets, with "oil" referring to liquid and "fat" to solid lipids at room temperature.
• Lipids are a concentrated source of energy, with a gram of fat/oil generating 9 kilocalories upon combustion.
• Fat should comprise 20 to 35% of daily calories.
• Lipids also serve as energy storage, in structural functions, and make diet more palatable.
• Stored fats serve as fuel reserves for the body, storing excess calories.

Proteins

• Protein carries out a variety of functions in the body, including building and repairing body tissues.
• Protein is essential for optimal growth and development.