Chapter 1 – What is Nutrition?

Introduction to Nutrition

Nutrition is the science that studies the interactions between living organisms and the substances they consume for sustenance, growth, and health. It encompasses the processes of ingestion, digestion, absorption, metabolism, and excretion of food.

• Sensory Aspects of Food: Sensory factors such as taste, smell, texture, and appearance influence food choices by affecting palatability and preference.

• Food Selection Influences: Food choices are shaped by cultural history, social factors, personal preferences, and availability.

• Dietary Changes: Historical and cultural shifts in diet can impact health outcomes and nutritional status.

• Classes of Nutrients: Nutrients are classified into six major groups: carbohydrates, proteins, fats, vitamins, minerals, and water.

• Macronutrient Caloric Values: Carbohydrates and proteins provide 4 kcal/g, while fats provide 9 kcal/g.

• Scientific Inquiry in Nutrition: Nutrition science relies on peer-reviewed research and evidence-based practice.

• Evaluating Information: Reliable nutrition information should be based on scientific studies and reputable sources.

• Types of Studies: Epidemiological studies, case-control studies, and clinical trials are common research methods in nutrition.

• Nutrition Professionals: Nutritionist, Dietitian, and Registered Dietitian Nutritionist (RDN) have distinct qualifications and roles.

• American Diet: The typical American diet is often high in processed foods, added sugars, and saturated fats.

• Improvement Areas: Increasing intake of fruits, vegetables, whole grains, and lean proteins can improve diet quality.

• Caloric Needs: Caloric requirements vary by age, sex, activity level, and physiological status.

• Energy Calculation: Energy content of food is calculated based on macronutrient composition.

• Essential Nutrients: Essential nutrients are those that must be obtained from the diet because the body cannot synthesize them.

• Phytochemicals: Phytochemicals are bioactive compounds found in plants that may have health benefits.

• 2,000 Calorie Diet: A 2,000 calorie diet is commonly used as a reference for daily nutritional needs.

Key Definitions

• Nutrition: The study of nutrients in food and how the body uses them.

• Macronutrients: Nutrients required in large amounts: carbohydrates, proteins, and fats.

• Micronutrients: Nutrients required in smaller amounts: vitamins and minerals.

• Essential Nutrients: Nutrients that must be obtained from the diet.

Example: Calculating Energy from Macronutrients

• To calculate the energy provided by a food item, use the following formula:

Chapter 2 – Tools for Healthy Eating

Dietary Reference Intakes (DRIs)

DRIs are a set of reference values used to plan and assess nutrient intakes of healthy people. They include several types of recommendations:

• Estimated Average Requirement (EAR): The average daily nutrient intake level estimated to meet the requirement of half the healthy individuals in a group.

• Recommended Dietary Allowance (RDA): The average daily intake sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals.

• Adequate Intake (AI): Established when evidence is insufficient to develop an RDA; a recommended intake level based on observed or experimentally determined estimates.

• Tolerable Upper Intake Level (UL): The highest daily intake likely to pose no risk of adverse health effects.

Acceptable Macronutrient Distribution Range (AMDR)

• AMDR provides recommended ranges for macronutrient intake as a percentage of total energy:

• Carbohydrates: 45–65%

• Fats: 20–35%

• Proteins: 10–35%

Energy Requirement Calculations

• Estimated Energy Requirement (EER): The average dietary energy intake predicted to maintain energy balance in a healthy adult.

Dietary Guidelines and Food Labels

• Dietary Guidelines: Recommendations for healthy eating patterns to promote health and prevent chronic disease.

• MyPlate: A visual guide to help consumers build healthy meals with appropriate portions of fruits, vegetables, grains, protein, and dairy.

• Food Labels: Provide information on nutrient content, serving size, and ingredients to help consumers make informed choices.

Interpreting Food Labels

• Key information includes serving size, calories, macronutrient content, vitamins, minerals, and % Daily Value.

• Understanding food labels helps in managing dietary intake and making healthier choices.

Chapter 3 – The Basics of Digestion

Overview of Digestion

Digestion is the process by which food is broken down into absorbable components. It involves mechanical and chemical processes throughout the gastrointestinal (GI) tract.

• Digestion in the Mouth: Mechanical digestion begins with chewing; enzymes in saliva start carbohydrate breakdown.

• Digestion in the Stomach: Proteins are primarily digested by gastric enzymes and acid.

• Mechanical vs. Chemical Digestion: Mechanical digestion involves physical breakdown (chewing, mixing), while chemical digestion involves enzymatic reactions.

• Bolus and Chyme: A bolus is a mass of chewed food; chyme is the semi-liquid mixture in the stomach.

• Peristalsis and Segmentation: Peristalsis is wave-like muscle contractions; segmentation mixes and moves food along the GI tract.

• Saliva: Composed of water, enzymes, and mucus; produced by salivary glands.

• Organs of Digestion: Includes mouth, esophagus, stomach, small intestine, large intestine, liver, pancreas, and gallbladder.

• Accessory Organs: Liver (produces bile), pancreas (produces digestive enzymes), gallbladder (stores bile).

• Enzymes: Biological catalysts that speed up chemical reactions; specific enzymes digest carbohydrates, proteins, and fats.

• Small Intestine: Main site of nutrient absorption; surface area increased by villi and microvilli.

• Duodenum: First section of the small intestine; receives chyme and digestive secretions.

• Large Intestine: Absorbs water and electrolytes; forms and stores feces.

• Excretory System: Removes waste products from the body.

• Digestive Disorders: Common disorders include acid reflux, ulcers, irritable bowel syndrome, and lactose intolerance.

Table: Comparison of Mechanical and Chemical Digestion

Example: Enzyme Action in Digestion

• Amylase: Breaks down starches into sugars in the mouth.

• Pepsin: Breaks down proteins in the stomach.

• Lipase: Breaks down fats in the small intestine.

Additional info:

• Functional foods are foods that provide health benefits beyond basic nutrition, such as probiotics or fortified foods.

• Hormones like gastrin and secretin regulate digestive processes.