Nutrition Fundamentals

Definition of Nutrition

Nutrition is the scientific study of nutrients and other substances in food, their action, interaction, and balance in relation to health and disease. It also includes the processes by which the body ingests, digests, absorbs, transports, utilizes, and excretes food substances.

• Nutrients are substances in food that provide energy, structure, and help regulate body processes.

• Nutrition is essential for growth, development, and maintenance of health throughout life.

Registered Dietitian vs Nutritionist

• Registered Dietitian (RD): A health professional who has met specific academic and professional requirements, including a bachelor's degree in nutrition or a related field, supervised practice, and passing a national exam. RDs are credentialed and regulated.

• Nutritionist: A general term for someone who provides nutrition advice. The title is not regulated in many regions, so qualifications can vary widely.

• Key Difference: All RDs are nutritionists, but not all nutritionists are RDs.

Macronutrients and Micronutrients

Macronutrients: Composition, Examples, and Calories per Gram

Macronutrients are nutrients required in large amounts that provide energy to the body.

• Carbohydrates: Composed of carbon, hydrogen, and oxygen. Main source of energy. 4 kcal/gram.

• Proteins: Made of amino acids (carbon, hydrogen, oxygen, nitrogen). Essential for growth and repair. 4 kcal/gram.

• Lipids (Fats): Composed of fatty acids and glycerol (carbon, hydrogen, oxygen). Energy storage and cell structure. 9 kcal/gram.

• Water: Does not provide energy but is vital for all bodily functions.

Examples:

• Carbohydrates: Bread, rice, fruits

• Proteins: Meat, beans, dairy

• Lipids: Oils, butter, nuts

Micronutrients: Vitamins and Minerals

Micronutrients are required in smaller amounts but are essential for health.

• Vitamins: Organic compounds needed for various metabolic processes.

• Minerals: Inorganic elements that play structural and regulatory roles.

Vitamins: Categories and Examples

• Fat-soluble vitamins: A, D, E, K (stored in body fat)

• Water-soluble vitamins: B-complex (e.g., B1, B2, B6, B12, folate) and C (not stored, excess excreted)

Minerals

• Major minerals: Needed in larger amounts (e.g., calcium, potassium, sodium, magnesium)

• Trace minerals: Needed in smaller amounts (e.g., iron, zinc, iodine, selenium)

Healthy Diet Principles

Components of a Healthy Diet

• Adequacy: Provides sufficient energy and nutrients.

• Balance: Includes appropriate proportions of food groups.

• Moderation: Limits excesses of unhealthy components.

• Variety: Includes many different foods from all food groups.

2020-2025 Dietary Guidelines for Americans: Food Pattern Food Groups

• Fruits

• Vegetables

• Grains (at least half whole grains)

• Protein foods (meat, poultry, seafood, eggs, nuts, seeds, soy products)

• Dairy (including fortified soy alternatives)

• Oils (healthy fats)

Nutrient Dense vs Calorie Dense

• Nutrient Dense: Foods high in vitamins, minerals, and other beneficial substances with relatively few calories (e.g., vegetables, fruits, lean meats).

• Calorie Dense: Foods high in calories relative to weight, often with fewer nutrients (e.g., fried foods, sweets).

Hunger, Appetite, and Satiety

Hunger vs Appetite

• Hunger: Physiological need for food, regulated by internal cues (e.g., low blood glucose).

• Appetite: Psychological desire to eat, influenced by external cues (e.g., sight, smell, emotions).

Hunger Physiology

• Regulated by the hypothalamus in the brain.

• Hormones such as ghrelin (stimulates hunger) and leptin (promotes satiety) play key roles.

Satiety

• The feeling of fullness and satisfaction after eating, which suppresses the urge to eat for a period of time.

• Influenced by meal composition (protein and fiber increase satiety), volume, and hormonal signals.

Dietary Reference Intakes (DRIs)

Key Terms

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

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

• UL (Tolerable Upper Intake Level): Maximum daily intake unlikely to cause adverse health effects.

• AMDR (Acceptable Macronutrient Distribution Range): Range of intake for a particular energy source (carbohydrate, fat, protein) associated with reduced risk of chronic disease.

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

Nutrition Labeling

Nutrition Label

• Provides information on serving size, calories, macronutrients, micronutrients, and % Daily Values.

• Helps consumers make informed food choices.

• Key nutrients listed: total fat, saturated fat, cholesterol, sodium, total carbohydrate, dietary fiber, total sugars, protein, vitamins, and minerals.

Human Body Organization and Digestion

Body System Organization

• Levels: Cells → Tissues → Organs → Organ Systems → Organism

• The digestive system is one of the major organ systems involved in nutrition.

Mechanical and Chemical Digestion

• Mechanical digestion: Physical breakdown of food (e.g., chewing, churning in stomach).

• Chemical digestion: Enzymatic breakdown of food into absorbable molecules.

Gastrointestinal (GI) Organs and Accessory Organs

• GI Tract Organs: Mouth, esophagus, stomach, small intestine, large intestine, rectum, anus.

• Accessory Organs: Salivary glands, liver, gallbladder, pancreas (produce or store substances needed for digestion).

Digestion and Absorption

• Digestion breaks down food into smaller components.

• Absorption is the process by which nutrients pass from the GI tract into the blood or lymph.

• Most absorption occurs in the small intestine.

Digestive Enzymes

• Amylase: Breaks down carbohydrates (produced by salivary glands and pancreas).

• Proteases: Break down proteins (produced by stomach, pancreas, small intestine).

• Lipases: Break down fats (produced by pancreas).

Food Sensitivities and Disorders

Celiac Disease

• An autoimmune disorder where ingestion of gluten (a protein in wheat, barley, rye) damages the small intestine lining.

• Symptoms: diarrhea, weight loss, malabsorption, fatigue.

• Treatment: strict gluten-free diet.

Food Intolerance vs Allergy

• Food Intolerance: Non-immune response, often due to enzyme deficiency (e.g., lactose intolerance).

• Food Allergy: Immune system reaction to a food protein (e.g., peanut allergy), can be life-threatening.

• Key Difference: Allergies involve the immune system; intolerances do not.