Nutrition: Linking Food and Health

Definition of Nutrition and Wellness

• Nutrition is the science that studies the interactions between living organisms and the substances they consume for sustenance, growth, and health.

• Wellness refers to an overall state of health, encompassing physical, mental, and social well-being, not merely the absence of disease.

• Relationship: Good nutrition is a foundational component of wellness, influencing energy levels, disease risk, and quality of life.

Nutrition vs. Food

• Food is any substance consumed to provide nutritional support for the body.

• Nutrition is the process by which the body takes in and uses food substances.

• Key Difference: Food is the source; nutrition is the process and science of utilizing food for health.

Energy, Calorie, and Kilocalorie

• Energy is the capacity to do work, required for all bodily functions.

• Calorie (cal): The amount of energy needed to raise the temperature of 1 gram of water by 1°C.

• Kilocalorie (kcal): Equal to 1,000 calories; used in nutrition to express the energy content of foods.

• In nutrition, "calorie" typically refers to the kilocalorie (kcal).

Six Classes of Essential Nutrients

• Carbohydrates

• Fats (Lipids)

• Proteins

• Vitamins

• Minerals

• Water

Energy Nutrients

• The three nutrients that provide energy are carbohydrates, fats, and proteins.

• Each provides a specific amount of energy per gram:

  • Carbohydrates: 4 kcal/g

  • Proteins: 4 kcal/g

  • Fats: 9 kcal/g

Calculating Calories from Nutrients

• To calculate calories from a nutrient, multiply the grams of the nutrient by its energy value:

• Example: 10g of fat provides kcal.

Macronutrients vs. Micronutrients

• Macronutrients: Nutrients required in large amounts (carbohydrates, proteins, fats, water).

• Micronutrients: Nutrients required in small amounts (vitamins and minerals).

Vitamins vs. Minerals

• Vitamins: Organic compounds essential for normal growth and nutrition, required in small quantities.

• Minerals: Inorganic elements needed for various body functions.

• Major minerals: Needed in amounts >100 mg/day (e.g., calcium, sodium, potassium).

• Trace minerals: Needed in amounts <100 mg/day (e.g., iron, zinc, copper).

Dietary Reference Intakes (DRIs)

• DRIs are a set of reference values for nutrient intake to be used for planning and assessing diets.

• Components include:

  • RDA (Recommended Dietary Allowance)

  • AI (Adequate Intake)

  • UL (Tolerable Upper Intake Level)

  • EAR (Estimated Average Requirement)

Credible Sources for Nutritional Information

• Peer-reviewed journals

• Government agencies (e.g., USDA, NIH)

• Registered dietitians (RD or RDN)

• Academic institutions

The Scientific Method in Nutrition

• Steps include:

  1. Observation

  2. Hypothesis formation

  3. Experimentation

  4. Data analysis

  5. Conclusion

  6. Peer review and publication

Prebiotics, Probiotics, Epigenetics, and Nutrigenomics

• Prebiotics: Non-digestible food components that promote the growth of beneficial gut bacteria (e.g., inulin, oligosaccharides).

• Probiotics: Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host (e.g., Lactobacillus species).

• Role of Probiotics: Improve gut health, enhance immune function, and may prevent certain gastrointestinal disorders.

• Epigenetics: The study of heritable changes in gene expression that do not involve changes to the DNA sequence, often influenced by environmental factors including diet.

• Nutrigenomics: The study of how nutrients and genes interact to affect health.

Phytochemicals

• Phytochemicals: Biologically active compounds found in plants that may provide health benefits.

• Five major groups:

  • Flavonoids

  • Carotenoids

  • Phenolic acids

  • Phytoestrogens

  • Organosulfur compounds

• Role in the body: Antioxidant activity, modulation of detoxification enzymes, stimulation of the immune system, and reduction of inflammation.

Designing a Healthful Diet

Components of a Healthful Diet

• Adequacy: Provides sufficient energy and essential nutrients.

• Balance: Includes appropriate proportions of all food groups.

• Moderation: Limits excesses of unhealthy components (e.g., added sugars, saturated fats).

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

Reading Food Labels and the Nutrition Facts Panel

• Food labels provide information on serving size, calories, and nutrient content.

• The Nutrition Facts Panel lists:

  • Serving size and servings per container

  • Calories per serving

  • Macronutrient content (carbohydrates, proteins, fats)

  • Micronutrient content (vitamins and minerals)

  • Percent Daily Values (%DV)

• Application: Use the panel to compare products and make informed choices.

Dietary Guidelines for Americans

• Evidence-based recommendations to promote health and reduce risk of chronic diseases.

• Key messages include:

  • Follow a healthy eating pattern across the lifespan.

  • Focus on variety, nutrient density, and amount.

  • Limit added sugars, saturated fats, and sodium.

  • Support healthy eating patterns for all.

Food Groups, Servings, and Serving Sizes

• Major food groups:

  • Fruits

  • Vegetables

  • Grains

  • Protein foods

  • Dairy

• Each group has recommended daily servings and serving sizes, which can be found in resources like MyPlate or the Dietary Guidelines.

Comparing Pyramid Plans

• Different dietary pyramids (e.g., MyPyramid, Mediterranean Pyramid) emphasize various aspects of healthy eating.

• Similarities: Both encourage fruits, vegetables, whole grains, and moderation.

• Differences: Mediterranean Pyramid emphasizes olive oil and fish; MyPyramid focuses on physical activity and portion sizes.

The Human Body: Are We Really What We Eat?

Appetite vs. Hunger

• Appetite: Psychological desire to eat, influenced by senses, emotions, and social factors.

• Hunger: Physiological need for food, regulated by internal cues such as hormones and nutrient levels.

• Mechanisms: Hunger is stimulated by hormones like ghrelin; appetite can be triggered by sight, smell, or thought of food.

Role of Senses and Emotions in Appetite

• Sight, smell, taste, and texture of food can stimulate appetite even in the absence of hunger.

• Emotions such as stress, boredom, or happiness can influence eating behavior.

Factors Influencing Satiation

• Satiation: The feeling of fullness and satisfaction that signals the end of eating.

• Influenced by:

  • Stomach distension

  • Hormones (e.g., leptin, cholecystokinin)

  • Nutrient composition (protein and fiber increase satiation)

Pathway of Food Through the Gastrointestinal Tract

• Food passes through the following organs:

  1. Mouth

  2. Esophagus

  3. Stomach

  4. Small intestine

  5. Large intestine

  6. Rectum

  7. Anus

Organs Involved in Digestion and Absorption

• Directly involved: Mouth, esophagus, stomach, small intestine, large intestine.

• Accessory organs: Salivary glands, liver, gallbladder, pancreas.

Enzymes and Hormones in Digestion and Absorption

• Enzymes: Amylase (carbohydrates), protease (proteins), lipase (fats).

• Hormones: Gastrin, secretin, cholecystokinin (CCK), insulin, glucagon.

Common Digestive Disorders

• Gastroesophageal Reflux Disease (GERD): Stomach acid flows back into the esophagus, causing heartburn.

• Ulcers: Sores in the stomach or duodenal lining, often caused by Helicobacter pylori infection or NSAIDs.

• Food Allergies: Immune response to specific proteins in food.

• Celiac Disease: Autoimmune reaction to gluten, damaging the small intestine.

• Diarrhea: Frequent, watery stools; can result from infection, food intolerance, or digestive disorders.

• Constipation: Infrequent or difficult bowel movements, often due to low fiber or fluid intake.

• Irritable Bowel Syndrome (IBS): Functional disorder causing abdominal pain, bloating, and altered bowel habits.

• Treatments: Vary by condition; may include dietary changes, medications, or probiotics.