1. Food Choices

1.1 What We Need

Nutrition is the study of nutrients in food and how they affect bodily functions and health. Understanding what the body needs is essential for making informed food choices.

• Nutrients: Compounds that sustain bodily processes and provide energy, build tissues, and regulate metabolism.

• Six Classes of Nutrients:

  • Carbohydrates

  • Lipids (fats and oils)

  • Proteins

  • Vitamins

  • Minerals

  • Water

• Energy in Food: Measured in kilocalories (kcal).

• Influences on Food Choices: Taste, cost, convenience, culture, and emotions.

2. Good Nutrition

2.1 Definition and Importance

Good nutrition involves consuming the right balance of nutrients to support health and prevent disease.

• Malnutrition: Poor nutrition due to insufficient or excessive intake of nutrients.

• Chronic Diseases: Many leading causes of death are linked to nutrition (e.g., heart disease, diabetes).

3. Essential Nutrients

3.1 Definition and Types

Essential nutrients are required for body function and must be obtained from the diet.

• Macronutrients: Carbohydrates, proteins, and fats; provide energy and are needed in large amounts.

• Micronutrients: Vitamins and minerals; needed in smaller amounts for regulatory functions.

• Water: Vital for all bodily processes.

3.2 Energy-Yielding Nutrients

• Carbohydrates: Body's preferred energy source.

• Fats: Provide energy and support cell structure.

• Proteins: Build and repair tissues, can be used for energy.

Energy Values:

• Carbohydrates: 4 kcal/g

• Proteins: 4 kcal/g

• Fats: 9 kcal/g

4. The Average American Diet

4.1 Quality and Concerns

The typical American diet is often high in added sugars, sodium, and saturated fat, and low in fruits, vegetables, and whole grains.

• High rates of overweight and obesity among adults and children.

• Dietary patterns contribute to chronic diseases.

5. Nutrition Research and Guidelines

5.1 Scientific Method in Nutrition

Nutrition research uses the scientific method to study the effects of diet on health.

• Observational and experimental studies are common.

• Peer review ensures quality and reliability.

5.2 Dietary Reference Intakes (DRIs)

DRIs are a set of reference values for nutrient intake to maintain health and prevent chronic disease.

• Recommended Dietary Allowance (RDA): Average daily intake sufficient for most healthy individuals.

• Estimated Average Requirement (EAR): Intake estimated to meet needs of 50% of individuals.

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

• Acceptable Macronutrient Distribution Range (AMDR): Healthy range of energy-providing nutrients.

6. Dietary Guidelines and Food Labels

6.1 Dietary Guidelines for Americans

These guidelines provide advice on healthy eating patterns to promote health and prevent disease.

• Emphasize fruits, vegetables, whole grains, lean proteins, and low-fat dairy.

• Limit added sugars, saturated fats, and sodium.

6.2 Food Labels

Food labels provide information about the nutrient content of packaged foods.

• Nutrition Facts Panel: Lists serving size, calories, and nutrient amounts.

• Ingredients List: Shows all ingredients in descending order by weight.

• Daily Value (DV): Reference values for nutrients based on a 2,000 kcal diet.

7. Functional Foods

7.1 Definition and Examples

Functional foods contain bioactive compounds that provide health benefits beyond basic nutrition.

• Phytochemicals: Plant chemicals with health-promoting properties (e.g., antioxidants).

• Probiotics: Live beneficial bacteria found in foods like yogurt.

8. Digestion

8.1 Overview of Digestion

Digestion is the process of breaking down food into smaller components for absorption and use by the body.

• Mechanical Digestion: Physical breakdown of food (chewing, mixing).

• Chemical Digestion: Enzymatic breakdown of macromolecules.

8.2 Organs of the Digestive Tract

• Mouth: Begins mechanical and chemical digestion.

• Esophagus: Transports food to the stomach via peristalsis.

• Stomach: Mixes food with gastric juices; protein digestion begins.

• Small Intestine: Major site of nutrient absorption; enzymes from pancreas and bile from liver aid digestion.

• Large Intestine: Absorbs water and forms feces.

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

8.3 Digestive Enzymes

8.4 Absorption

Absorption is the process by which digested nutrients move into the blood or lymphatic system for distribution.

• Villi and Microvilli: Increase surface area for absorption in the small intestine.

• Passive and Active Transport: Nutrients cross cell membranes by different mechanisms.

9. Transport, Storage, and Excretion

9.1 Nutrient Transport

• Circulatory System: Transports nutrients via blood.

• Lymphatic System: Transports fats and fat-soluble vitamins.

9.2 Storage and Excretion

• Storage: Excess nutrients are stored in liver, muscles, or adipose tissue.

• Excretion: Waste products are eliminated via urine and feces.

10. Common Digestive Disorders

10.1 Overview and Examples

11. Nutritional Genomics

11.1 Nutrition and Gene Expression

Nutritional genomics studies how nutrients affect gene expression and how genetic variation influences nutritional needs.

• Gene: Segment of DNA coding for specific proteins.

• Epigenetics: Mechanisms that affect gene expression without altering DNA sequence.

Key Equations

• Energy Provided by Macronutrients:

• Body Mass Index (BMI):

Additional info: Some explanations and examples have been expanded for clarity and completeness.