Food and Nutrition Overview

Food and Nutrition

• Foodstuffs: All products eaten or drunk. Classified as vegetable (plants) or animal-based (animals or animal products).
• Nutrients: Usable components of foodstuffs. Categorized as:
  • Building blocks: Construct cells and tissues, crucial for growth, development, and recovery.
  • Fuels: Provide energy for movement, body temperature, growth and repair.
  • Food reserves: Stored in the body.
  • Protective substances: Maintain health.

Nutrient Groups and Functions

• Proteins: Primarily building blocks but also fuel. Excess converted to fat and stored.
• Carbohydrates: Primarily fuel, also building blocks and reserves. Examples include sugars (glucose), starch, and glycogen. Excess converted to fat. Glucose can be stored as glycogen in the liver and muscles.
• Fats: Primarily fuel, also building blocks and reserves. Can be stored under the skin.
• Water: Essential for building materials and transporting substances.
• Minerals (salts): Building materials and protective substances. Example: calcium phosphate for bones.
• Vitamins: Building materials and protective substances. Identified by letters (e.g., A, B, C, D, K). Examples include vitamin A for skin and vision, and vitamin D for bone calcium absorption.

Digestion

• Digestion: Conversion of nutrients unable to pass through the gut wall into usable forms. Proteins, most carbs, and fats are digested. Glucose, minerals, vitamins, and water don't need digestion.
• Mechanical Digestion: Breaking food into smaller pieces (chewing).
• Chemical Digestion: Converting nutrients using digestive juices, containing enzymes.
• Enzymes: Substances speeding up chemical reactions, crucial in digestion.

Digestive System Components and Functions

• Oral Cavity (Mouth): Salivary glands produce saliva (water, mucus, starch-digesting enzyme).
• Oesophagus (Gullet): Transports food from the throat to the stomach.
• Stomach: Temporary storage; gastric glands produce gastric juice (water, hydrochloric acid (kills bacteria), protein-digesting enzyme). Pyloric sphincter controls stomach exit.
• Liver: Produces bile (contains enzymes; emulsifies fats), stored in the gallbladder.
• Pancreas: Produces pancreatic juice (contains enzymes to digest proteins, carbohydrates, and fats).
• Duodenum: Site where bile and pancreatic juices mix with chyme (food pulp).
• Small Intestine: Absorbs nutrients, digestion products, and water into the blood. Highly folded, with villi containing blood vessels.
• Large Intestine: Absorbs water from undigested food, producing thicker waste. Bacteria digest cellulose, producing glucose.
• Rectum: Collects and stores waste (faeces).
• Anus: Sphincter controlling waste elimination.

Digestive Juices

• Saliva: Water, mucus, and an enzyme for partial starch digestion.
• Gastric juice: Water, hydrochloric acid (kills bacteria), and an enzyme for partial protein digestion.
• Bile: Contains enzymes, emulsifies fats.
• Pancreatic juice: Various enzymes for protein, carbohydrate, and fat digestion.

Diet and Health

• Balanced Diet: Necessary to get nutrients from each food group.
• Body Mass Index (BMI): Formula comparing weight and height to assess healthy weight. Different thresholds based on age group.
• Overweight/Obesity: Health risks include cardiovascular disease, type 2 diabetes, and joint problems.
• Underweight: Higher risk of illness and fatigue.
• Healthy Weight Choices: Eat healthily, avoid skipping meals, and limit unhealthy foods.

Eating Disorders

• Causes: Cultural/media influences, life events, control issues, fear of failure or perfectionism.
• Types: Anorexia nervosa, bulimia nervosa, binge eating disorder.
• Consequences: Malnutrition, internal damage (anorexia, bulimia), possible obesity (binge eating).

Dietary Adaptations for Different Diets

• Harder Plant-Based Digestion: Plant cell walls (cellulose) are slower to digest than animal-based foods.
• Herbivores: Longer intestines, ridged molars, lack of canines.
• Carnivores: Shorter intestines, molars for shearing/cutting, pointed canines, wider upper jaw.
• Omnivores: Medium intestines, molars for both cutting and grinding, generally with canines.