NUTR-120-02 (20363.202501) on 2/25/2025 (Tue)

Return from Break

• Welcome back from February break

• Review of fiber and carbohydrates

• Transition to protein

Benefits of Fiber

• Colorectal Cancer: Science has demonstrated fiber reduces cancer risk, especially due to butyric acid from soluble fiber fermentation.

• Cholesterol Levels: Fiber aids in lowering blood cholesterol.

• Weight Management: Sufficient fiber is essential for managing healthy weight, promoting fullness and satiety.

Mechanism of Satiety

• Feeling Full: Fiber-rich foods increase feelings of fullness and take longer to digest.

• Delayed Gastric Emptying: More fiber prolongs the time food remains in the stomach.

• Glycemic Response: High fiber intake leads to a flatter glycemic response, aiding in blood sugar regulation.

• Eating Behavior: Foods high in fiber require more chewing and time to consume, allowing the body to sense fullness and prevent overeating.

Recommendations for Fiber Intake

• Current Intake: Average intake is 12-15 grams per day, much lower than recommended.

• Recommended Intake: 14 grams of fiber per 1000 calories consumed.

• Example Calculation: For a 2500-calorie diet, fiber requirement = 35 grams.

• Emphasis on Complex Carbohydrates: Majority of carbohydrate choices should derive from whole grains, vegetables, and fruits, which are also rich in fiber.

Addressing Misconceptions

• Cleansing Myths: Claims of needing to 'cleanse' the body, such as colonic irrigation, lack scientific backing and can be dangerous.

• Natural Cleansing: A fiber-rich diet naturally helps maintain digestive health.

Transition to Protein

• Market Trends: Increased focus on protein consumption over the past decade; awareness of marketing claims around protein-rich products.

• Critical Thinking: Encourage scrutiny of protein claims in ads.

Protein Structure and Function

• Definition: Protein is a component of every living cell made from amino acids (20 total, 9 essential).

• Nitrogen Source: Unique among macronutrients as protein includes nitrogen.

• Protein Function: Proteins serve various vital roles including enzymes, hormones, and structural components.

Types of Amino Acids

• Essential Amino Acids: Must be consumed via diet.

• Nonessential Amino Acids: Can be synthesized by the body.

• Significant Examples: Methionine and phenylalanine – relevance in diets and metabolic disorders like PKU.

Protein Formation

• Peptide Bonds: Formation occurs via dehydration (condensation reaction) leading to peptide and polypeptide chains.

• Hydrolysis: The process of breaking down proteins into amino acids, aided by enzymatic actions.

• Protein Structure Levels:

  • Primary Structure: Linear sequence of amino acids.

  • Secondary Structure: Folding of the linear structure due to interactions between amino acids.

  • Tertiary Structure: 3D shape formed by further folding and interactions.

Denaturation and Functionality

• Denaturation: The process where proteins lose their functional shape due to heat or chemicals; affects functionality.

• Importance of Structure: The unique shape of proteins is crucial to their specific functions (e.g., insulin).

Sickle Cell Anemia Example

• Genetic Mutation: A single amino acid change can dramatically alter protein functionality (e.g., hemoglobin structure).

• Consequences: Sickle-shaped red blood cells result from this mutation, reducing oxygen transport capacity.

Protein Digestion and Absorption

• Process Overview:

  • In the Stomach: HCl denatures proteins; pepsin initiates protein digestion into peptides.

  • In the Small Intestine: Further breakdown by pancreatic enzymes (trypsin, chymotrypsin) into amino acids and small peptides.

  • Absorption: Primarily occurs through di- and tripeptides, later converted to amino acids in intestinal cells; absorbed into portal circulation.

Final Notes

• Importance of understanding protein function beyond muscle growth.

• Protein serves critical roles in metabolism, immune response, hormone production, etc.

• Examining protein intake sources among different populations.

• Emphasis on whole food sources of protein versus processed foods.