Biochem - Principles of Nutrition

Learning Outcomes

• Ability to describe healthy diet composition and caloric content.
• Understanding of energy balance principles within the body.
• Knowledge of Basal Metabolic Rate (BMR) and diet-induced thermogenesis (DIT).
• Explanation of Daily Energy Expenditure (DEE).
• Familiarity with Dietary Reference Intakes (DRI).
• Overview of Total Parenteral Nutrition (TPN).
• Recognition of essential dietary factors and nutritional deficiency consequences.

A Healthy Diet

• Focus on fruits, vegetables, and whole grains.
• Inclusion of fat-free or low-fat dairy products.
• Incorporates lean meats, poultry, fish, beans, eggs, and nuts.
• Emphasizes foods low in saturated fats, cholesterol, and added sugars.

Important Principles of Nutrition

• Adequacy: Sufficient essential nutrients intake.
• Balance: Avoid reliance on a single food type.
• Energy Control: Prevent overeating and undereating.
• Moderation: Maintain appropriate quantities of food.
• Variety: Include a diversity of foods for nutrition.
• Encourage healthy weight maintenance and physical activity for 30-60 minutes daily.

Nutrient Classification

• Macronutrients: Required in large quantities (g).
  • Includes carbohydrates, fats, and proteins.
• Micronutrients: Needed in smaller amounts (mg).
  • Includes vitamins and minerals.

Energy Yielding Nutrients

• Carbohydrates: Organic compounds that provide energy; includes sugars (sucrose, lactose, glucose) and starches.
• Lipids (Fats): Triglycerides yield more energy during oxidation; essential for growth and critical illness recovery.

Vitamins and Minerals

• Vitamins: Organic, divided into water-soluble (B vitamins, Vitamin C) and fat-soluble (Vitamins A, D, E, K); deficiencies can cause diseases.
• Macro-minerals: Required above 100 mg/day; examples include calcium, phosphorus, potassium, and magnesium.
• Micro-minerals: Essential in small amounts; include iron, zinc, and iodine.

Energy Units

• Caloric intake measured in kilocalories (kcal); SI unit is kilojoule (kJ).
• Energy content per gram: Carbohydrates 4.0 kcal, Protein 4.0 kcal, Fat 9.0 kcal, Alcohol 7.0 kcal.

Basal Metabolic Rate (BMR)

• Energy expended at rest, awake, in a neutral environment, 12 hours after eating.
• Roughly 24 kcal/kg of body weight daily; varies with age, sex, and health status.

Daily Energy Expenditure (TDEE)

• Total calories burned in a day, including BMR, physical activity, and thermic effect of food (about 10% of BMR).
• Maintains weight balance: Energy intake equals energy expenditure.

Dietary Reference Intakes (DRI)

• Reference values for nutrient intake used in assessing diets for populations.
• Include Lower Reference Nutrient Intake (LRNI), Estimated Average Requirement (EAR), Recommended Dietary Allowance (RDA), and Upper Limit (UL).

Total Parenteral Nutrition (TPN)

• Clinical practice of administering nutrition intravenously, bypassing the digestive system.
• Nutritional components: water, glucose, salts, amino acids, and vitamins.

Body Mass Index (BMI)

• Formula: BMI = body weight (kg) ÷ height (m²).
• Identifies obesity risks and correlates with body fat percentage.
• Example calculation for 72 kg weight and 1.83 m height yields a BMI of 21.5 kg/m².

Principles of Nutrition

• Adequacy involves consuming sufficient amounts of all essential nutrients.
• Balance emphasizes not depending solely on one food type for nutrition.
• Energy control focuses on avoiding both overeating and under-eating.
• Moderation suggests maintaining a healthy intake of all food groups, neither too much nor too little.
• Variety encourages including a diverse range of foods for overall nutritional benefit.
• Aiming for a healthy weight is vital for overall health.
• Physical activity should be practiced for 30-60 minutes daily for optimal health.

Regulator Nutrients: Micro-Minerals

• Iron (Fe): Critical for biological functions; body content is 2.4g; RDA is 8mg (male), 18mg (female).
• Zinc (Zn): Essential for various bodily processes; body content is 1.5 - 2.5g; RDA is 11mg (male), 8mg (female).
• Molybdenum (Mo): Unknown body content; RDA is 45mcg.
• Selenium (Se): Important for antioxidant functions; body content is 15mg; RDA is 55mcg.
• Iodine (I): Required for thyroid function; body content is 15 - 20mg; RDA is 150mcg.
• Manganese (Mn): Necessary for bone formation and metabolism; body content is 10 - 20mg; RDA is 2.3mg (male), 1.8mg (female).

Energy Yielding Nutrients and Metabolism

• Understanding energy yielding nutrients is essential for assessing metabolism and caloric needs.

Basal Caloric Requirements

• Males require approximately 1800 kcal/day to maintain basic metabolic rate (BMR).
• Females require approximately 1300 kcal/day for BMR.
• Recommended Dietary Allowances (RDA) escalate to 2800 kcal/day (male) and 2100 kcal/day (female) to support daily functions.
• Additional caloric intake: +300 during pregnancy and +500 during lactation.

BMI Ranges

• Body Mass Index (BMI) is a measure used for assessing body weight relative to height, indirectly indicating healthy weight ranges.

This quiz focuses on the principles of nutrition as covered in the DEM Year 2 course at RCSI. Students will describe the composition and caloric content of a healthy diet, explain energy balance, and discuss BMR and thermogenesis. Prepare to test your understanding of these foundational concepts in gastrointestinal biology.