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Nutrition

The science of how food affects the body, including the study of nutrients, their functions, dietary requirements, and the relationship between diet and health.

Macronutrients

Macronutrients is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Micronutrients

Micronutrients is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Energy Balance

Energy Balance is a fundamental physics concept explaining the behavior of matter and energy, with formulas and real-world applications.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Dietary Reference Intakes

Dietary Reference Intakes is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Nutritional Assessment

Nutritional Assessment is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Malnutrition

Malnutrition is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Functional Foods

Functional Foods is a core mathematics topic covering definitions, formulas, and problem-solving techniques essential for mastery.

Key points: Formal definition, derivation, worked examples, and common applications with step-by-step solutions.

Nutrition Through Life Cycle

Nutrition Through Life Cycle is a clinical topic covering pathophysiology, diagnosis, evidence-based treatment, and patient care.

Key points: Core principles, practical applications, and advanced concepts that build deep understanding.

Key Formulas & Equations

Basal Metabolic Rate (Mifflin-St Jeor):
Men: BMR = 10W + 6.25H - 5A + 5
Women: BMR = 10W + 6.25H - 5A - 161
(W = kg, H = cm, A = years)
Total Daily Energy Expenditure: TDEE = BMR × Activity Factor
Activity Factors: Sedentary = 1.2; Light = 1.375; Moderate = 1.55; Active = 1.725; Very Active = 1.9
BMI: BMI = weight(kg) / height(m)²
Energy Content: Energy = 4 kcal/g protein + 4 kcal/g carb + 9 kcal/g fat + 7 kcal/g alcohol
Atwater System: kcal = 4P + 4C + 9F
Nitrogen Balance: N-balance = N intake - N output
Protein Quality (PDCAAS): PDCAAS = (mg limiting amino acid in 1 g test protein / mg same amino acid in 1 g reference protein) × digestibility
Biological Value: BV = N retained / N absorbed × 100
Net Protein Utilization: NPU = BV × digestibility
Glycemic Index: GI = (AUC test food / AUC glucose) × 100
Glycemic Load: GL = (GI × carbs per serving) / 100
Water Requirement: Water (L) = 0.033 × body weight (kg)

Core Concepts

Macronutrients

Nutrients required in large amounts: carbohydrates (4 kcal/g), proteins (4 kcal/g), and fats (9 kcal/g). Each has specific functions in energy production and body structure.

Micronutrients

Vitamins and minerals required in small amounts. Essential for metabolism, immune function, bone health, and prevention of deficiency diseases.

Energy Balance

The relationship between energy intake (food) and energy expenditure (BMR, activity, thermogenesis). Positive balance leads to weight gain; negative to weight loss.

Dietary Reference Intakes

Recommended Dietary Allowance (RDA), Adequate Intake (AI), and Tolerable Upper Intake Level (UL) for nutrients. Vary by age, sex, and life stage.

Nutritional Assessment

Methods to evaluate nutritional status: anthropometric measurements, biochemical tests, clinical examination, and dietary analysis.

Malnutrition

Undernutrition (wasting, stunting, micronutrient deficiencies) and overnutrition (obesity, diet-related chronic diseases). Affects billions worldwide.

Functional Foods

Foods that provide health benefits beyond basic nutrition. Includes probiotics, prebiotics, omega-3 fatty acids, antioxidants, and phytochemicals.

Nutrition Through Life Cycle

Nutritional needs change throughout life: pregnancy, infancy, childhood, adolescence, adulthood, and older age. Each stage has specific requirements.

Worked Examples

Example 1: BMR Calculation

Problem: Calculate BMR for a 30-year-old male, 80 kg, 180 cm.

Solution:

BMR = 10 × 80 + 6.25 × 180 - 5 × 30 + 5 = 800 + 1125 - 150 + 5 = 1780 kcal/day

Example 2: Energy Content

Problem: A meal contains 30g protein, 50g carbs, and 20g fat. Calculate total energy.

Solution:

Energy = 4 × 30 + 4 × 50 + 9 × 20 = 120 + 200 + 180 = 500 kcal

Example 3: Glycemic Load

Problem: A food has GI = 70 and contains 30g carbs per serving. Calculate GL.

Solution:

GL = (70 × 30)/100 = 21 (high GL: ≥20)

Practice Problems

Problem 1

Calculate BMR for a 25-year-old female, 60 kg, 165 cm.

Answer: BMR = 10×60 + 6.25×165 - 5×25 - 161 = 600 + 1031 - 125 - 161 = 1345 kcal/day

Problem 2

Calculate TDEE for a moderately active person with BMR = 1500 kcal.

Answer: TDEE = 1500 × 1.55 = 2325 kcal/day

Problem 3

Calculate BMI for a person weighing 70 kg and 1.75 m tall.

Answer: BMI = 70/(1.75)² = 22.9 kg/m² (normal weight)

Problem 4

Calculate nitrogen balance if intake = 15g N and output = 12g N.

Answer: N-balance = 15 - 12 = +3g (positive, anabolic state)

Problem 5

Calculate water requirement for a 60 kg person.

Answer: Water = 0.033 × 60 = 1.98 L/day

Problem 6

Calculate energy from 25g protein, 40g carbs, 10g fat.

Answer: Energy = 4×25 + 4×40 + 9×10 = 100 + 160 + 90 = 350 kcal

Problem 7

Calculate GL for GI = 55 and 25g carbs per serving.

Answer: GL = (55 × 25)/100 = 13.75 (medium GL: 11-19)

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