Chapter 1: The Science of Nutrition

Unit Conversions in Nutrition

Understanding unit conversions is essential for interpreting nutrition data and dietary recommendations.

• Pounds (lb) to Ounces (oz): 1 lb = 16 oz

• Pounds (lb) to Kilograms (kg): 1 lb = 0.454 kg

• Kilograms (kg) to Grams (g): 1 kg = 1000 g

• Ounces (oz) to Grams (g): 1 oz = 28.35 g

Macronutrients and Micronutrients

Nutrition is divided into macronutrients and micronutrients, each with distinct roles in the body.

• Macronutrients: Nutrients required in large amounts; provide energy. Includes carbohydrates (CHO), proteins (Pro), and fats (lipids).

• Micronutrients: Nutrients needed in smaller amounts; do not provide energy. Includes vitamins and minerals.

Elements in Macronutrients

• Carbohydrates (CHO): Carbon (C), Hydrogen (H), Oxygen (O)

• Proteins (Pro): Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N)

• Fats (Lipids): Carbon (C), Hydrogen (H), Oxygen (O)

Energy-Yielding Nutrients

• Carbohydrates: 4 kcal/g

• Proteins: 4 kcal/g

• Fats: 9 kcal/g

• Alcohol (not a nutrient): 7 kcal/g

Calculating Kilocalories and Percentages

• Total kcal from a meal: Multiply grams of each macronutrient by its kcal/g value and sum.

• Percent of calories from a macronutrient:

  • Calculate kcal from the macronutrient.

  • Divide by total kcal and multiply by 100.

Formula:

Dietary Reference Intakes (DRIs)

• AMDR (Acceptable Macronutrient Distribution Range): Range of intake for each macronutrient associated with reduced risk of chronic disease.

• RDA (Recommended Dietary Allowance): Average daily intake level sufficient for nearly all (97-98%) healthy individuals.

• AI (Adequate Intake): Recommended intake based on observed or experimentally determined estimates.

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

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

Types of Research Studies

• Observational Studies: Observe relationships between variables without intervention.

• Experimental Studies: Involve intervention and control groups to test hypotheses.

• Randomized Controlled Trials (RCTs): Participants randomly assigned to groups; considered the gold standard.

Quality Research Characteristics

• Peer-reviewed

• Large sample size

• Control of variables

• Reproducibility

Reliable Sources of Nutrition Information

• Registered Dietitians (RD or RDN)

• Government agencies (e.g., USDA, FDA)

• Peer-reviewed journals

Energy Density vs. Nutrient Density

• Energy Density: Amount of energy (kcal) per gram of food.

• Nutrient Density: Amount of nutrients per kcal of food.

• Example: Vegetables are nutrient-dense but low in energy density; chips are energy-dense but low in nutrient density.

Body’s Main Form of Stored Energy

• Triglycerides (fat) stored in adipose tissue are the primary energy reserve.

Most Abundant Nutrient

• Water is the most abundant nutrient in both food and the human body.

Chapter 2: Tools for Healthful Eating

Food Labeling Requirements

• Required Elements: Serving size, servings per container, calories, total fat, cholesterol, sodium, total carbohydrate, dietary fiber, sugars, protein, vitamins, and minerals.

• Daily Values (DV): Based on a 2,000 kcal diet.

• Regulation: The Food and Drug Administration (FDA) regulates food labeling in the US.

Interpreting Food Labels

• Compare serving size to actual consumption.

• Check %DV to assess if a food is high or low in a nutrient (5% or less is low; 20% or more is high).

Dietary Guidelines for Americans

• Updated every 5 years to promote health and prevent disease.

• Recommendations: Increase fruits, vegetables, whole grains, lean proteins; limit saturated fat, added sugars, sodium.

Prepared and Fast Foods

• Typically high in sodium, added sugars, and unhealthy fats.

Visual Representation of Guidelines

• The MyPlate icon (a plate shape) is the current pictorial guide.

Discretionary Calories in MyPlate

• Calories remaining after meeting nutrient needs with healthy foods; can be used for treats or extras.

Structure-Function Claims

• Describe the role of a nutrient or dietary ingredient in normal structure or function of the body (e.g., "calcium builds strong bones").

• Not evaluated by the FDA for effectiveness.

Processing Grains

• Whole Grain: Contains bran, germ, and endosperm.

• Refined Grain: Bran and germ removed; only endosperm remains.

• Enriched Grain: Nutrients added back after processing.

• Example: 100% whole wheat bread is a whole grain; white bread is refined.

Components of a Healthy Diet

• Adequacy: Sufficient energy and nutrients.

• Balance: Proper proportions of nutrients.

• Moderation: Not too much or too little.

• Variety: Diverse foods from all groups.

Nutrient Density vs. Energy Density

• Nutrient-dense foods provide more nutrients per calorie, helping meet nutritional needs without excess energy intake.

Intuitive Eating vs. Diet Mentality

• Intuitive Eating: Listening to internal hunger and satiety cues rather than external diet rules.

• Diet Mentality: Following restrictive or prescriptive eating patterns, often ignoring body signals.

Chapter 3: The Human Body & Digestion

Why Do We Eat? Appetite vs. Hunger

• Hunger: Physiological need for food.

• Appetite: Psychological desire to eat, often influenced by environment or emotions.

Blood Glucose and Hunger

• Low blood glucose stimulates hunger; high levels promote satiety.

Hormones Regulating Blood Glucose

• Insulin: Lowers blood glucose by promoting uptake into cells.

• Glucagon: Raises blood glucose by stimulating glycogen breakdown.

Organ Triggering Food Desire

• Hypothalamus in the brain regulates hunger and satiety signals.

Satiety Signals

• Stretch receptors in the stomach and hormones (e.g., cholecystokinin) signal fullness to the brain.

Digestion vs. Absorption

• Digestion: Breakdown of food into smaller components.

• Absorption: Uptake of nutrients into the bloodstream or lymphatic system.

Accessory Organs of Digestion

• Liver: Produces bile.

• Gallbladder: Stores and releases bile.

• Pancreas: Produces digestive enzymes and bicarbonate.

Where Digestion Begins

• Digestion begins in the mouth with chewing and salivary enzymes (e.g., amylase for carbohydrates).

Key Terms in Digestion

• Enzymes: Proteins that speed up chemical reactions (e.g., amylase, lipase, protease).

• Peristalsis: Wave-like muscle contractions moving food through the GI tract.

• Chyme: Semi-liquid mixture of partially digested food and digestive juices.

Macronutrient Digestion in the Mouth

• Carbohydrate digestion begins in the mouth via salivary amylase.

Absorption in the Small Intestine

• Most absorption occurs in the jejunum (middle section of the small intestine).

Water Absorption

• Most water absorption occurs in the large intestine (colon).

Cholecystokinin (CCK)

• Hormone released by the small intestine in response to fat; stimulates gallbladder to release bile and pancreas to release enzymes.

Pancreas and Liver in Digestion

• Pancreas: Produces digestive enzymes (amylase, lipase, protease) and bicarbonate to neutralize stomach acid.

• Liver: Produces bile to emulsify fats.

Role of the Pancreas

• Secretes digestive enzymes and hormones (insulin, glucagon).

Process of Food Breakdown

• Mechanical (chewing, peristalsis) and chemical (enzymes, acids) processes break down food.

Gastrin

• Hormone that stimulates secretion of gastric acid in the stomach.

Bile

• Produced in the liver, stored in the gallbladder.

• Emulsifies fats, aiding in digestion and absorption.

Circulatory vs. Lymphatic Systems

• Circulatory System: Transports water-soluble nutrients (e.g., glucose, amino acids) via blood.

• Lymphatic System: Transports fat-soluble nutrients (e.g., fatty acids, fat-soluble vitamins) via lymph.

Gastroesophageal Reflux Disease (GERD)

• Chronic reflux of stomach acid into the esophagus.

• Causes: Weak lower esophageal sphincter, obesity, certain foods.

• Treatment: Lifestyle changes, medications, avoiding trigger foods.

Celiac Disease

• Autoimmune disorder triggered by gluten (protein in wheat, barley, rye).

• Treatment: Lifelong gluten-free diet.

Peptic Ulcers

• Open sores in the lining of the stomach or duodenum.

• Causes: Helicobacter pylori infection, NSAIDs, excessive acid.

Table: Comparison of Circulatory and Lymphatic Transport of Nutrients