Macronutrients and Micronutrients

Macronutrients

Macronutrients are nutrients required by the body in relatively large amounts. They provide energy and are essential for growth, metabolism, and other bodily functions.

• Carbohydrates: Provide 4 kcal per gram. Main source of energy for the body.

• Proteins: Provide 4 kcal per gram. Essential for tissue repair and building body structures. Building blocks: Amino acids.

• Lipids (Fats): Provide 9 kcal per gram. Most energy-dense macronutrient. Important for energy storage, cell membranes, and hormone production.

• Water: Considered an inorganic macronutrient, vital for all physiological processes.

Example: A meal containing 210g carbs, 60g protein, and 52g fat provides a total of 1548 kcal, with carbohydrates contributing 54% of the energy.

Micronutrients

Micronutrients are nutrients required in smaller amounts but are crucial for proper body functioning. They do not provide energy but are essential for metabolic processes.

• Vitamins: Organic molecules that help regulate body functions.

  • Fat-soluble: Vitamins A, D, E, K

  • Water-soluble: Vitamin C, B-complex vitamins

• Minerals: Inorganic substances.

  • Major minerals: Calcium, phosphorus, sodium, potassium, chloride, magnesium, sulfur

  • Trace minerals: Iron, zinc, copper, manganese, fluoride

Energy and Nutrient Density

Kilocalorie (kcal)

A kilocalorie is the amount of energy required to raise the temperature of 1 kilogram of water by 1 degree Celsius. (Note: The original note says 12 kg, but the standard definition is 1 kg.)

Most energy-dense nutrient: Fats (lipids).

Nutrient Density

Nutrient-dense foods provide the highest amount of nutrients for the lowest number of calories.

Functional Foods

Functional foods provide health benefits beyond basic nutrition.

• Probiotics: Live beneficial bacteria that support gut health.

• Prebiotics: Non-digestible food components that promote the growth of beneficial bacteria in the gut.

• Phytochemicals: Bioactive compounds found in plants that have health-promoting properties.

Dietary Reference Intakes (DRIs)

DRIs are a set of reference values used to plan and assess nutrient intakes of healthy people.

• EAR (Estimated Average Requirement): Average daily nutrient intake level estimated to meet the requirement of half the healthy individuals in a group.

• AI (Adequate Intake): Recommended intake based on observed or experimentally determined approximations of nutrient intake by healthy people.

• EER (Estimated Energy Requirement): Average dietary energy intake predicted to maintain energy balance.

• AMDR (Acceptable Macronutrient Distribution Range): Range of intake for a particular energy source (carbs, fats, proteins) expressed as a percentage of total energy intake.

Scientific Studies in Nutrition

• Single-blind study: Researchers know who receives the placebo, but participants do not.

• Double-blind study: Neither researchers nor participants know who receives the placebo.

• Placebo: An inactive substance or treatment used as a control in an experiment.

• Bias: Systematic error in research. Types include selection bias and researcher bias.

Evaluating Diet Quality

• Adequate diet: Provides enough energy, nutrients, and fiber to support health.

• Nutrient-dense foods: High in nutrients, low in calories.

• Hunger vs. Appetite: Hunger is the physiological need to eat; appetite is the psychological desire to eat.

Food Labels and Processed Foods

Food Label Requirements

• Statement of identity

• Contents of package

• Ingredient list (listed in descending order by weight)

• Mandatory nutrients on labels: Vitamin D, potassium, calcium, iron

Processed Foods

• Fortified: Nutrients have been added.

• Enriched: Lost nutrients have been replaced.

• Organic: At least 95% of ingredients are organically produced by weight.

Dietary Guidelines

• Promote health

• Prevent diseases

Basic Chemistry for Nutrition

• Atoms: Smallest unit of matter.

• Molecules: Groups of atoms bonded together.

The Human Body and Digestion

Levels of Organization

• Cell: Smallest unit of life. The human body contains approximately 40 trillion cells.

• Enterocytes: Cells lining the intestine, involved in nutrient absorption.

• Cell membrane: Composed of a double layer of phospholipids.

• Organelles: Nucleus, endoplasmic reticulum, ribosomes, etc.

• Tissue: Group of cells performing a common function.

• Organ: Group of tissues working together.

• Organ system: Group of organs working together for a specific function.

Hormones in Nutrition

• Insulin: Produced by the pancreas; lowers blood glucose levels.

• Glucagon: Produced by the pancreas; raises blood glucose levels.

• Ghrelin: Produced in the stomach; stimulates hunger.

• CCK (Cholecystokinin): Produced in the small intestine; signals satiety and stimulates bile release.

• Leptin: Produced by adipose (fat) cells; regulates long-term food intake and satiety via the hypothalamus.

Proteins have the highest satiety value among macronutrients.

Digestive System Overview

Structure of the GI Tract

The digestive system starts at the mouth and ends at the anus. It is composed of four major layers (from inside out):

• Mucosa: Secretes mucus to protect the lining of the GI tract.

• Submucosa: Contains nerves that regulate GI functions.

• Muscularis: Responsible for movement of food through the tract.

• Serosa: Outermost layer; slippery to prevent sticking to other organs.

Digestive Organs

• GI Tract Organs: Mouth, esophagus, stomach, small intestine, large intestine, anus.

• Accessory Organs: Liver, gallbladder, pancreas (produce or store substances needed for digestion).

Phases of Digestion

• Cephalic phase: Prepares the GI tract for food by stimulating digestive juices.

• Mechanical digestion: Physical breakdown of food (e.g., chewing).

• Chemical digestion: Enzymatic breakdown of food (e.g., salivary amylase for carbohydrates).

Key Digestive Processes and Structures

• Saliva: Moistens food and contains salivary amylase to digest carbohydrates.

• Tongue: Assists in digestion, including some lipid digestion.

• Epiglottis: Covers the trachea during swallowing to prevent choking.

• Stomach: Varies in size; can hold up to a gallon of fluid when full. Secretes gastric juices (stimulated by gastrin from G cells). Contains parietal cells (secrete hydrochloric acid) and chief cells. Highly acidic environment kills bacteria and denatures proteins. Absorbs water, fluoride, some lipids, some drugs, and alcohol.

• Small intestine: Main site of nutrient absorption; divided into three sections (duodenum, jejunum, ileum).

• Large intestine: Main function is storage; material is stored for 12–24 hours prior to elimination. Absorbs very little water and nutrients. Synthesizes vitamin K (important for blood clotting).

Accessory Organs and Bile

• CCK: Signals the gallbladder to contract and release bile into the duodenum.

• Bile: Synthesized by the liver; emulsifies fats for digestion.

Summary Table: Macronutrients and Their Properties

Key Equations

• Total Energy Calculation:

• Percent of Energy from a Macronutrient:

Additional info: Standard definition of kilocalorie is the energy needed to raise 1 kg of water by 1°C. The three sections of the small intestine are the duodenum, jejunum, and ileum. The main accessory organs are the liver, gallbladder, and pancreas. The tongue primarily aids in mechanical digestion and taste, but some enzymes in saliva begin lipid digestion.