Essential Nutrients, Digestion, and Macronutrients
Chapter One: Introduction to Nutrients
Essential Nutrients: Cannot be produced by the body. Non-essential Nutrients: The body can produce them.
Six Classes of Nutrients:
- Macronutrients: Carbohydrates, proteins, and lipids.
- Micronutrients: Vitamins, minerals, and water.
Energy Yielding Nutrients (kcal/gram):
- Carbohydrates: 4 kcal/gram
- Proteins: 4 kcal/gram
- Fats: 9 kcal/gram
- Alcohol: 7 kcal/gram
Acceptable Macronutrient Distribution Ranges (AMDR):
- Carbohydrates: 45%-65% of total calories
- Protein: 10%-35% of total calories
- Fats: 20%-35% of total calories
Nutrient Intake Recommendations:
- EAR (Estimated Average Requirement): Intake level estimated to meet the needs of 50% of healthy individuals in a group.
- RDA (Recommended Dietary Allowance): Ideal amount of a nutrient.
- AI (Adequate Intake): Used when RDA isn’t available.
- UL (Upper Intake Level): Maximum safe amount of a nutrient.
- Malnutrition: Can be either too much or too little nutrition.
Chapter 2: Designing a Healthful Diet
Four Components of a Healthful Diet:
- Adequate: Enough energy and nutrients.
- Balanced: Ideal proportions of foods and nutrients.
- Moderate: Reasonable amounts of food.
- Varied: Wide range of foods from different food groups.
%DV on Nutrition Facts Panels:
- Low: 5% or less
- High: 20% or more
Dietary Guidelines for Americans Intake Limits:
- Added Sugars: Less than 10% of daily calories.
- Saturated Fats: Less than 10% of daily calories.
- Sodium: Less than 2,300 mg.
Serving Size vs. Portion Size: Serving size is the label amount, while portion size is what you eat.
Nutrient Density: Lots of nutrients, few calories.
Chapter 3: Digestion, Absorption, and Transport
Brain’s Role in Digestion: The brain controls digestion and sends hunger cues based on signals like an empty stomach, low blood sugar, and hormones.
Organs of the GI Tract (in order): Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus.
Accessory Organs of Digestion:
- Salivary Glands: Produce saliva.
- Liver: Produces bile.
- Gallbladder: Stores bile.
- Pancreas: Produces enzymes and bicarbonate.
Mechanical Digestion:
- Mouth: Chewing.
- Stomach/Intestine: Peristalsis/segmentation.
Chemical Digestion:
- Mouth: Carbohydrates.
- Stomach: Protein.
- Small Intestine: Carbohydrates, fats, and proteins.
Role of Stomach Acid: Kills bacteria and denatures protein.
Stomach Protection: Mucus lining protects the stomach from being digested by acid and digestive enzymes.
Absorbable Forms of Nutrients:
- Carbohydrates: Monosaccharides (glucose, fructose, and galactose).
- Proteins: Amino Acids.
- Fats: Fatty acids and monoglycerides.
Digestion Start for Macronutrients:
- Carbohydrates: Mouth.
- Proteins: Stomach.
- Fats: Small intestine.
Most Digestion/Absorption: Occurs in the small intestine, due to a large surface area from villi and microvilli.
Large Intestine Role: Absorbs water and electrolytes, forms feces; bacteria ferment undigested materials.
Absorption Definition: Nutrients move into the blood.
Food Intolerance vs. Food Allergy: Intolerance involves digestive issues, while an allergy is life-threatening.
GERD (Gastroesophageal Reflux Disease): Stomach acid flows back into the esophagus.
Celiac Disease: Gluten damages the intestine.
IBS (Irritable Bowel Syndrome): Gut issues with an unknown cause.
Chapter 4: Carbohydrates
Simple vs. Complex Carbohydrates: Simple carbs are small molecules and are quickly digested, while complex carbs are large molecules and take longer to digest.
Monosaccharides: Glucose, fructose, galactose.
Disaccharides:
- Sucrose (glucose + fructose)
- Lactose (glucose + galactose)
- Maltose (glucose + glucose)
Oligosaccharide: Short chains of 3-10 monosaccharides.
Polysaccharide: Long chains of monosaccharides.
Naturally Occurring vs. Added Sugar: Natural sugars are found naturally in foods, while added sugars are added during processing.
Storage Forms of Carbohydrates: Plants store starch, while animals store glycogen.
Types of Fiber: Soluble and insoluble. Fiber is good for digestion and heart health, and lowers cholesterol; found in fruits, vegetables, and grains.
Hormones Impacting Blood Glucose: Insulin (lowers blood glucose) and glucagon (raises blood glucose).
Cells that Use Carbohydrates: Some cells (red blood cells) can only use carbohydrates; the brain prefers them.
No Carbohydrates: If carbohydrates are not available, the body uses protein and fat.
AMDR for Carbohydrates: 45%-65%; athletes may need more.
Chapter 5: Lipids
Main Type of Fat: Triglycerides (glycerol backbone with three fatty acids attached).
Fatty Acid Classification: Chain length (short, medium, long) and saturation (saturated, monounsaturated, polyunsaturated).
Health Effects of Fats: Unsaturated fats are heart-healthy, while saturated fats increase the risk of heart disease.
Fats at Room Temperature: Saturated fats are solid, while unsaturated fats are liquid.
Phospholipids: Major component of cell membranes.
Sterols: Cholesterol (found in cell membranes and hormones).
Essential Fatty Acids: Linoleic Acid (Omega-6) and Alpha-Linolenic Acid (Omega-3); the body can’t make them.
Food Sources of Essential Fatty Acids: Omega-6 (vegetable oils, nuts, seeds) and Omega-3 (fatty fish, flaxseeds, walnuts); most Americans don’t get enough Omega-3 fatty acids.
Fat Digestion/Absorption: Bile emulsifies fats, pancreatic lipase breaks down triglycerides, micelles help with absorption, enterocytes package fats into chylomicrons, and lipoproteins transport fats.
Trans Fat: Unsaturated fats with a rearranged double bond, solid at room temperature, and increase the risk of heart disease; intake should be as low as possible.
Trans Fat Indicator on Labels: “Partially hydrogenated oil”.
Functions of Fat: Energy, insulation, cell membranes, hormone production, carries fat-soluble vitamins.
AMDR for Fat: 20-30%.
Saturated Fat: Less than 10%. Trans Fat: As low as possible.
Chapter 6: Proteins
Amino Acid Structure: Amino group, carboxyl group, hydrogen atom, and a side group (R); the unique element is nitrogen.
Essential Amino Acids: The body can’t make them; they must be obtained from food.
Non-Essential Amino Acids: The body can make them.
Conditionally Essential Amino Acids: Become essential under certain conditions (illness & stress).
Protein Structures: Primary, secondary, tertiary, and quaternary.
Protein Digestion/Absorption: Pepsin begins breakdown in the stomach, pancreatic proteases and peptidases break down proteins in the small intestine, and amino acids are absorbed into the bloodstream and transported to cells.
Roles of Proteins: Structure, enzymes, hormones, antibodies, transport, fluid balance, and pH balance.
Edema: Swelling caused by fluid buildup; can occur with protein deficiency.
Food Sources of Protein: Meat, poultry, fish, eggs, dairy, legumes, nuts, seeds, and grains.
Incomplete Protein Sources: Plant proteins may lack one or more essential amino acids.
Limiting Amino Acid: The essential amino acid present in the smallest amount in a given food protein.
Protein Recommendations: 0.8 grams per kilogram of body weight for the average adult; factors include body weight, activity level, age, and health status.
Protein Synthesis: The body makes protein when needed; supplements may not help if already getting enough.
Malnutrition Types:
- Marasmus (low calories and protein)
- Kwashiorkor (low protein only)