Carbohydrates

Main Energy Source for the Brain

The brain relies primarily on glucose as its main energy source. Glucose is a simple carbohydrate that circulates in the blood and is essential for normal brain function.

• Key Point: The brain cannot efficiently use fat for energy and depends on a steady supply of glucose.

• Example: During fasting or low-carbohydrate diets, the body produces ketone bodies as an alternative fuel for the brain.

Fiber Recommendation and Intake Among Most Americans

Dietary fiber is a type of carbohydrate that is not digested by human enzymes. It is important for digestive health and disease prevention.

• Recommended Intake: 25 grams per day for women and 38 grams per day for men (ages 19-50).

• Actual Intake: Most Americans consume less than half the recommended amount.

• Example: Whole grains, fruits, vegetables, and legumes are good sources of fiber.

Parts of a Whole Grain

Whole grains contain all three parts of the grain kernel:

• Bran: The outer layer, rich in fiber, B vitamins, and minerals.

• Germ: The nutrient-rich core, containing vitamins, minerals, and healthy fats.

• Endosperm: The starchy middle layer, providing carbohydrates and some protein.

Glycemic Index and Its Effect on Blood Glucose Levels

The glycemic index (GI) measures how quickly a carbohydrate-containing food raises blood glucose levels.

• High GI foods: Cause rapid spikes in blood glucose (e.g., white bread, sugary drinks).

• Low GI foods: Cause gradual increases in blood glucose (e.g., whole oats, legumes).

• Formula:

Diverticulosis: Definition and Prevention

Diverticulosis is a condition where small pouches (diverticula) form in the wall of the colon.

• Prevention: High-fiber diets help prevent diverticulosis by promoting regular bowel movements and reducing pressure in the colon.

Monosaccharides and Disaccharides

Carbohydrates are classified by the number of sugar units:

• Monosaccharides: Single sugar units (e.g., glucose, fructose, galactose).

• Disaccharides: Two sugar units linked together (e.g., sucrose = glucose + fructose, lactose = glucose + galactose, maltose = glucose + glucose).

Number One Source of Added Sugar in the Average American Diet

• Key Point: Sugar-sweetened beverages (such as sodas and energy drinks) are the leading source of added sugars.

Sugar Substitutes

Sugar substitutes are used to sweeten foods with fewer or no calories.

• Types: Artificial sweeteners (e.g., aspartame, sucralose), sugar alcohols (e.g., xylitol, sorbitol), and natural alternatives (e.g., stevia).

• Example: Sucralose is 600 times sweeter than sucrose and is used in many diet products.

Enzyme That Breaks Down Starch into Maltose in the Small Intestine

• Key Enzyme: Pancreatic amylase breaks down starch into maltose in the small intestine.

Hormones Used to Balance Blood Sugar Levels and Their Functions

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

• Glucagon: Raises blood glucose by stimulating the release of glucose from liver stores.

Diabetes: Symptoms, Outcomes of Uncontrolled Blood Sugars, and Prevention

• Symptoms: Frequent urination, excessive thirst, unexplained weight loss, fatigue.

• Outcomes: Uncontrolled diabetes can lead to heart disease, kidney failure, blindness, and nerve damage.

• Prevention: Healthy diet, regular physical activity, maintaining a healthy weight.

Physical Activity and Carbohydrate Needs

• Key Point: Physical activity increases carbohydrate needs to replenish muscle glycogen stores.

• Example: Endurance athletes may require 6-10 grams of carbohydrate per kilogram of body weight per day.

Lipids (Fats)

Primary Fat in Our Body and Its Structure

• Triglycerides: The main form of fat in the body and in food, composed of three fatty acids attached to a glycerol backbone.

• Structure:

Healthy Dietary Fats vs. Unhealthy Dietary Fats

• Healthy Fats: Unsaturated fats (monounsaturated and polyunsaturated), found in olive oil, nuts, and fish.

• Unhealthy Fats: Saturated fats (found in animal products) and trans fats (found in processed foods).

Saturation in Fats: Definition

• Saturated Fats: Fatty acids with no double bonds between carbon atoms; solid at room temperature.

• Unsaturated Fats: Fatty acids with one or more double bonds; liquid at room temperature.

Sources of Saturated and Unsaturated Fats

• Saturated Fats: Butter, cheese, red meat, coconut oil.

• Unsaturated Fats: Olive oil, avocados, nuts, fatty fish.

Phospholipids

• Definition: Lipids with a phosphate group, important for cell membrane structure.

• Example: Lecithin is a common phospholipid in food and the body.

Function of Fats

• Energy storage

• Insulation and protection of organs

• Absorption of fat-soluble vitamins (A, D, E, K)

Triglycerides: Uses in Our Body

• Provide energy

• Store excess calories

• Support cell structure

Good and Bad Cholesterol – Know the Difference

• HDL (High-Density Lipoprotein): "Good" cholesterol; removes cholesterol from the bloodstream.

• LDL (Low-Density Lipoprotein): "Bad" cholesterol; deposits cholesterol in artery walls, increasing heart disease risk.

Which Fats Are Made in the Body and Which Need to Be Consumed in Our Diet

• Non-essential fatty acids: Can be synthesized by the body.

• Essential fatty acids: Must be obtained from the diet (e.g., linoleic acid and alpha-linolenic acid).

How to Improve Blood Lipid Levels

• Increase intake of unsaturated fats

• Reduce saturated and trans fat intake

• Increase dietary fiber

• Engage in regular physical activity

Proteins

Types of Vegetarian Diets

• Lacto-ovo vegetarian: Includes dairy and eggs, excludes meat, poultry, and fish.

• Lacto vegetarian: Includes dairy, excludes eggs, meat, poultry, and fish.

• Vegan: Excludes all animal products.

Energy Density for Carbohydrates, Fats, and Proteins

Gluconeogenesis

• Definition: The process of producing glucose from non-carbohydrate sources, such as amino acids and glycerol.

• Occurs in: The liver (and to a lesser extent, the kidneys).

Amino Acid Structure and What Sets Amino Acids Apart

• Structure: Central carbon atom, amino group, carboxyl group, hydrogen atom, and a unique side chain (R group).

• Key Point: The R group determines the properties and identity of each amino acid.

Enzyme That Breaks Down Proteins

• Pepsin: The main enzyme in the stomach that begins protein digestion.

• Proteases: Enzymes from the pancreas that continue protein digestion in the small intestine.

Transamination: Definition

• Definition: The transfer of an amino group from one amino acid to a keto acid to form a new amino acid.

Health Problems Associated with High and Low Protein Intake

• High intake: May stress kidneys, increase risk of dehydration, and displace other nutrients.

• Low intake: Can lead to muscle wasting, weakened immune function, and protein-energy malnutrition (e.g., kwashiorkor, marasmus).

Immune Health and Protein

• Key Point: Proteins are essential for the production of antibodies and immune system function.

Functions of Protein in Our Body

• Build and repair tissues

• Enzymes and hormones

• Immune function

• Transport molecules

• Maintain fluid and acid-base balance

Complete vs. Incomplete Proteins and Their Sources

• Complete proteins: Contain all essential amino acids in adequate amounts (e.g., animal products, soy).

• Incomplete proteins: Lack one or more essential amino acids (e.g., most plant proteins).

Complementary Plant-Based Protein Sources

• Key Point: Combining different plant foods (e.g., rice and beans) can provide all essential amino acids.

Protein Digestion and Absorption

• Begins in the stomach with pepsin and hydrochloric acid.

• Continues in the small intestine with pancreatic proteases.

• Amino acids are absorbed into the bloodstream and transported to the liver.