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). 10-35 grams

• 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, each with unique nutritional properties.

• 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 (e.g., sucrose = glucose + fructose, lactose = glucose + galactose, maltose = glucose + glucose).

Number One Source of Added Sugar in the Average American Diet

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

Sugar Substitutes

Sugar substitutes are compounds that provide sweetness with little or no calories.

• Examples: Aspartame, sucralose, stevia, saccharin.

• Application: Used in diet sodas, sugar-free gum, and other low-calorie products.

Enzyme That Breaks Down Starch into Maltose in the Small Intestine

• Pancreatic amylase is the enzyme responsible for breaking 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, and Prevention

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

• Outcomes of Uncontrolled Blood Sugars: Heart disease, kidney damage, nerve damage, vision loss.

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

Physical Activity and Carbohydrate Needs

• Physical activity increases the body's need for carbohydrates to replenish muscle glycogen stores.

• Athletes may require higher carbohydrate intake than sedentary individuals.

Lipids (Fats)

Primary Fat in Our Body and Its Structure

• Triglycerides are the main form of fat in the body and in food.

• Structure: One glycerol molecule bonded to three fatty acids.

Healthy Dietary Fats vs. Unhealthy Dietary Fats

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

Phospholipids

• Phospholipids are a type of lipid with a glycerol backbone, two fatty acids, and a phosphate group.

• They are key components of cell membranes, providing structure and regulating transport.

Function of Fats

• Energy storage

• Insulation and protection of organs

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

• Cell membrane structure

Triglycerides: Uses in Our Body

• Stored in adipose tissue as an energy reserve

• Provide insulation and cushioning

• Transported in the blood as a source of energy

Good and Bad Cholesterol – Know the Difference

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 (triglycerides, phospholipids and sterols).

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

Proteins

Types of Vegetarian Diets

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

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

• Ovo-vegetarian: Includes eggs, excludes dairy, meat, poultry, fish.

• Vegan: Excludes all animal products.

Energy Density for Carbohydrates, Fats, and Proteins

How to Improve Blood Lipid Levels

• Increase intake of unsaturated fats

• Reduce intake of saturated and trans fats

• Increase dietary fiber

• Engage in regular physical activity

Gluconeogenesis

Gluconeogenesis is the metabolic process of producing glucose from non-carbohydrate sources, such as amino acids and glycerol.

• Occurs mainly in the liver.

• Important during fasting or low-carbohydrate intake.

Amino Acid Structure and What Sets Amino Acids Apart

• All amino acids have a central carbon, an amino group (), a carboxyl group (), a hydrogen atom, and a unique side chain (R group).

• The R group distinguishes one amino acid from another and determines its properties.

Enzyme That Breaks Down Proteins

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

• Other enzymes, such as trypsin and chymotrypsin, continue protein digestion in the small intestine.

Transamination: Definition

Transamination is the process of transferring 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 protein intake: May strain kidneys, increase risk of dehydration, and lead to calcium loss.

• Low protein intake: Can cause muscle wasting, weakened immune function, and in severe cases, protein-energy malnutrition (e.g., kwashiorkor, marasmus).

Immune Health and Protein

• Proteins are essential for the production of antibodies and immune system cells.

• Protein deficiency impairs immune response and increases susceptibility to infections.

Functions of Protein in Our Body

• Building and repairing tissues

• Enzyme and hormone production

• Immune function

• Transport of molecules (e.g., hemoglobin)

• Maintaining 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

• Combining different plant foods (e.g., beans and rice, vegetable chili and corn bread) can provide all essential amino acids.

• This practice is called protein complementation.

Protein Digestion and Absorption

• Protein digestion begins in the stomach with pepsin and hydrochloric acid.

• Continues in the small intestine with pancreatic enzymes (trypsin, chymotrypsin).

• Amino acids are absorbed into the bloodstream and transported to cells for use.

Kwashiorkor vs Marasmus

• Kwashiorkor: protein deficiency → growth impairment/stunting can occur.

• Marasmus: severe calorie + protein deficiency → growth failure and severe wasting.