/ Carbohydrates

Main Energy Source for the Brain

The brain relies primarily on glucose as its main energy source. Glucose is a simple carbohydrate that cir culates 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 energy source for the brain.

Fiber Recommendation and Intake Among 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 antioxidants, vitamin E, B vitamins, 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 cereals).

• Low GI foods: Cause gradual increases in blood glucose (e.g., 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 American Diet

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

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 in the Small Intestine

• Pancreatic amylase is the enzyme responsible for breaking down starch into maltose in the small intestine.

Hormones That Balance Blood Sugar Levels

• 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 Diabetes: Heart disease, kidney failure, 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 for optimal performance and recovery.

Lipids (Fats)

Primary Fat in the Body and Its Structure

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

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

Healthy vs. Unhealthy Dietary Fats

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

• Unhealthy Fats: Saturated fats (found in animal products, s ome tropical oils) and trans fats (partially hydrogenated oils).

" 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, canola oil, avocados, nuts, 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.

Functions of Fats

• Energy storage

• Insulation and protection of organs

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

• Cell membrane structure

Triglycerides: Uses in the Body

• Stored in adipose tissue as an energy reserve

• Provide insulation and cushioning

• Transported in the blood as a source of energy for muscles

Good and Bad Cholesterol

• HDL (High-Density Lipoprotein): "Good" cholesterol; removes cholesterol from the bloodstream and transports it to the liver for excretion.

• LDL (Low-Density Lipoprotein): "Bad" cholesterol; delivers cholesterol to tissues, can contribute to plaque buildup in arteries.

Fats Made in the Body vs. Essential Fats

• Non-essential fats: Can be synthesized by the body (e.g., most saturated and monounsaturated fatty acids).

• 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 intake of saturated and trans fats

• Increase dietary fiber

• Engage in regular physical activity

Proteins a

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

Gluconeogenesis

Gluconeogenesis is the metabolic process by which the body produces 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 Them 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 (in the stomach) and proteases (in the small intestine) are enzymes that break down proteins into smaller peptides and amino acids.

Transamination: Definition

Transamination is the process by which an amino group is transferred from one amino acid to a keto acid, forming a new amino acid.

Health Problems Associated with High and Low Protein Intake

• High protein intake: May stress kidneys, increase calcium loss, and is associated with higher risk of some chronic diseases if from animal sources.

• Low protein intake: Can lead to muscle wasting, weakened immune function, and conditions like kwashiorkor and 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 the 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) can provide all essential amino acids.

• This is important for vegetarians and vegans to ensure adequate protein quality.

Protein Digestion and Absorption

• Begins in the stomach with pepsin and hydrochloric acid.

• Continues in the small intestine with proteases.

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