Carbohydrates

Main Functions and Sources

Carbohydrates are a primary macronutrient, serving as the main energy source for the human brain and body. They are found in a variety of foods, especially grains, fruits, and vegetables.

• Main energy source for our brain: Glucose, a simple carbohydrate, is the preferred fuel for brain function.

• Fiber recommendation and intake: Dietary fiber is a type of carbohydrate important for digestive health. Most Americans do not meet the recommended daily intake, which is typically 25-38 grams per day for adults.

• Parts of a whole grain: Whole grains consist of the bran, germ, and endosperm. Refined grains have the bran and germ removed, reducing fiber and nutrient content.

• Glycemic index and its effect on blood glucose levels: The glycemic index (GI) measures how quickly a carbohydrate-containing food raises blood glucose. High-GI foods cause rapid spikes, while low-GI foods result in gradual increases.

• Diverticulosis definition and prevention: Diverticulosis is the formation of small pouches in the colon wall, often due to low fiber intake. Prevention includes a high-fiber diet and adequate hydration.

• Monosaccharides and disaccharides: Monosaccharides (e.g., glucose, fructose, galactose) are single sugar units. Disaccharides (e.g., sucrose, lactose, maltose) consist of two monosaccharide units.

• Number one source of added sugar in the American diet: Sugar-sweetened beverages, such as sodas and energy drinks, are the leading source.

• Sugar substitutes: These are non-nutritive sweeteners (e.g., aspartame, sucralose) used to reduce calorie intake.

• Enzyme that breaks down starch to maltose in the small intestine: Pancreatic amylase is responsible for this process.

• Hormones that regulate blood sugar: Insulin lowers blood glucose by promoting uptake into cells; glucagon raises blood glucose by stimulating glycogen breakdown.

• Diabetes symptoms and management: Diabetes is characterized by uncontrolled blood sugars. Symptoms include excessive thirst, frequent urination, and fatigue. Management involves diet, exercise, and sometimes medication.

Example:

Eating whole grain bread instead of white bread increases fiber intake and helps regulate blood sugar levels.

Fats (Lipids)

Types, Functions, and Health Implications

Fats are essential macronutrients that provide energy, support cell structure, and aid in the absorption of fat-soluble vitamins.

• Physical activity and body fat needs: Physical activity increases energy expenditure and can influence body fat requirements.

• Primary fat in our body and its structure: Triglycerides are the main form of fat stored in the body, consisting of three fatty acids attached to a glycerol backbone.

• Healthy dietary fats vs. unhealthy dietary fats: Unsaturated fats (found in nuts, seeds, fish, and plant oils) are considered healthier than saturated and trans fats (found in animal products and processed foods).

• Saturation in fats definition: Saturated fats have no double bonds between carbon atoms; unsaturated fats have one or more double bonds.

• Sources of saturated and unsaturated fats: Saturated fats are found in butter, cheese, and red meat; unsaturated fats are found in olive oil, avocados, and fatty fish.

• Phospholipids: These are a type of lipid that form cell membranes and are important for cellular function.

• Function of fats: Fats provide energy, protect organs, insulate the body, and help absorb vitamins A, D, E, and K.

• Triglycerides in our body: The most common type of fat in the body, used for long-term energy storage.

• Good and bad cholesterol: HDL (high-density lipoprotein) is considered "good" cholesterol, while LDL (low-density lipoprotein) is "bad" cholesterol. High LDL increases heart disease risk.

• Which fats are made in the body and which need to be consumed: The body can synthesize most fats, but essential fatty acids (omega-3 and omega-6) must be obtained from the diet.

Example:

Replacing butter (saturated fat) with olive oil (unsaturated fat) can improve heart health.

Proteins

Structure, Function, and Dietary Considerations

Proteins are complex molecules made of amino acids, essential for growth, repair, and maintenance of body tissues.

• Types of vegetarian diets: Lacto-ovo vegetarian (includes dairy and eggs), lacto-vegetarian (includes dairy), ovo-vegetarian (includes eggs), and vegan (excludes all animal products).

• Energy density for carbs/fats/proteins: Carbohydrates and proteins provide 4 kcal/g, while fats provide 9 kcal/g.

• How to improve blood lipid levels: Increase intake of unsaturated fats, reduce saturated and trans fats, and include fiber-rich foods.

• Gluconeogenesis: The process by which the body produces glucose from non-carbohydrate sources, such as amino acids.

• Amino acids structure and classification: Amino acids are organic compounds with an amino group, carboxyl group, and unique side chain. Essential amino acids must be obtained from the diet; non-essential amino acids can be synthesized by the body.

• Enzyme that breaks down proteins: Pepsin in the stomach and proteases in the small intestine digest proteins into amino acids.

• Transamination definition: 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 can strain kidneys; low intake can lead to muscle wasting and impaired immune function.

• Functions of protein in our body: Proteins are involved in enzyme activity, hormone production, immune response, and tissue repair.

• Complete vs. incomplete proteins and their sources: Complete proteins contain all essential amino acids (e.g., animal products, soy); incomplete proteins lack one or more essential amino acids (e.g., most plant sources).

• Complementary plant-based protein sources: Combining foods like beans and rice provides all essential amino acids.

• Protein digestion and absorption: Proteins are broken down into amino acids in the stomach and small intestine, then absorbed into the bloodstream.

Example:

Vegetarians can obtain complete protein by eating a combination of legumes and grains.

Key Definitions and Formulas

• Glycemic Index (GI): A ranking of carbohydrates on a scale from 0 to 100 based on their effect on blood glucose levels.

• Transamination:

• Energy Provided by Macronutrients:

Table: Comparison of Macronutrients

Table: Types of Dietary Fats

Table: Complete vs. Incomplete Proteins

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard academic nutrition knowledge.